Evaluation of Steel Braced Frames under Vertical and Horizontal Components of Near Field Earthquake

In the common practice design of structures, Often the effect of vertical component of earthquake is ignored, but this component is important parameter especially in near field Earthquakes. The objective of this paper is study the effect of vertical and horizontal component of earthquake ground motion in steel braced frames. First verification of numerical models through finite element software package (ABAQUS) is carried out. Comparison of the result of load displacement curve for numerical and experimental model shows matching result. After this, two concentrically braced frames with X-configuration are selected from previous researches. Four earthquake records have been used for this study. Kobe, Northridge, Tabas and Imperial Valley. Two components of earthquake are applied simultaneously to frames under nonlinear time history analysis. The results that extract from the analysis content of vertical and horizontal displacement of roof and plastic dissipated energy during earthquakes. the intensity of the former parameters is depend of earthquake intensity and frequency content of them. Assessing the result reveal that in the three story frame, the ratio of maximum vertical displacement to maximum horizontal displacement is crucial parameter with respect to seven story braced frame. Also the time of plastic energy dissipated for frames is short because of nature of near field earthquake.