Study On Torsional Response Of Single-story Symmetric Frame Structure Subjected To Wave Passage Excitation

The study on the torsional response of symmetrical building structures subjected to seismic wave passage excitation has not been reported through analytical analysis and discussing the influence of excitation frequency on the torsional response of structures.In this paper,taking the single-story symmetric frame structure as the research object,the torsional response of the symmetrical structure is studied by considering the wave passage effect by means of theoretical and numerical simulation.Firstly,frequency influencing factors have been studied for the torsional response of single-story symmetric frame structure subjected to sinusoidal wave passage excitation.The equation of motion is established for the symmetric structure subjected to wave passage excitation.The analytical solutions of floor torque and column shear are presented by solving the equation of motion.The steady-state amplitudes of floor torque and column shear force are calculated for a single-story symmetrical reinforced concrete frame structure subjected to sinusoidal wave passage excitation under ground motion apparent wave velocities 1000m/s,2000m/s,3000m/s and 4000m/s,and are also compared with the corresponding results of uniform excitation.The analytical solutions and the calculating results show that the torsional vibration of floor and lateral vibration of columns in the unexcited direction as well as torsional resonance occur for the symmetric structure subjected to sinusoidal wave passage excitation.The steady-state amplitude of floor torque is related to the ground motion apparent velocity as well as the excitation frequency.The steady-state amplitude of column shear are not only related to the ground motion apparent velocity and excitation frequency,but also related to the square of the ratio of natural frequency of structure to excitation frequency.Besides the apparent velocity,the excitation frequency is also the main influencing factor on wave passage effect of symmetric structure.The lower excitation frequency shows more remarkable wave passage effect on the column shears for the excitation frequency within a certain range less than the natural frequency of structure.Secondly,the torsional response has been studied for single-story symmetric frame structure subjected to seismic wave passage excitation.The dynamic force equation of singlestory symmetric structure is discretized in time domain by Newmark method,and the discrete absolute displacement of dynamic force is solved.The floor torque and column shear force of single-story symmetric frame structure subjected to seismic wave passage excitation are given.The seismic waves RSN1108 Kobe,RSN15 Taft,RSN6 El-centro and RSN759 Loma-prieta are selected according to the site category.The floor torque and column shear force are calculated for a single-story symmetrical structure subjected to seismic wave passage excitation under ground motion apparent velocities 200m/s,400m/s,600m/s and 1000m/s,and are also compared with the corresponding results of uniform excitation.The calculatingresults show that the torsional vibration of floor and lateral vibration of columns in the unexcited direction as well as torsional resonance occur for the symmetric structure subjected to seismic wave passage excitation.Compared with the uniform excitation,the column shear force of the symmetrical structure increases significantly subjected to seismic wave passage excitation in the excited direction.The floor torque and the column shear force in the unexcited direction of the symmetrical structure subjected to uniform excitation are zero.The floor torque and the column shear force in the unexcited direction of the symmetrical structure subjected to seismic wave passage excitation are significant.Finally,the torsional response of single-story symmetrical frame structure subjected to seismic wave passage excitation is studied by using ABAQUS software.Using the separate modeling method,the single-story symmetrical reinforced concrete frame structure is modeled by ABAQUS software,and the natural vibration characteristics of the single-story symmetrical structure are analyzed.Adjust seismic waves according to the situation of rare earthquakes.The column lateral displacement and column shear force are calculated for a single-story symmetrical frame structure subjected to seismic wave passage excitation under ground apparent wave velocities 200m/s and are also compared with the corresponding results of uniform excitation.At the same time,the Mises stress diagram of the structure is studied.The results show that the column lateral displacement and column shear force in the excitation direction of the single-story symmetrical structure subjected to seismic wave passage excitation are more significant than those subjected to uniform excitation.The column lateral displacement and the column shear force in the unexcited direction of the symmetrical structure subjected to uniform excitation are zero.There are large column lateral displacement and column shear force in the unexcited direction of the symmetrical structure subjected to seismic wave passage excitation.The stresses in the Mises stress cloud images of symmetrical structures subjected to wave passage excitation and uniform excitation are mainly concentrated at the base of columns and beam-column top joints,and the maximum stress values of structures subjected to wave passage excitation are greater than the calculated results under uniform excitation.The single-story symmetrical frame structure subjected to seismic wave passage excitation is significant.