Seimic Failure Mechanism And Design Recommendations Of Cover-plate Reinforced Box Strengthen-joint Region Connections Of I-section Column For Weak Axis

Box strengthen-joint region moment connection in the weak axis of I-section column is a new type of weak-axis column bending connection of steel moment frames,which is designed on the seismic design idea of high ductility and high bearing capacity.The finished experiment and finite element analysis of weak-axis connections in fringe frame joint have preliminarily showed that the new weak-axis column bending connection has better seismic performance.Compared with steel moment frame with box-shaped column,steel moment frame with H-shaped column using the new beam-to-column connection has better economic benefits in structural engineering.A cover-plate reinforced box strengthen-joint region moment connection in the weak axis of I-secion column was tested under cyclic loading.And the seismic performance of the specimen,such as the failure mode,the hysteretic behavior,the ductility and the energy capacity was studied.The finite element models considering damage to the structure were established by ABAQUS and the nonlinear analyses were performed.The critical parameters that influence the seismic performance of the connection were analyzed to determine the reasonable value of parameters.Moreover,the design method of the connection is put forward according to the experimental study and finite element analysis.The rationality and reliability of the design method are verified by the actual property.The results of the experimental study and finite element analysis are summarized as follows:1.The cover-plate reinforced box strengthen-joint region moment connections can make plastic hinges relocate effectively,and the stress at the weld of beam and column were reduced to avoid premature brittle failure.The hysteresis curve of the joint are full fusiform,which shows good capability of energy consumption.But displacement ductility coefficient is lower than 3 due to fracture of welding.2.Shear deformation occurred in joint region loading process,however,the stress were being elasticity deformation,marking by ‘strong joint region' feature.3.The thickness of the skin panel has significant influence on the seismic performance of the joints.Thus,it should be ensured to satisfy the design requirements of the minimum thickness of the skin panel.4.The shape of cover-plate has little impact on the performance of joints,while the length and thickness are key factors.Thus,the rectangular cover-plate is selected first,the length is recommended as 0.5~0.7 times beam depth,and the thickness should not be less than 0.5 times thickness of beam flange or 6mm.5.The changes of beam-column linear stiffness ratio has obvious influence on the performance of joints,but the linear stiffness for beam and column has big difference on law and extent of affection.The beam-column linear stiffness ratio should be controlled less than 1.5.6.This paper puts forward a design method that is proved to be reasonable and reliable for the new type of weak-axis beam-column bending connection,and provides technical basis for engineering applications of this kind of connection.