Estimation Method of Inelastic Displacement Demands of Moment Resisting-Frame Buildings in Moderate Seismic Zones

摘要

The growing trend of performance-based engineering has set an imperative request for assessment of displacement, as characterization of damage, in the seismic design process. This paper proposes an adjustment of the code-estimate of inelastic displacement for structures in Cairo which represent the highest seismic risk in Egypt because of its high population density even though it is located in a moderate seismic zone. The employed estimation method is based on the conventional force-based-design procedure of equivalent static load adopted by the Egyptian code, with a relaxation in the imposed limits on the spectral acceleration and the fundamental period used in determination of the design base shear, and also with an adjustment of the proposed value for displacement amplification factor (DAF) used to modify the displacement resulting from an elastic analysis to its inelastic counterpart. Rigorous inelastic time-history analyses using a commercial package for fiber-element-modeling are performed on varying-heights RC moment-frames and the results are compared to those of equivalent static load method to reach an accurate ratio of inelastic to code-calculated elastic displacement. Real un-scaled ground motion records are used and selected to reflect the seismological features and soil type of Cairo while simultaneously match the code-prescribed response spectrum. To test the reliability of the proposed DAF's, the sensitivity of the results to building model assumptions and configuration is studied. The results show that the recommended method provides closer estimates of displacement demands to actual ones than the current design-code while highlighting any limitations related to the sensitivity factors.