By Aerik Carlton
While working with private space industry clients on launch complex structures, we have found some notable structural challenges. This article is meant to share some of Nishkian Dean’s recent launch site design experience. Specifically, an atypical structural load consideration that was identified and requested to be evaluated by our client.
Recently, launch tower structures, designed by others, near one of our project sites had been found to present weld failures at circular structural member support connections. The design and construction team that completed the nearby tower believed the weld failures to be representative of “bad welds” during construction. This conclusion was drawn because there appeared to be random failure locations. The failed connections were rewelded, but the repaired welds were found to have failed at the same locations in a follow-up inspection.
The failure of these members was surprising, mostly because they had been designed for large pressures associated with launch activities and hurricane wind forces for these structures, which the structure had not experienced. The second weld failures also occurred in the absence of either launch activities or hurricane activity, and there were only low-wind-velocity days between weld repairs and the second failure. The determined cause was attributed to wind-induced flutter, or gallop, of the members that resulted during low-velocity-wind cyclical loading. The team’s solution was to install air foils for fluid flow disruption around the circular members that experienced weld failures.
Due to the large rocket thruster impingement loadings present during launch activities, circular structural members have been found to be advantageous. Circular cross-sections allow for the same structural section properties: moment of inertia, section modulus, etc. to be present regardless of the direction of load (i.e. as the rocket gains elevation and the angle of load from the engine thrust changes, the structural member maintains the same resistance without reduction due to the change in loading angle). Wind and rocket thrust loads can be reasonably reduced by 20-30% of the projected area due to the allowable shape factor for circular structural cross-section. Fluid shedding, due to the rounded shape, is what allows the reduction in projected area for pressure loadings. When we are talking about 8 psi (1152 psf) of thrust pressure on the structure, shape factor reduction to the projected area is significantly beneficial. The use of circular framing members presents a slightly different issue, however, when considering relatively light wind loading conditions as evident from the nearby tower weld failures our client highlighted.
Nishkian Dean was tasked with mitigating the same type of behavior for a new tower at a nearby launch site in conjunction with the structural design for the client’s new facilities; for crew to vehicle access and lightning protection. The client asked that we design these operations support structures to accommodate their current vehicles as well as allowing for larger, more powerful, and greater range vehicles planned for the future.
A circular cross-sectional shape can exhibit interesting behavior in calm, steady wind. The phenomena our neighboring tower experienced is called “Karman vortex street,” and it happens during steady state fluid flow (or steady non-gusting wind) around a cylinder. You can be forgiven for not having that term readily available for recall from your fluid dynamics course work. I was fully unaware of the term until researching a solution to our issue. Karman vortex street is when the laminar (steady, non-gusting) fluid flow (or calm steady wind) around the cross-section begins to “stick” to the back side (leeward side) of the member and results in an alternating, rhythmic pattern of pressure differences from either side of the shape. This alternating pattern of “stick” creates a turbulent flow condition behind the member, and similar to an airplane wing, induces lift on the member due to the pressure differences. Pairing the lifting force in each direction and the gravitation pull on the member’s self-weight with respect to time, we end up with a vortex-induced vibration (VIV) loading condition.
To further explain and give a visual example of Karman vortex street, let’s take a look at the photo below. In the image, we can see an atmospheric example of Karman vortex street in cloud formations (located at the top of the photo) at the leeward (downwind) side of an island in the northern Sea of Japan. The photo has a wind directionality, moving from the bottom of the photo to the top, and the island is located at the bottom of the photo. As the clouds pass around the island, they swirl into eddies which alternate from the left and right sides of the island. This phenomenon is known as Karmon vortex street and was determined to be the cause of our client’s experience with weld failures.
Rishiri-to island, Sea of Japan off the northwest coast of Hokkaido, Japan
Taken: between April 19 and May 1, 2001
Photo Credit: NASA STS-100 Shuttle Mission https://spaceflight.nasa.gov/gallery/images/shuttle/sts-100/html/sts100-710-182.html
Licensing Agreement: https://www.nasa.gov/audience/formedia/features/Advertising_Guidelines.html
Determining which members in a structure will present VIV is the first step in designing for the issue. As our client saw with the neighboring launch tower, the structural members to exhibit VIV failures appeared to be random at first glance. To understand the nature of the failure, we needed to discover that we are dealing with a vibrational load that is time-dependent, and as such, we need to calculate the natural resonant frequency of our individual structural members. This process is very similar to what we, as structural engineers, do for seismic design when establishing our earthquake lateral loads. The load is dependent on the natural period of the structure. Turning to Roark’s Formulas for stress and strain, we obtain equations for the natural frequency of our members based upon support condition, length, material, and cross-sectional properties.
We can then establish the wind loading environment to see at what wind velocities moving around our individual structural member sizes will elicit vortex shedding frequencies in the vicinity of our structural members’ resonant frequencies. The tricky part here is establishing what makes sense for applicable wind velocities at the site and what boundary conditions can be set. Because hurricane activity was a design issue already being evaluated, the lower- to mid-velocities associated with hurricane wind were the upper boundary (assuming gusting would break up the required laminar flow required for Karman vortex street to occur long enough to gain a vibrational response). Evidence to the issues on the neighboring tower was given, as some of our tower’s members had resonant frequencies close to vortex shedding frequencies at wind velocities between 5 and 10 mph.
At this point we identify the members in the structure that are at risk of VIV. Using an equation for harmonic vortex shedding lifting force from Blevins (2001), we can establish a time-history load function. The load is then applied to a single degree of freedom model for the member, and we find the deflection versus time plot for the member during VIV that accounts for stiffness and damping. From the deflections and member properties, the reaction loads to the support connections are determined. And, from there, we evaluate our connections for cyclical loading.
In our design, we were able to simply lengthen our welds on the members that exhibited VIV to add the required weld capacity to overcome cyclical fatigue. However, there are many ways of mitigating the negative response to vortex conditions. Blevins (2001) outlines several options, including: helical strakes, shrouds, axial slats, streamlined fairings, splitters, ribbons, pivoting guiding vanes, and flat spoiler plates. The neighboring tower took advantage of the streamlined fairing option, while we implemented helical strakes on our tower topping fiber reinforced plastic (FRP) mast similar to those used on exhaust chimneys in other industrial applications.
Please contact Nishkian Dean if your project has vibration analysis considerations – we would be happy to share more of our expertise on this subject.
Aerik Carlton is an Engineering Designer with Nishkian Dean. Aerik can be reached at firstname.lastname@example.org.
AISC. American Institute of Steel Construction (2011). Steel Construction Manual. 14th Ed. AISC. Chicago, IL.
Biggs, J. M. (1964). Introduction to Structural Dynamics. McGraw-Hill. New York.
Blevins, R. D. (2001). Flow-Induced Vibration. 2nd Ed. Krieger Publishing Company. Malabar, FL.
Young, W. C., Budynas, R. G. (2002). Roark’s Formulas for Stress and Strain. 7th Ed. McGraw Hill. New York.
A January 2018 update to our blog post from July 2017
Nishkian Dean previously reported on the URM Building Policy Committee back in July, which you can read here. This shorter post is intended to be a supplement to the original post, and to cover items not addressed in the previous article.
The URM Building Policy Committee had a final meeting on November 8, 2017 and completed a final draft of their report and recommendation in December, which the Portland City Council is likely to review in early 2018.
In summary, the Committee’s proposal is to require seismic strengthening of URM buildings using a tiered approached based on the building’s use and occupancy. The only exceptions to these recommended requirements are for one- and two-family homes and URM buildings that were previously seismically strengthened to an acceptable defined standard, as well as buildings serving religious functions or other buildings owned by non-profits that are not being used as schools. The exemption for Class 3 churches and other buildings used by non-profits would require that a placard noting the earthquake risk be placed at or near the entrances.
The Committee has defined 4 categories of URMs with differing levels of seismic strengthening requirements and corresponding time allotments to complete the requirements. The Classes range from 1 to 4, with Class 1 for Critical Buildings and Essential Facilities and Class 4 for Low-Occupancy structures. Class 2 is for Schools and High-Occupancy structures (such as churches and theaters), while Class 3 is for is the largest class of building and covers every other URM building not included in the other classes. For Class 3 buildings, the allotted time period to complete upgrades was reduced from 20 years to 15 years. Class 3 buildings make up over 80% of the URM building inventory.
Another recommendation by the Committee involves changing the current city code by modifying the thresholds for required seismic upgrades per Title 24.85. Title 24.85 requires owners to seismically retrofit their buildings when an owner spends approximately $43 per square foot on improvements within a two-year period. The Committee recommends lengthening the consideration period for cost-per-square-foot improvement periods from two to five years, and adding an upper limit to the total cost of improvements over a 15 year period to be twice the allowed five year costs. Title 24.85 also requires that the parapets be braced and the roof diaphragm be tied to the walls when more than 50% of the roof is replaced over a five-year period. The committee recommends that the trigger for roofing requirement upgrades happen over a fifteen-year period rather than a five-year period.
In our previous post, we calculated a considerable cost to implement the recommendations citywide. During the period for public comment, building owners expressed grave concern about the considerable costs. The Committee recommended that the City provide some funding mechanisms prior to implementing measures that would give funding assistance for owners, such as a property tax exemption through Oregon Senate Bill 311, and/or a few other sources laid out in the report.
These recommendations are on the docket to be considered by the Portland City Council in early 2018. At that point, the Council will need to decide if it will implement all or part of the recommendations. Possible outcomes may include an ordinance mandating seismic strengthening of URM buildings, the continuation of the status quo as required by Title 24.85, or the modification of Title 24.85 per the committee’s recommendation.
Nishkian Dean will continue to monitor the development of this important issue affecting many of our clients, so stay tuned.
By Robert A. Aman, PE, SE
Many buildings constructed today extend one or more stories below grade level to maximize building area and provide additional spaces for parking, storage, mechanical/electrical rooms, and sometimes even office space or living units. In many cases the soil excavations required for these below-grade structures are constrained by the site’s property lines and surrounding buildings, and therefore require that a vertical excavation cut is made within the property lines and construction boundaries. Since the soil excavations are vertical, temporary excavation shoring must be installed to prevent the soil from caving. In cases where there is available space adjacent to it, the excavation typically will be laid back on a slope at a 1 ½ horizontal to 1 vertical to prevent caving and to eliminate the need for excavation shoring. In situations in which this is not possible, shoring provides a means to safely accomplish the site excavation and greatly improve the utilization of the site development.
The design of excavation shoring can be complex and must take into account many factors, including depth of cuts, groundwater elevations, horizontal loads imposed by soil, resistance loads provided by soil at embedded shoring, and superimposed vertical loads from traffic, construction equipment, construction material storage, and adjacent structures. The vertical loads that occur adjacent to shoring walls usually result in additional horizontal loads applied to the shoring. The geotechnical engineer is responsible for providing all soil design parameters for the temporary shoring design, and works together with the foundation and structural engineer to accomplish this.
