This paper presents a probabilistic damage analysis method to generate seismic fragility curves of structures. Uncertainties in earthquake and structure are quantified by evaluating uncertainties in parameters that define the earthquake‐structure system. The uncertainty in each parameter is characterized by several representative values that are selected considering the uncertainty range of the parameter and its use in engineering practices. Samples of structures and earthquake motions are constructed from the combination of these representative values, then the Latin hypercube sampling technique is used to construct the samples of earthquake‐structure system. For each sample, the nonlinear seismic analysis is performed to produce response data, which are then statistically analyzed. On the other hand, five limit states representing various degrees of structural damage are defined and the statistics of the structural capacity corresponding to each limit state can be established. The fragility curve is gen...

Probabilistic Damage Analysis of Structures

Performance-based assessment and design of squat reinforced concrete shear walls

Results from a series of experiments designed to measure the stiffness of low-aspect-ratio, reinforced-concrete shear walls subjected to simulated seismic inputs on a shake table are reported. The geometry of the test structures allows them to be modeled as single-degree-of-freedom systems. Forces were estimated from accelerometer measurements on masses attached to the structures. Dynamic relative-displacement measurements were obtained from groups of strain gages wired in series to act as one continuous gage. Because this method measures relative displacements, potential sources of error associated with unspecified base motion are avoided. tiffness values determined from the relative displacement measurements were compared with stiffness values determined indirectly from frequency-response functions. Measured, accelerometer data were used to calculate the frequency-response functions. The stiffness values determined from the relative-displacement measurements gave results similar to those given by mechanics-of-materials beam theory that accounts for shear deformation. The stiffness values determined from the frequency-response functions were considerably less than those from the theory.

Measuring the stiffness of concrete shear walls during dynamic tests

A summary of available data concerning the structural response of low-rise shear walls is presented. These data will be used to address two failure modes associated with shear wall structures. First, the data concerning the seismic capacity of the shear walls are examined, with emphasis on excessive deformations that can cause equipment failure. Second, the data concerning the dynamic properties of shear walls (stiffness and damping) that are necessary for computing the seismic inputs to attached equipment are summarized. This case addresses the failure of equipment when the structure remains functional.

Failure Modes of Low‐Rise Shear Walls

An extensive analysis of previously measured seismic response data from the Seismic Category I Structures program was made to determine if reduced stiffness linear models can be used to predict the response of damaged nuclear power plant structures Four structures ranging from one to three stories were analyzed for three different peak acceleration inputs All inputs were scaled versions of the 1940 El Centro earthquake measured at the base of the test structures during shake-table testing Comparisons between measured and analytically predicted responses were made in terms of floor response spectra Stiffness in the analytical models was adjusted to obtain a match in frequency and damping was adjusted to obtain a match in amplitude Results showed that the reduced-stiffness linear models could accurately predict the response of the damaged structures and these results were consistent with the response observed during static cyclic testing of similar structures Changes in damping with excitation levels are also discussed In addition to the analysis of the seismic response data, the stiffness of these structures was analyzed by a variety of methods currently used by industry and the stiffness values were compared with the values in the analytical models that best fit the measured responsemore » 10 refs, 73 figs, 5 tabs« less

Use of linear reduced-stiffness analytical models to predict seismic response of damaged concrete structures

The accomplishments of the Seismic Category I Structures Program for FY 1986 are reported The background leading to the FY 1986 Program Plan is summarized and the design of a new geometric configuration of a reinforced concrete shear wall test structure is described The report discusses static and seismic testing of two of these structures, a 1/4-scale, 1-in-thick shear wall model of microconcrete and a 4-in-thick shear wall prototype Results and conclusions regarding degrading stiffness characteristics, natural frequencies, and scalability of microconcrete with actual concrete are compared with past fiscal year results Possible base rotation effects for the large structure are examined analytically Finally, tentative conclusions are stated regarding the degrading stiffness and scaling of these structures and recommendations are made about future seismic testing of large structures 11 refs, 28 figs, 9 tabs

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The Seismic Category 1 Structures Program: Results for FY 1985

Two scale-model structures representing an idealized auxiliary building were seismically tested. The scales (1/42, 1/14) were chosen so that both structures were models of the prototype, and the 1/42-scale model was a 1/3-scale model of the 1/14-scale structure. Both models were constructed out of microconcrete. The 1/42-scale used wire mesh to simulate reinforcing, and the 1/14-scale used model deformed bars. The general result verified previous test experience in this program: the frequency response of these structures, when subjected to seismic design loads, will be below that predicted for the structure using conventional analysis methods. This implies the frequency content and magnitude of floor response spectra, in general, will not be as predicted from the structural analysis. The implication of this result for equipment and piping is under investigation. The recommendation of this program, based on testing thus far, is to verify the conclusions on larger real concrete structures of a geometry that will be agreed upon by the technical review group for this program. 5 refs., 17 figs., 7 tabs.

W.E. Dunwoody

Papers

The Seismic Category 1 Structures Program: Results for FY 1985

Simulated seismic tests on 1/42- and 1/14-scale category 1, auxiliary building

Latest results from the seismic category I structures program