Experimental Study On Seismic Behavior Of Welded CHS T-joints Of High Strength Steel

High-strength steel is a kind of structural steel produced by micro-alloying and thermomechanical rolling technology,which is characterized by high strength(yield strength not less than 460 MPa),good ductility,toughness and workability.For some large steel tubular structures with large span or severe loading conditions,the strength and specifications of commonly used ordinary strength steel can not meet the requirements of structural stress and use,but the use of high strength steel can solve this problem well.However,the minimum yield ratio of high-strength steel is generally close to or greater than 0.80,and the yield ratio increases with the increase of strength grade,while the yield ratio is too high,which means that brittle failure often occurs when the structure or component fails.Therefore,Standard for Design of Steel Structures(GB50017-2017)and Code for Seismic Design of Buildings(GB50011-2010)(Edition 2016)have strict restrictions on the yield ratio of steel.Steel tubular joints are the key parts of high-strength steel tubular structures.The research on the mechanical behavior of steel tubular joints under cyclic loading is of great significance for the analysis of seismic performance,failure mechanism and seismic design of structures.In order to study the seismic behavior of welded CHS T-joints of high strength steel,the seismic behavior of Q460C high strength steel welded tubular T-joints was studied by experimental study and finite element analysis.The main research work is as follows:Fivewelded CHS T-joints of high strength steel with different geometrical parameters were designed and tested to study the hysteretic behavior of the joints under brace axial force.The failure modes,hysteretic curves,skeleton curves,energy dissipation and ductility of the joints were analyzed,and the effects of geometrical parameters on the hysteretic behavior of the joints were investigated.Considering the influence of chord length,boundary conditions,weld simulation and mesh generation on the hysteretic behavior of tubular T-joints,a high-precision finite element model was established to simulate the hysteretic behavior of welded CHS T-joints of high strength steel.At the same time,the validity of the model is verified by the experimental results.An extensive parametric study of welded CHS T-joints of high strength steel with braces subjected to axial cyclic loading and with braces subjected to in-plane cyclic bending has been carried out using finite element models validated by experiments.The effects of chord length,ratio of chord to brace diameter,ratio of chord radius to chord wall thickness and ratio of brace to chord wall thickness on the hysteretic curves,skeleton curves,ductility factor and energy dissipation factor of the joints are studied,and the influence laws of various factors on the hysteretic behavior of the joints are obtained.