Excavation shoring, on most projects, is delegated to a specialty contractor who is also typically responsible for its design. In many jurisdictions, including the City of Portland, excavation shoring design drawings and calculations must be approved as part of the building permit submittal process. Site construction cannot begin without this information in hand, so it is important to understand the jurisdictional requirements before getting to this point so that the start of the project is not impacted.
When needed, there are several different shoring systems that can be utilized. The selection of the best system for each particular project considers the site soil conditions, adjacency with other elements, depth of excavation, and the experience of the specialty excavation contractor. Two common systems are soldier pile walls, and soil nail walls, which we go more in depth about below (pun intended):
Soldier Pile Walls
This method is fast to construct and typically consists of structural steel H-shaped piles that are inserted into a deep round hole filled with concrete that is spaced at regular intervals, usually in the 6- to 12-foot range. The concrete hole is typically 24” in diameter and the H-Pile is 10” to 14” wide/deep. Alternatively, the steel piles may be driven or vibrated into the ground without the use of any concrete. Where the excavation is located adjacent public property, the temporary shoring wall is typically located directly outside the property line, where permitted on a public right-of-way, and is used to apply a reinforced shotcrete wall that then serves as the permanent structural wall. Where shoring walls are located adjacent to a private property it can only be located over the property line with an easement from the property owner.
Between the soldier piles, 4×12 horizontal wood lagging is installed to retain the soil behind the wall. The lagging is installed in 3- to 4-foot increments as the vertical excavation cut proceeds downward. The soldier pile is typically embedded 10 to 12 feet below the bottom of the final excavation, and is designed to cantilever out of the ground. Where the excavation exceeds a range of 10 to 12 feet, the soldier piles may require a soil anchor/tieback or internal diagonal brace near the top of the wall for additional support. For deeper excavations, additional tiebacks are required as the depth increases further.
Soil anchor (or tiebacks) usually consist of a steel tendon or rod encased in a hole filled with a concrete grout mixture. The anchors are tensioned after installation is complete to fully engage the soil. Soil anchor tiebacks are installed at a downward angle and typically extend into the ground a minimum of 25 feet and may therefore encroach into the adjacent properties or the city’s right-of-way (in which case, permission from the property owner is required.) Encroachment into a public right-of-way is typically allowed for temporary construction.
Location of all existing utilities must be confirmed prior to the installation of the anchors. The City of Portland requires an additional encroachment permit, and states that the anchors are de-tensioned after the temporary wall is no longer needed. Additionally, the City requires that any shoring elements in the public right-of-way that are located within 5-feet below grade must be removed, including soldier piles and tiebacks. The use of internal shoring bracing eliminates encroachments, but the shoring is located where the building construction occurs and must not conflict with those activities.
Pros: fast to construct, can be used in deep excavations, flexible layout geometry, can be designed for large surcharge loads
Cons: in certain cases, may require additional soil anchors/tiebacks or support, tiebacks in adjacent property will require an easement, internal braced configurations can be obstructing.
Soil Nail Walls
Another common excavation shoring wall solution is a soil nail wall, which is purely an anchor tieback wall. A soil nail wall consists of steel bars installed in a drilled hole filled with a concrete grout mix spaced at approximately 5 feet on center. The rods are typically installed at a 15-degree downward angle and embedded in the 15-foot range. The nails are then covered with a 4”-thick reinforced shotcrete facing wall that retains the soil behind the wall. The walls are constructed from the top down in 3- to 6-feet-tall sections, depending on the soil type and its ability to withstand caving.
Soil nail walls may be advantageous where overhead construction requirements are tighter because they do not require drilling equipment or the installation of soldier piles. Smaller equipment is generally needed with this method, and no additional embedment of a vertical structural element is required. Embedment of soil nails is also much less than with tieback walls, which may reduce conflicts with adjacent underground obstructions or utilities. A soil nail wall will require a more specialized and experienced contractor, however. Like a traditional soldier pile wall, the structural wall for the building would be a shotcrete wall installed on the face of the soil nail wall. The design of the soil nails is typically provided by the geotechnical engineer, while the shotcrete facing wall is designed by a structural engineer.
Pros: do not require drilling equipment or the installation of soldier piles, needs smaller equipment, no additional embedment of a vertical structural element is required
Cons: limited depth of excavation, limited wall surcharge loads can be accommodated, requires a more specialized and experienced contractor
Basement excavations are a common necessity of many projects, and as you can see above, there are many options and avenues for selecting the right system for each individual project. Developing a strategy to address the excavation is an important part of the early design effort – it helps with creating a scheme that is readily buildable for a specific site and ensures that everything is in place for the permit application. The Nishkian firms are regularly involved in the design of many projects that incorporate basement excavations and are available to consult on your project needs.
Robert A. Aman, PE, SE is an Associate with Nishkian Dean a structural engineering consulting firm in Portland, Oregon.
We are honored and thrilled that the Q21 mixed-use project in NW Portland was a recent recipient of the Structural Engineers Association of Oregon (SEAO) 2017 Excellence in Structural Engineering Award for a New Building Over $10M. Designed by YBA Architects and constructed by Andersen Construction Company, Nishkian Dean served as the Structural Engineer of Record on the project.
SEAO is a nonprofit organization that works to educate the design industry and the community at-large on structural engineering topics, and provides a valuable forum for structural engineers to interact throughout Oregon.
“We would like to thank SEAO and the awards committee for this honor and we appreciate the continuous efforts of the organization to educate our members and strengthen our industry. We also want to thank the entire Q21 project team and especially YBA Architects for selecting us as the Structural Engineer for such a fun and challenging project.”
Rob Aman, Associate, Nishkian Dean
Located adjacent to the Conway District at NW 21st & Quimby in Portland, the 7-story, 202,200-SF project provides 162 living units, a courtyard, offices, parking, and ground-floor retail. The mixed-use project consists of two 3-story wood-framed residential buildings separated by a courtyard, all of which is situated above a two-level post-tensioned concrete parking structure that is partially below-grade.
The two buildings are connected directly to a seven-story post-tensioned concrete structure that includes residential units at the upper levels, an office floor level, and retail spaces at the ground floor. The concrete structure’s lateral force-resisting system consists of reinforced concrete shear walls, and a seismic joint was detailed to separate the wood and concrete buildings where they adjoin.
A one-story retail space extends off the north side of the structure, and 8 two-story townhomes occupy the ground level along the building’s south side. The project is highlighted by three-story double-tapered steel columns at the main entrance that form an “XXI” shape to symbolize the project name and street number location. These specialty steel columns were constructed with two tapered dodecagon (12-sided) steel sections welded together at the column midpoint to form a double-tapered member. A tapered cantilevered post-tensioned concrete beam spans the top of the steel columns to support four stories of structure above.
One of the most unique and challenging aspects of the project included preserving and modifying the 35-foot tall existing concrete tilt-up wall panels from the existing warehouse building on the site. The team incorporated the panels into the architectural and structural design as a non-structural exterior wall element to preserve the heritage of one of the early buildings that Andy Andersen, the founder of Andersen Construction, constructed and to promote the conservation of materials. This effort was significant and meaningful for Andersen Construction now that the family-owned business is being led by its third generation.
The existing concrete wall panels were cut, reinforced with steel backing and fiber reinforcement, and temporarily braced during construction. A few of the panels were lowered and transported to off-site storage to allow for site access during construction. Nishkian Dean provided full engineering support for this entire process during the initial phase of construction.
“The project afforded many opportunities for creative solutions to meet an ambitious and innovative vision. It was an honor to be a part of the cutting-edge design team on one of the first two-story podium structures in the City of Portland. We are very proud to receive such a prestigious award and grateful to SEAO for establishing a platform to recognize excellence in structural design.”
Dave Beh, Project Engineer, Nishkian Dean
Robert Aman, PE, SE (email@example.com) is an Associate with Nishkian Dean a structural engineering consulting firm in Portland, Oregon.
Dave Beh, PE (firstname.lastname@example.org) is a Project Engineer with Nishkian Dean a structural engineering consulting firm in Portland, Oregon.
Xylia Buros, (Xylia@xyliaburos.com) Marketing Consultant, provided copy and editing for this article.
By Edwin T. Dean, PE, SE
Having completed the initial designs for the innovative CoreFirst system, we at Nishkian Dean believe that it is a viable alternative to doing nothing and accepting fate when it comes to the next earthquake that may devastate Oregon buildings and put occupants in harm’s way. There is little argument that a full seismic strengthening of a building is the best solution, but for many building owners, it is simply not an expense that they can afford. If a full seismic upgrade is not a financially viable option, an alternative that would potentially provide a robust sanctuary to shelter occupants as the building around them shakes apart during a seismic event is a good one.
The CoreFirst system functions as a seismic shelter erected within an existing building, providing improved life safety during a seismic event without the need to retrofit the building to current seismic standards. Coupled with an earthquake early-warning system that can provide more than 60 seconds to evacuate, CoreFirst both alerts building occupants and provides a safe place to congregate during an earthquake.
Composed of a one or two-story steel special moment frames oriented in both principal directions, the CoreFirst system includes a steel grating plank platform at each level to provide protection from debris and existing building failure. The moment frames are isolated from the existing structure, ensuring that they only resist load generated by the seismic weight of the CoreFirst shelters. While the moment frames are not tied to the building’s existing seismic-force-resisting system, they are designed with a large reserve capacity for additional lateral load, with the added benefit of potential use as a component of a future comprehensive seismic upgrade of the building.
The shelters are designed so that their floor levels are located below the floor structure of the existing building. These floor levels are framed out with infill gravity framing supporting steel planks or channels that form a debris shield, preventing debris from falling through the floor of the existing structure into the shelter’s protective zone. The platforms are designed for a floor live load of 100 psf, a roof live load of 20 psf, and a vertical seismic load of 50 psf (representing both the dynamic load of debris falling on the platform and the static load of accumulated debris). Ultimately, all the gravity load is supported by the moment frames.
The moment frames are designed to the requirements of a Risk Category IV structure, which primarily impacts the drift limit, or the typical governing limit state for steel moment frames. Based on the seismic weight of the frames and grating platforms, seismic loads are generated for the frame per the equivalent lateral force procedure of ASCE 7. To enable the potential use of the frames as a component of a future full seismic upgrade of the building, additional seismic load is assigned at each level of the moment frames. It is not always possible to predict what shape a future seismic upgrade would take, and what loads the moment frames might need to carry, but a conservative load is estimated by assuming that a certain tributary area is assigned to the moment frames based on their location in the building. The total lateral load the frames are designed for is indicated on the construction drawings for future reference.
Footings are also designed for the additional seismic load described above. Because the frames are isolated from the main structure, they have very little dead load to resist overturning. As a result, there are three footing options:
1) Very large isolated footings with enough weight to prevent overturning
2) A mat footing designed to resist overturning
3) Small isolated footings/pile caps utilizing helical piles to resist uplift and downforce
The seismic gap required around all interfaces between the shelters and the existing structure is determined by estimating the maximum seismic drift of the building (based on the drift limits for the building’s structural system at the time it was constructed), determining the maximum seismic drift of the moment frames, and calculating the resulting maximum drift in any direction for both cases by combining the maximum drift in one direction with 30% of that drift in the orthogonal direction. The sum of the two maximum drifts is the minimum required seismic gap.
