Experimental Study On The Flexural Behavior Of Coral Concrete Beams Reinforced With CFRP Bars

In order to implement the strategy of ocean power and develop island engineering construction,coral debris distributed on the islands and reefs is used as coarse aggregate of concrete,seawater replaces fresh water,and local materials are obtained to configure coral concrete without destroying the marine ecological environment,which can not only save cost,shorten time limit,but also save resources.However,there are a lot of chloride ions in seawater,which may lead to a series of durability problems such as corrosion of steel bars,corrosion cracking of protective layer and so on.CFRP bars are used to replace steel bars because of their light weight,high strength,corrosion resistance and so on.It can fundamentally solve the durability problem of engineering structures under marine corrosion environment.Based on this application,two reinforced coral concrete beams,six CFRP reinforced coral concrete beams and two CFRP-steel composite reinforced coral concrete beams are tested,in order to popularize the CFRP reinforced coral concrete members in the future.The main contents of the study are as follows:(1)The effects of different reinforcement types as well as reinforcement ratios on the failure phenomenon,ultimate bearing capacity,deflection,crack distribution and development law of coral concrete beams are studied,and the development law of longitudinal reinforcement strain,deflection and crack width with load is analyzed.(2)According to the characteristics of relatively large slip between CFRP bars and coral concrete,the strain between them is no longer in accordance with the assumption of plane section.Therefore,based on the bond-slip theory of corroded reinforced concrete beams and the calculation method of lossing capacity caused by slip effect in steel-concrete composite beams,the principle of lossing capacity caused by slip effect of CFRP reinforced coral concrete beam is explained,and a quantitative calculation model of bearing capacity degradation caused by slip effect is established.(3)The factors influencing the flexural stiffness of CFRP reinforced coral concrete beams are analyzed,and the relative slip between CFRP bars and coral concrete is defined as the key factor to affect the flexural stiffness.Besides,the strain disharmony coefficient of CFRP tendons is introduced by stiffness analysis method to reflect the strain lag effect of tensile CFRP tendons relative to the same position.The experimental data are regressed by regression analysis.The relationship between the strain disharmony coefficient of CFRP reinforcement and the relative roughness of the surface of the CFRP bars is obtained,and the difference between coral concrete and ordinary concrete is taken into consideration at the same time.Furthermore,the internal force arm coefficient,the elastic plastic resistance moment coefficient of cross section and the strain inhomogeneous coefficient of CFRP tendons between cracks were corrected,and the calculation model of flexural stiffness of CFRP reinforced coral concrete beams was established.(4)According to the formula of crack width of FRP reinforcement formula,the relative bond characteristic coefficient of CFRP bar and coral concrete is revised,and the correction coefficient of crack width of coral concrete is put forward.In this case,a model for calculating crack width of coral concrete beams with CFRP bars is established.