Elastic-plastic Analysis Of Frames Based On The Vertical Torsional Component Of Multidimensional Ground Motion

Along with the high development of urban construction, people’s requirements on thearchitectural aesthetics and function are improving continuously, the appearance of the buildingform is transforming from the regular matchbox to the rich and diverse styles, and more andmore complex and asymmetric building structures has emerged. Plenty of research andearthquake disaster show that only taking unidirectional earthquake into account when designingthe structure is not safe, multi-dimensional seismic wave should be considered. At present, therehas been some research about the response of the structure under the bidirectional seismic, butlittle research about vertical seismic torsional component, this is mainly due to the currentlimited observation level, and it’s difficult to get it. The researchers mostly deduced torsionalcomponent from the existing translation component, and about how much influence seismictorsional component on the structural hasn’t form a complete research system.In this paper, two sets of regular and irregular rectangular column frame structure modelswith different length-width ratio are built, then selects EI seismic wave and wenchuan seismicwave adjusted as the seismic wave that dynamic time history analysis need, then putbidirectional and torsional, bidirectional, and Y direction unidirectional seismic wave into themodels respectively. After that, the paper analyzes the elastic-plastic response of translationalreaction, torsional response, internal force and hysteretic characteristics of all the models in orderto obtain the influence that multidimensional nature of the ground motion (including seismicvertical torsion component) has on the two sets of regular and irregular frame structure with thedifferent length-width ratio. The main conclusions got are as follows:1. The translational and torsional time-history curves of the structure are similar to thetime-history curves of the seismic acceleration; there is a close relationship between the seismicresponse and the characteristic of the frequency spectrum of seismic waves, and the closer seismic predominant period is to the structural basic period, the more severe response.2. Compared with unidirectional seismic action, under multi-dimensional seismic action thestructural translation displacement, torsion angle and the internal force increase obviously.Compared with bidirectional seismic action, when considering the vertical torsion component,structural translation reaction has little change, torsional response increases obviously, andinternal force also has a certain degree of increase.3. The influence seismic vertical torsion component on the long frame structure is muchmore than the short frame structure, and irregular frame structure much more than the regularstructure. In some cases, long regular frame structure is more dangerous than the short irregularstructure under the same earthquake, therefore, structural should not too long in the seismicdesign of structures.4. Seismic vertical torsion component has more effect on the bottom of the structure, andthe higher the less effect, the greatest effect on the corner column, for the irregular “L” shapestructure, remote corner column is the largest, side column followed, and minimum effect on thecenter column. In the seismic design we should pay attention to strengthen the weak layer at thebottom and reinforcement and structural requirements of the corner column.