Synthesis Of Rotational Components Of Ground Motion And Dynamic Elastoplastic Analysis Of Curved Girder Bridge Under Earthquake Action

With the gradual progress of seismic observation technology,people have realized that the ground motion contains not only three translational components but also three rotational components,and began to study the rotational components of ground motion and its influence on building structures.Due to the difficulty in using the rotating component observation equipment,the synthetic rotating component of ground motion is still a common method to obtain the rotating component in engineering field.With the rapid development of China’s social economy,curved-continuous girder Bridges,which are widely used in expressway Bridges and on-ramp Bridges,are becoming more and more popular.However,the influence of rotational component of ground motion on spatial asymmetric structure of curved-continuous girder Bridges is not considered in the seismic code of China’s highway Bridges.To this end,the following work has been carried out:1.Seven actual ground motion translational components are selected based on the basic principle of the body wave decomposition method,and the body wave decomposition method is used to synthesize the ground motion rotational components,and the Fourier spectrum analysis and acceleration response spectrum analysis are performed on them.The following are the primary conclusions:(1)The horizontal component of the ground motion’s translational component is rich in frequency ranges of 0.5Hz-2Hz,whereas the vertical component is rich in 1Hz-10 Hz.The amplitude of the swing component is greater than that of the torsional component;the rotational component is rich in frequency bands of 1Hz-50 Hz and contains more high-frequency components than the translation component,especially in the frequency band above 10Hz;and the swing component’s average amplitude is greater than that of the torsional component.(2)The rotational component has more short-period components,with a structural period of less than 0.1s when the spectral angular acceleration reaches its peak value,which is closer to the vertical component’s response spectrum,and the horizontal component’s response spectrum has more long-period components;it is more discrete than the translational component’s response spectrum,and the rotational component’s response spectrum of differen.2.A refined finite element model based on the SAP2000 finite element platform was established to study the influence of the ground motion rotational component on the dynamic elastic-plastic response of the curved continuous girder bridge,and the translational component conditions,rotational component conditions,and sixcomponent ground motion conditions were analyzed.The following are the primary conclusions:(1)The dispersion coefficient of the average value of structural response of curved continuous beam bridge under the action of seismic rotation component is large.Considering the rotation component will increase the dispersion coefficient of the average value of structural response of curved continuous beam bridge under the action of six seismic components and reduce the representativeness of the average value of structural response.(2)The rotating component of ground motion has a significant impact on the curved continuous girder bridge’s seismic response.It is simple to underestimate or exaggerate the response of the structure during earthquake action if the rotating component is not taken into account.Considering the rotational component of the internal force of the pier bottom,the maximum pier bottom shear force of the side pier will increase,up to 25.5percent;the maximum pier bottom bending moment of the middle pier will be reduced,up to-16.2 percent;and the maximum pier bottom torque of the middle pier will be increased,up to 64.33 percent.(3)Under the action of the rotational component,the maximum reaction of the members of the curved continuous girder bridge differs from that under the action of the translational component.The position of the structure’s maximum reaction will change after considering the rotating component of the ground motion.(4)The sway component of ground motion plays a significant influence in the majority of structural reactions of continuous curving girder bridges,while the torsional component has little effect on other responses save the pier bottom torque.3.In order to study the sensitivity of ground motion rotation component to the center angle and pier height of curved continuous beam bridge,eight models with different center angles are established under the condition of keeping the pier height and span unchanged,and eight models with different pier heights are established under the condition of keeping the center angle and span unchanged.The dynamic elastoplastic response of the structure and the influence law of the rotation component on the structural response under the rotation component condition and the six component ground motion condition.The main conclusions are as follows:(1)When the central angle is too large,the ground motion rotational component will increase the partial response of the curved continuous beam bridge.For example,when the central angle is 120°,the ground motion rotational component will make the side piers(1# pier and 5# pier)the largest pier bottom The shear force increases by 9.91%and 9.05% on average,and the maximum increases by 16.63% and 25.5%;the rotation component of ground vibration will also increase the partial response of the curved continuous beam bridge when the central angle is too small.For example,when the central angle is 15°,The rotational component of the ground motion increases the maximum pier bottom torque of the middle pier(3# pier)by 72.89% on average and125.77% at the maximum.Therefore,it is suggested that the influence of the ground motion rotational component on the structural response should be considered for the curved continuous girder bridge with each central angle.(2)When the pier height is too low or too high,it is more likely that the rotational component of the ground motion will increase the structural response.For example,when the pier height is 45 m,the maximum pier bottom shear force of the 4# pier increases by 43.32% after considering the rotational component.increased by 30.90%;the maximum pier bottom bending moment increased by 38.55% and the average increased by 22.52% after considering the rotational component.For example,when the pier height is 10 m,the maximum pier bottom torque of the 3# bridge pier increases by87.30% and 34.19% on average after considering the rotational component.