Research On Time-Dependent Reliability Of FRP Bars Reinforced Beam Under Marine Environment

As a new kind substitution of steel bars in concrete construction, FRP bars can solve the corrosion issue of steel bars effectively owing to its property of light weight and high strength and outstanding corrosion resistance. GFRP bars (Glass Fibre Reinforced Polymer) become very popular because of its low price. At rencent years, many relative researches about reliability of GFRP bars in corrosion environments have been studied by scholars at home and abroad. However, researches on long-term behavior of reliability of GFRP bars reinforced concrete structures are still in exploratory stage. This paper presents the time-dependent reliability of GFRP bars reinforced concrete beam (GRCB) and discusses its flexure capacity and deflection control. The main works of this paper show as follows:(1) The models of concrete strength degradation and GFRP bars strength degradation are summarized and capacity loss caused by slip effect is discussed. Using datas from accelerating aging test under different environments, the degradation of tensile strength of GFRP bars in service life is predicted by forecasting method based on Arrhenius models. The mechanism and quantification method of capacity loss is explained and proposed by consulting bond-slip theory of steel bars reinforced concrete beam and steel-concrete composite beam.(2) Based on the former models, time-dependent reliability index of GRCB under marine environment is calculated and analyzed with Monte carlo-JC method. The result shows that the degradation of tensile strength of GFRP bars has little influence on the degradation of flexure capacity. And the degradation of concrete strength is the major factor leading to the durability degradation. Slip effect can create reduction of flexure capacity and its reliability index.(3) The time-dependent reliability index of steel bars reinforced concrete beam under marine environment is calculated by consulting pre-existing results. The result shows that its velocity of degradation of flexure capacity is slower than GRCB and the latter has better durability.(4) Time-dependent reliability index of midspan deflection of GRCB is calculated based on the design formula and limit of ACI 440.1R. The results shows that degradation of concrete strength and elasticity modulus are the major reasons of reduction of reliability index.