We believe that building owners could benefit from this affordable system. If you have any questions about CoreFirst, please contact us at the Nishkian Dean office or visit the CoreFirst website. We are happy to discuss this innovative system!
Edwin T. Dean, PE, SE is Vice President and Managing Principal of Nishkian Dean a structural engineering consulting firm in Portland, Oregon.
Nishkian Dean is proud to have served as the structural engineer on the recently opened 10 Barrel Brewing brewpub in the Maker’s Quarter district in San Diego’s East Village. The restaurant and social gathering place, situated in a converted warehouse, offers guests a chance to view many different aspects of the brewing process. Each level of the building incorporates different brewing equipment that is visible to guests, with a grain silo on the roof, brew tanks on the interior mezzanine, and fermenters on the ground floor, adding points of visual interest.
At roughly 10,000 square feet and with three separate levels, the brewpub and restaurant has ample space for dining and events. The main level incorporates a dining room and bar connected to an outdoor patio through roll-up industrial doors. The exterior mezzanine deck and rooftop patio bar provide additional space for patrons to the enjoy the sights of the surrounding bustling residential area.
The space, converted from an existing warehouse, required substantial seismic upgrades due to the change in occupancy and extensive improvements made to the building façade. New lateral-force-resisting elements include concrete masonry shear walls at portions of the building perimeter, and steel-braced frames to support the interior steel mezzanine that houses the brew equipment. The existing roof framing required strengthening to support the increased loading from the rooftop patio.
Due to poor soil conditions on the site, a network of grade beams at the ground level was used to support the new brew mezzanine and rooftop deck. These grade beams are supported by deep cast-in-drilled-hole concrete piles to minimize settlement.
It was a pleasure to have teamed with Scott|Edwards Architecture and general contractor Bergman KPRS on this exciting new project.
If you have any questions about an upcoming commercial or hospitality/restaurant project, do not hesitate to contact any of our offices. We’d be happy to assist you.
By Edwin T. Dean, PE, SE
Unreinforced masonry (URM), or the use of stone or brick masonry for structural walls, was a common approach in Portland building construction from the late 1800s to as recently as the 1950s. These buildings range in size from small one-story residences to large 10- or 12-story buildings, most with wood-framed floors with some structural steel or cast-iron components. Many of these buildings are historically registered and represent a valuable part of the City’s cultural heritage. Several are public buildings used for government operations or public schools. The characteristic of concern for this type of building construction is that they are extraordinarily vulnerable to earthquake damage, where even moderate ground shaking could result in partial collapse.
Earthquake occurrences in other West Coast cities, such as Loma Prieta in 1989 in the San Francisco Bay Area and Northridge in 1994 near Los Angeles, have demonstrated that this type of construction is susceptible to devastating collapse and associated loss of life and property damage. There were many URM buildings that were damaged in these events, including those that had been seismically strengthened. This damage represented a very significant economic cost, though fortunately not a large number of deaths and URMs did not represent the deadliest type of buildings. These cities now have URM mandates: in the Bay Area, this was largely put into place after the Loma Prieta event, and in Los Angeles it had been implemented prior to the Northridge event.
The Portland metro area has so far been spared from a major earthquake in recent history, though geoscientists believe that large damaging earthquakes are possible. Beginning in the 1980s, the building codes have progressively increased the seismic design requirements in recognition of the potential for such natural disasters. The rate at which URMs have been retrofitted to resist earthquakes on par with current code requirements has been slow.
The City of Portland’s Unreinforced Masonry (URM) Building Policy Committee (Committee) estimates that since 1995, roughly 8% of URMs have been demolished. Of those that remain, about 5% have been fully retrofitted and about 9% have been at least partially upgraded. At that rate, it could take almost another 100 years for the URM building inventory in Portland to be either strengthened or demolished. Based on the risks posed by URM buildings to public safety, the Committee is proposing a tiered retrofit approach, requiring URM upgrades to buildings over a defined period of time. See our prior blog article, Portland Poised to Mandate URM Building Seismic Strengthening, for more background information on this.
The Committee proposal to require seismic strengthening of URM buildings is a tiered approach based on the buildings’ use and occupancy. The only exceptions to these recommended requirements are for one- and two-family homes and URM buildings that were previously seismically strengthened to an acceptable defined standard.
The Committee has defined four categories or classes of URMs with differing levels of seismic strengthening requirements and time horizons to complete them. The classes range from 1 to 4 with Class 1 for Critical Buildings and Essential Facilities and Class 4 for Low-Occupancy structures. In between these, Class 2 is for Schools and High-Occupancy structures (Churches and Theaters), and Class 3 is for is the largest class of building (approximately 2/3 of all URMs) and covers every other URM building not in the other classes. The City has compiled a detailed inventory of the buildings and the classification that they would fall under. The timeframe for implementation of the seismic strengthening varies by Class, but generally requires a seismic assessment in 3 or 5 years and strengthening implementation in 10 to 20 years.
Step 1 – A seismic assessment (ASCE 41-13) with a schematic seismic upgrade strategy including detailed cost estimates must be completed within three or five years.
Step 2 – Parapets, cornices and chimneys must be braced, and the roof must be attached to walls within 10 years.
Step 3 – All floors must be attached to walls and the roof must be sheathed within 15 years.
Step 4 – A complete retrofit must be performed within 20 years.
Separately, the Portland Bureau of Emergency Management and Bureau of Development Services commissioned Goettel & Associates, Inc. to prepare a Benefit-Cost Analysis of the Proposed Seismic Retrofit Ordinance. The report was published on November 23, 2016, and concluded, “The benefit-cost results indicate that the benefits of the URM building seismic retrofits current under consideration exceed the retrofit costs for the defined “typical building” for each URM Class of buildings.” The Committee intends to present their codified recommendations for mandatory seismic strengthening of URM to City Council for adoption. The City Councils adoption of the mandatory ordinance will start the clock and require building owners to either strengthen their URM buildings, demolish them, or face growing fines and the eventual loss of the use of their buildings.
Cost to Implement
The implementation of this mandatory ordinance will have a significant financial impact on the building owner. The objective of such an ordinance from the City’s perspective would be to reduce the life-safety risk these buildings pose to the occupants and those people who may be nearby these buildings in the event of an earthquake. The benefit-cost analysis demonstrated that there was a net benefit to the seismic strengthening; however, those benefits are not directly correlated to the financial return of the building. The Committee in its recommendations were not able to identify anything more than $5M in available Urban Renewal Area (URA) capital funds to assist building owners with the high costs of implementing the seismic strengthening. There are also possible State and Federal tax exemptions or credits and funding from the State Seismic Rehabilitation Grant Program (SRGP) for schools and emergency service facilities and potentially the sale of Floor Area Ration (FAR) transfers to another site. Additionally, the current Committee recommendations do not provide any material relief to buildings with “special considerations,” meaning those with occupants needing affordable housing, schools, religious or non-profit users, or historic structures. The Committee report does not identify the total cost to implement the required mandate. The cost-benefit study identifies the current costs to seismically retrofit or strengthen the four classes of building types on a square-foot basis in Table 15 of their report. Combining these square foot costs with the building areas contained in the inventory list provides the following total costs:
Table 1: Estimated Total Retrofit Costs Based on BDS Inventory
|URM Class||UPGRADE||Cost per Square Foot||No. of Buildings||AREA in Square Foot||TOTAL||AVG per Building|
|Class 1||Immediate Occupancy||$111.45||10||49,329||$5,487,717||$549,772|
|Class 2||Damage Control||$82.62||92||3,253,423||$268,797.808||$2,921,715|
|Class 3||Life Safety||$68.77||220||8,379,527||$576,260,072||$2,619,364|
|Class 4||Modified Bolts Plus||$51.00||1,339||10,915,945||$556,713,195||$415,768|
This would indicate that the cost to implement this mandate, if all the buildings are strengthened, to be on the order of $1.4 billion. However, this amount is an oversimplification. Faced with these costs, which in many cases exceeds the economic value of the property, it is reasonable to assume that many building owners will either abandon the properties or opt to have the buildings torn down until market conditions favor the cost of rebuilding. This will particularly impact buildings at the lowest economic value, such as those being used for affordable housing. The mandate will also allow the seismic assessments to be performed and permit the seismic strengthening to be implemented over a period of up to 20 years, assuming that building owners will wait as long as possible to seismically strengthen their buildings. When this is factored in, and the time-value of the construction costs at a 4% annual escalation are accounted for in the total cost to implement this regulation, the total costs rises to approximately $4.6 billion. Again, this assumes that all the recommended buildings will be strengthened and the reality is that many will not due to the financial restraint.
“total cost to implement this regulation, rises to approximately $4.6 billion”
The URM Building Policy Committee will continue meetings and prepare final recommendations. These recommendations will be taken up by the Portland City Council, possibly as soon as the fall of 2017. At that point, the Council will need to decide if it will implement the recommendations, or some aspects of the recommendations, as an ordinance mandating seismic strengthening of URM buildings, or continue with the status quo as required by Title 24.85. Nishkian Dean will continue to monitor the development of this important issue that affects many of our clients.
Edwin T. Dean, PE, SE is Vice President and Managing Principal of Nishkian Dean a structural engineering consulting firm in Portland, Oregon.
 City of Portland Policy Committee, DRAFT Unreinforced Masonry (URM) Building, Policy Committee Report, dated October 2016, pg. 8
 Kenneth A. Goettel, Benefit-Cost Analysis of the Proposed Seismic Retrofit Ordinance, City of Portland, November 23, 2016, pg. iv
 Religious facilities would be provided relief from completing steps 3 & 4.
 Kenneth A. Goettel, Benefit-Cost Analysis of the Proposed Seismic Retrofit Ordinance, City of Portland, November 23, 2016, Table 15, pg. 31
By Nathan J. Hoesly, PE, SE
The use of engineered wood products is an essential component of nearly all wood-framed buildings. This article will focus on two specific types of engineered wood products, structural composite lumber (SCL) and glue laminated (Glulam) timber framing. Understanding the intended uses and differences between various SCL products and glulam framing is essential for design professionals.
Structural composite lumber (SCL) is a term used to describe a family of engineered wood products created by layering wood veneers or strands and bonding them with moisture-
Laminated Strand Lumber (LSL) is manufactured from flaked wood strands and resembles oriented strand board (OSB) in appearance, though the strands are arranged parallel to the longitudinal axis of the member. Members are commonly fabricated in 1 ¼”, 1 ½”, 1 ¾” and 3 ½” widths, and in 9 ¼”-16” depths to match common i-joists. Stud options are available in equivalent 2×4, 2×6, and 2×8 sizes that are stronger, straighter, and (as needed) longer than sawn lumber. LSL is typically less expensive than other engineered wood beams.
