Study On The Response Of Earthquake Torsion Component To Eccentric Structure

Earthquakes occur frequently in the world,some of which are large in scale and have a wide range of impacts,which have brought great harm to human society.Earthquake prediction and prevention is an important means for human to mitigate earthquake disasters.It is necessary to use the knowledge of seismology,geology and other disciplines to study and analyze the earthquake motion,and it is also necessary to combine the knowledge of civil engineering disciplines to strengthen the earthquake resistance of buildings and infrastructure.An earthquake produces three translational(two horizontal and one vertical)and three rotational(two swaying and one torsion)motions in the ground.At present,most scholars have studied the influence of the three translational components of ground motion,but there are few studies on the influence of the three rotational components.The actual engineering earthquake damage shows that the rotational ground motion may be significant in some cases,even surpassing the translational ground motion,and it is more likely to cause greater torsional damage to irregular building structures.The reason for the torsional vibration of the structure is the torsional ground motion or the asymmetry of the structure itself.These two factors will cause the structure to produce a response different from that of a symmetrical structure under the input of translational ground motion.Therefore,it is necessary to study the response of eccentric structures under rotational ground motions.In this paper,a 5-story steel frame seismic and isolation scale model is designed for shaking table tests.Input the response of the rotational seismic wave observation structure.And use abaqus software modeling to compare the time history curve of shaking table test,verify the feasibility and accuracy of abaqus modeling and rotational wave input.Then design the seismic structure with one-way mass eccentricity and two-way mass eccentricity of the superstructure with four eccentricities of 0%,5%,10% and 15%.Design the isolation structure with four eccentricities of 0%,3%,10% and 15% for the one-way isolation layer stiffness eccentricity and the two-way isolation layer stiffness eccentricity.Then input the translational seismic wave,torsional seismic wave,translational plus torsional seismic wave respectively,and analyze the dynamic response of the seismic structure and the isolation structure under the action of non-pulse and pulsed earthquakes.The main conclusions drawn are as follows:(1)When there is eccentricity in the structure,the acceleration,interstory displacement,displacement of the isolation layer,torsion angle of the interstory and the torsion angle of the isolation layer all increase with the increase of the eccentricity.However,the interstory shear force will decrease with the increase of eccentricity.(2)In the case of the same eccentricity,the acceleration,interstory displacement,displacement of the isolation floor,torsion angle between the floors and the torsion angle of the isolation floor in the case of translation plus torsion are larger than those in the case of translation.The interstory shear force of the aseismic structure under the condition of translation plus torsion is greater than that under the condition of translation.The interstory shear force of the isolated structure under the condition of translation plus torsion is smaller than that under the condition of translation.(3)Under translational conditions,for the seismic structure with eccentric mass and the seismic isolation structure with eccentric stiffness of the isolation layer,the interstory torsion angle and the isolation layer torsion angle of the unidirectional eccentric structure are larger than those of the bidirectional eccentric structure.It shows that when the two-way eccentricity is positive eccentricity and the ground motion input is positive input,the torsional effect of the structure will be suppressed.(4)In the fortification earthquake,when the eccentricity of the isolation layer is 3% under the translational condition,the maximum increase of the acceleration,interstory displacement,interstory torsion angle and interstory shear force of the superstructure is 5.87%.At this time,it is recommended that the eccentricity requirements can be appropriately relaxed if the requirements of various specifications are met,but it should not exceed 10%,because at an eccentricity of 10%,the maximum increase of the structure can reach 15%.In the case of translation plus torsion,the eccentricity of the isolation layer is recommended not to exceed 3%.