Assistant Professor | Civil & Architectural Engineering & Construction Management
Milwaukee, WI, UNITED STATES
Dr. Pouria Bahmani focuses on designing structures to resist seismic and wind loads.
California (No. 84369)
Oregon (No. 93040)
Washington (No. 54651)
Wisconsin (No. 47763)
Structural and Earthquake Engineering, Colorado State University
Structural Engineering, South Dakota State University
Structural and Earthquake Engineering, Isfahan University of Technology
Colorado State University 2014 - 2015
Colorado State University 2013
The world has always been a dangerous place, so how do we increase our odds of survival? In “Making Stuff: Safer,” David Pogue explores the cutting-edge research of scientists and engineers who want to keep us out of harm’s way. Some are countering the threat of natural disasters with new firefighting materials and safer buildings. Others are at work on technologies to thwart terrorist attacks. A next-generation vaccine will save millions from deadly disease. And innovations like smarter cars and better sports gear will reduce the risk of everyday activities. We’ll never eliminate danger—but science and technology are making stuff safer...view more
PBS LearningMedia tv
Learn how structures with large open spaces on the ground floor—called soft-story buildings—are vulnerable to earthquakes but can be retrofitted to be safer in this video excerpted from NOVA: “Making Stuff Safer.” Host and technology columnist David Pogue examines how soft-story buildings have collapsed in past earthquakes and visits a testing site to see how retrofits improve their safety. In order to study methods to improve the seismic safety of soft-story buildings, researchers from five universities collaborated to build a typical soft-story building on a shake table that simulates earthquakes.view more
ABC 10 News tv
A 4-story building was built and tested to collapse at UC San Diego shake table facility. The building was designed and retrofitted by a group of researchers and engineers led by Colorado State University.view more
ASCE 2015 Structures Congress Portland, OR, April 2015
14thWorld Conference on Timber Eng. (WCTE) Quebec City, Canada, August 2014
ASCE 2014 Structures Congress Boston, MA, April 2014
ASCE 2013 Structures Congress Pittsburgh, PA, May 2013
15th World Conference on Earthquake Engineering Lisbon, Portugal, September 2012
ASCE 2012 Structures Congress Chicago, IL, March 2012
American Concrete Institute (ACI) Convention Pittsburgh, PA, October 2010
Code-based and performance-based design of tall buildings subjected to extreme seismic and wind loads
Dynamic response of structures with emphasis on response of structures to earthquake loading
Determining earthquake and wind loads on structures; linear and nonlinear response of structures subjected to lateral loads, detailing for inelastic response
Application of finite element method in structural engineering
Bahmani, P., van de Lindt, J.W., Pryor, S.E., Mochizuki, G.L.
Recent earthquakes such as Loma Prieta and Northridge in California have highlighted the poor performance of a specific class of existing buildings known as soft-story building. This is because many older buildings were designed prior to the implementation of modern seismic design codes. Although building codes have clearly evolved, the problem is still unresolved for older buildings that are code-deficient such as soft-story wood-frame buildings. Retrofitting these types of buildings came to the forefront after the 1989 Loma Prieta, 1992 Cape Mendocino, and 1994 Northridge earthquakes. This paper presents a new performance-based seismic retrofit (PBSR) methodology for existing wood-frame buildings with an extreme soft-story and torsional irregularity at their first story, i.e. the most common case for these types of buildings in the San Francisco Bay Area. The method was validated numerically using non-linear time history analysis and then was validated experimentally by conducting full-scale shake table test.
Bahmani, P., Van de Lindt, J., Iqbal, A. and Rammer, D.
Soft-story wood-frame buildings have been recognized as a disaster preparedness problem for decades. There are tens of thousands of these multi-family three- and four-story structures throughout California and other cities in the United States. The majority were constructed between 1920 and 1970, with many being prevalent in the San Francisco Bay Area in California. The NEES-Soft project was a five-university multi-industry effort that culminated in a series of full-scale soft-story wood-frame building tests to validate retrofit philosophies proposed by (1) the Federal Emergency Management Agency (FEMA) P-807 guidelines and (2) a performance-based seismic retrofit (PBSR) approach developed within the project. Four different retrofit designs were developed and validated at full-scale, each with specified performance objectives, which were typically not the same. This paper focuses on the retrofit design using cross laminated timber (CLT) rocking panels and presents the experimental results of the full-scale shake table test of a four-story 370 m2 (4000 ft2) soft-story test building with that FEMA P-807 focused retrofit in place. The building was subjected to the 1989 Loma Prieta and 1992 Cape Mendocino ground motions scaled to 5% damped spectral accelerations ranging from 0.2 to 0.9 g.
Bahmani, P., van de Lindt, J.W., Mochizuki, G.L., Gershfeld, M. and Pryor, S.E.
