Evaluating the effect of masonry infi lls on natural period of buildings with moment-resisting frame‡

摘要

Building design codes generally provide empirical formulas for estimating the fundamental period. Thesenformulas are developed on the basis of observed periods of real buildings during ground motion, and thenperiod is generally expressed as a function of building height, type (frame or shear wall), etc. In this study,nthe fundamental period of vibration of a series of regular steel-framed buildings is studied using fi nitenelement modelling and modal eigenvalue analysis including the effect of infi ll. It has been found that whennthe models do not include infi ll, the period given by the analysis is signifi cantly longer than that predictednby the codes equation. However, when the effect of infi ll is included in the models, the time periods determinednfrom eigenvalue analysis were remarkably close to those predicted by the code formulas. The fi ndingnof the study has shown us a practical way to determine the fundamental period of steel frames using rationalnapproaches like modal analysis. After an evaluation of the results, a modifi ed formula has been proposednfor estimation of natural period of steel buildings with moment-resisting frame system having infi ll. Usingnthe proposed formula, we can estimate natural period of this kind of structural systems more accuratelynthan the one approximated by code formula. Copyright © 2009 John Wiley & Sons, Ltd.