Experimental Study On Axial Bearing Capacity Of Recycled Aggregate Concrete Short Columns Confined By Steel Tubes

With the continuous advancement of new urbanization and old city reconstruction,the disposal and recycling of building solid waste has become a hot research issue in the field of recycled concrete.Recycled aggregate concrete,as a new type of energy-saving building materials,can effectively solve the problems caused by the unreasonable use of existing waste concrete.Compared with ordinary concrete,recycled coarse aggregate forming process leads to low strength of recycled concrete.Recycled aggregate concrete has a certain discrete type and poor ductility,which is mainly used in non-structural systems such as wallboard in engineering.In order to control the strength of recycled aggregate concrete,it is necessary to put recycled aggregate concrete into the steel tube to form a new type of composite column,which name is recycled aggregate concrete short column confined by steel tube.A total of 18 recycled aggregate concrete short columns confined by steel tubes were researched in this paper.The main completed work was as follows:.(1)The axial compression test results showed that the failure modes of the mostly specimens were oblique shear failure,and some of the specimens showed the damage of drum bending.The axial compressive strength and the deformation performance was greatly improved because of steel pipe's constraint,and the round steel tube was better.With the increase of the recycled coarse aggregate replacement rate,the ultimate bearing capacity decreased slightly.When the cross-sectional shape was the same,the peak strain gradually increased with the increase of the recycled coarse aggregate replacement rate.(2)Based on the experimental results and theoretical calculations,the linear relationship between the axial compressive strength and the recycled coarse aggregate replacement rate was obtained.The calculation method for the ultimate bearing capacity under different cross-sectional shapes was given with reference to the classic Mander model.The calculated results were compared with the experimental results.The deviations range from 0.07% to 10.0%,the theoretical and experimental results indicated that they were consistent with each other.(3)The Mander model,the Li Bing model and the Han Linhai model were studied.The prediction results and the test results were compared in the peak stress and the peak strain.The constitutive model of the confined recycled concrete with steel tube was selected.Considering the influence of recycled coarse aggregate substitution rate,the model was modified.The predicted results of the revised formula were in good agreement with the test results,which can provide a reference for the calculation of axial bearing capacity of recycled aggregate concrete short columns confined by steel tubes.