Study On The Mechanical Behavior And Stress-strain Model Of Self-compacting Recycled Concrete Confined By Stirrups Under Concentric Loading

The application of recycled coarse aggregate in self-compacting recycled concrete can not only reduce the massive exploitation of natural sand and stone and the continuous generation of construction waste,which have caused great harm to the environment,but also solve the problem that the tall and complex concrete structure is difficult to pour and vibrate in practical engineering.Stirrup confined concrete is one of the most common components in engineering practice.Stirrup is used to restrain concrete to meet the requirement of ductility and bearing capacity.Through literature review,it is found that domestic and foreign scholars have little research on stirrup confined self-compacting recycled concrete.Therefore,the application of self-compacting recycled concrete in stirrup confined concrete specimens has a good prospect.On 31 stirrup of specimen with six plain concrete specimen of confined concrete axial compression test,the destruction of confined concrete form,stress-strain curve and ductility performance are studied,such as analysis of the variety of reinforcement ratio,concrete,concrete strength,stirrup strength,shape and diameter of stirrup stirrup on the influence of mechanical properties.The results show that,similar to the ordinary concrete specimens,with the increase of the stirrup ratio,the development speed of cracks in the stirrup confined self-compacting recycled concrete specimens is slowed down.When the specimens are finally destroyed,the spalling degree of the concrete between stirrups is weakened,the peak stress of the specimens is gradually increased,and the ductility coefficient of the specimens presents an increasing trend.The spalling surface of the protective layer of the self-compacting recycled concrete specimen is smoother and smoother than that of the ordinary concrete specimen,and the type of concrete has little effect on the peak stress.In order to improve the ductility of specimens,stirrup restraining self-compacting recycled concrete requires a larger stirrup ratio than ordinary concrete.With the increase of concrete strength grade,the peak stress of the specimen decreases with the growth rate of stirrup ratio.Compared with the specimens with the stirrup strength grade of HRB400,the specimens with the stirrup strength grade of HPB300 have a more gentle downward trend in the stress-strain curve and a larger ductility coefficient under the same stirrup ratio.Under the same stirrup ratio,the restraint effect of thediamond stirrup and octagonal stirrup is better than that of the wellhead stirrup,while that of the rectangular stirrup is the worst,and the restraint effect of the small diameter stirrup on the concrete is better.By analyzing the test results and combining with the domestic and international research results,the axial compression constitutive model of stirrup-constrained self-compacting recycled concrete is proposed,and the calculation formula of the characteristic points of the stirrup-constrained self-compacting recycled concrete model is given.The values agree well with the experimental values.Finally,through comparison,the proposed constitutive model is agreement well with the experimental results.