Study On The Durability Of Reinforced Concrete Beams With CFRP Mesh Stirrups Under The Coupling Action Of Load And Seawater

In the marine environment,reinforced concrete beams will not only be immersed in seawater,but also subjected to external loads,and the two will be coupled for a long time.These two effects will accelerate the corrosion of the steel bars in the concrete beams,especially the outer stirrups,which will cause the strength and stiffness of the concrete beams to degrade,which will result in the loss of the function of the concrete structure and the reduction of service life.Carbon fiber reinforced composite material(hereinafter referred to as CFRP)mesh is a new type of material with good corrosion resistance and overall performance made by carbon fiber infiltration in resin with good corrosion resistance.Replacing traditional steel stirrups with CFRP mesh stirrups can effectively improve the corrosion resistance of reinforced concrete structures,thereby enhancing the durability of concrete structures and increasing service life,which can be better used in marine environments.However,there is no research on the long-term durability of reinforced concrete beams with CFRP mesh stirrups under the coupling effect of load and seawater corrosion.This paper combines experimental research and theoretical analysis to study the creep and shear performance of CFRP mesh stirrup concrete beams under the coupled action of load and seawater immersion.The specific research contents are as follows:(1)Through the comparative test of four concrete beams and unloaded unoaked concrete beams with load-bearing level(24%P_u,48%P_u)and immersion time(90 d,180 d),the CFRP net under the coupling effect of load-seawater immersion is studied.Creep performance of lattice stirrup beams.The research results show that:the higher the load level,the later the deflection reaches a stable time,and the greater the deflection value;the creep of concrete beam increases with the coupling action time first and then remains stable;the deflection calculation results of the revised ACI209R prediction model are compared with the test results It can accurately predict the deformation law of CFRP mesh stirrup beam under the coupling effect of short-term load and seawater immersion.(2)Eight concrete beams with load-holding level(0%P_u,24%P_u,48%P_u)and immersion time(0 d,90 d,180 d,360 d)were used to study the CFRP under the coupling effect of load and seawater immersion.Shear performance of mesh stirrup beams.The research results show that:seawater immersion and load do not change the failure mode;both effects will increase the ultimate shear capacity of concrete beams;as the time of seawater immersion increases,the strength of concrete continues to increase,and the flexural rigidity of concrete first decreases and then increases.The overall plastic deformation capacity of the beam shows the opposite trend to the flexural rigidity of concrete,which gradually decreases after a period of improvement;the coupling effect reduces the strain of the stirrup to exert its strength.(3)Based on the truss-arch model,perform theoretical analysis on the shear performance of CFRP mesh stirrup beams under load-seawater immersion coupling,and introduce elastic modulus correction and concrete strength correction coefficients in combination with test data and existing research results.The calculation formula of the shear capacity of the CFRP mesh stirrup concrete beam under the coupling action of load and seawater immersion is obtained,and the calculation result can better match the experimental value.