Located in Oakland’s Lakeside neighborhood, 250 17th Street will be five levels of wood construction over two levels of concrete. The new apartment building will be comprised of a ground-level parking garage and 74 units of studio, one- and two-bedroom apartments. The building will offer tenants many amenities such as a gym, bicycle parking and repair, charging stations for electric vehicles, and a roof deck. The roof deck will feature a garden, a barbeque area, a trellis, and a water feature. The extra weight of planting and water drive the structural design of the roof.
The concrete podium at the second level will consist of a two-way post-tensioned structural slab. The slab is supported by bearing shearwalls and concrete columns. The floor framing of the timber superstructure will consist of ¾ ply supported by timber joists, LVL, and PSL beams. The beams will be supported by stud walls and wood columns. The lateral load resisting system will consist of concrete shearwalls beneath timber shearwalls. The ground floor slab will be a slab-on-grade over spread foundations at the columns, continuous wall foundations, and a partial mat foundation under the shearwall core.
Simeon Properties collaborated with San Francisco-based architecture firm Kotas/Pantaleoni Architects and Nishkian Menninger to construct the Class A, transit-oriented multi-housing development in Oakland, California. The transit-oriented site has a WalkScore© of 99 and is convenient to the 19th Street BART station, Interstates 880 and 980, Amtrak and ferry service, connecting residents to major employment centers in downtown Oakland, San Francisco, Emeryville and Silicon Valley. With Lake Merritt and Broadway Street within a few blocks, the live-work-play property will also provide residents with access to numerous dining, nightlife and recreational options.
Kotas/Pantaleoni Architects designed a façade that will incorporate seamlessly into the residential neighborhood between Oakland’s busy Broadway Street and Lake Merritt. Rendering can be seen at their website: http://kp-architects.com/work/alice-street/
Wood is often seen in multi-family mid-rise buildings as the most economical construction material. While the purpose of joists, beams, and wood stud walls are easily understood in their role carrying the gravity loads of a building, the lateral load resisting elements and how they work can be more confusing.
Lateral Load Resisting Shear Walls
When lateral loads due to wind forces or a seismic event hit a building, the loads travel through the floor, collecting into and being resisted by wood shear walls. The top and bottom plates of the shear walls act as continuous collectors, moving the lateral loads from the diaphragm into the shear wall. Plywood sheathing, the nailing of the plywood to wood studs, and anchor bolts at the sill plate resist the shear forces. As the lateral loads move from a horizontal plane (i.e. the floor) to a vertical plane (i.e. the wall), the lateral loads also create vertical tension and compression forces, which are resisted by end posts and a hold-down system located at each end of the shear wall.
Figure 1: Components of a Shear Wall
At the beginning of a project, as unit layouts and floor plans are being set, it is important to ensure that the building will have an appropriate shear wall layout. In multi-family buildings, corridors usually afford a sufficient length of interior shear walls, but exterior shear walls must be carefully coordinated between the client, architect, and structural engineer. Façade features, window sizes, and window locations can all critically affect exterior shear wall designs.
Stacking Shear Walls
Structurally, it is always more efficient to stack shear walls from the top of the building to the foundation (or podium). This allows the components that resist the compressive and uplift forces to be continuous. When shear walls do not stack, the building code requires that components be designed for an increased load, and extra framing members and connections are required to transfer the loads.
Figure 2: Stacked Shear Walls
The shear wall design is not just determined by the number of shear walls, but also the length of each shear wall. As shear walls get shorter, the hold-down system gets loaded more heavily. The minimum length of shear wall permitted on a project depends on the floor-to-floor height – the taller a floor, the longer a shear wall must be. This aspect ratio is determined by taking the height (h) and dividing it by the shear wall length (bs). Shear walls cannot have an aspect ratio greater than 3.5 but as a rule of thumb, aspect ratios should be less than 2. Where the aspect ratio exceeds 2, the wall’s shear capacity is penalized. In other words, shear wall lengths should always aim to be greater than half the floor height.
Nishkian Chamberlain has extensive experience with multi-family construction and would be happy to help you find cost-effective solutions to your construction and development needs. Please do not hesitate to contact us at NCInfo@Nishkian.com, or give us a call at (310) 853-7180. You can also go to our Contact page to connect with any one of our offices in your region.
Figure 3: Aspect Ratio
As spring gives way to summer, construction crews are making swift progress at Yellowstone Club Core Village’s ongoing, $312 million mixed-use base village project to add more amenities for its growing list of members. Andy Sandoval, GE Johnson Construction Company’s project superintendent, sheds light on the progress being made at the largest construction project ever to take place in the Rocky Mountain region.
