Capacity Evaluation of MDOF Systems Subjected To Near-Fault Ground Motion Pulse

Student: Chethan Gouder
Supervisors: Prof.A.Papageorgiou


This study aims at investigating the applicability of an improved ATC-40 Procedure-A suggested by Chopra and Geol to structural systems subjected to a set of near-fault ground motion pulse. The improved ATC-40 Procedure-A is also known as capacity spectrum method, which is a nonlinear analysis technique to evaluate the capacity of structural systems. For this purpose, constant ductility design spectra proposed by Papageorgiou and Mavroeidis for regions having near-fault effect are used to generate demand diagrams which are plots of spectral acceleration vs. maximum displacement. The structural systems used are SAC Three Storey Pre-Northridge buildings designed for three different regions; Los Angeles, Seattle and Boston. Capacity curves are obtained for three different structural systems. P-Delta effects have been included in the analysis.

The capacity of all structural systems for different earthquakes is obtained as the point of intersection of the capacity diagram and demand diagram. The results obtained from capacity spectrum method are compared with time history analysis results. The input for time history analysis are a set of near-fault ground motion pulses generated using the mathematical model suggested by Papageorgiou and Mavroeidis.

The comparison of results obtained from capacity spectrum method and those obtained from time history analysis revealed that the capacity spectrum method gives good results in most of the cases except a few .The discrepancies in results obtained exist due to the impulsive nature of near-fault ground motion.

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