Experimental Study Of Compression Performance Of RPC100 Cylindric Column Bounded By Grade 800 MPa Spiral Stirrup

Reactive powder concrete(RPC)is a new type of cement-based composite which was developed by Bouygues laboratory in France in 1993.RPC consists of cement,active mineral admixture,quartz sand,efficient water reducer,and water which are mixed formed in a certain proportion,and then is hardened under high temperature and pressure curing conditions.The advantages of RPC are high strength,super durability,and high toughness.Therefore,RPC has a promising application prospect in civil engineering.There are no initial cracks between gel and coarse aggregate,because RPC do not have coarse aggregate.The lateral deformation of RPC is small with the development of cracks in RPC under compression.Therefore,RPC lateral deformation will present new features under vertical load,research on the compressive behavior of RPC confined by spiral stirrups has practical significance.The paper titled experimental study of compression performance of RPC cylindrical column confined by high-strength spiral steel,the main work in this paper is as follows:(1)The compressive strength,peak strain,strain corresponding to the peak stress,elastic modulus and Poisson’s ratio are determined through the compressive test of RPC.Besides,the yield strength,ultimate strength,yield strain,and the strain corresponding to the maximum tension force of HRB600 reinforcing bars and the proportion limits,nominal yield strength,ultimate strength,and the strain corresponding to the maximum tension force of PC800 pre-stressed steel wire were obtained by tensile test and the stress-strain relationships calculation models for both HRB600 and PC800 were obtained;(2)Five grade 800 spiral stirrups confined RPC circular columns in different the volumetric ratio of stirrups(1.0%～2.0%)were tested under axial compression.The results showed that when the volumetric ratio of stirrups was in the ranges of1.0%～2.0%,the compressive strength of all specimens can be increased by15%～32%,while the peak strain of all specimens can be increased by 27%～85%.Thus,the effects of volumetric ratio of stirrups on the compressive strength of confined concrete were not obvious,while the volumetric ratio of stirrups had significant influence in the ductility of confined concrete;(3)The lateral strain-axial strain curves of Grade 800 spiral stirrups confined RPC circular columns in different the volumetric ratio of stirrups(1.0%～2.0%)were obtained.The characteristics of lateral strain-axial strain curves of all specimens were analyzed and the prediction models were established to indicate the variationbetween lateral strain and axial strain.According to the lateral strain of stirrups at the axial peak strength of specimens,stirrups did not reach yield strength at axial peak strength.Regression analysis prediction model for tensile strain of stirrups corresponding to axial peak strength of specimens by considering the effects of elastic modulus and the volumetric ratio of stirrups,as well as the axial compressive strength of RPC;(4)The axial stress-strain curves of Grade 800 spiral stirrups confined RPC circular columns in different the volumetric ratio of stirrups(1.0%～2.0%)were obtained.According to test results,when specimens damaged,the compressive strength of specimens was within the ranges of 52%～76% peak stress,which was higher than 50% peak stress,thus,the strain corresponding to the stress at the 85%peak stress in the descending branch was adopted to describe the ultimate strain of specimens.The characteristics of axial stress-strain curves of all specimens were analyzed.The regression analysis prediction model for the axial stress-strain curves of all specimens was obtained by adopting Mander’s model and Guo’s model to describe the ascending branch and descending branch of stress-strain curves.Besides,the effective lateral confining pressure provided by stirrups was calculated by the lateral stress of stirrups.The peak stress,peak strain,and ultimate strain prediction models of Grade 800 spiral stirrups confined RPC were obtained by considering the effects of effective confining pressure of stirrups and the axial compressive strength of concrete which fit well with experimental results.The proposed models for the axial stress-strain relationships,peak stress,peak strain,and ultimate strain of Grade 800 spiral stirrups confined RPC circular columns can be utilized to evaluate the compressive behavior of confined RPC.