Safety-Margin Design for Gravity-Type Anchorage of Suspension Bridges over 2,000 m Long Based on Target Reliability

The traditional design method, with overall factors of safety, is still employed in Chinese specifications for gravity-type anchorages (GTAs) in suspension bridges. In this work, we investigated the safety-margin design method of the GTAs of over-2,000-m-long suspension bridges based on the safety factor and target reliability. The variability features of the design parameters involved in the GTAs are presented. The safety-margin analysis of the GTAs was conducted based on the target reliability and a method of calculation of the corresponding partial factors, and considered sliding and overturning failure. Taking the Zhangjinggao Yangtze River Bridge as an example, the proposed design method was applied to this superlong suspension bridge and the partial factors under different design parameters are discussed. The results showed that the overall factors of safety of the GTAs were decreased by the proposed method, and the construction cost of the GTAs could be greatly reduced. The partial factors of the resistance and load effects are presented, considering the sliding and overturning of the GTAs. The design method proposed, with the suggested partial factors, was finally verified using the GTAs of two superlong-span suspension bridges.