ارزیابی روشهای تخمین تغییرمکان جانبی واقعی ساختمانهای بتنی در برابر زلزله

Abstract
For seismic design, it is important to estimate the, maximum lateral displacement (inelastic
displacement) of the structures due to earthquakes for several reasons. Seismic design
provisions estimate the maximum roof and storey drifts occurring in major earthquakes by
amplifying the roof displacement and drifts of the structures obtained by elastic analysis
subjected to seismic design load, with a coefficient named “displacement amplification
factor” which is greater than one. Here, this coefficient depends on various parameters such
as ductility factor and overstrength factor. The present research aims to evaluate the value of
the displacement amplification factor in seismic design codes and then tries to propose a new
value as displacement amplification factor to estimate the maximum lateral structural
displacement due to severe earthquakes. In seismic codes, since the displacement
amplification factor is related to “force reduction factor”, hence; this aspect has been
accepted in the current study. Meanwhile, two methodologies were applied to evaluate the
value of displacement amplification factor and its relation with the force reduction factor. In
the first methodology, which is applied for all structures, the ratio of displacement
amplification and force reduction factors was determined directly. Whereas, in the second
methodology that is applicable just for the R/C moment resisting frames, the ratio was
obtained by calculating both factors, separately. The results were alike and both of them
could estimate the ratio of the two factors from 1 to 1.2. The results also indicated that the
ratio of the displacement amplification factor and the force reduction factor differs to those
proposed by seismic provisions such as NEHRP, IBC and Iranian seismic code (Standard no.
2800).