Study On Mechanical Properties Of Recycled Aggregate Concrete- Filled Square Steel Tube

With the rapid development of our economy, a lot of construction waste have been generated, which have a effect on sustainable development of China. Application of recycled concrete provides a good method for the construction waste disposal and provides the guarantee for the recycling of building resources. But compared with common concrete, the recycled concrete has less intensity, larger contraction and poorer durability. These make the promotion of recycled concrete very limited. In order to overcome the shortcomings of recycled concrete, recycled concrete-filled steel tube came into being.Recycled concrete-filled steel tube is produced by filling the recycled concrete into steel tube, which provides a new approach to dispose the wasted concrete and to compensate the lack of bearing capacity of the recycled concrete itself. For the moment being, researches on recycled concrete-filled square steel tube columns haven’t been very profound, no complete calculating theory can be applied to instruct the practice. In this paper, ABAQUS was applied to simulate the static behavior of the recycled concrete-filled square steel tube columns. Combined with experimental data from relevant literature review, load-displacement curve and load-deflection curve are obtained. Main contents and achievements of the research are as follows:(1) Among all the specimens under eccentric load, the flexural rigidity in every regulation and protocol is applied, and mid-span deflection is calculated. Compared with experimental values, elastic flexural rigidity in Han Linhai’s Modern Structural Technologies of Concrete-filled Steel Tube is recommended under small eccentric load; the calculating formula of elastic flexural rigidity in AIJ(1997) is recommended under large eccentric load.(2) Through analysis of preference setting, the finite element models of the recycled concrete-filled square steel tube columns are established. The accuracy of simulation is validated through comparison between load-strain curve and experimental values, S,Mises stress nephogram of 15 recycled concrete-filled square steel tube columns is drawn.(3) On the basis of finite element models and analysis of recycled concrete-filled square steel tube columns, at 1 / 2 cross section, strain changes with loading time, it is concluded that under axial compressive load, at 1 / 2 cross section of square recycled concrete-filled steel tube columns, the four straight edges and the circle center are forced to the maximum, the midpoint of the four straight edges are forced to the minimum and evenly distributed; under eccentric load, at 1 / 2 cross section of recycled concrete-filled columns, compressive stress appears in the center of cross section area, where the midpoint of the straight edge is forced less than the two ends.(4) On the basis of finite element models and analysis of load-deflection curve of recycled concrete-filled square steel tube columns, it is concluded that, at the ascending stage of the curve for same eccentricity and different replacement rate, the changes on the specimens mid-span deflection under eccentric load are not obvious. At the elastic-plastic stage, the deflection rate of the specimens raises greatly with the increase of the replacement rate; At the descending stage of the curve, the higher replacement rate raises, and the smoother the deflection rate of the specimens decline.