Study On Mechanical Properties Of RC Beams Strengthened With CFRP Under The Coupling Effects Of Colliery Environment And Load

Coal is the main resource for producing energy in China for now.As the policy limits building new coal industries,and the buildings that under using have varying degrees of damages caused by the harsh colliery environment,to reinforce the buildings is becoming critical to satisfy the production.In this paper,the model of reinforced concrete beams is 1:1.Then the mechanical properties of deteriorated concrete,corroded steel bars and reinforced concrete beams which have been strengthened by CFRP are studied under the coupling effects of colliery environment and load.Compared the results of this study with the preliminary research results,this paper shows the conclusions of the mechanical degradation laws for mildly deteriorated concrete and concrete beams strengthened by CFRP.The main conclusions and innovations are shown as below:1.This paper shows the degradation laws for deteriorated concrete material: The production of gyp and ettringite keeps decreasing the pores of concrete,resulting in the expansion of the volume.Finally,the concrete will be cracked.In the meanwhile,the load accelerates the corrosion,and the rate of the damaged beams are significantly higher than the deteriorated beams.Therefore,in the simulated environment,the compressive strength and elastic modulus of studied concrete cubic increase during the period 1-3,decrease in the period 4-6.While the compressive strength of deteriorated concrete core specimen increases in the period 1-3 and the damaged beams decrease during the period 1-3.2.This paper shows the relationship between the mechanical properties and the corrosion rate under the laws of deterioration: The corrosion rate of the steel bar increases with the increase of the corrosion period.The corrosion rate of the steel from the damaged beams is greater than that from the deteriorated beams.This study established linear relationship between yield strength,ultimate strength,and corrosive rate of the beams in the coal environment by the statistical regression equation.3.This paper shows the degradation laws of mechanical properties of concrete beams which have been strengthened by CFRP: During the period 1-3,sticking a layer of carbon fiber to the bottom of the concrete beam which can basically satisfy the flat cross-section assumption,and fully expand the advantages of the material.This method makes the concrete beam damage more like to the damage of suitable reinforced beam.More than that,the ultimate strength and displacement ductility factor of the concrete beams can be effectively improved by 20% and 30% respectively.With the increase of the corrosion period,the stiffness of the deteriorated beams which have been reinforced is increasing,and the growth rate slows down.However,the stiffness of the damaged beams is decreasing after the reinforcement.4.This paper also shows the revised calculation formula for the bearing capacity of mildly deterioration and damage reinforced concrete beams which have been strengthened by CFRP.This is based on the previous research results and the consideration of the influence of concrete deterioration and steel corrosion.