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.