Post-Fire Compressive Performance Of Concrete-Filled Stainless Steel Tubular Stub Columns With Embedded Steels

Concrete-filled stainless steel tubular stub columns with embedded steels is a new type of steel-concrete composite structure which consists of centrally-placed outer stainless steel tubes and inner tubes(or H-shaped steel)with concrete filled in between.It has high capacity,large stiffness,good corrosion resistance and is easy for construction.It also performs well in seismic loads and fire conditions.It is believed that these specimens is potential in power-transmission towers,high-rise buildings and off-shore structures.Fire is one of the main hazards that endangers modern buildings.The repair and reinforcement of the building after fire require sufficient scientific support.Thus,experimental and theoretical research have been conducted in this study to investigate the post-fire performance of concrete-filled stainless steel tubular stub columns with embedded steels.The main work is listed as follows:1.A total of six stub columns went through temperature field experiments and post-fire compression experiments.The parameters included the cross-sectional type of the member and the fire duration.The temperature-time curves at different points in the middle cross-section are obtained from the temperature field experiments.The load-nominal compressive strain curves of different specimens are also obtained from the post-fire compression experiments.The tests showed that the concrete-filled stainless steel tubular stub columns with embedded steels stub columns remained high capacity after exposed to fire.2.The heat transfer model and the post-fire compression model where the whole heating and cooling process was considered are established.In the heat transfer model,the thermal conductance of interface between steel and concrete were selected.In the post-fire compression model,the confinement that outer tubes provided to the concrete and the influence of the fire on constitutive models of different materials.The two models are both verified with the test results got from previous researches and this paper.They are both proved to be reasonable and accurate.3.The mechanism analysis and parametric analysis are carried out based on the verified models.The stress and strain development of steel and concrete,load distribution,contact stress are obtained and discussed both before and after fire.The effects of different parameters(fire duration,compression ratio,confinement factor,hollow ratio,yield stress of the both the outer tube and the compressive strength of the concrete)on the post-fire capacity are also analyzed.