Due its high allowable shear strength, LSL beams have capacity for larger penetrations than other engineered wood beam options. While not as strong as LVL or PSL beams, LSL is generally cheaper and are ideal for short spans. LSL is also ideal for use in rim conditions due to minimal shrinkage, cupping, and high fastener holding strength when used in highly loaded diaphragms or for shear transfer at plywood shear walls.
Parallel Strand Lumber (PSL) is manufactured from veneers laid into long, parallel strands and bonded together. PSL beams are primarily used in beam and header applications where high strength is required. Common PSL beam sizes are available in widths of 3 ½, 5 ¼” and 7”, and depths matching I-joists from 9 1/2” – 24” deep. PSL columns are also available in sizes comparable with sawn wood members from 4×4 to 8×8 in size.
PSL beams are generally more expensive than glulam, LSL, or LVL beams. PSL beams can be stained or finished where an aesthetically pleasing exposed application is desired.
Laminated Veneer Lumber (LVL) is a commonly available engineered product that is manufactured similarly to PSL. Available sizes, strengths, and stiffnesses are similar to PSL but are generally cheaper, making it a commonly specified beam type. A benefit to LVL is that it can be fabricated in narrower beam widths (1 ½, 1 ¾”), and multiple plys can be nail-laminated together to form a larger beam. This is especially beneficial in retrofit options where lifting a wide, heavy beam into place is cumbersome or infeasible. LVL stud and columns are available as well from some manufacturers.
Glued Laminated Timber (Glulam) is manufactured by face-bonding layers of kiln-dried timber members, typically 2×4 or 2×6 in size, together with waterproof adhesives to form timber section. Glulams are popular due to their engineered strength, versatility, availability, and cost. Typical stock beams widths are available in 3 1/8”, 3 ½”, 5 1/8”, 5 ½”, 6 ¾” widths and depths exceeding SCL beams. However, custom glulams can be fabricated in almost limitless widths, depths and profiles, giving glulam beams a distinct advantage over SCL beams in their versatility and architectural appeal. Glulams have a long history of being used beautifully in exposed, large open areas such as vaulted ceilings, churches, theatres and a vast array of other public spaces. Manufacturing processes for glulams allow for members to be cambered, curved, and fabricated in unique shapes, such as arches or as bridge members. Different appearance grades for exposed conditions may also be specified to increase architectural appeal.
For exterior or weather-exposed conditions, glulam beams are generally preferred over SCL beams. Weyerhaeuser, one of the few manufacturers of PSL in the U.S., has a Wolmanized PSL product that is approved for weather-exposed framing beam applications, but it is relatively expensive. Few other SCL treatment options exist. Alternatively, pressure treated or preservative treated options exist for glulam members. Additionally, several naturally durable species of glulam beams are produced in the U.S., including Alaskan Yellow Cedar and Port Orford Cedar, which provide green alternatives to chemical treatments.
Both SCL and glulam beams may be used where a fire-rated exposed member is required, subject to meeting the provisions of Chapter 16 of AWC’s National Design Specification® (NDS®) for Wood Construction. Typically, only wider beam sections will meet the required fire rating due to the depth of charring of any exposed face. This often eliminates the use of LSL, and glulams are usually preferred over LVL and PSL due to cost, appearance, or available beam sizes.
Design professionals should be knowledgeable about specific product availability and costs in their areas during design as this can help drive which types of engineered wood beams are specified. Although SCL and glulam beams can be used interchangeably at times, they also have unique advantages and limitations to be aware of.
Nathan Hoesly, PE, SE is an Associate of Nishkian Dean, a structural engineering consulting firm in Portland, Oregon
Aerospace is one of the most remarkable market segments in which the Nishkian firms have been privileged to contribute their engineering expertise. Nishkian Dean VP and Managing Principal, Edwin T. Dean, designed rocket launch facility infrastructure prior to founding Nishkian Dean in 1999 and, since then, this small firm in Portland, Oregon, has designed or assisted in the construction of some major aerospace projects throughout the United States. During this same time, the aerospace industry has transformed from a large institutionally-focused bureaucratic process to one that has embraced commercial innovation.
In recent years, entrepreneurial disruptors like SpaceX, headed by Elon Musk of Tesla fame, and Blue Origin, headed by Amazon founder Jeff Bezos, have driven the industry to commercialize space forward in ways not imagined only a few years ago. But even prior to their entrepreneurial disruption of the space industry, there had been great movement toward commercialization by the United States Air Force and NASA. With the EELV[i] program, the US Air Force, being the largest single user of launch services, pushed the industry to reduce costs through innovation and commercialization, to which Boeing and Lockheed Martin responded. NASA has promoted commercialization through its support of the ISS[ii] with the end of the Shuttle era. This cultural shift within the industry created the opportunity for firms like ours to bring a fresh way of looking at these infrastructure projects. We relish the opportunities we have had so far to help foster this transformation.
As an engineering consultant, Nishkian Dean’s success working in the recent revolution of the aerospace industry is a direct result of our being able to infuse our commercial design mindset into this transformation. Our focus on responsive functional design and constructability has made us a valuable consultant in this industry. At their core, major launch facilities are driven largely by structural requirements, which aligns with our core discipline of structural design, but they are far more complex than that. This allowed us to create a strong team and collaborate with experienced consultants to help support our efforts. We recognized the opportunity that we had to champion and organize a team of consultants and expand our role beyond our core discipline. We had to accept the expertise of our consultants to handle systems that we had no prior experience with, such as cryogenic fuel systems dealing with super-cold liquid oxygen, liquid hydrogen, or, more exotically, hypergolics that fuel spacecraft. We brought in experts in electrical power, communications, including specialized GC3[iii] systems, environmental control, and specialized mechanical systems. With our cadre of consultants, we have taken on many adventurous projects.
In 2004, we had the opportunity to propose on a small portion of the structural design on the renovation of the existing SLC-3 launch complex at Vandenberg AFB for a new Atlas V. It was a small, 12-person structural consultant competing against the titans of the engineering industry, such as URS, Jacobs, and others, that won the confidence of the builder, Hensel Phelps, and the owner/operator, Lockheed Martin, to bring us on to eventually be the key design entity. In the end, our design team had committed over 50,000 man-hours in less than 16 months in supporting the incredible success of this project to meet the schedule and budget goals that it demanded. Our team helped the project meet its mission requirements and it helped establish ourselves as the team that can get this done.
We have had many continued successes following this project, both in the Western Range and at facilities at Cape Canaveral Air Force Station and Kennedy Space Center in Florida. When disaster struck on October 24, 2005, with Hurricane Wilma destroying the 280-foot-tall door on Lockheed Martin’s Vertical Integration Facility (VIF), it put NASA’s New Horizons[iv] mission to Pluto in jeopardy. We were there the very next day to assess the damage and to work with the team to design, fabricate, install, and test new doors in 7 weeks’ time, ultimately ensuring the mission’s success. New Horizons launched on January 19, 2006, and flew by Pluto 9 years later, on July 14, 2015.
We have also been called on to assist in erecting the 600-foot-tall lightning towers at Launch Complex 39B at the John F. Kennedy Space Center, and the erection of the nearly 380-foot-tall NASA Mobile Launcher for Constellation[v] and now for use with SLS[vi]. Additionally, we have worked on the complex installation of moveable platforms within the historic NASA Vertical Assembly Building (VAB) in support of NASA’s quest to send astronauts to Mars. In a further testament to commercialization, we are now working with private entrepreneurs’ facilities on their own quests to go to Mars.
Closer to Earth, one of our latest challenges has been to support restoring America’s ability to once again launch astronauts from US soil. Boeing and United Launch Alliance (ULA), as a part of their $4.2 billion CCtCap award, are developing infrastructure to support manned spaceflight launches from Launch Complex 41. And how do you get astronauts from the ground into a capsule 200 feet in the air on a “clean pad”? You build a 250-foot tall access tower less than 60 feet from the launch pad with an articulating arm so that they can safely walk over and climb in, naturally. Now substantially complete, this installation provides astronauts with a state-of-the-art means to reliably and safely begin their journey to the International Space Station. Restoring manned spaceflight to American soil through the design of this complex is something we are proud to have played a part in.
Launch systems are complex and often extremely large mechanical structural systems. Buildings weighing more than 8 million pounds that need to move, be jacked up, and driven by hydraulic power systems as fast as a person can walk; an 70,000-lb arm that must be able to swing in seconds while being remotely monitored and controlled; and precision-operable platforms powered by nitrogen motors are just a few examples of the challenges we have faced in our aerospace work. To develop these designs, we bring together a diverse group of engineers with broad technical backgrounds to address the structural-mechanical-electrical challenges.
These challenges make the aerospace market uniquely exciting for us to tackle. The projects involve the integration of a multi-disciplined design team with the suppliers, fabricators, and constructors who put it all together, and the testing engineers who, along with us, validate functionality. This teamwork creates an organization that has a far-reaching expertise beyond what is done in the conventional building market. Moving parts, intricate control systems, and the requirement that these systems function every single time that they are employed is a tall order that punctuates the care and coordination that goes into each design.
Unsurprisingly, the launch environment is very extreme. In conventional design, we may deal with a 100 PSF live load, or perhaps at maximum a 250 PSF live load to accommodate a truck on a sidewalk. In the launch environment, we may see loads as high as 250 PSI – that is pounds per square inch, or 144 times the sidewalk load example, or 36,000 PSF, with a total launch load in the millions of pounds. We also work with extreme temperatures from liquid oxygen or LOX at -350°F or even colder liquid hydrogen at -425°F.
Liquid oxygen, in addition to being extremely cold, is incredibly corrosive and like hydrogen is explosive in the presence of an ignition source. The fuel for solid rocket motors is largely composed of aluminum perchlorate, which when burned leaves a hydrogen chloride residue that combines with water to create a highly-destructive, corrosive byproduct of hydrochloric acid that coats the surfaces of the structures on the launch pad. If not properly cleaned and coated, these chemicals can literally melt steel structures.
Nishkian Dean has developed over many years a unique niche where we are able to provide specialized design services for rocket launch facility infrastructure. Leading a design team of consultants, or supporting the structural design of aerospace launch facilities, has proven to be a market in which we truly enjoy working. Playing a role in helping the US space program excel is an incredible legacy to be able to look back on.
Edwin T. Dean, PE, SE is Vice President and Managing Principal of Nishkian Dean a structural engineering consulting firm in Portland, Oregon.
[i] Evolved Expendable Launch Vehicle (EELV) is an expendable launch system program of the United States Air Force (USAF), intended to assure access to space for Department of Defense and other United States government payloads. The program, which began in the 1990s with the goal of making government space launches more affordable and reliable, resulted in the development of two launch systems, Delta IV and Atlas V. These were later joined by the Falcon 9. These launch systems are the primary methods for launching U.S. military satellites. The USAF plans to use the EELV family of launch vehicles until at least 2030. (Wikipedia)
[ii] The International Space Station (ISS) is a space station, or a habitable artificial satellite, in low Earth orbit. Its first component launched into orbit in 1998, and the ISS is now the largest man-made body in low Earth orbit and can often be seen with the naked eye from Earth. The ISS consists of pressurized modules, external trusses, solar arrays, and other components. ISS components have been launched by Russian Proton and Soyuz rockets, and American Space Shuttles. (Wikipedia)
[iii] Ground command, control and communications (GC3) systems used to communicate with flight vehicles and spacecraft systems.
