【正文】 0 .1 0 0 .0 8 0 .0 6 0 .0 4 0 .0 2 0 2 4 6 8 10 12 displacement (cm) 0 .0 0 0 2 4 6 8 1 0 1 2 1 4 1 6 dis p la cem ent (c m ) Rectangular Triangular IBC A and B site classes C site class D site class R e c ta n g u lar Trian g u la r IB C A a n d B s ite c la s s es C s ite c la s s D s ite c la s s a) 3Story Frame b) 5Story Frame 0 2 4 6 8 10 12 14 16 18 20 displacement (cm) 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 displacement (cm) Rectangular Triangular IBC A and B site classes C site class D site class Rectangular Triangular IBC A and B site classes C site class D site class c) 8Story Frame d) 15Story Frame Figure 6. Pushover and Nonlinear Time History Results of 3, 5, 8 and 15story Frames 。 ABSTRACT The objective of this study is to evaluate the performance of the frame structures or various load patterns and variety of natural periods by performing pushover and nonlinear dynamic time history analyses. The load distributions for pushover analyses are chosen as triangular, IBC (k=2) and rectangular. Four different framed structures are used, which are typical reinforced concrete (R\C) frame systems and have four different natural periods. Even though the nonlinear dynamic time history analysis is the best way to pute seismic demands FEMA273 and ATC40 proposes to use of nonlinear static procedure or pushover analysis. This paper is also intended to pare the results of pushover and nonlinear dynamic time history analyses. To evaluate the results from the pushover analyses for three load patterns and also four natural periods, nonlinear dynamic time history analyses are performed. Earthquake ground motions recorded at 50 stations during various earthquakes overall the world are used in the analyses. Pushover and nonlinear time history analyses results are pared to choose the best load distribution for specific natural period for this type of frame structure. Keywords: Pushover analysis, nonlinear time history, load patterns, momentresisting frame INTRODUCTION Only the life safety and collapse prevention in general earthquake resistant design phenomena are explicitly prevented in seismic design codes. The design is generally based on evaluating the seismic performance of structures. It is required to consider inelastic behavior while evaluating the seismic demands at low performance levels. FEMA273 and ATC40 use pushover analysis as nonlinear static analysis but nonlinear time history analysis has more accurate results on puting seismic demands (ATC40, 1996, FEMA273, 1997). The purposes in earthquakeresistance design are: (a) to prevent nonstructural damage in minor earthquakes, which may occur frequently in life time, (b)to prevent structural damage and minimize nonstructural damage in moderate earthquakes which may occur occasionally, (c) to prevent collapsing or serious damage in major earthquakes which may occur rarely. Designs are explicitly done only under the third condition. The objective of this study is to evaluate the performance of the frame structures for various load patterns and variety of natural periods by performing pushover and nonlinear dynamic time history analyses. 3, 5, 8 and 15 story R\C frame structures are used in the analyses and the load distributions for pushover analyses are chosen as triangular (IBC, k=1), IBC (k=2) and rectangular, where k is the an exponent related to the structure period to define vertical distribution factor (IBC, 2020). The four frame structures have been analyzed using nonlinear program DRAIN2D (Prakash, V., Powell, G., Campbell, S., 1993) and the results have been pared by recorded response data. Both nonlinear static pushover analysis and nonlinear dynamic time history analysis are performed. The correlations between these nonlinear analyses are studied. The performance of the buildings subjected to various representative earthquake ground motions is examined. Finally, pushover and nonlinear time history analyses results are pared to choose the best load distribution (pattern) for specific natural period for these types of reinforced concrete frame structures. GROUND MOTION DATA For this study, it is considered as 50 different data used in the nonlinear dynamic time history analyses, given in the Table 1. All the data are from different site classes as A, B, C and D. The shear velocities for the site classes A, B, C and D are Vs 750 m/s, 360m/s to 750 m/s, 180 m/s to 360 m/s, and 180 m/s, respectively. The ground motion data are chosen from different destructive earthquakes around the world earthquake name, date of earthquake, data source, record name, peak ground accelerations (pga) for the ponents, effective durations and fault types for each data are presented in the Table1., respectively. The peak ground accelerations are in the range to , where g is acceleration due to gravity. All ground motion data are recorded in nearfield region as in maximum 20 km distance. DESCRIPTION OF THE FRAME STRUCTURES 3, 5, 8 and 15story R\C