Evaluation of Accuracy of Simplified Methods of Analysis and Design of Buildings with Damping Systems for Near-Fault and for Soft-Soil Seismic Motions

摘要

This report assesses the validity of the simplified methods of analysis and design of buildings with damping systems specified in FEMA's National Earthquake Hazard Reduction Program Recommended Provisions for Seismic Regulations for New Buildings and Other Structures issued in 2000 and updated for 2003, and the upcoming ASCE-7 Standard for 2005 when the effects of near-field and soft-soil ground motions are taken into account. The procedures outlined in these documents are largely based on studies that excluded these effects. To determine their impact, both single- and multidegree- of-freedom structures with linear and nonlinear viscous damping devices were studied using two sets of near-field ground motions and one set of soft-soil ground motions. The study found that the damping coefficient values are accurate or conservative$ the ductility demand for near-field and soft-soil motions are very similar to those previously observed for far-field motions$ simplified methods of analysis for single-degree-of-freedom systems produce results on displacement and acceleration that are generally of acceptable accuracy or conservative for near-field or soft-soil motions and are very similar to that previously observed for far-field motions$ and their application to steel moment frames with linear and nonlinear viscous damping systems provided conservative estimates of drift and predictions for damper forces and member actions in good overall agreement with the average of results of nonlinear response-history analysis.