Reliability analysis of the maximum crack width of FRP bar reinforced concrete flexural members

FRP bars are always used in concrete structures with strong corrosion environments or electromagnetic insulation because of their good corrosion resistance performance. But it is a non-metallic material with low elastic modulus, which leads to larger crack width of FRP reinforced concrete members. However, the calculation formula of the maximum crack width in the current code is a simple change of that in the concrete design code. The difference is that the load combination adopts the characteristic combination and the limit of the maximum crack width is relaxed to be 0.5 mm. the rationality of the formula remains to be verified without reliability calibration. Therefore, the reliability level of crack width of FRP bars of those parameters (including the load effect ratio, the reinforcement ratio, the elastic modulus of FRP bars, the diameter of FRP bars, the section height, the thickness of the protective layer and the concrete strength) were carried out, the influence rule of these factors on the reliability index was analyzed and the limit values of the reliability index are obtained. It is shown that the current reliability index of the maximum crack width of FRP bars is relatively conservative, especially when the load effect ratio is relatively higher, the reliability index exceeds 2.0, which would cause unnecessary waste. Hence, it is suggested that the load quasi-permanent combination should be used to calculate the maximum crack of the FRP bar reinforced concrete flexural members, so that the reliability control level is more appropriate. © 2021, Central South University Press. All rights reserved.