Studies On Mechanical Behavior Of Extra-Large And Extra-Thick Cold-Formed Rectangular Steel Tube

Cold bending sectional steel is a high efficient,economic,and environmentally friendly building materials.It has reasonable section shape,good mechanical properties and high utilization rate of steel,which has wide application prospects in the modern construction.At home and abroad,the study of cold bending sectional steel is mainly concentrated in the cold-formed thin-walled steel.Study of cold bending thin-walled steel is more perfect,and systematic regulations and guidelines are issued.With the progress of cold bending technology and large engineering construction,the demand of cold bending thick-walled steel is growing.But researches of mechanical properties and design methods for the cold bending of thickwalled steel,especially the super cold bending thick-walled l steel research is relatively lack.Therefore,combining with the Tianjin million square steel structure projects,through full scale test and numerical simulation,systematic studies are made for axial compression performance and bias performance of the large super thick-walled cold bending rectangular steel tube,and the following conclusions have been made:1)Through a large amount of material test,the cold hardening effect of large super thick-walled cold bending rectangular steel tube material is obvious.Material has yielding steps,but the ductility have reduced.Basic meet the elongation of " code for seismic design of buildings "(GB50011-2011),which is not less than 20%.But for individual materials of the steel tube used in the test is not meet the requirements of elongation is 20%.2)Axial compression test of two sets of large super thick-walled cold bending rectangular steel tube had completed.Testing bearing capacity is around 2100 tons,is 1.27 times of calculation section strength 1654 tons for Q235 B material strength design value,and 87.5% of the ultimate strength 2400 ton with material test to calculate the intensity of cross section.Due to the material test specimen from the original shape will release some of the residual stress,it is normal phenomenon that the value is slightly lower than the calculated one.The load strain curve again points that the large super thick-walled cold bending rectangular steel tube has yielding steps and certain ductility.3)Using ABAQUS finite element software,the finite element analysis model of large super thick-walled cold bending rectangular steel tube has established.And axial compression test data demonstrate verified the effectiveness of the model.After validation of numerical analysis model,axial compression performance and bias performance have been studied of large super thick-walled cold bending rectangular steel tube.The analysis results show that,large super thick-walled cold bending rectangular steel tube has better axial compression performance and bias performance.