“The precast erection from Stresscon had a great month by erecting 556 pieces. The total piece count now stands at 2,762 pieces erected and 62% complete for the total project. To date, 768 precast deliveries were made travelling from Colorado Springs to Big Sky, MT. That’s a round trip of 1,617 miles or a total 1.2 million total miles of trucking just to get the team to this point of the structure. The largest piece of precast concrete for the project weighing approximately 83,000 pounds was installed this past month. Our GE Johnson/Jackson and Schmueser concrete crews also eclipsed a nice milestone in the last month by placing our 10,000th cubic yard of concrete for the project. Earthworks group has also continued backfilling the foundations within the building footprint as well as the exteriors of the building right behind A+ Waterproofing installing the foundation waterproofing. Encore Electric has continued doing the in-slab rough in, overhead rough-in and underground work for the project. Thus far, Encore has installed over 30,000 feet of conduit for the project. That’s 5.7 miles of conduit! Encore Electric and Apollo Plumbing and Mechanical have expedited their work by each pre-fabricating over 3,000 man-hours worth of product at the Bozeman Hub facility during the winter months inside a controlled environment saving the project both time and money.
In Area 1, True North and Sowles completed the Area 1 steel structure and Rooftop Solutions has completed the roof dry-in for Area 1. This has allowed Advanced Fireproofing to begin spraying the steel structure on Levels 3 and 4. Safway Scaffolding is nearly complete installing the scaffold around the Area. This has allowed SCS Drywall to complete a substantial amount of exterior framing and sheathing on the levels below. Patriacca Construction is right behind them installing the exterior envelope and aluminum clad wood windows. Patriacca has also been busy in our Bozeman Hub fabricating the exterior timbers to prepare them for installation. Gallegos Corporation is busy in this area installing the steel lintel angles and will begin installing stone in the next two weeks. The first elevator should be ready for construction use by the end of the month.
In Area 2, precast erection has been completed on the East side. The West side of this area is currently getting garage walls and shafts completed with the CMU while Paradigm is continuing to place the concrete slabs on the West side through Level 3. Area 2 is nearly fully connected to Area 3 making the building perimeter of the structure easily defined visually. The conventional cranes are now setting in Area 4 and beginning to work their way out of the project. As the cranes move, the foundations in Area 4 is rapidly progressing and completion is anticipated to be as scheduled.
Area 5 and 6 are also off to a great start. In fact, the Area 6 (The CUP), is the first Area to have exterior stone installed. The CUP has also completed all the structural ramps and Superior Waterproofing has completed the hot-applied waterproofing and protection board and foam on the upper level. 4G has installed the hydronic snowmelt in the topping slab for the ramp and it will be placed next week. Inside the CUP, generators, boilers and other major infrastructure are in place and being hooked up to be the lifelines of the project by this coming fall/winter. Western States has installed the fire protection systems inside and the waterproofing and exterior backfill are in progress around the perimeter. Sime has now completed the work around the pond to allow the CUP and the project to connect to the Yellowstone Club infrastructure. Area 5 is busy getting the framing and MEP rough-in going on the interiors. Steel Erection is continuing on the North side of this area and the South side began metal decking for the roof. The Area 5 exterior scaffolding is going into place and the exterior framing and sheathing have begun and are right behind the scaffold erection.
We are now over 300 employees on site and will begin running the 6th daily bus on June 19th from Bozeman to the jobsite. This project represents employees from 38 states boasting multiple nationalities and who can collectively speak over a dozen languages. The ages of the men and women on site vary from the ages of 18 through 74 years. Our entire team here have shown through their efforts and actions thus far that construction may be the greatest team sport!”
The Nishkian team couldn’t be more proud to work with Hart Howerton, GE Johnson Construction/Jackson Contractor Group JV, Schmueser & Associates, Stresscon/EnCon United, Terracon, Earthworks, Encore Electric, Apollo Plumbing & Mechanical, True North, Sowles, Rooftop Solutions, Advanced Fireproofing, Safway Scaffolding, SCS Drywall, Patriacca Construction, Gallegos Corporation, Paradigm, Superior Waterproofing, 4G, Western States, Sime Construction, Steel Erection, and various subconsultants on this exciting and complex project in Big Sky, MT.
Click here to view GE Johnson/Jackson Montana’s flyover video showing progress made to the Yellowstone Club Core Village project. The video was shot from a GoPro camera from a hook of a tower crane that spins around.
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
Formerly a storage site, the 3.3-acre lot at 100 and 150 Hooper Street in San Francisco just off of 7th Street and Mission Bay Dr. is being developed into office space and manufacturing space. Zoning requirements in San Francisco’s Design District dictate that one-third of the space must remain industrial space. The ground level of each building has been designed as such. This development will be ideal for a technology company requiring production space. 100 Hooper will feature an “urban farm” and solar panels on the roof.