[iv] New Horizons is an interplanetary space probe that was launched as a part of NASA’s New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institute (SwRI), with a team led by S. Alan Stern, the spacecraft was launched in 2006 with the primary mission to perform a flyby study of the Pluto system in 2015, and a secondary mission to fly by and study one or more other Kuiper belt objects (KBOs) in the decade to follow. (Wikipedia)
[v] The Constellation Program (abbreviated CxP) was a manned spaceflight program developed by NASA, the space agency of the United States, from 2005 to 2009. The major goals of the program were “completion of the International Space Station” and a “return to the Moon no later than 2020″ with a crewed flight to the planet Mars as the ultimate goal. The program’s logo reflected the three stages of the program: the Earth (ISS), the Moon, and finally Mars—while the Mars goal also found expression in the name given to the program’s booster rockets: Ares (The Greek equivalent of the Roman god Mars). The technological aims of the program included the regaining of significant astronaut experience beyond low Earth orbit and the development of technologies necessary to enable sustained human presence on other planetary bodies. (Wikipedia)
[vi] The Space Launch System (SLS) is an American Space Shuttle-derived heavy expendable launch vehicle. It is part of NASA’s deep space exploration plans including a manned mission to Mars. SLS follows the cancellation of the Constellation program, and is to replace the retired Space Shuttle. The NASA Authorization Act of 2010 envisions the transformation of the Constellation program’s Ares I and Ares V vehicle designs into a single launch vehicle usable for both crew and cargo, similar to the Ares IV. The SLS is to be the most powerful rocket ever built with a total thrust greater than that of the Saturn V, putting the SLS into the super heavy-lift launch vehicle class of rockets. (Wikipedia)
VIF courtesy of Lockheed Martin
NASA 39B Lightning courtesy of NASA
NASA ML erection courtesy of NASA
CAT Astronaut courtesy of NASA
By Aerik Carlton
Structural fire consideration has been taking some large steps recently, with several codes and standards having added or altered structural fire sections. At Nishkian Dean, we have examined these structural fire design codes and methods from a structural engineering prospective for our clients and readers below.
A summary of these structural fire design codes includes:
ASCE 7-16 Minimum Design Loads and Associated Criteria for Buildings and Other Structures has added a new appendix to address structural fire considerations.
AISC 360-16 Specification for Structural Steel Buildings has refined and made additions to Appendix 4: Structural Design for Fire Conditions.
The National Institute of Science and Technology (NIST) has drastically expanded the Gaithersburg, Maryland, Fire Testing Lab to include a live-fire hood capable of testing a multi-story building portion with the aim of obtaining empirical large-scale structural system data to further refine and validate their free computational fluid dynamics fire modeling software. Europe, the United Kingdom, New Zealand, and Japan have all adopted performance-based methods for structural fire, and the US industry has been slow to recognize and allow this building design approach. These developments considering structural fire represent a paradigm shift for structures in a fire situation.
Prescriptive methods are the standard for structures in the US, but structural engineering codes and standards are trending toward performance-based methods. Fire Protection Engineers (FPE) have been using performance-based methods for fire for a couple of decades in the US, and Structural Engineers (SE) are beginning to develop similar methods (to be on par with our international colleagues). However, there are some marked differences in focus between FPE and SE. FPE considers smoke ventilation, egress, fire prevention systems, notification systems, and compartmentalization to restrict fire spread, while SE considers the effect fire has on the structures’ ability to remain stable and support service loadings.
Meuller et al. (2014) illustrated this difference in dramatic fashion by testing a reinforced concrete bearing wall under a single-sided heating condition. Prescriptive fire resistance methods consider the tested bearing wall as having a 2-hour rating, due to its thickness. However, the project found upon testing the wall, a complete failure occurred at approximately 42 minutes.
Building fires are rare events—the annual likelihood that a business-occupied building will experience a fire in any given year is on the order of 0.05% (Xin and Huang 2013). But just because the chances are rare does not mean we should not keep improving and refining our fire designs. We have been using prescriptive methods for building fire resistance for nearly 100 years, and yet we still don’t have a good representation of the effectiveness of these provisions.
We could potentially eliminate a lot of conservatism in our fire-resisting elements and still maintain a similar, or possibly improved, building performance at a lesser cost to building owners and developers. Through performance-based design approaches, we could eliminate prescriptively required fire resisting elements (pending jurisdictional fire official approval) such as a reduction of compartment walls thickness through polypropylene fiber addition to the concrete mix to reduce fire response spalling or by refining structural member fire resistance with intumescent paint. There is also a possibility that we could shift our designs toward structures that are more easily reparable after a fire, thus increasing the resilience and life cycle of our buildings.
If your project has structural fire requirements, or you have any questions about the updated codes, please feel free to contact Nishkian Dean.
Aerik Carlton, is an Engineering Designer with Nishkian Dean a structural engineering consulting firm in Portland, Oregon.
Mueller, K. A., Kurama, Y. C., and Mcginnis, M. J. (2014). “Out-of-Plane Behavior of Two Reinforced Concrete Bearing Walls under Fire: Full-Scale Experimental Investigation.” ACI Structural Journal, 111(5).
Xin, J., and Huang, C. (2013). “Fire risk analysis of residential buildings based on scenario clusters and its application in fire risk management.” Fire Safety Journal, 62, 72–78.
We were thrilled to hear the news: Chad Norvell, a project engineer at Nishkian Dean in Portland, was named one of ten New Faces of Civil Engineering Professionals in 2017 by the American Society of Civil Engineers (ASCE).
The nationwide recognition program promotes the bold and humanitarian future of civil engineering by highlighting the achievements of the next generation of C.E. leaders. Presented annually, the recipients are chosen based on their contributions to society and their dedication to improving the quality of life for all.
Norvell was officially recognized during ASCE’s annual Outstanding Projects and Leaders (OPAL) Gala on March 16, 2017, in Arlington, Virginia.
Photo 1: 2017 OPAL Awards for New Faces of Civil Engineering
At Nishkian Dean, Norvell specializes in the seismic retrofit of buildings—he has designed efficient seismic retrofits for more than a dozen schools in the greater Portland area, and he works closely with the state government to help school districts fund these projects. He also promotes the profession through his participation with Engineers Without Borders (EWB), and through his ongoing work with the Earthquake Engineering Research Institute (EERI) to help with earthquake relief in Haiti and Nepal.
We took a moment to speak with Chad and to learn more about his dedication to serving the public good through his work. Read on for our Q&A:
Let’s start at the beginning—what inspired you to become an engineer?
I had a fascination with architecture since childhood, and originally studied it in college with the intention of becoming a practicing architect. After two years in architecture school, I realized that while there were some things I was good at, there were more things that I just wasn’t good at. I decided to leverage my strength in math and science and switch to structural engineering, which ended up being a perfect fit.
There are so many different specialties within our field. What prompted you to focus on seismic issues specifically?
As a structural engineer educated and practicing on the West Coast, some study and understanding of seismic phenomena and loads is unavoidable. I find seismic issues interesting for two reasons: for one, it’s just more challenging and requires another level of ingenuity and creative problem-solving beyond typical structural design.
Secondly, seismic issues can have a large impact on society beyond the engineering of structures. For example, the National Earthquake Hazards Reduction Program (NEHRP), the federal government program that funds seismic research, supports the study of social science issues related to earthquakes, in addition to the geologic sciences and structural engineering topics that we would expect. This kind of interdisciplinary field of study is interesting to me.
Could you tell us more about your work with Engineers Without Borders in Nicaragua? What types of projects are you working on with them?
In college, I spent four years as a member of our EWB chapter, serving as chapter president for two of those years. We worked primarily in a region on the West Coast of Nicaragua to provide engineering support for community problems that the government did not have resources to address. This was valuable for the local communities, and was a great learning experience for us as engineering students.
One of the two major projects we worked on was mitigating yearly flooding at an elementary school, and our second major project aimed to help a remote coastal community produce enough potable water to serve the communities’ needs.
I’ve also worked with several other EWB chapters to provide support for their projects. Most recently, I helped establish seismic criteria and perform structural analysis for a school in Ethiopia.
Could you tell us more about your relief work with Earthquake Engineering Research Institute?
After the earthquakes in Nepal and Haiti, I worked with teams in the US that were developing rebuilding guidelines for each country. We developed a guide to earthquake-safe construction for Haiti that was later translated to Haitian Creole, and for Nepal, we provided support for the revision of their building code.
You’re also participating in EERI’s first Learning from Earthquakes field study program—what does that entail?
After major earthquakes occur around the world, EERI and other organizations send reconnaissance teams to investigate building failures. This information is studied, and eventually leads to valuable technical information that advances our seismic design procedures. But this investigation only happens in the weeks immediately after an earthquake.
The idea behind “resilience reconnaissance” is to continue doing field investigation in earthquake-affected regions periodically for years after the event, tracking changes in various critical community services like housing, business, health care, and education. By doing this, we get an understanding of a community’s resilience to earthquakes, not just a building’s, which also serves as valuable information for communities in areas of seismic risk.
Photo 2: EERI Team in Chile 2017
Today, non-profit organization DiscoverE announced that Chad Norvell is one of the winners of the 2017 class of New Faces of Engineering honorees. The announcement coincides with the second annual Global Day of the Engineer, a worldwide day of celebration and volunteerism that shines a spotlight on the work done by engineers and inspires the next generation of engineering and technology professionals. DiscoverE’s New Faces of Engineering recognizes the work of up-and-coming engineering professionals, age 30 or younger, who are making their mark on their industry. These talented individuals are honored for having dedicated themselves to using their skills and education to help engender a better world. These young engineers serve as inspirations both for their colleagues and for the next generations coming up behind them. The highly-coveted award, started in 2003, is recognized nationally by their peers as a top honor for young engineers and continues to grow in prestige. In addition to recognizing young engineering professionals, DiscoverE also honors engineering students through its New Faces of Engineering College program. This year’s class includes young professionals innovating solutions throughout a cross-section of industries, including energy, food security, infrastructure, medicine, aerospace and the environment. Previous honorees have gone on to launch global businesses and NGOs.
All four Nishkian firms join together in congratulating Chad. To learn more about the 2017 New Faces of Engineering Honorees, please visit DiscoverE at http://www.discovere.org/our-programs/awards-and-recognition
By Chad Norvell, PE
Historically, tsunamis have been poorly understood by the public. Films often show tsunamis as towering tidal waves that cast deep shadows over tall buildings on the coast before violently crashing down. Video footage from the 2004 Indian Ocean tsunami showed the world what tsunamis really are—a wall of water that doesn’t necessarily tower over the coast, but that moves through with unstoppable force.
In this article, we will explore important tsunami basics, review the tsunami risk in Oregon, introduce changes to structural loading standards that now include tsunami loads, and discuss essential research findings out of Chile that affect our local understanding of tsunami risk.
