Experimental And Theoretical Analysis Of Exterior Composite Joints With Large Size Double Web Angles And Top-and-seat Angles

On the premise of vigorously promoting assembly building in China,steel structure has the characteristics of light weight,high strength,convenient construction and high reuse rate.Top-and-seat angle connection with double web angles has good assembly performance.The study of top-and-seat angle connection with double web angles cann't ignore the composite effect of concrete slabs on the structure.At the same time,in order to better match the bearing capacity requirements of the joints,large-sized angle will be applied in engineering practice.Therefore,the structure of large-size angle connecting steel beam,column and concrete floor in composite frame is called composite joints with large size double web angles and top-andseat angles.The main purpose of this paper is to study the mechanical properties of exterior composite joints with large size double web angles and top-and-seat angles,including the following studies:(1)Reading a large number of domestic and foreign literatures,this paper summarizes the top-and-seat angle connection,top-and-seat angle connection with double web angles and composite joints with angle,including the classification of connections,mechanical properties of this type connections and so on.(2)Cyclic loading tests were carried out on four composite joints with large size double web angles and top-and-seat angles.The moment-angle curves of the joints were obtained by beam-end loading tests and the experimental phenomena were described in detail.The seismic performance of composite joints,including ductility,energy dissipation capacity,strength degradation and stiffness degradation,is analyzed based on the experimental data.(3)Finite element modeling based on the size of composite joints is conducted.The validity of finite element simulation is verified by comparing the results of finite element simulation with the experimental results.At the same time,the stress of each component of composite joints is analyzed and compared.(4)Based on the validity of the numerical model,the numerical model is established by changing the key parameters of the composite joints,and the mechanical properties of the composite joints are compared,which provides the basis for the design proposals of the composite joints.(5)Based on the experimental and numerical analysis,a initial rotational stiffness models of composite joints with large size double web angles and top-and-seat angles under sagging and hogging moments is proposed by a revised component method.Through the above work,experiments and theoretical studies are carried out,and the following important conclusions are obtained:(1)The moment-angle curves of composite joints with large size double web angles and top-and-seat angles show obvious pinching effect,which is mainly due to the obvious slip effect of web angle steel and large-size angle steel in the direction of bearing shear force.(2)In the case of neglecting the upper confined concrete,the composite joints of largesized angle steel are adopted both up and down,which have the strongest energy dissipation capacity and can still meet the seismic design requirements of special bending steel frames in American AISC seismic design code.(3)Welding longitudinal steel bar in floor can effectively improve the stiffness and bearing capacity of joints under negative bending moment.(4)Under the action of positive bending moment,the local bearing capacity of concrete slab in composite joints is more effective than that of large angle steel in improving the flexural and ultimate bearing capacity of joints.(5)For large-sized angle steel composite joints,adding stiffeners to top and bottom angle steel can significantly improve the stiffness and ultimate bearing capacity of the joints,and the ductility of the joints is good.Therefore,it is suggested to add stiffeners to large-sized angle steel in engineering examples.