| The reinforced concrete slab-column structure has so many advantages such as saving space, high flexible layout, easy construction,so that it is widely used in practical engineering.But without beams,stress concentration in slab-column joints is more serious,prone to brittle punching failure.Therefore the study of slab-column connections under vertical loads is very necessary. In the past,the research focused in the punching shear capacity of slab-column connection,with less attention to the deformation of slab-column connection under vertical load.In 2008,Muttoni proposed a method to obtain the final punching capacity and final deformation by crossing the load-deformation demand curve and capacity curve,and the formula of demand curve, capacity curve are given. By this method,one can obtain the final bearing capacity and deformation as well,But the demand curve for this method is deduced by limit equilibrium theory, there are unreasonable assumption in the derivation process. Finite element simulation method is used to obtain more accurate and reasonable load-displacement demand curve. Previous slab-column connection finite-element analysis mostly used only one finite element model, did not compare different models of finite-element,and the number of the components is small,lack of the comparation of different groups of slab-column connections,lack of the finite-element model parameter discussion of different component parameters.In this paper, two kinds of finite-element simulation methods are applied as ABAQUS solid element model and grid-beam model, and the selected representative 56 experimental components of 5 groups are simulated and analyzed.The paper discusses the model parameters with different component parameters,then obtains more accurate load-deformation demand curves,then obtains the failing point of the demand curve by using the capacity curve of Muttoni.At last,the paper discusses the influence of different component parameters to the bearing capacity and deformation of the slab-column connections under vertial loads.To obtain better demand curves of the load and displacement,this paper analysises the 56 slab-column connections of 5groups by the two methods a s the ABAQUS solid element model and grid beam model.Then discusses the influences of different finite-element model parameters to the simulation results.After that,the paper find out the failure point of the demand curves by Muttoni capacity rules.Compare the two finite-element methods.Then,the paper discusses the connection parameters by the grid-beam model.The main conclusion as below:(1) The solid element model of ABAQUS can give a good simulation to the compoents with low steel ratios.but for the high steel ratio components,its results is not so good beacuse the simulation curves will fall down in the later part.If making the damage factor of compression in the falling part of stress-strain curve smaller,the simulation results will be better.(2) The grid-beam model can give a good simulation result for components with low steel ratio as well as high steel ratio.The A-1 grid pattern is the best.As to the yield curvature coefficient,for components with low steel ratio it can be 2.0,for components with high steel ratios it can be 1.6,then the results will be better.(3) The two finite-element models both can give good simulations.Even though the solid element model looks better,but the grid beam model has unique advantages such as high computational efficiency and so on.(4) Through the parameter analysis, it is found that the compressive strength of concrete cubes, washed away ratio, longitudinal reinforcement ratio and yield strength have a great influence on the punching shear bearing capacity and deformation. |
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