100 Hooper comprises the majority of the site’s area. 100 Hooper is two long buildings connected by two “skybridges” at the second and third floors. The two buildings total 427,255 square feet of leasable space. Both buildings are four stories of concrete construction, utilizing shear walls and post-tensioned slabs. The two skybridges are steel, utilizing concentric braced frames as their lateral force resisting systems. The skybridges are connected to the buildings at one end by a frictionless surface, allowing the two buildings to move independently in a seismic event.
Developer Kilroy Realty Corporation collaborated with design architect Pfau Long Architecture, and implementation architect Forge Architecture on the design of this new PDR development in the city’s Potrero Hill. The general contractor is DPR Construction, and Nishkian Menninger served as the structural engineer for 100 & 150 Hooper Street. For photos and more information about the project and development, please visit 100 Hooper.
The Los Angeles Times proclaimed the start of a “New Frontier” for earthquake safety: a phenomenon kicked off by the city of Santa Monica, which recently adopted the most comprehensive seismic retrofit ordinance in the nation.
An Owner’s desire to evaluate the seismic performance of an existing building varies. Some national, regional and local Owner’s simply have a genuine concern for knowing the seismic vulnerability of their buildings. Other reasons Owners perform evaluations can include an adopted City Ordinance, a policy trigger for analysis or modification of the building, a requirement for a financial transaction, or buildings with State employee tenants requiring special analysis, just to name a few.
We are currently performing dozens of these evaluations on projects throughout California, efficiently utilizing the ASCE standard ASCE/SEI 41-13. Copyrighted in 2014 by the American Society of Civil Engineers, the standard was developed and written to combine the previously adopted standards ASCE 31 and 41 into a single document for the Seismic Evaluation and Retrofit of Existing Buildings. Whereas past retrofit designs often did not align with evaluations due to having documents with differing criteria for evaluations versus design, this single document coalesces both evaluation and design of existing building retrofits providing one coordinated methodology. Seismic evaluation is defined as an approved process or methodology of evaluating deficiencies in a building that prevent the building from achieving a selected Performance Objective. Seismic retrofit is defined as the measures taken to improve the seismic performance of a building by the correction of deficiencies identified in the evaluation relative to a selected Performance Objective.
The initial step in the process is to assist the client in establishing or selecting a Performance Objective which is a combination of a desired Structural and Non-Structural Performance Levels paired with Seismic Hazard Level(s). The chart below demonstrates the different Performance Level terminology:
Following the establishment of a Performance Level, the Seismic Hazard is established based on the seismicity at the building site determined by historical data, with consideration of proximity to known faults and their activity as well as the specified Seismic Hazard Level(s).
Evaluation procedures based upon the selected Performance Objective, level of seismicity and building type are identified in the following flowchart:
Each Tier of evaluation becomes more detailed and complex. The Tier 1, Screening Procedure, is a quick checklist of structural and non-structural components of the building. A Tier 2, Deficiency-Based Evaluation procedure, utilizes more involved checks of the building to provide a deeper understanding of the building’s design. A Tier 3, Systematic Evaluation Procedure, provides a full building review including linear and non-linear / performance based analysis and design options.
The final step in the review process is to prepare an evaluation report to communicate the results of the evaluation to the owner, local jurisdiction or agency requesting the evaluation. Depending upon the availability of information and the scope of the evaluation, the extent of the report may range from a letter to a detailed document.
If the seismic evaluation suggests that a seismic retrofit is warranted, the next step is to perform the design for the retrofit. A Seismic Retrofit design will utilize the evaluation report to identify the seismic deficiencies relative to the selected Performance Objective. One or more of the following strategies to retrofit the deficiencies may be considered:
Nishkian Chamberlain has extensive experience in seismic retrofit projects and is currently working with building owners to assist in identifying the impact that retrofitting in accordance with the City Ordinances will have on their building assets. We are currently working as part of an advisory council to evaluate over 50 buildings for one client that is proactively looking to understand the overall vulnerability of their portfolio.
Should you need the assistance of a trusted advisor to guide you through the uncertainty of the City Ordinances, evaluate an existing building or make additions/modifications to an existing building, contact us at NCInfo@Nishkian.com or give us a call at 310.853.7180 for cost effective, creative seismic retrofit solutions. You can also go to our Contact page to connect with any one of our offices in your region.
