Study On Judging The Collapse Of Q460 Gantry Frame

The application of high-strength steels is currently gaining popularity both at home and abroad.Therefore,the study of its seismic performance become increasingly important.However,little research has been done on the seismic performance and collapse of high-strength steel components or structures,and there are no provisions for earthquake resistance and collapse of Q460 and higher strength steels in the specifications.Based on this,for research purposes of the conditional decision,the collapse of portal frames has been reported with numerical simulation and theoretical analysis methods.The main research work is as follows:1.To verify the correctness and scientific of the model,finite element simulation was performed on the existing test,using ABAQUS finite element analysis software,based on the material damage constitutive and implicit algorithm of element deletion and on the basis of defining the mechanical properties of Q460 high-strength steel material.2.As the main load-bearing member of the portal frame,the seismic performance of the column has an important impact on the collapse of the structure.In this paper,48 I-shaped and box-section members with different axial-to-pressure ratio,flange width-thickness ratio,web-height-to-thickness ratio,and wall-to-thickness ratio are designed and tested under low cyclic loading.The results were compard and analyzed,and the following main conclusions were obtained:The experimental results are analyzed and calculated,and the recommended values corresponding to the limit displacement angle of Q460 column are given.The I-shape is 0.028,and the box type is 0.035;It is recommended that the width-thickness ratio limit of the flange in seismic design should not exceed 9(the specification should not exceed 7.1),and the ratio of web thickness to thickness should not be too large;The stiffness decreases with increasing axial compression ratio during loading.The greater the ratio of flange width to thickness and the lower ratio of web height to thickness,the larger the initial stiffness,but the more severe the stiffness degradation.Therefore,reasonable cross-sectional dimensions should be selected in engineering design;The ductility coefficient is 4 compared to the ordinary steel column,while the ductility coefficient of Q460 is only about 2;For the specimens with different flangewidth to thickness ratios,the difference in energy dissipation coefficient is not particularly noticeable.The greater the ratio of the thickness to the thickness of the web(I-shaped)and the wall thickness ratio(box type),the smaller the apparent energy dissipation coefficient.3.The Q460 portal frame is simulated under reciprocating load,its seismic performance and failure process are analyzed.Based on this,for the purpose of determining the conditions for the collapse of the Q460 steel structure,the structure of the portal frame with 16 different axial-to-axial ratios was constructed,the results are as follows:Based on the criterion of maximum interlevel drift angle,the proposed value of the Q460 girder frame collapse is 0.04.Compared with the conclusion of the column simulation experiment,the elastoplastic limit displacement angle 0.02(1/50)is used as the Q460 structure in the code.The displacement angle at the time of collapse is too conservative;based on the cumulative plastic ductility criterion,the recommended value at collapse is 14;based on the equivalent energy dissipation factor criterion,the recommended value at collapse is 44.