Finite Element Analysis Of Reinforced Hollow High Strength Concrete Filled Steel Tube Short Columns Under Axial Compression

Hollow concrete-filled steel tubular(CFST)structure is widely used in power transmission and transformation towers because of its advantages such as light weight,simple fabrication process,high degree of industrialization,good seismic and impact resistance.However,the concrete-filled hollow steel tube structure still has the disadvantages of low bearing capacity and brittle failure.These shortcomings make it not widely used in building structures.In order to improve this situation,this paper improves the hollow concrete-filled steel tube structure,including the arrangement of steel bars in its interior,the limitation of its interior hollow area,the increase of the steel strength of the exterior steel tube and the strength of the interior concrete,etc.,and carries out the finite element analysis to explore its mechanical properties.Combined with the existing research and the structural form of reinforced hollow steel tube high-strength concrete short columns under axial compression,the suitable material constitutive relation,contact form and grid division are selected,and the finite element analysis model is established.The failure modes of reinforced hollow steel tube high-strength concrete circular members and square members are analyzed,the stress stages are divided,and the inner surface,outer surface,section and middle section of each component material are analyzed The surface stress nephogram shows the change of axial stress on the inner and outer surfaces of sandwich concrete and tubular concrete along the height direction,and the change of interaction relationship between steel tube and concrete along the height direction.The failure process and stress change of circular and square members are obtained.The influence of the parameters on the load displacement curve and the load sharing level of concrete is quantified.From the above analysis,it can be concluded that:(1)the circular component starts to be damaged from the upper and lower 1 / 2 of the hollow part of the pipe column concrete,and the failure trend extends to the end and the middle of the pipe column concrete.After the failure of the pipe column concrete,the middle of the sandwich concrete reaches the maximum stress,and the failure trend is transmitted from the middle to both ends,and then the whole component is damaged.(2)the square component is damaged first from the middle of the column concrete and the middle of the sandwich concrete slab area,and the failure trend develops from the middle to the end,from the slab area to the corner area,and then the whole component is damaged.(3)with the increase of each parameter,the ultimate bearing capacity of members can be increased.(4)for circular members,when the steel related parameters increase,the concrete load sharing decreases,and when the concrete related parameters increase,the concrete load sharing increases.For square members,increasing the strength of steel tube has no significant effect on the load sharing capacity of concrete members.Increasing the wall thickness of steel tube and the diameter of ordinary reinforcement can reduce the load sharing capacity of concrete;increasing the wall thickness and strength of sandwich concrete can increase the load sharing capacity of concrete.