| Based on degenerated three-dimension solid virtual laminated element theory,a space frame test under vertical load and a space frame test with special shaped column under horizontal load are simulated.The comparison between the simulation results and the experimental results shows that the theory and method have enough feasibility and accuracy of finite element analysis in Frame Structures.According to this method,the nonlinear finite element analysis of multiple RC frames considering the spatial interaction of beam-slab-column is carried out.According to the seismic fortification intensity,four different seismic grade frameworks were designed,and the effect of "strong column and weak beam" of frames with slab were evaluated separately,it was concluded that under rare earthquakes RC frames of seismic grade 2 based on 7 seismic fortification intensity and seismic grade 1 based on 8 seismic fortification intensity can achieve the expected effect of "strong column weak beam" while seismic grade 4 and 3 based on6 seismic fortification intensity can not fully or almost impossible to realize the "strong column weak beam" seismic design mechanism.Then,the frame of seismic grade 3 is used as an example to explore the reason that it can not achieve the "strong column and weak beam";ways to improve the bottom frame column reinforcement ratio and the reinforcement ratio of the bottom and the upper column are improved at the same time are adopted.The results show that the plastic hinges of frame beam in the lower layer first appeared,which accelerates appearance of the plastic hinges of the bottom frame column,and then lead to the increase of the bending moment of frame column in the upper layer.The improvement of the reinforcement ratio at the bottom of the column can delay the generation of the plastic hinges of the bottom column and improve the ultimate bearing capacity of the frame,but it has negative influence on column hinges in the upper layer and the reinforcement ratio of the bottom column is not as high as possible.The column bottom and columns in the upper layer enhanced synchronously in order to achieve the "strong column weak beam" mechanism,and the enhancement coefficient can be based on the layer position using different values.Based on the grade 3 framework,the control variable method is used to transform the thickness of slab,the bottom reinforcement ratio and the roofreinforcement ratio of slab,their influences on mechanical properties of frame,especially influences on the "strong column weak beam" are studied.The results show that with the increases of slab thickness,the bottom reinforcement ratio and the roof reinforcement ratio of slab,the bearing capacity and displacement of the frame are increased but it have a negative impact on the "strong column-weak beam".And the impact of three factors from large to small were the roof reinforcement ratio of slab,the bottom reinforcement ratio of slab,the thickness of slab.By analyzing the stress of the slab and the beam,some conclusions are obtained,such as,the degree of participation of the slab reinforcement is related to the level of the load,the type of the node in which the slab is located,the span of the beam;the closer the slab reinforcement is to the beam,the higher the degree of participation;The degree of reinforcement at the top of the slab is higher than that of the bottom of the slab,and the participation of the slab reinforcement in edge node is higher than that in the middle node and so on. |
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