Experimental And Finite Element Analysis On The Mechanical Performance Of Damaged Reinforced Concrete Short Columns Strengthened With RPC

With the rapid development of the construction industry,people’s requirements for building materials are becoming increasingly high.Reactive Powder Concrete(RPC),as a new type of building material with excellent mechanical and durability properties,is receiving increasing attention in engineering applications.Based on the demand for the reinforcement of damaged reinforced concrete(RC)columns and the promotion of RPC in the field of reinforcement,this article uses a combination of experimental and numerical analysis to conduct experimental research on the mechanical performance of damaged RC short columns reinforced with 100MPa grade RPC,and proposes a calculation method for their bearing capacity.The main research content is as follows:(1)This study conducted 11 tests on the mechanical properties of reinforced concrete columns strengthened with reactive powder concrete.The objective was to investigate the effects of initial damage level,thickness of RPC strengthening layer,and eccentricity on the compressive mechanical behavior of RPC-strengthened columns.The test results show that RPC can significantly improve the bearing capacity of damaged columns.With the increase of reinforcement layer thickness,the amplitude of bearing capacity of columns also increases,with a maximum increase of 143%and a minimum increase of 28%.Under eccentric load,RPC material can significantly improve the bearing capacity and vertical deformation capacity of the test piece,with a minimum increase in bearing capacity of 36.6%and a maximum increase of 144.6%,and a minimum increase in vertical displacement of 13.6%and a maximum increase of 57.2%.With the increase of reinforcement layer thickness,the bearing capacity of RC columns with different initial damage and eccentricity increases.When the reinforcement layer thickness is the same,the smaller the initial damage of the original specimen,the higher the increase in bearing capacity after reinforcement.When the original specimen suffers from a certain initial damage,with the increase of reinforcement layer thickness,the bearing capacity increases,but there is a threshold for the increase in vertical displacement corresponding to the peak load.(2)Based on the experimental results,a finite element model for the RPC strengthened damaged column was established,and the reliability of the model was verified by comparing it with the experimental results.On this basis,the influence of different strengthening layer thicknesses,reinforcement ratios,and hoop ratios on the bearing capacity of RPC strengthened damaged RC columns was further explored.The results show that increasing the hoop ratio can significantly improve the bearing capacity of RPC strengthened axially compressed short columns.Increasing both the reinforcement ratio and the hoop ratio of the strengthened column also leads to a significant increase in the bearing capacity of axially compressed short columns.Under high stress levels,the damaged column reinforced with 25mm-thick RPC can restore its original section size and slightly increase its bearing capacity.When the reinforcement thickness is greater than 25mm,the section size of the strengthened column is larger than that of the original column,resulting in a significant increase in the bearing capacity,ranging from 30.7%to 110.3%.When the reinforcement layer thickness is kept between 25mm and 50mm,the ultimate bearing capacity of the strengthened column increases almost linearly with the reinforcement layer thickness.(3)Based on the experiments and finite element analysis,taking into account factors such as the initial damage level of the original column,the combined restraining effect of stirrups and RPC strengthening layer,the utilization rate of strengthening layer strength,and the adverse effects of long-term load on the original specimen,and combining with the calculation method of the normal section bearing capacity of the axial and eccentric compressed members using the method of enlarging the section in the Design Specification for Concrete Strengthening,a formula for calculating the ultimate bearing capacity of RPC-strengthened damaged RC square columns has been proposed.The calculated results are similar to the experimental results,which can provide reference for similar strengthening methods in practical engineering.