Tsunami Causes & Terminology
In the Pacific Northwest, we are increasingly aware of the risk of a devastating Cascadia Subduction Zone earthquake. This potential future earthquake is likely to be associated with a large tsunami that will strike the coasts of Washington, Oregon, and Northern California, as well as echo around the Pacific basin, reaching as far as Japan and Australia. The figure below illustrates how a subduction zone earthquake triggers a tsunami.
When discussing tsunamis, it is important to understand the terminology used. What does it mean to say that in Pulicat, India, during the 2004 Indian Ocean tsunami, the maximum runup was 3.2 m and the inundation limit was 160 m? The figure below illustrates the primary tsunami measurements.
Source: U.S. Geological Survey Tsunami Terms
RUNUP ELEVATION: The difference between the elevation of maximum tsunami inundation and the reference sea level elevation.
INUNDATION DEPTH: The depth of the tsunami relative to grade level at the point of interest (e.g., where the structure is).
INUNDATION DISTANCE or INUNDATION LIMIT: The maximum horizontal distance inland inundated by the tsunami.
Oregon’s Tsunami Risk
According to the U.S. Geological Survey (USGS), Oregon has 25,000 residents, in addition to 55,000 tourists, who could be at direct tsunami risk (defined as being within the Tsunami Design Zone, or TDZ) along 300 miles of coastline subject to inundation. Two ports, a fuel depot hub, and $8.5 billion in essential facilities are located within this risk zone as well. The Oregon Department of Geology and Mineral Industries (DOGAMI) has produced a series of tsunami inundation maps covering the entire Oregon coastline, showing the areas at risk of inundation for both Cascadia Subduction Zone earthquakes [the left figure below] and Alaskan-Aleutian Subduction Zone earthquakes [the right figure below.]
Source: Oregon Department of Geology and Mineral Industries
Analysis by Oregon Public Broadcasting in 2015 showed that “about a third of schools, hospitals, police and fire stations along the Oregon coast are within a potential tsunami zone.” In Seaside, approximately 80% of residents live at elevations of 15 feet above sea level or lower, when DOGAMI estimates that even a small Cascadia Subduction Zone tsunami would have a wave height of over 20 feet. Further development on the Oregon coast will rely on structural designs that are tsunami-resistant.
New Tsunami Structural Load Standards in ASCE 7-16
The American Society of Civil Engineers (ASCE) publishes a document called “Minimum Design Loads for Buildings and Other Structures,” commonly referred to as ASCE 7. This consensus-based standard specifies the minimum required design loads for all the types of load commonly encountered in the structural design of buildings, including dead, live, wind, and seismic. ASCE 7 is incorporated by reference in the International Building Code (IBC), making its provisions law in much of the United States. The recently published 2016 edition of ASCE 7 (ASCE 7-16) includes a new chapter on tsunami loads, and new regulations on when buildings must be designed with consideration of tsunami loads.
In line with current practice for earthquake loads, ASCE 7-16 defines a Maximum Considered Tsunami (MCT) as the tsunami that has a 2% probability of exceedance in 50 years, or an average return period of 2,500 years. The runup elevation associated with the MCT is designated as the Tsunami Design Zone (TDZ), and hazard maps (like Oregon’s tsunami inundation maps) are based on that elevation. TDZ maps for Washington, Oregon, California, Alaska, and Hawaii are included in ASCE 7-16.
The provisions of ASCE 7-16 require consideration of tsunami loads only for Risk Category III and IV structures within the TDZ, generally meaning structures that could pose a great risk to human life if they failed (such as schools) or emergency services buildings (such as police and fire departments.). However, local jurisdictions have the option of designating threshold elevations under which even Risk Category II buildings (typical commercial and residential structures) would need to be designed to resist tsunami loads. In areas characterized by flat coastal planes (for example, Tillamook, Oregon), evacuation from the tsunami zone may be impossible, in which case vertical evacuation into relatively tall public or commercial buildings designed to resist tsunamis could save thousands of lives.
Designing structures to resist tsunamis requires consideration of four types of tsunami load:
ASCE 7-16 includes procedures for determining each of these loads.
Lessons Learned from Tsunami Research in Chile
Chile suffered significant tsunami damage associated with the M8.8 Maule earthquake in February 2010. Since then, observations from the tsunami, along with sophisticated research at the Universidad Técnica Federico Santa María and CIGIDEN (National Center for Investigation of Integrated Management of Natural Distasters) under Dr. Patricio Catalán, have yielded important and surprising lessons about tsunami behavior, two of which are summarized below.
The understanding of risk to our infrastructure from tsunamis is still not as mature as that of seismic and wind risk, but significant advances are being made, particularly via lessons learned from recent tsunamis like the 2004 Indian Ocean Tsunami, the 2010 Maule Tsunami in Chile, and the 2011 Tohoku Tsunami in Japan. These lessons are now being incorporated into the standards that structural engineers use to design buildings, providing us valuable tools for building more resilient communities in areas of tsunami risk. This is particularly important for us in the Pacific Northwest, where we have long coastlines and many communities at risk of inundation in a Cascadia Subduction Zone earthquake and tsunami.
Contact Nishkian Dean for more information or to discuss your project on the Oregon coast.
Chad Norvell, PE is a Project Engineer with Nishkian Dean a structural engineering consulting firm in Portland, Oregon.
The bombing of the Alfred P. Murrah Federal Building on April 19, 1995 in Oklahoma City, Oklahoma marked a turning point. The years that followed, arguably the most damaging and shocking domestic terrorism event in our nation’s history, resulted in the tightening of standards for our government buildings. These standards are not isolated to security protocols, but to the requirements for the way these buildings are design.
While, we are sure everyone can empathize with the extra effort and time it takes to pass through security check points while entering courthouses, police stations, and airports. Terrorism, unfortunately, has become a driving force in the added scrutiny we all face while traveling or entering government buildings. What most people do not see, however, is that most occupied government buildings are designed to resist the effects of explosive blast. And increasingly, architectural and engineering firms are tasked with designing buildings to minimize damage and loss of life from explosives.
The major consideration and design efforts by engineers for blast loads on buildings are focused on the exterior envelop. The window systems, exterior walls, the roof system, door systems, evaluating disproportionate progressive collapse risk, and even blast induced base shear have all become subject of blast engineering analysis. However, buildings are not the only structures that have entered this domain. Chemical processing facilities, bridges, and even rocket engine testing structures have all issued requirements to resist the effects of explosive load.
While most structural loads are defined statically, blast loading is dynamic. Unlike wind loads which are converted to static equivalent, the penalties of converting a blast load into a static equivalent can yield cost prohibitive designs. While the dynamic characterization in seismic design is like blast, the time durations very greatly. Seismic loads are defined in seconds while blast loads are measured in milliseconds.
Alfred P. Murrah Building taken April 20, 2015
Photo Credit: Tulsa District United States Army Corps of Engineers
Licensing Agreement: https://creativecommons.org/licenses/by/2.0/
Blast loads are typically defined by a peak positive pressure and associated impulse for design purposes. The negative pressure associated with suction after the passing of positive pressure waves is neglected in most building design criteria. Based upon the location of the structural element in relation to the blast origin, a simplified load shape is defined, and an equivalent duration is calculated. More complex blast time-histories can be developed from Computational Fluid Dynamics (CFD) analysis methods, however validation of CFD models can be difficult.
Single Degree of Freedom (SDOF) analysis methods are the industry standard, however Multi-Degree of Freedom (MDOF) and Finite Element Analysis (FEA) methods can, and have, also been used successfully. MDOF and FEA do not, in many blast cases, yield better or more correct results when compared with SDOF methods. The blast community has at-large, agreed upon SDOF as the standard, because of the quantity of necessary assumptions and the limited available empirical data related to modeling the complexities of detonated explosives.
SDOF evaluation is completed on an element by element basis, where the forcing function is defined by the blast time-history, a damping constant and stiffness function are defined, and the momentum effects of mass are all considered. From the SDOF results, the ductility, rotation, and demand to capacity ratios for shear and moment are derived, then compared with project specific performance limits.
Project specific requirements typically define an acceptable level of damage to defined structural element types. Damage levels are defined by accepted ductility, rotation, and demand to capacity ratio values. Because of the large forces involved in blast loads, it is typical for elements to be pushed into the plastic range, and large deformations can be expected.
Contact Nishkian Dean if your project has blast design considerations.
Aerik Carlton, is an Engineering Designer with Nishkian Dean a structural engineering consulting firm in Portland, Oregon.
Biggs, J. M. (1964). Introduction to Structural Dynamics. McGraw-Hill, New York.
Unified Facilities Criteria (2008). UFC 3-340-02: Structures to Resist the Effects of Accidental Explosions. Change 2 dated 1 September 2014, Department of Defense.
By Robert A. Aman, PE, SE
This 7-Story, 202,200 square feet project with 162 living units located adjacent to the Conway District at NW 21st & Quimby in downtown Portland will be ready to rent out units starting next month. Nishkian Dean proudly worked with YBA Architects and Andersen Construction Company on this unique and challenging project. The project is highlighted by three-story tapered steel columns at the main entrance that form an “XXI” shape to symbolize the project name and street number location. These specialty columns were constructed with two tapered 12-sided steel sections welded together at the column midpoint to form a double-tapered member. A cantilevered post-tensioned concrete beam spans across the tops of the tapered steel columns to support four stories of structure above.
By Dave Beh
Structural engineers design the primary structure to withstand seismic forces, as a minimum, as outlined by the design code. However, during an earthquake people can be injured and costly damage can result by falling non-structural components such as; kitchen hoods, bookcases or mechanical/electrical equipment. The code also requires seismic anchorage for certain non-structural components but these can sometimes get overlooked by designers/owners/plans examiners that simply don’t yet have the information or are unaware of the requirements.
Mid-rise construction continues to see a steady demand throughout many parts of the U.S. Common mid-rise occupancies include apartments, condominiums, assisted living facilities, hotels, dormitories, office and various other uses, and are often mixed with other occupancies such as retail, restaurants, office, and parking. These “mixed-use” buildings, named due to their mix of occupancy types, have been popular for decades but surged during the current economic recovery. While mid-rise construction is utilized for all types of building occupancies, this article will be focusing on residential and mixed-use commercial/residential developments due to their prevalence in today’s market.
Edwin T. Dean, PE, SE
Wood frame is an economical construction type and if properly detailed durable and fire-safe. The level of fire resistance required of a building is established by the building code and is a function of the size, use and occupancy of the building. The fire rating is driven by the need to provide ample time for occupants to exit the facility, retain structural stability long enough for fire-fighting personnel to combat the fire and for the protection of the contents of the building and adjacent structures.
The City of Portland is laced with seismic faults and is vulnerable to the looming Cascadia subduction zone earthquake, which could have a magnitude as high as 9.0. Despite this risk, Portland has one of the highest concentration of unreinforced masonry (URM) buildings in the Pacific Northwest. URM buildings are particularly vulnerable to potential catastrophic collapse in earthquakes. To alleviate this risk, the Portland Bureau of Emergency Management (PBEM) convened a series of committees to propose new URM seismic retrofit standards, which are currently under deliberation with the goal of passing the new standards in the City Council in 2017.
