Progressive Collapse Analysis Of Long-span Steel Truss Structure Subjected To Vertical Large Load

With the rapid development of China's economy,large space structures are more and more widely used due to their beautiful appearance and reasonable force,such as stadiums,railway stations,industrial buildings and so on.Due to the large space structures has a large number of people and involves large assets,under the influence of earthquake,snow disaster,construction design defects,human error accidents or other factors,the single or partial space structures member is instability or strength failure,space structures progressive collapse is caused,it will cause unpredictable losses to people's lives and assets.Therefore,it is necessary to consider the progressive collapse resistance of large space structures.In this paper,an actual engineering is taken as the research object,and the analysis model is established by MIDAS GEN finite element software,the progressive collapse analysis of long-span steel truss structure subjected to vertical large load is carried out by using alternate path method.The main research content of this paper:(1)On the basis of summarizing the related research on the progressive collapse of building structures at home and abroad,selecting the method from the existing building structures progressive collapse resistance analysis method and the parameter of failure model for the research object of this paper;(2)An actual engineering is taken as the research object,the progressive collapse analysis of the residual structures is carried out by the full-dynamic equivalent load unloading method of considering the initial state,the effects on its truss members,adjacent truss members and the overall structure of different types of truss members and columns failure are studied,and the strength criterion and deformation criterion are combined to evaluate the progressive collapse resistance of residual structures;(3)The applicability of long-span steel truss structure subjected to vertical large load is studied according to the current standard of China about the dynamic increase factor,and exploring the dynamic increase factor's influencing factor of similar structures with this research.The following conclusions were obtained:(1)The component importance analysis results with the response of truss members stress and node vertical displacement have the same law,the key members are concentrated in the architectural sketch area(area of subjected to the vertical large load),top chord at the middle column support,lower chord at the middle column and side column support,vertical web member has the smallest importance coefficient;(2)After vertical web member and lower chord at the middle column support fails,only partial truss members will enter the yield situation,no progressive collapse occurs;after top chord at the architectural sketch area(area of subjected to the vertical large load)and diagonal web member near the support fails,local progressive collapse occurs;(3)Since the integrity of steel truss is not damaged,the integral rigidity of roof truss is large,only a small part of truss members are yielded under corner column and internal column failure,and no truss members are yielded under long side column failure,no progressive collapse occurs in these failure conditions;the deformation of short side middle column failure is large,more truss members are yielded and a small part of truss members are strength failure,local progressive collapse occurs;(4)The number of members entering the yield situation or strength failure under the column failure condition is less than the failure condition of truss members,the reason is that steel truss is not damaged and integral rigidity is large;(5)For the research object of this paper,the calculation results of linear static analysis is too large when dynamic increase factor is taking 2.0,when the dynamic increase factor of nonlinear static analysis is taking 1.35,the calculation results of corner column,short side middle column and internal column failure is too small,and the calculation results of long side middle column failure is too large;(6)When the damping ratio is in the range of 0.02?0.04,the influence on the dynamic increase factor is not obvious;(7)The equivalent load unloading time has a certain influence on dynamic increase factor,failure time is taking 0.1s can reflect the maximum dynamic response of residual structures and meet the calculation accuracy requirements under corner column failure.