LAUSR

Structural pounding can lead to local or total damage to the stories at the collision level or to the overall collapse of the building. On the other hand, lateral stiffness irregularity is common in the form of soft or very soft stories, which is due to the alternation in the type of function of the first story of the building. This paper estimates the demand for the normalized separation gap (NSG) at adjacent buildings highest collision level that were a combination of regular and irregular frames. For this purpose, the steel moment resisting frames (MRF), compounds with a total of 700 adjacent states and their NSG, is calculated by the dynamic time history analysis. In addition, irregularity increment in lateral stiffness for the first story could lead to an increase in the NSG of 84% of the adjacent combinations. In this study, a new relationship is proposed to estimate the demand for the NSG with the consideration of the effects of irregularity of lateral stiffness in the lowest story.