By Edwin T. Dean, PE, SE
The start of construction brings new demands on the designers to respond to questions from the field and review submittals for the products being installed. The designer’s participation in the construction process is critical to the success of the project being built and to provide a high level of confidence that it is being built consistent with the design intent. This article discusses some of the management procedures used to provide engineering support for our projects as they are being built.
Before he joined Nishkian Dean as Project Engineer, Chad Norvell spent three years in India directing the engineering department of a social enterprise building affordable housing for some of the poorest and most vulnerable segments of the Indian population. Recently, Chad was invited to present on his experiences to Architects Without Borders Oregon, based in Portland, OR.
Reinforced concrete slabs have been used in buildings from the middle of the 19th century. Post-tensioned concrete slabs have been used since the 1930’s, and have become commonplace in the last 30 years.
Architects like concrete slabs because the designs can allow for longer spans and thinner slabs. Longer spans give more column-free space and more available square footage. Thinner slabs allow for higher floor-to-floor heights.
Critical Lift Cranes are used to handle “critical” hardware. In the aerospace industry this could include high-value components, like spacecraft or satellites (in excess of $100 millions) or components that contain hazardous or highly toxic materials (like hypergolic fuels). This is an overview of some of the key considerations that go into specifying critical lift cranes. The procurement, installation and operation of critical lift cranes requires the definition of additional requirements above and beyond the national consensus standards (i.e. OSHA 1910.179, ASME B30 series, CMAA 70/74) typically specified for a standard commercial crane. It is imperative that these additional requirements be addressed in the initial procurement documentation prior to initiating a contract, since it will be difficult or impossible to incorporate them at a later date into a typical commercial crane without substantial modifications and significant cost. What follows is a summary of the more significant recommended requirements that must be specified for all critical lift cranes.
Post tensioned concrete is a method of casting sheathed steel cables inside of the concrete. The concrete is allowed to cure for a period usually between two and seven days, and afterward the cables are tensioned using hydraulic jacks. The application of tension provides internal stresses in the concrete to counteract forces that the concrete member is subjected to during the life of the structure. A post-tensioned concrete member can be a reduced member size compared to a conventionally reinforced concrete member subject to the same forces thus making post tensioning an attractive option for owners, architects and engineers. Post tensioning can also reduce the potential for cracking and the amount of conventional steel reinforcing. Using post tensioned concrete construction can improve the quality and durability of the structure often also saving on the cost of the construction.
Finding the information necessary to understand the current coding requirements for tilt-up wall panels within the ACI Standard and Report can be frustrating and confusing for new engineers as the information seems to be scattered among multiple sections. The current ACI318 forces designers to seek out information contained in different sections and have a deep understanding of the current code to meet necessary requirements. The new code organization and simplified design process eases the process and makes design procedures more accessible.
ACI318, Building Code Requirements for Concrete and Commentary, is updated every three years. These code updates and changes stem from comments submitted to the American Concrete Institute (ACI) from professors, practicing professionals, and industry users about the modernization, common practices, industry consistency, and engineering accuracy. ACI 318-14* will completely change the format of the code from previous versions to a more user friendly and logical focus for designers.
Aging and historic structures bring a style of their own into the skyline as they mesh with the sleek lines and polished surfaces of modern construction. Old age, poor or nonexistent drawings, past renovations, and other unknown conditions mean bringing these structures up to current code represents a unique challenge. The design team should be aware of the most up to date code standards and how they can be utilized in the project jurisdiction. American Society of Civil Engineers (ASCE) 41-13 is one such code that deserves attention.
How safe is the fire escape attached to your building? The City of Portland currently has more than 600 fire escapes that are attached to older buildings and are part of the required emergency egress system or serve as firefighting platforms. Often they are neglected and deterioration can result in these fire escapes becoming unsafe for use by occupants or firefighters during an emergency.
Administrative Rule ARB-FIR-2.08 was adopted by the City of Portland in 2008. The main purpose of this policy is to establish procedures for the inspection, evaluation and testing of fire escapes, and to provide information pertaining to the acceptable methods of repair when needed.
Cross-laminated timber (CLT) continues to receive more attention nationally and locally as an innovative and economical solution for utilizing wood construction in taller buildings. While multi-story CLT buildings have been constructed in Europe, Canada, and Australia over the past 20 years, its use as a primary building material in the United States is still in the early stages of development.
CLT may also be classified as mass timber construction, which is building construction that uses large prefabricated wood panel members such as CLT and engineered wood for wall, floor, and roof construction. Glulam material may also be used in beam and column applications.
In addition to the SRGP funding put in place late last year to support seismic rehabilitation towards safety in schools (see previous blog post), the state recently passed House Bill 5005 which includes $125M in bonds for grant matching and $175M for seismic upgrading and retrofitting in local K-12 and higher education buildings.
Senate Bill 447 represented the $125M in local bond matching and would run from 2015-2017. It requires that each district provide matching funds from local bonds with minimum matching amounts of $4M or a GO bond amount. The lesser of the two will be used for the match and the maximum amount is $8M.
First it is very difficult to determine a specific relationship between bolt tension and torque. Tension is the application of force that causes stretching whereas torque causes twisting and tightening of the bolt and is an indirect indication of tension. In other words, tension is the stretch or elongation of a bolt that provides the clamping force of a joint where torque is a measure of the twisting force required to spin the nut up along the threads of a bolt.
High-strength bolts are designed to stretch slightly, and this elongation is what clamps the joint being connected together. Torque is best viewed as a very indirect indication of tension, as many factors can affect this relationship, such as, temperature, tolerance, surface texture, rust, oil, debris, thread series and material type just to name a few. This variability can be on the order of +/- 40% or more. The relationship between Torque and tension based on the following formula:
A recent article in The New Yorker entitled “The Really Big One: An earthquake will destroy a sizable portion of the coastal Northwest. The question is when.” has caused a media storm with outlets across the country now talking about, what was for many, a previously little-known fault line, the Cascadia Subduction Zone, and its anticipated impact on the Pacific Northwest.
The Cascadia Subduction Zone refers to a fault line just off the Oregon/California/Washington coastlines, paralleling a series of volcanic mountains called the Cascade Range, where the North American and Juan De Fuca tectonic plates meet in the Pacific Ocean. These tectonic plates are so tightly wedged against one another and the pressure is so intense that when they eventually slip along its length, scientists are anticipating a 9.0, or higher, magnitude earthquake accompanied by a potentially 45-foot tall tsunami that will batter the north Pacific coastline from California to Canada. And, according to those same scientists, we are 315 years into a 243-year recurrence cycle.
These are simple questions that require a complex answer. Reshoring is the process of utilizing multiple levels of shores below the story being cast to distribute the applied construction loads to multiple stories. Concrete is heavy and without a sufficient number of levels to support the weight the slabs can become overloaded.
Construction was recently completed on Fire Station 76 for Multnomah County Rural Fire Protection District No. 10, located in Gresham, OR. Nishkian Dean participated in the project as the structural engineer of record, working directly with Hennebery Eddy Architects and Bremik Construction. The station is operated by The City of Gresham fire department.
The new 11,600 square foot facility replaces a smaller facility located across the street near 302nd Avenue and SE Dodge Park Blvd. A new station was required to serve the increasing demands caused by growth of the surrounding areas.
There are many things to take into account when designing and operating cryogenic systems. Possibly the most important consideration is the extreme temperature ranges involved. Two of the most commonly used propellants (rocket fuels) are liquid oxygen (LO2) and liquid hydrogen (LH2). The boiling point of LO2 is 297 degrees below zero Fahrenheit, while LH2 boils at -423 degrees Fahrenheit. Moving these super-cold liquids from Point A (likely, a storage tank) to Point B (a rocket or shuttle) requires a great deal of careful engineering.
For example, a 100 foot-long section of stainless steel pipe, exposed to super-cold LO2 temperatures, will shrink about four inches in length. Although this may not seem like much of a difference, it equates to thousands of pounds per square inch of stress on the piping. If the pipe section is rigidly restrained, the stress forces could cause pipe supports to fail, welds to crack, and rocket fuel to leak from the piping.
The solution is to design cryogenic systems with enough flexibility that the piping is allowed to contract and expand as necessary. This is commonly accomplished through the use of expansion loops (see Figure 1). These loops are essentially U-shaped pipe sections that allow for cryogenic piping to move and flex when necessary.
The Cascadia Subduction Zone, an area where tectonic plates off the coast of Oregon typically grind and slip to relieve pressure, have become “locked.” All of this pressure building along the fault line must be released at some point, which has significant implications for risk of major earthquake in the Pacific Northwest.
In response to this, Oregon’s Seismic Rehabilitation Grant Program (SRGP) was initiated by Oregon Emergency Management to fund earthquake retrofitting and seismic upgrade efforts for schools, higher-education institutions, and emergency services buildings.
As 2015 began, the New Horizons spacecraft awoke from an extended hibernation period on its journey to Pluto and the Kuiper Belt. The spacecraft, currently in the ninth year of its trip, is nearing the outer fringe of our solar system and is documenting this previously unexplored area. It has flown over 3 billion miles so far and will conclude its planned mission after completing approximately 135 million more, sending images of Pluto and its’ moons 4.67 billion miles back to Earth. This monumental undertaking would have been postponed for years if not for the rapid response of support firms, including Nishkian Dean, in the late Fall of 2005.
On October 24, 2005, Hurricane Wilma, part of that year’s record breaking hurricane season, moved through the Yucatan Peninsula, into the Gulf of Mexico, eventually making first landfall on US soil in Cape Romano, Florida. The storm devastated the coast and blew through Cape Canaveral Air Force Station and SLC-41, causing catastrophic failure of a major potion of the 40’ wide by 280’ tall folding fabric door (Megadoor) on the vertical integration facility (VIF), which housed the launch vehicle for the New Horizons mission. This nearly resulted in an estimated three-year delay of NASA’s planned New Horizon’s launch.
The planning and design process for private or public building construction is a critical component for a successful project. Every building project faces its own unique set of challenges, including finances, site location, schedule, public approval, environmental impacts, owner satisfaction, and meeting building code requirements. While the decision or need to construct a building typically determines its use and function, the size, shape, height, construction materials, and structural systems utilized tend to develop during the process. The building code plays a role in defining and shaping the building’s aspects by requiring adherence to a method of classification. The current 2012 International Building Code (IBC) requires that all buildings and structures, both existing and new, be classified under two categories:
The ending of the Shuttle program in 2011 meant that the US would no longer possess the capability to put men and women into space, making us completely reliant on other nations for transit to the International Space Station and destinations beyond. Although our team has the opportunity to work on many exciting projects every day, no challenge has been as exciting as our role in restoring US capabilities to support human space flight. On December 4, 2014, NASA’s Orion Exploration Flight Test 1 is scheduled to launch aboard a Delta IV Heavy off of Launch Complex 37 (LC-37) at Cape Canaveral Air Force Station. During the planning process for the upcoming launch, Orion’s preparations hit some complications that Nishkian Dean was excited to have a hand in repairing.
