Experimental Research On Welded Haunch Reinforced Of Box Strengthen-joint Region Connection For Weak Axis Of I-section Column Under Monotonic Loading

A lot of brittle fracture of steel frame beam-column joints happened in previousearthquake reveals the disadvantages of traditional steel frame connections.research for nodeimprovement mainly concentrated in the strong axis.However,it is important of that strongaxis connections of I-section column in a steel frame as same as same as weak axisconnections,while the analysis theory and detail design are more difficult.There is also nocode requirement.In this case,The associate professor of The Chang’an University,Dr.LuLinfeng provided a box strengthen-joint region of beam-column connections,and he did a lotof research for this.This paper is introduced a new type of beam to column connection jointwith beam stiffener node based on the new connection details.It also solved the problem thatit is very hard to get the requirement of plastic deformation in the traditional weak axial withfix joint.The selected frame node was studied to explore the basic mechanical properties andthe effect of composite slab for the node properties was also investigated for further study.There were4full-scale specimens in this paper.Two of them are normal weak axisconnections without any treatment at the end of beam and with corresponding combined slabjoints,the other two are node with stiffener in the lower flange and the correspondingcomposite slab node.The specimens were designed according to the current Code of Chinaand refer to America Code FEMA351.The load-displacement curve,bending moment-route angle curve,shearstress-deformation curve through beam mono-loaded test shown that initial route stiffness,andyield displacement and limit load,plastic angle,ductility and other basic mechanicalfactors.The stiffness are classification,while contrast analysis has node zone,Mongolian skinBoard and key member along the width direction of beam.the conclusions are following:1. The location of plastic hinge can be effectively controlled due to beam stiffener.Theprimary route stiffness can be increased,the welding stress between beam column are reducedthe ULS (ultimate limited state) capacity of joint will increase41.2%.2. The max.plastic rotation angle in four specimens are larger than0.03rad,rotationductility are greater than4,they are good deformation and plastic rotation capacity.Theseismic design requirements can be satisfied. 3. The new connections of weak axis in the node zone to the local box-strengthen.Thiswill improved mechanical properties of the joint region.However,there is shear deformationhappen in the joint region,but the strong node properties was shown.4. The classification criteria for joint stifness according to EC3can be used todetermine the joint with stiffener is rigid.But normal specimens are semi-rigid connections inthe unbraced frame case.5. There is insufficient reinforcement anchorage in the design of slab so that there is notgood behavior between slab and steel frame.It need to consideration of combination of theslab in the actual condition.The above research results are not only in practical engineering application,but alsoprovide information for further research improvement of joint details and weak axialconnections.These research results not only in practical engineering application has the certainreference value,but also to further research the modified node connection,improving the weakaxis connection content provides a test basis.