MORE EFFICIENT SHEAR BUILDING MODEL OF ECCENTRICALLY BRACED FRAMES

Both structural and nonstructural damage sustained during earthquake ground motions are primarily produced by lateral displacements. Thus, the estimation of lateral displacement demands is of primary importance in performance-based earthquake-resistant design. Nonlinear time history analysis of a detailed analytical model may be the best option for the estimation of deformation demands. However, there are many uncertainties associated with the generation of site-specific input and with the analytical models presently employed to represent structural behavior. In many cases, the effort associated with detailed modeling and analysis may not be feasible; therefore, it is prudent to have a simpler analysis tool in order to assess the seismic performance of a frame structure. In this Paper the reliability of the pushover analysis has been verified by conducting nonlinear dynamic analyses on 5, 10 and 15 story EBF frames. It is shown that pushover analysis with predetermined lateral load pattern provides questionable estimates of inter-story drift. To overcome this inadequacy, a multistory frame is reduced to an equivalent shear building model. It is shown that the introduced shear building model can estimate the deformation demand of structures more exactly than nonlinear static procedure.

Keywords:

Shear building model , Time history analysis , Pushover analysis , eccentricallybraced frames