Recycled Coarse Aggregate Concrete Pressed Stress-Strain Curve Experimental Research After High Temperature And Finite Element Heat Exchange Analysis

Modern times, building industry is booming fastly and fire suffers frequently, leading to a large number of construction waste and safety hidden troubles. Therefore, this article combining with the new concrete code damage constitutive theory method, recycled coarse aggregate concrete stress-strain curve test after fire and finite element fire resistance analysis for specimens of recycled concrete in the high temperature has been carried out. Mainly completed works are as follows:Firstly, by considering the temperature and replace rate of recycled coarse aggregate for orthogonal combination, the recycled concrete homotaxial pressed stress-strain curve experiment after high temperature has been carried out. With the rise of temperature, we discover that curve tend to flat, peak point drop down hardly and move to the right, peak strain increases slowly, the value of fragile index B increase, RC100’s compression strain energy density D constantly decrease, and RC50and NC showed no harmonious evolutive discipline; With substitution rate increasing, constitutive curve shape is similar as NC at normal temperature, peak stress constantly decreases, peak strain increases slowly, the value of fragile index B increases, and the area of the curve surrounded by X axis decrease obviously.It shows that material becomes brittle and ductility poor.Secondly, transient heat transfer analysis and temperature-force order coupling thermal stress analysis for recycled concrete specimens have been carried on by using abaqus finite element software. They verify that constant temperature6h can basicly eliminate specimens temperature difference inside and outside, forecasting that they can basicly recover to room temperature field state by natural cooling7h after high temperature, simulating the specimens’all stages of the stress and strain evolution in heating up-constant temperature-cooling down. With the passage of time, the stress presents the first increased second decreased to balance third increased last decreased again changing trend, while the strain presents a first catch increased second sharply increased third a trace increased last gradually decreased the evolution rule, which concludes that the variable temperature is the reason of temperature strain having nothing to do with other factors.Finally, profiting from the GB50010-2010-concrete structure design code’method which introduces damage variables into the stress-strain relation-ship of the concrete, recycled coarse aggregate concrete in high temperature of the damage evolution equation has been theoretical deduced based on the test results after high temperature. Through establishing fine micro structure model of common concrete and recycled concrete, it was considered that evolution mechanism can devide into initial damage period, elastic damage period, aggravate development and stripping of destruction four stages, and contrast evaluating to found that the latter high temperature damage and burst damage have a greater extent than the former.