Orion is assembled in the Neil Armstrong, Operations and Checkout Building, commonly known as the O&C. Recently renamed after astronaut Neil Armstrong, the facilities heritage goes back to processing Apollo missions when it was first built in 1964. In 2012 the O&C was totally re-outfitted and restored to operational condition in order to support the assembly and future refurbishment of the Orion space capsule and Crew Service Module (CSM). Nishkian Dean took on an important role in the restoration when the Orion tooling and test fixtures proved to be far heavier than what the O&C floor was capable of supporting. Our team worked with Lockheed Martin Space Systems and Hensel Phelps to install an innovative pile underpinning system to permanently shore up the floor. The 140 piles were installed through the floor and bear on the heel of the basement retaining wall below, leaving only a 20-inch hole to patch in the clean-room environment of the O&C. The need to shore the floor was realized only late in the construction process so it was critical that a method be developed that wouldn’t damage existing construction, disrupt ongoing work, or contaminate the clean environment of the O&C. The solution proved to be efficient, keeping the O&C project on schedule, and Orion was successfully assembled and tested in the O&C then shipped out for the next step on its journey into space.
Earthquakes versus hurricanes…which natural disaster proves to be more damaging to buildings? This is an interesting question to compare and contrast. Each event affects buildings in fundamentally different ways, yet there are some striking similarities, as well. Let’s examine them.
Earthquakes are strong ground movements that result from ruptured crustal faults. And although regions that are seismically active and prone to earthquakes are largely known and geoscientists have mapped at least the potential for strong ground motions throughout the United States, earthquakes are unpredictable. The strength of the ground shaking below a particular building is a function of the distance from the rupture (both depth and distance along the surface), the type of soil the building sits on, and, of course, the size of the rupture/the extent to which the fault fractures during the event. The ground accelerations manifest themselves in forces within the building (remember from science class, F = ma where “m” is the mass of the building and “a” is the ground accelerations). Some of the strongest ground accelerations mapped by the USGS can be found in:
The most recent building Code changes in the 2012 International Building Code included what seem to be increases in the design wind speeds used throughout the country. Is it getting windier? The answer is no. But there have been changes in the determination and application of wind speed and their use in designing buildings and their components.
In the spring of 1999, Edwin T. Dean had a chance meeting while attending an Applied Technology Council board meeting in New York. That connection led to an introduction to Levon Nishkian.
The Nishkian family established the San Francisco, CA based Nishkian Engineering Firm in 1919. Levon Nishkian joined the firm in 1974 and later became the owner. The firm became Nishkian & Associates in 1989 with Kevin Menninger and later the Nishkian Menninger. Several conversations after meeting, Levon, Kevin and Ed partnered to form Nishkian Dean. Since then, the Association has grown, adding affiliate offices Nishkian Monks, located in Bozeman, MT, and Nishkian Chamberlain, in Los Angeles, CA.
By Ken Oliphant, MSCE, PE, SE
The Nishkian firms are often consulted at the onset of a renovation, tenant improvement, or building addition or following unexpected building damage caused by wind, earthquake, flood, fire, or vehicle strike. In these cases, our Client – the architect, contractor, developer, insurance company, or building owner want to know the structural implications of the building addition, alteration, or repair and what upgrades, if any, the building code and building official will require. Questions that often arise include:
- Will the entire structure need to be analyzed?
- What forces will the building be required to resist?
- Are there any code-triggered upgrades?
- Is a complete seismic upgrade required?
These questions are of critical importance to our clients as they play a pivotal role in shaping both the project scope and budget.
The need for parking grows as the number of cars on the road increases and as local ordinances mandate more and more parking for new developments. Structured parking is no doubt a growth “industry”. Parking structures designed and built to efficiently use the space provided in a safe and appealing way is key to architectural success; while a durable, cost effective structural system is key to structural success. Combined they deliver a functional design that provide for a parking environment that will serve the users and owner well for many years. There are many choices when it comes to building materials, structural systems and even aesthetic styles to consider when building a parking structure.
The Prescott Apartments placed in the top three in the outstanding Private Buildings category at the Daily Journal of Commerce’s TopProjects 2014 awards show last May 15th.
This mixed-use project is comprised of 155 apartments and six commercial spaces surrounding a beautiful courtyard. It is in a prime location in the Interstate Corridor of North Portland. Since it is adjacent to the light rail line and has easy freeway access, it’s a great building for commuters in a growing community. The impressive rows of windows were made possible in the structural design by using rigid wood frames, moving all of the plywood shearwalls into the interior of the building. Nishkian Dean is proud to be part of the team that contributed so much time and energy into making this a TopProject award winner!
The Nishkian firms have recently worked on more than a dozen Buffalo Wild Wings Grill & Bar across California and Washington State, teaming up to work on both new construction and tenant improvements. With our offices located throughout the west, we were able to efficiently support multiple sites from Washington to California. Buffalo Wild Wings is an expanding retail restaurant chain that caters to anyone from sports enthusiasts to families and welcomes them in with cheery colors and an inviting feel. Although each building sports the distinctive yellow color, every location is different, as we learned throughout the course of these projects.
Building Information Modeling is the process of creating and managing building data through a three-dimensional model. BIM software, such as Autodesk REVIT, creates a database of building components complete with properties and attributes in a single building model. The workflow and thought process differs from AutoCAD since the software handles more than just graphics. The BIM process also produces construction documents, reports, and detailed simulations.
There are many benefits to both the owner and design team when using BIM, as highlighted below. The intuitive interface combined with the technology behind the program allows people across many disciplines and offices to create, share, manage and maintain building information efficiently throughout the entire life of a building.
Basics of Lateral Load Resisting Systems in Wood Frame Buildings
Buildings resist wind and seismic forces through a combination of horizontal and vertical lateral force resisting systems. The lateral forces are first transferred through the horizontal elements at each floor which then act as deep beams to distribute the loads to the vertical elements. In wood frame construction, the horizontal elements are typically floor and roof diaphragms consisting of plywood sheathing nailed to wood framing members, such as joists, beams, and blocking. The vertical elements are typically shear walls consisting of plywood sheathing nailed to studs and blocking. Shear walls are anchored to the building foundation or an elevated concrete podium slab, both of which are designed to resist lateral loads and uplift forces.
Bolts, washers and other types of fasteners might be small, but they are a fundamental part of a structure. That is why having the right corrosion protection for the bolts that hold together a structure and knowing the environment it is exposed to is crucial to the safety and strength of the structure.
There are many types of metal high-strength carbon steel fastener assemblies available offered with different coatings, each with its own advantages and disadvantages. Some coatings are highly resistant to chipping, high heat, or certain chemicals. The specifications that cover the performance of coatings are covered by various ASTM (American Society for Testing and Materials) committees who investigate and review what fastener requirements currently are and specify how there are to manufactured, applied and used. These committees continue to develop coating standards specifically for metal fasteners.
Concrete formwork is the temporary structure built to support and confine concrete until it hardens and it is commonly broken into two categories: formwork and shoring. Formwork refers to vertical forms used to form walls and columns whereas shoring refers to horizontal formwork to support slabs and beams.
Forms must be designed to resist all vertical and lateral loads exposed onto the formwork during transport and in-use. Forms can be either pre-engineered panels or custom-built for the job. The advantage of pre-engineered panels is the speed of assembly and the ease of reconfiguring the forms to cycle to multiple pour locations. The disadvantages are fixed panel and tie dimensions that limit their architectural applications and allowable design loads that may limit their use for certain applications. Custom-built forms are designed to maximize the efficiency for each application but they are not as easy to reconfigure for other pour locations. Custom forms can be built to accommodate any architectural consideration or loading condition.
A new exhibit is coming soon to Portland Children’s Museum. The Outdoor Adventure exhibit will transform a 1.3-acre education-based play space behind Portland Children’s Museum. The Observation Deck and Pavilion will provide both parents and children with a place to play, create, and grow together year-round all while experiencing the outdoors!
Do you remember seismic zones? Depending on how long you have been involved in the building industry you may or may not remember seismic zones. May be you had experience with Zone 4 rated components or even today we get asked to design to Zone 3 or other seismic Zone requirements.
Portland, OR – As part of the North Interstate Corridor Plan adopted by the Portland City Council in 2008, The Prescott is one of the five major developments meant to contribute to the urban “boom” in North Portland, and to set the precedent for future growth in the area. Sitting regally on the corner of Interstate Avenue and Skidmore Street, The Prescott mixed-use offers not only 9,500 sf. of ground floor retail space, but 155 market-rate apartments, and an underground garage with 111 parking stalls. Many of the apartment patios look out over the Willamette River toward downtown Portland and the West Hills with scenic views of Mt. Hood and Mt. Rainer in the background. The Prescott is meant to be the focal point of this gateway station, and Myhre Group Architects can be thanked for the creative design that truly embraces the future theme of the Interstate Corridor.
Our Portland office is pleased to announce two recent additions to their team, Kolby Sniff and Casea Peterson.
Over the past few decades, earthquake knowledge and understanding has seen significant progress through scientific advancement, research and testing, and investigating the performance and failures of existing structural systems following major earthquakes. This progress has allowed building codes to further evolve by providing stricter requirements and requiring more resilient structural systems for addressing seismic safety in new buildings. Technology has also played a key role by allowing structural engineers to build advanced computer models that predict seismic behavior of buildings more accurately, and produce more robust structural systems for earthquake protection.
New buildings and those constructed more recently have already realized the benefits of this progress, however there are still many existing buildings in use with varying levels of seismic deficiencies that present a risk to life safety depending on the era they were constructed. Despite these issues, most national and local building codes do not require that existing buildings are brought to comply with current code for seismic requirements unless there is a change to the building that triggers a seismic upgrade.
During the design process, it’s essential to consider the anticipated structural load of a project.
Loads are commonly understood as forces that cause stresses, deformations, or accelerations. These loads are applied to a structure or its components that cause stress or displacement.
There are many types of structural loads that you need to account for during the design process. And some – like live loads – present specific challenges that require a deeper understanding to conceptualize.
Nishkian Dean is proud to have provided Hensel Phelps and the United Launch Alliance with their engineering consultation services in support of the NROL-65 launch mission on August 28th. Congratulations to all of the team members who helped make the launch of Delta IV Heavy a success!
For the full article and a video of the launch, visit CNN.
Gladstone Center for Children & Families:
Cost: $4.94 Million
Square Footage: 30,000
Gladstone, Oregon is small residential community in Clackamas County, located twelve miles south of Portland. A primarily residential community, Gladstone is home to a number of locally-owned businesses, many that have served Gladstone families for generations. One of these businesses, often referred to as the heart of Gladstone, was the Danielson’s Thriftway store on Portland Avenue.
August 7, 2012, 10:34am PDT | by Mary Ann Azevedo | The Business Journals
Federal Realty Investment Trust is so eager to build a new 230,000-square-foot office building in Santana Row that it’s willing to give up some retail and residential for the right to do it.