Study On Seismic Performance Of Irregular Structures And Chinese And American Steel Structures Based On Collapse Analysis

The seismic collapse resistance of structures has received widespread attention and can be scientifically quantified by IDA-based collapse fragility analysis.In this paper,suggestions for the selection of ground motion input suitable for IDA are proposed,firstly.And then,the influence of plan and vertical irregularities on the collapse resistance of structures are systematically studied.Finally,IDA-based collapse fragility analysis is used to compare the seismic performance and collapse resistance of two groups of typical steel structures designed based on the Chinese and the U.S.code systems respectively.The main works of this study are as follows:（1）The suggestions for the selection of ground motion input suitable for IDA-based collapse fragility analysis are proposed and compared with the widely used ground motion selection methods at the present stage.The results reveal that the method proposed by this paper is not only easy to operate,but also can effectively reduce the dispersion in collapse fragility analysis.（2）The common rectangular,L-shaped and concave structures are selected as the research objects to study the influence of plan irregularities on the seismic performance and collapse resistance of structures.The time-history analysis results reveal that the plan irregularities have a limited impact on the seismic performance of the structures under the three seismic intensity levels of Chinese codes.The results of component damage analysis show that the damage of corner columns of the plan irregular structures is greater than that of the center columns,which means corner columns are more critical.The collapse analysis results reveal that the decline in collapse resistance of structures is limited,when the plan irregularity coefficient exceeds the limit of the standard,which shows that the requirements on the plan irregularity coefficient can be appropriately relaxed.（3）Two groups of typical RC structures（frame and shear wall structures）are selected as the research objects to study the influence of different story shear capacity ratios（Rv）on the collapse resistance of RC structures.The results reveal that the seismic performance and collapse resistance of RC structures will decrease with the increase of Rv.When Rv exceeds 1.5,the collapse resistance of structures will decline significantly.The seismic performance and collapse resistance of RC structures can be effectively improved by controlling Rv not to exceed 1.5.（4）Two groups of typical steel structures（steel moment frame and steel frame-braced core-tube structure）designed based on the Chinese and the U.S.code systems respectively,are selected as the res earch objects to compare the seismic performance and collapse resistance with the consideration of local buckling effect.The comparison results reveal that,under the same design conditions,both the strength requirement and deflection limit are critical factors that control the design outputs following the Chinese codes.However,the strength requirement is the primary factor that controls the design outcomes following the U.S.codes.Moreover,the collapse resistance of the steel moment frames from both codes are similar,but the material consumption based on the Chinese design code is comparatively higher.In contrast,the material consumption of the steel frame-braced core-tube structures are comparable,but the collapse resistance of the Chinese model is close to or lower than that of the US model.Furthermore,the collapse analyses indicate that the local buckling effect could significantly reduce the collapse resistance.