Research On The Fire Resistance Performance Of Bolt-connected Fabricated Beam-beam Joints

Due to its low cost,low noise,low pollution,high efficiency and other characteristics,prefabricated buildings have increasingly become an important form of building structure.For prefabricated buildings,the connection method of nodes is the most important factor affecting its fire resistance.The research in this paper is a new type of bolt-connected fabricated beambeam node.Its static and seismic performance have been studied,but the fire resistance is unknown.Therefore,it is necessary to study the temperature field and fire resistance limit of this node.This paper firstly establish 50 specimen models based on the ABAQUS finite element simulation software,simulate their fire conditions under the ISO-834 international standard heating curve,and obtain the temperature field distribution and heating characteristics of the bolt-connected fabricated beam-beam node and the influence of the thickness of the steel plate and the thickness of the concrete protective layer on its temperature field;then the thermalmechanical coupling of the model is carried out by applying a static load,and the fire time-midspan deflection curve of the joint is obtained.The analysis is carried out as the fire time increases,the growth characteristics of its mid-span deflection,as well as the influence of the bolt pre-tightening force,concrete strength grade,load ratio,bolt strength grade,concrete protective layer thickness and other parameters on the fire resistance of joints.Analyzing the simulation results:(1)When the node is exposed to fire,the temperature rise of the core connecting component bolts is relatively gentle,which is linear heating,which is beneficial to the structure’s fire resistance;but the overall temperature of the lower bolt is significantly higher than that of the upper bolt;the temperature in the middle of the bolt is significantly higher than At both ends of the bolts,this phenomenon should be paid attention to when designing the joints for fire resistance.(2)Increasing the thickness of the concrete protective layer has a certain effect on the decrease of the overall temperature of the node temperature field,and the effect of reducing the temperature of the bolt is obvious,which can be used as a means to improve the temperature field of the node.(3)The size of the load ratio,the concrete strength grade,and the thickness of the concrete protective layer have a greater influence on the fire resistance limit of the joint.The smaller the load ratio of the structure,the higher the concrete strength level,the thicker the concrete protective layer,and the longer the fire resistance limit of the joint.(4)Under the action of fire,when the joints are close to the fire resistance limit,they will deform continuously,and then reach the limit state of the structure,and the damage has certain predictability.(5)Considering the material cost and the influence of the studied parameters,it is recommended to use C30 concrete for this node with a concrete protective layer thickness of 35mm...