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Award Abstract #0421551

NEESR-II: Sidesway Collapse of Deteriorating Structural Systems

NSF Org: CMMI
Division of Civil, Mechanical, and Manufacturing Innovation
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Initial Amendment Date: September 13, 2004
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Latest Amendment Date: September 13, 2004
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Award Number: 0421551
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Award Instrument: Standard Grant
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Program Manager: Joy Pauschke
CMMI Division of Civil, Mechanical, and Manufacturing Innovation
ENG Directorate for Engineering
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Start Date: October 1, 2004
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End Date: September 30, 2008 (Estimated)
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Awarded Amount to Date: $449,320.00
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Investigator(s): Helmut Krawinkler krawinkler@stanford.edu (Principal Investigator)
Andrew Whittaker (Co-Principal Investigator)
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Sponsor: Stanford University
3160 Porter Drive
Palo Alto, CA 94304-1212 (650)723-2300
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NSF Program(s): NEES RESEARCH
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Program Reference Code(s): 1057, 1576, CVIS
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Program Element Code(s): 7396

ABSTRACT

Understanding, predicting, and preventing collapse have always been major objectives of earthquake

engineering. Collapse is the main source of injuries and loss of lives. Thus, it constitutes an engineering

limit state that needs to be predicted in order to evaluate, in a probabilistic format, the life safety

performance level, which is of primary societal concern. In the context of earthquake risk management, a

process is needed that permits a rigorous assessment of the probability of collapse to make informed

decisions in the best interest of society. In the context of earthquake resistant design, this process needs

to be simplified so that the engineering profession can use engineering techniques, which are based on

parameters such as strength, stiffness, and ductility (deformability), to derive structural properties that

comply with specified targets for a required level of collapse safety, or a tolerable probability of collapse.

This project will address both contexts. It will provide a methodology and reliable data for predicting a

critical mode of collapse, namely that associated with sidesway instability in which an individual story (or

a series of stories) displaces sufficiently so that the second order P-delta effects fully offset the first order

story shear resistance and dynamic instability occurs, i.e., the structural system loses its gravity load

resistance. Prediction of this mode of collapse is a challenging problem because structural components

will deteriorate in strength and stiffness before the collapse limit state is reached, and great uncertainties

are associated with the description of the seismic input and of the parameters that control the response of

structures close to collapse.

The methodology will be based on a combination of analytical and experimental simulations, with the

former being carried out at Stanford University and the main effort of the latter, a shaking table collapse

test of a model of a steel structure, being carried out at the NEES facility at the University at Buffalo.

The outcomes of the proposed research will be (a) a methodology for predicting sidesway collapse of

deteriorating structural systems, (b) an extensive database on deterioration properties of structural steel

and reinforced concrete components, including uncertainty measures accounting for modeling and

material uncertainties, (c) incorporation of component deterioration models in the OpenSees platform, (d)

documentation of a comprehensive collapse experiment with data that covers the range of response of a 5-

story steel frame structure from elastic behavior to incipient collapse, (e) a methodology for computing

the probability of sidesway collapse that accounts for hazard, ground motion, and structural (material,

modeling) uncertainties, and (f) engineering recommendations for design for collapse safety.

Intellectural Merit. The proposed research will lead to seminal advances in understanding and predicting

sidesway collapse of structures subjected to severe earthquakes. The major challenges are to account for

deterioration in structural behavior in combination with P-delta effect, and for the uncertainties inherent

in ground motion description and in modeling the behavior of the components that control the dynamic

response at large inelastic deformations (or at small deformations in the case of brittle elements). These

challenges imply extensive modeling efforts at the component and structure level and the incorporation of

reliability concepts in assessing collapse safety of structures. Another major challenge will be the

planning and execution of a shaking table collapse experiment, whose main purpose is to demonstrate that

collapse prediction indeed is feasible. The research involves an integrated approach of physical

simulations at a NEES site shaking table and computational simulations on the OpenSees platform, while

fully utilizing the simulation, visualization, and collaboration tools of the NEESgrid.

Broader Impacts on Earthquake Engineering Research and Practice. The research is motivated by

professional needs to provide adequate and consistent collapse safety in new designs and to assess the

collapse hazard of existing structures. These needs require the filling of knowledge gaps that exist in

regard to data and tools and the understanding of collapse phenomena. The impact of the proposed work

on research and practice will be the development of databases, advanced deterioration models, and

computational tools that will make it feasible to predict the collapse safety of complex structures and will

permit more rational allocation of resources in the context of performance-based seismic risk

management. The impact will be felt in the academic environment in teaching and research, in

engineering design offices, and in organizations concerned with risk management.

BOOKS/ONE TIME PROCEEDING

Lignos, D.G., and Krawinkler, H.. "A Database in Support of Modeling of Component Deterioration for Collapse Prediction of Steel Frame Structures", 10/01/2006-09/30/2007,  2007, "Proceedings, 2007 Structures Congress - Structural Engineering Research Frontiers; ASCE/SEI".

Lignos, D.G., and Krawinkler, H.. "A Database in Support of Modeling of Component Deterioration for Collapse Prediction of Steel Frame Structures", 10/01/2007-09/30/2008,  2007, "Proceedings, 2007 Structures Congress - Structural Engineering Research Frontiers; ASCE/SEI".

D.G. Lignos, H. Krawinkler and A.S. Whittaker. "Shaking Table Collapse Tests of Two Scale Models of a 4-Story Moment Resisting Steel Frame", 10/01/2007-09/30/2008,  2008, "Proceedings of the 14th World Conference on Earthquake Engineering".

Krawinkler, H., and Lignos, D.. "How to Predict the Probability of Collapse of Non-ductile Building Structures", 10/01/2007-09/30/2008, , Springer"Seismic Risk Assessment and Retrofitting of Existing Low-Rise Structures",  2009, "Seismic Risk Assessment and Retrofitting of Existing Low-Rise Structures - awaiting publication".

Lignos, D.. "Sidesway Collapse of Deteriorating Structural Systems Under Seismic Excitations", 10/01/2007-09/30/2008,  2008, "Ph.D. Dissertation, dept. of Civil and Environmental Engineering, Stanford University".

 

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