In the San Francisco Bay Area and throughout much of California, there are a large number of wood-frame buildings with garage space at ground level, resulting in open fronts on one or two sides. This type of geometry results in a soft and weak first story, and buildings of this archetype are generally referred to as soft-story buildings. During an earthquake, these buildings are susceptible to severe damage and collapse and have been recognized as a disaster-preparedness problem. The five-university Network for Earthquake Engineering Simulation (NEES)-Soft project culminated in a series of full-scale soft-story wood-frame building tests to validate two different retrofit philosophies and included a 2-month test program encompassing four different retrofits. The building had 370m2 of living space and was designed to be generally representative of older San Francisco Marina and Mission District construction, circa 1950s. Following the retrofit testing, which only moderately damaged the test building, retrofits were removed, repairs were conducted, and the building was nominally instrumented for testing without retrofits in place. A series of unidirectional shake table tests was conducted, beginning with the Cape Mendocino acceleration record scaled to 0.4g spectral acceleration up to two successive shakes with the Superstition Hills acceleration record scaled to 1.8g spectral acceleration. Little residual lateral displacement was observed until the last two earthquakes. The objectives of the collapse testing phase of the NEES-Soft project were to (1) observe and document the nature of the soft-story collapse mechanism and (2) quantify the collapse drift for these types of soft-story wood-frame buildings. The building collapsed at approximately 19% interstory drift of the soft story (ground floor).
Jennings, E., van de Lindt, J., Ziaei, E., Bahmani, P., Park, S., Shao, X., Pang, W., Rammer, D., Mochizuki, G., and Gershfeld, M.
The FEMA P-807 Guidelines were developed for retrofitting soft-story wood-frame buildings based on existing data, and the method had not been verified through full-scale experimental testing. This article presents two different retrofit designs based directly on the FEMA P-807 Guidelines that were examined at several different seismic intensity levels. The effects of the retrofits on damage to the upper stories were investigated. The results from the hybrid testing verify that designs following the FEMA P-807 Guidelines meet specified performance levels and appear to successfully prevent collapse at significantly higher seismic intensity levels well beyond for which they were designed. Based on the test results presented in this article, it is recommended that the soft-story-only retrofit procedure can be followed when financial or other constraints limit the retrofit from bringing the soft-story building up to current code or applying performance-based procedures.
Bahmani, P., van de Lindt, J.W., Gershfeld, M., Mochizuki, G.L., Pryor, S.E., Rammer, D.
Soft-story wood-frame buildings have been recognized as a disaster preparedness problem for decades. There are tens of thousands of these multifamily three- and four-story structures throughout California and other parts of the United States. The majority were constructed between 1920 and 1970 and are prevalent in regions such as the San Francisco Bay Area in California. The NEES-Soft project was a five-university multiindustry effort that culminated in a series of full-scale soft-story wood-frame building tests to validate retrofit philosophies proposed by (1) Federal Emergency Management Agency’s recent soft-story seismic retrofit guideline for wood buildings and (2) a performance-based seismic retrofit (PBSR) approach developed as part of the NEES-Soft project. This paper is the first in a set of companion papers that presents the building design, retrofit objectives and designs, and full-scale shake table test results of a four-story 370-m2 (4,000-ft2) soft-story test building. Four different retrofit designs were developed and tested at full scale, each with specified performance objectives, which were typically not the same. Three of these retrofits were stiffness or strength–based strategies and one applied supplemental damping devices in a pinned preassembled frame. This paper focuses on the building and retrofit design methodologies and specifics and the companion paper presents the experimental results of full-scale shake table tests ranging from 0.2- to 1.8-g spectral acceleration for all four retrofits.
van de Lindt, J.W., Bahmani, P., Mochizuki, G., Pryor, S.E., Gershfeld, M., Tian, J., Symans, M.D., Rammer, D.
Soft-story wood-frame buildings have been recognized as a disaster preparedness problem for decades. The majority of these buildings were constructed from the 1920s to the 1960s and are prone to collapse during moderate to large earthquakes due to a characteristic deficiency in strength and stiffness in their first story. In order to propose and validate retrofit methods for these at-risk buildings, a full-scale four-story soft-story wood-frame building was constructed, retrofitted, and subjected to ground motions of various intensities. The tests were conducted to validate retrofit guidelines proposed in a “Federal Emergency Management Agency’s recent soft-story seismic retrofit guideline for wood buildings” and a performance-based seismic retrofit (PBSR) methodology developed as part of the NEES-Soft project. This paper is the second in a set of companion papers and presents the full-scale shake table test results using the two new approaches. The companion paper to this paper presents the design philosophies, design details, and numerical analysis of the retrofitted building for each of the four retrofits.
Shao, X., van de Lindt, J., Bahmani, P., Pang, W., Ziaei, E., Symans, M., Tian, J., Dao, T.,
Real-time hybrid simulation (RTHS) of a stacked wood shear wall retrofitted with a rate-dependent seismic energy dissipation device (viscous damper) was conducted at the newly constructed Structural Engineering Laboratory at the University of Alabama. This paper describes the implementation process of the RTHS focusing on the controller scheme development. An incremental approach was adopted starting from a controller for the conventional slow pseudodynamic hybrid simulation and evolving to the one applicable for RTHS. Both benchmark-scale and full-scale tests are discussed to provide a roadmap for future RTHS implementation at different laboratories and/or on different structural systems. The developed RTHS controller was applied to study the effect of a rate-dependent energy dissipation device on the seismic performance of a multi-story wood shear wall system. The test specimen, setup, program and results are presented with emphasis given to inter-story drift response. At 100% DBE the RTHS showed that the multi-story shear wall with the damper had 32% less inter-story drift and was noticeably less damaged than its un-damped specimen counterpart.
