| Domestic and foreign research on the problem of progressive collapse pays more attention to the progressive collapse performance of structures.From the whole process,the progressive collapse ability of structures subjected to accidental loads(explosion,impact,earthquake,fire,etc.)is relatively small,especially the progressive collapse problem of structures under earthquake.In the field of structural reliability theory,there are many studies on the ultimate state of bearing capacity and normal service limit state of structures,while the current research on the third ultimate state of "progressive collapse limit state" is almost blank.In view of the insufficiency of the above-mentioned research on progressive collapse,this paper uses finite element analysis and reliability calculation method to analyze the reliability of progressive collapse and the redundancy of progressive collapse of typical spatial steel frames under earthquake,taking the space steel frame structure designed in accordance with the current codes of our country as the research object.The main contents of each chapter are as follows:(1)Seismic reliability analysis of structures: the lateral collapse resistance of structures under earthquake is analyzed from two aspects of bearing capacity and deformation capacity,and the failure components of structures are determined.Firstly,based on uncertain random variables of structure,Latin hypercube sampling is used to generate random samples of structure;ABAQUS software is used to build finite element model;ultimate state equation of bearing capacity and ultimate state equation of deformation capacity are established;probability of local failure of structure is obtained by seismic reliability analysis of components,and failure structure of structure is determined by combining target seismic reliability.Pieces.The results show that with the increase of earthquake action level,the reliability index of beam-column component decreases greatly,and the structure becomes more unsafe;the side-span beam-column is the most disadvantageous in the lateral member of the structure,and the possibility of failure under large earthquake is the greatest;the reliability index of bearing capacity of beam-column component under large earthquake action is less than 3.2,and the range of variation is about 1.0-3.2;and the deformation of the structure under large earthquake action is about 1.0-3.2.The reliability index of capability is less than 1.43,the range of variation is between 1.0 and 1.43,and that of failure components is between 0.9 and 1.4.(2)Reliability analysis of progressive collapse of structures: including reliability of progressive collapse condition and total probability of progressive collapse after local failure.Based on the determinate failure components,the non-linear dynamic demolition component method is used to analyze the progressive collapse of the structure;the limit state equation of the progressive collapse of the structure is established;the reliability analysis of the progressive collapse condition of the damaged structure is carried out by using the reliability method;and then,according to the total probability theorem,combined with the risk of earthquake action and the reliability of the failure components,the seismic action of the structure is analyzed.The total probability reliability of the progressive collapse is obtained.The results show that the reliability index of progressive collapse condition is less than 2.3,and the reliability index of progressive collapse condition is greater than that of progressive collapse condition considering seismic risk,and the reliability index of progressive collapse condition is greater than 4.7.Considering that the maximum probability of progressive collapse under all failure modes is 8.5532 x 10-06,which is slightly less than the limit of collapse probability,the steel frame structure designed according to the code has a general ability to resist progressive collapse.(3)Redundancy analysis of structure against progressive collapse: Based on conditional reliability and total probability reliability of structure after local failure,redundancy index of structure and component against progressive collapse is established to quantitatively analyze the capability of structure against progressive collapse and reasonable load transfer path.The results show that the redundancy index of progressive collapse is less than 1.9 in all failure modes,and the range of variation is between 1.6 and 1.9.According to the objective reliability of catenary mechanism,the degree of exertion of beam mechanism and catenary mechanism of frame beam connected with failure point after component failure is judged.Because the corner column does not have catenary mechanism,the ability of progressive collapse resistance of structure after failure is the worst.The variation range of redundancy index of frame columns after load transfer is between 1.0 and 1.2. |
