Study On Progressive Collapse Resistance And Strengthening Measures Of Bidirectional Beam String Structure Under Fire

As a semi-rigid semi-flexible hybrid structure,Beam String Structure is widely used in airports,gymnasiums,conference centers,storage facilities and other large-span and even oversized-span buildings because of its advantages of self-weight,reasonable force,rich and beautiful shape,and is a kind of structure form that has developed rapidly in recent years.The whole material of Beam String Structure is mostly steel,although the steel is non-combustible material,but its mechanical properties with the temperature increase and reduce,when the temperature reaches 500 degrees,the elastic modulus of steel is less than 2/3of the room-temperature,which is prone to damage in the fire,Beam String Structure transmission path is simple,low redundancy,local components after damage easy to spread,serious when the structure will collapse continuously.At present,the analysis of the anti-collapse performance of the two-way Beam String Structure is mainly the method of dismantling the components,and the accidents that cause structural damage are usually ignored,even if the accidents are mainly considered under the conditions of impact,explosion,earthquake and sudden failure of the corrosion effect of rod parts,the study of the anti-continuous collapse performance of the two-way Beam String Structure and the measures of anti-continuous collapse reinforcement under fire conditions are less involved.This paper summarizes the analysis methods and research results of the anticollapse properties of steel structures and the anti-fire properties of steel structures at home and abroad,and summarizes the methods of structural thermal analysis and the physical characteristics and mechanical properties of steel at high temperatures.Taking the thermal heating curve of the fire fire in the practical large space building as the heating model,the cross-sectional temperature field of the components of the Beam String Structure is analyzed,and the stretch ingon test is carried out at high temperature for the key component of the Beam String Structure called cable,and the loss of rope force under the high temperature of the steel strand is explored and the effect of the initial defect on the loss of the steel stranding clue force.In view of the characteristic Beam String Structure under the accidental load called fire,considering the effects of nonlinear structure and material nonlinearity,the anti-continuous collapse performance of the Beam String Structure in the whole process of fire was analyzed on the basis of the multiload path method.Using finite element analysis software ANSYS to establish a two-way Beam String Structure model and a force model that acts together with the loading and temperature load,Using ANSYS's unit life-and-death function to simulate the multi-load path method to simulate the whole process of fire attack on the two-way Beam String Structure,Exploring the effect of fire source position,support rod number,pole crosssection and other factors on the structural anti-continuous collapse performance,and proposing several strengthening measures for the continuous collapse of the tensile beam structure to meet the strengthening requirements and with the minimum amount of steel as the target,select the appropriate strengthening measures scheme to provide a suggestion for the fire-resistant design of the Beam String Structure.This paper has 50 graphics,table 14,55 references...