Elastic-plastic Analysis Of Lattice Shells Under Rare Earthquake Considering Compression Bar Post-buckling

To analysis the dynamic behavior of the lattice shell structure in the earthquake, the damage of bar and combining work of the upper and lower parts of structures should be considered. In this paper, the equivalent elastic-plastic bar mode considering the yielding of tension link and the buckling of the compression bar is built up. And the dynamic responds of the lattice shell in the rare earthquake are further researched with this new model. In the calculation of the vertical response of the whole modeling of long-span roof structure in the earthquake using the response spectrum analysis, It is pointed out that there exist some limits using the traditional modal mass participation factor to determine the model numbers and its reasonable forms are discussed. The paper includes three main parts of researches as follow:(1) this paper determines the buckling load and post buckling path of compression bar with the initial bending deformation and builds up the equivalent relationship of material modeσ-ε. The relationships between the relative node displacement of axial force member and slenderness ratio, the axial force and slenderness ratio are established and the simple material modeσ-εis defined accordingly, using which realizes the geometrical and material nonlinear in the buckling process of compression bar.(2) the equivalent material mode and ideal elastic-plastic material model are applied to a lattice shell to calculate the dynamic response under the seismic action respectively and the difference is compared. The weaknesses of members and zones of the lattice shell designed by normal code under the rare earthquake are found out and reinforced, and the reference of refinement and reinforcement are supplied accordingly. It is find that inner force distributions of the lattice shell show the disagreement according to traditional designing and under the rare earthquake respectively, and some members near the supports and some members with lower inner force analyzed using the shell theory would buckle easily.(3) In the vertical response analysis of the whole modeling of long-span roof structure in the earthquake, it is found that the demand for modal mass participation coefficient up to 90% in traditional Code could not be achieved. This is because the stiffness and quality of the supporting system are far greater than those of the upper roof system, which requires a higher frequency vibration load to excite the lower part of supporting systems to vibrate. Therefore, the concept of local modal mass participation factor is defined in this paper and examples of sphere and cylindrical lattice shell structures are calculated and prove that the local modal mass participation factor is more reasonable comparing with the traditional one.