Engineering News-Record recently published a list of the largest new projects started in the Mountain States region last year. The list ranks the 60 largest projects that broke ground and real construction got under way on them between January 1 and December 31, 2016. The projects are located in the following states: Utah, Colorado, Wyoming, Idaho, Montana, and the Dakotas. The 2016 list of top starts is ranked in order by dollar volume, and shows the cost of the top projects in the region totaled over $4.5 billion. The list also enumerates an impressive mix of public- and private-sector work reflective of the growing economic diversity of most states in the region, with projects launched in the health care, hotels and resorts, transportation, educational facilities, office, mixed-use, and multi-family residential sectors.
At the top of this year’s regional list is our Yellowstone Club Core Village project, a 550,000 square feet mixed-use base village in which 48 ultra-luxurious residences, a spa, pool, fitness area, restaurants, and full-skier service facilities are being added to Yellowstone Club, a world-class private resort in Big Sky, Montana. With a $312-million construction cost, the Yellowstone Club Core Village is one of the largest projects in price and size in the history of Montana.
The Nishkian team is incredibly proud to be involved in the Yellowstone Club Core Village project. Credit and kudos also go to our project team: Hart Howerton, GE Johnson Construction/Jackson Contractor Group JV, Stresscon/EnCon United, Cross Harbor Capital Partners LLC, Discovery Land Co., Yellowstone Development, and everybody else involved. We are thrilled for a great start on the largest project in the Rockies!
For the full list of the top 60 projects, please visit ENR 2016 List of Top Project Starts in the Mountain States
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.
IMPORTANT UPDATE – CORRECTION TO THIS BLOG POST:
The earlier version of the blog article “Cadence Apartments project in South San Francisco starts construction soon” posted on April 27, 2017 incorrectly noted Devcon Construction as the architect. This blog post has been corrected. The design architect for Cadence Apartments is TCA Architects. Our sincere apologies for this error.
Construction is scheduled to start in May at an old Ford car dealership in South San Francisco that has been sitting vacant for years. The development, on Cypress Avenue, will offer 260 luxury apartment units and 12 townhouses, two of which will be affordable by the standards of the city’s Below Market Rate Inclusionary Housing Program. The development will be only one quarter mile from the South San Francisco Caltrain station, offering tenants access to downtown San Francisco to the north and Silicon Valley to the south.
The two buildings are each comprised of five levels of wood framing above two levels of concrete parking. Both buildings use wood and concrete shear walls as their primary lateral force resisting system.
Sares Regis is a major developer and property manager in Northern California. The Cadence development will add to their portfolio of over 7 million square feet of developed space. Devcon is the architect and contractor for this project. The design architect for Cadence Apartments is TCA Architects. Devcon is the general contractor for this project.
By Rachel Wong, S.E., CAPM®
With the January 1st implementation of 2016 California Building Code (CBC), there is a new Building Code in town. Much of the 2016 CBC is similar to the previous 2013 CBC with respect to Structural Engineering with minor updates scattered throughout. However, one of the more significant updates was in regards to existing buildings. The 2015 International Existing Building Code® (IEBC) was adopted with the 2016 CBC as the latest and greatest guideline for existing building repair and modifications.
Originally drafted in 2003, the IEBC has been in the International Code Council (ICC) family of codes for over a decade, but faced limited adoption due to the presence of IBC/CBC Chapter 34 for existing buildings. Previously, IBC/CBC Chapter 34 was responsible for minimum requirements in existing building modifications, but had limited content for the variety of projects it covered. In 2014, the code committee decided that Chapter 34 should be eliminated in favor of the more fully-depicted IEBC. The IEBC maintains much of the prior CBC information, while expanding and clarifying specific topics. For example, a path for compliance of relocated buildings is provided in IEBC, and was previously considered to be a design “grey area”. Within IEBC Appendix A, a series of subsections are now provided for masonry, wood, concrete, and steel design, which previously were beyond the scope of Chapter 34.
But a lot of familiar requirements are present in IEBC, too. Previous CBC Sections 3402 to 3411 can now be found incorporated into the contents of IEBC Chapter 4, and Section 3412 has been relocated to IEBC Chapter 14. The CBC retrofit/strengthening threshold of 5% gravity/10% seismic modifications to existing elements without requiring strengthening to these elements is still applicable for Level 2 alterations that impact less than 50% of the building area.
The IEBC provides options for either prescriptive compliance of a structure or performance-based compliance, and permits the use of alternate methods as well. One of the seismic retrofit documents that go hand-in hand with these provisions is the relatively new ASCE 41-13 document, which will be featured in our upcoming May article.
Viscous Damper Brace Frames in an existing Steel Building
(Performance-Based Compliance Upgrade)
Each of the Nishkian offices has extensive experience with providing cost-effective solutions in retrofit, alteration and additions to existing structures. Should you need assistance with understanding how the new code will affect your existing building project, do not hesitate to contact one of our offices to receive expert assistance with any questions you may have. We are here to help!