Mechanical Behaviors Study On Space Frame Structures In Fire

In modern time, space frame structure is one of the most widely used structure style in space structures. Most of these structures are constructed by steel members and joints. However, the steel members share poor fire-resistant performance. So these structures will be damaged or even collapse under fire. And the further research of fire-resistance performance of these structures is very necessary.According to the thermal parameters of steel specified in the EC3, the experiments and numerical simulations on the fire performance of the welded hollow spherical joints that are normally used in these structures were firstly performed. Then the nonlinear finite element analysis on space frame structures under fire was studied in the present dissertation. The main research contents are as followings:(1) Experimental investigation on the compression performance of welded hollow spherical joints in fireBased of the standard fire temperature-time curve ISO 834, the experiments and numerical simulations on the fire performance of the welded hollow spherical joints that are normally used in these structures were firstly performed. The temperature field, the displacement and the failure modes of the joints are studied. And according to the experimental temperature curve, the nonlinear finite element analysis on the joints is simulated. The numerical results and the test results are researched, they are consistent. The results verified that the analysis method and the parameters selection are correct, and provide theoretical basis for the study on the fire performance of space frame structures.(2) Study on the mechanical performance of welded hollow spherical joints in fireBased of the standard fire temperature-time curve ISO 834, the fire performance of the welded hollow spherical joints is simulated. The distribution law of the temperature fields and the influencing factors of the ultimate fire resistant duration about joints are analyzed. By analyzing the stress and displacement variation characteristics of the hollow spherical joints under fire, their failure modes and the weakness area of the joint under fire are determined.(3) Mechanical properties study on space grid structures under fireBased on the utility temperature elevation empirical formula in large space, the nonlinear finite element analysis of the fire performance on one space grid structure is numerically simulated systematically and comprehensively with the thermal parameters of steel specified in the EC 3. The temperature fields, the stress and the displacement properties of the structure are studied under different local fire. The ultimate states of the structures are found, and the influencing factors of the ultimate states about the structures are analyzed, including different fire model and different structural parameters. The limit state of bearing capacity on the structure is decided, and some advices are given in the fire-resistant design of space grid structures.(4) Mechanical properties study on space reticulated shell structures under fireBased on the utility temperature elevation empirical formula in large space, the nonlinear finite element analysis of the fire performance on one space reticulated shell structure is numerically simulated systematically and comprehensively with the thermal parameters of steel specified in the EC 3. The temperature fields and the displacement properties of the structure are studied under different local fire. The ultimate states of the structures are found, and the influencing factors of the ultimate states about the structures are analyzed, including different fire model and different structural parameters. The limit state of bearing capacity on the structure is decided, and some advices are given in the fire-resistant design of space reticulated shell structures.Above of all, the mechanical performance of welded hollow spherical joints and space frame structures under fire are studied, their fire resistant properties are known comprehensively, the research results can provide theoretical basis for the fire-resistant design of space frame structures in future.