Research On The Mechanical Behaviors Of Steel Frames With High-strength Bolts And Extended Endplate Considering Semi-rigid Connections

With regard to semi-rigid steel frames with high-strength bolts and extendedend-plate connections, this paper mainly probes into the mechanical behaviors of thestructures, the nonlinear properties of the beam-to-column connection nodes. Someimprovement strategies are put forward for design of the end-plate connections insteel frames. The major contents and results are as following:1. The expansion inelastic matrix equations in the beam units and the columnunits are deduced in the nonlinear analysis of steel frames, and then an example wasadopted to testify the theoretic conclusions.2. From the principle of energy, the governing equations for determining theeffective length factor of column in un-braced steel frames with semi-rigidconnections are derived, considering the effects of the nonlinear moment-rotationcharacteristics of beam-to-column connections. The effects of various beam endconditions and column far end conditions are also considered.3. The amendatory stiffness factor method is wielded to explore the mechanicalbehaviors of the single-span single-layer, double-span, double-layer and double-spanmultilayer steel frameworks under different initial nodal stiffness compared with theresults of finite element analysis.4. To examine difference of the semi-rigid capability in the different nodes,twelve nodal models have been processed by means of the nonlinear analysesrespectively comparing their node stiffness, stress distribution in the interface,distortion and prying on the end-plate.5. The paper also analyzes the influence of the change of end-plate thickness, thedifferent array of the bolts and the bolts diameter on the mechanical behavior ofsemi-rigid joints by finite element analysis.The results show that the end-plate thickness, the spacing between bolts and thebolts diameter have great influence on the capacity of nodes. When the end plate andthe bolts simultaneously achieve the ultimate bearing capacity, the stress of boltsinside beam flange exceeds the bolts outside beam flange. While the mechanicalbehaviors of the end-plate joints are calculated, the tensile force of the high-strength bolts reaches to 10%～50% of the ultimate bearing capacity because of prying action.Therefore, the effect of the prying action must be taken into consideration.The results of this dissertation provide a good reference for actual projectdesigns as well as a theoretical foundation to compile the relevant design codes.