| Frame structures are widely used in public buildings such as schools,hospitals and office buildings because of their good seismic performance and flexible layout.Flexible spatial arrangement often leads to irregular plane of structure,large eccentricity increases torsional effect of structure,and aggravates seismic damage of frame structure in earthquake.Shear failure of beam-column joints on the first floor of frame structures is prone to occur during earthquakes.Under larger earthquakes,corner-column and sidecolumn joints are destroyed prior to mid-column joints.Therefore,it is of great engineering significance to study the torsion effect law of frame structures under earthquake and the failure mechanism of joint regions.Taking the torsional seismic damage of four frame structures as an example,the influence of plane irregularity on the seismic capacity of structures is emphatically analyzed.Then,from three aspects of plane irregularity judgment criteria,torsional design methods and structural measures,the article compares the changes of the provisions on controlling structural torsion in Seismic design code for industrial and civil buildings(TJLL-78),Code for seismic design of buildings(GBJ11-89),Code for seismic design of buildings(GB50011-2001)and Code for seismic design of buildings(GB50011-2010).Then a series of frame structure models with different eccentricities were designed based on the government office building of Jiange County in Sichuan Province during the Wenchuan Earthquake.Structural design was carried out in strict accordance with current codes.The corresponding numerical model was established by Abaqus and the elasticplastic time history analysis was carried out.Considering the adverse effect of the filled wall on the torsional effect of the frame structure,the filled wall was established.The finite element model is used to study the torsion effect and seismic performance of eccentric frame structures.At the same time,taking Lushan Middle School frame teaching building as an example,the stress distribution of beam-column joints in the first floor of frame structure under different earthquake magnitude,the similarities and differences of failure states of different beam-column joints under earthquake and the influence of volume ratio of horizontal stirrups in the joint area on the failure of the first floor frame structure joints are studied.In this paper,the following research results are obtained: firstly,the influence of eccentricity on the inter-story displacement angle and torsion angle of the structure is explored.Based on the working conditions set in this paper,the influence degree of eccentricity increment on inter-story displacement angle and inter-story torsion angle is quantified;secondly,based on ABAQUS elastic-plastic damage model,the seismic weak position of frame structures with different eccentricity is analyzed,and the influence of eccentricity on thin structure is analyzed.The influence of eccentricity on the maximum compressive strain of three types of columns is quantified.Thirdly,the influence of eccentricity on the maximum compressive strain of three types of columns is proposed.Thirdly,the lateral stiffness and load-bearing capacity of corner columns are improved by increasing the cross-section size of corner columns and increasing the concrete strength of corner columns,and then the seismic and torsional performance of the structures are improved.Two methods are analyzed quantitatively.Fourthly,the stress distribution of beam-to-column joints on the first floor of frame structures under different levels of earthquake and the similarities and differences of failure states of different types of beam-to-column joints are studied,and the influence of volume ratio of horizontal stirrups on the failure state of beam-to-column joints is quantitatively analyzed. |
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