Study on Area-Loss Limit of Cable-Strut Structures Considering Different Failure Modes

Corrosion of cable-strut structures during long-term service life will cause cross-sectional area loss of steel members, which will lead to redistribution of internal force and affect safety performance of the structure. This paper established three failure modes including member strength failure mode, cable relaxation failure mode and node deformation failure mode based on the reliability theory and structural limit state, and further obtained reliability limit control inequalities under critical states of different failure modes. Through mechanical derivation, it derived the formula for the members’ internal force variation as well as nodal displacement variation of cable-strut structure due to variation of cross-sectional area. Based on the formula, the influence coefficient matrix in the reliability limit control inequality can be calculated. By introducing the corrosion model of steel and combining it with nonlinear programming, it proposed the method to determine the members’ area-loss limit of cable-strut structure. The numerical example of a Levy cable dome was carried out and the calculated area-loss limits were compared with the current limit in specification. The result shows that the calculated area-loss limit of most members in the cable-strut structure under the strength failure mode and deformation failure mode is higher than the durability specification limit,but the area-loss limit under the relaxation failure model is smaller than the durability limit. If the structure is designed and maintained according to this limit value, the cable relaxation failure may occur. The safety specification limit is strict for steel cable members, but it is the same as durability specification limit for steel bar members. Therefore, the area-loss limit under three failure modes and specification limits should be considered comprehensively and the final limit should be controlled according to the most stringent results.