12.07.2015 Views

Report - PEER - University of California, Berkeley

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ON DRIFT LIMITS ASSOCIATED WITH DIFFERENT DAMAGE LEVELSAhmed GHOBARAH 1ABSTRACTPerformance objectives in performance-based design procedures have been described in severalways according to the operational status <strong>of</strong> the structure or the level <strong>of</strong> damage sustained up tocollapse. The selection <strong>of</strong> the appropriate drift associated with different levels <strong>of</strong> damage forthe design is significant in terms economy and safety. The identification <strong>of</strong> drift levelsassociated with different states <strong>of</strong> damage remains one <strong>of</strong> the unresolved issues in thedevelopment <strong>of</strong> performance objectives in performance-based design and assessmentprocedures. The objective <strong>of</strong> this study is to develop the approach to establish the drift <strong>of</strong>different structural systems that is associated with different definable levels <strong>of</strong> damage to use asperformance objectives in the design <strong>of</strong> new structures and the evaluation <strong>of</strong> the seismicresistance <strong>of</strong> existing structures.Analytical and experimental data were used to examine the correlation between drift anddamage <strong>of</strong> various structural elements and systems. The analytical procedures included timehistoryanalysis, dynamic and static pushover analyses <strong>of</strong> various designs <strong>of</strong> reinforcedconcrete walls and moment resisting frames. Recently conducted tests as well as availableexperimental research results in the literature are reviewed for the appropriateness andconsistency <strong>of</strong> the data. The experimental work included static and dynamic testing <strong>of</strong> wallsand frame components.It was found that the drift associated with various damage levels <strong>of</strong> different reinforcedconcrete elements and structural systems vary significantly. Two main sets <strong>of</strong> drift limits weredefined for ductile and nonductile structural systems.Keywords: Performance-based design; Performance objectives; Drift; Damage; Momentresisting frames; Walls.1. INTRODUCTIONEarthquakes continue to cause substantial damage and loss <strong>of</strong> life in many parts<strong>of</strong> the world. Although many buildings designed to current codes did not collapseduring recent earthquakes, the level <strong>of</strong> damage to structures was unexpectedly high.In addition to the high cost <strong>of</strong> repairs, economic loss due to loss <strong>of</strong> use wassignificant. Conventional methods <strong>of</strong> seismic design have the objectives to providefor life safety (strength and ductility) and damage control (serviceability drift limits).1 Department <strong>of</strong> Civil Engineering, McMaster <strong>University</strong>, Hamilton, Canada321

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