Bahmani, P., van de Lindt, J.W.
Woodframe buildings are unique in that the nonstructural finishes such as gypsum wall board and stucco provide significant stiffness and strength relative to the lateral force resisting system, e.g., wood shear walls. Wall finishes, or components within a woodframe wall subassembly, can consist of multiple layered modern and/or archaic elements such as wood planks, drywall, plaster on lathe, stucco, or plywood. There exist significant differences in ductility among these materials, raising questions about how best to superimpose single-degree-of-freedom hysteretic models or backbone curves during nonlinear time history analysis or when combining backbone curves for design and retrofit. This paper presents the method and results of an experimental study of 18 walls installed with one, two, or three of the previously described finishes. Testing was performed to determine the best approach to add the sheathing layers numerically when combining the backbone curves for analysis and design. Nonlinear dynamic analyses were conducted to quantify the difference between the behavior of the combined sheathing test and the superimposed single layer sheathings.
Tian, J., Symans, M.D., Gershfeld, M., Bahmani, P., van de Lindt, J.W.
Seismic damping systems have been shown to be effective in reducing the structural response of steel and concrete structures subjected to earthquakes. However, the successful application to light-framed wood structures remains a challenge due to a number of factors including the inherent flexibility of wood framing connections that leads to losses in displacement transfer between the wood framing system and the damper assemblies. Within the framework of the NEES-Soft project, such implementation issues have been investigated through the shake table testing of a full-scale, four-story woodframe building at the NEES-UCSD site. All dampers are installed in toggle-braced light steel frames that are located at the soft ground story so as to avoid construction-related disruptions to upper-story residents. The location of the damper frames in plan and the amount of supplemental damping introduced are strategically selected in order to achieve a high level of structural performance for the design ground motions. The damperstructure connections are carefully designed to reduce possible displacement transfer losses. In this paper, selected experimental test data is presented to demonstrate the degree to which energy dissipation devices are effective in protecting soft-story woodframe structures from earthquakes. Attention will be given to the displacement transfer losses between damper assemblies and wood structures.
Bahmani, P., van de Lindt, J., and Dao, T.
Direct displacement design (DDD) is a procedure that allows one to distribute the forces induced by an earthquake to the levels of a multistory building to ensure that the desired level of interstory drift is not exceeded. To date, DDD has only been applied to buildings that do not exhibit significant torsional response. This paper presents a methodology to perform displacement-based design (DBD) on multistory buildings with in-plane torsional irregularities, thereby generalizing DBD for buildings with torsion. The procedure includes decoupling the contribution of the deformation that results from translation and torsion by using an existing approximation technique. The approach is validated by using detailed finite-element models of asymmetric buildings; it is found to accurately reproduce the desired dynamic structural properties. Both linear and nonlinear (elastic-perfectly plastic) systems are demonstrated and the accuracy is verified.
Wehbe, N., Bahmani, P., and Wehbe, A.
The use of light-gauge steel framing in low-rise commercial and industrial building construction has experienced a significant increase in recent years. In such construction, the wall framing is an assembly of cold-formed steel (CFS) studs held between top and bottom CFS tracks. Current construction methods utilize heavy hot-rolled steel sections, such as steel angles or hollow structural section tubes, to transfer the load from the end seats of the floor joist and/or from the load-bearing wall studs of the stories above to the supporting load-bearing wall below. The use of hot rolled steel elements results in significant increase in construction cost and time. Such heavy steel elements would be unnecessary if the concrete slab thickening on top of the CFS wall can be made to act compositely with the CFS track. Composite action can be achieved by attaching stand-off screws to the track and encapsulating the screw shank in the deck concrete.
Jennings, E., Ziaei, E., Pang, W., van de Lindt, J., Shao, X., Bahmani, P.
Soft-story woodframe buildings have been identified as a disaster preparedness problem throughout California and are present in many other states of the United States. These buildings can be readily identified by their large openings at the ground floor, often for parking, which results in a soft and weak first story that is prone to collapse in moderate to severe earthquakes. This paper presents the hybrid test results of a full-scale collapse test program that was carried out on a 3-story soft-story woodframe building with an overretrofitted first story. The overretrofitted design was constrained to the soft story only, essentially representing a retrofit that would likely drive the soft-story failure mechanism into the upper stories. The objectives of the collapse testing were to (1) quantify the collapse shift into the upper stories when the first story is overstrengthened, (2) investigate the collapse mechanisms of a woodframe building constructed with archaic building materials and style in the upper level.