Experimental Behavior Of Recycle Aggregate Concrete-filled Stiffened Thin Walled Stainless Steel Stub Columns Under Axial Compression

Concrete-filled steel tube(CFST)is a composite structure composed of concrete and steel tube.The concrete core prevents local buckling of the steel tube,the steel stiffeners restricts the concrete core crushing,and the composite effect between the steel stiffeners and the concrete core has better structural performance than the hollow steel tube or reinforced concrete column.The combined action of concrete and steel tube increases the rigidity of the component.However,even though they have high rigidity and high load-bearing capacity,it was found that the life of CFST members is reduced due to corrosion effects.Stainless steel is introduced as a corrosion-resistant material and also has higher fire resistance and ductility.Concrete-filled stainless steel tubes(CFSST)also have higher rigidity than concrete-filled steel stiffened columns.But these types of new materials are more expensive than low-carbon steel tubes,contrary to their better performance.To reduce costs,this study chose thin-walled stainless steel tube and adopted strengthening measures to prevent the bending of square stainless steel thin-walled stiffeners.Besides,recycled aggregates were used to make construction more economical and environmentally friendly.Therefore,thin-walled reinforced square stainless steel stiffeners(SCFSST)filled with recycled aggregates were studied experimentally to study their behavior and failure modes in axial compression.Through the experimental scheme,the performance and failure mode of the recycled aggregate stiffened square stainless steel short column(SCFSST)under axial compression were studied.A total of 16 specimens were tested,two of which were unstiffened members.The replacement ratio(r)of recycled aggregate was taken 50%,and the two specimens were filled with ordinary concrete.The ratio of diameter to thickness varies from 75 to 125,and the width of the stiffeners was varied from 25 to 60 mm.The thickness of the stiffeners was taken 2 mm,the cross-section is 150 mm to 250 mm,and the length is 450 mm to 750 mm,respectively.Concrete strength of C40 was used.For all stiffeners members,the thickness of the stiffeners was kept constant(4mm).The main purpose of this study is to study the performance of recycled aggregate concrete-filled stainless steel tubes with stiffeners under axial compression.Also,failure modes were observed and the ultimate bearing capacity was determined.It can be concluded from the experiment that the use of stiffeners significantly delays local buckling and increases the cross-sectional capacity by an average of 6.94%.Despite the reduced ductility,the use of recycled aggregate significantly increased the cross-sectional strength by 10.9%,and the average recycled aggregate replacement rate was 50%.The width of the stiffeners has no significant effect on the ultimate load.In this paper,different specifications and literature are used to calculate the axial compression bearing capacity of the stiffened thin-walled stainless steel recycled concrete short column,and the bearing capacity measured in the experiment is compared.It is found that the predicted results by the exiting codes and previous literature are generally conservative.In subsequent studies,we can try to derive the suitable formula to calculate the axial bearing capacity of recycled concrete thin-walled stainless steel short columns.