Abstract
This paper presents a reliability analysis to assess the safety of corroded main cables of a long-span suspension bridge. A multiscale probability model was established for the resistance of the main cables considering the length effect and the Daniels effect. Corrosion effects were considered in the wire scale by relating the test results from accelerated corrosion tests to the corrosion stages and in the cable scale by adopting a corrosion stage distribution of the main cable section in NCHRP Report 534. The load effects of temperature, wind load, and traffic load were obtained by solving a finite element model with inputs from in-service monitoring data. The so-obtained reliability index of the main cables reduces significantly after operation for over 50 years and falls below the design target value due to corrosion effects on the mechanical properties of the steel wire. Multiple measures should be taken to delay the corrosion effects and ensure the safety of the main cables in the design service life.
Highlights
Long-span suspension bridges are generally located in severe corrosive environment which induces corrosion in main cables. e corrosion effects reduce the bearing capacity of the main cables with time and endanger the safety of bridges
Corrosion effects are considered in the wire scale by relating the test results from accelerated corrosion tests to the corrosion stages, and in the cable scale by adopting a corrosion stage distribution of the main cable section in NCHRP Report 534 [9]. e load effects of temperature, wind load, and traffic load are obtained by solving an finite element (FE) model with the in-service monitoring data of temperature, wind, and traffic modes
In companion papers [10, 11], an accelerated corrosion test was conducted on high-strength steel (HSS) wires to investigate the effect of strain levels and corrosion time. e HSS wires had a nominal diameter of 5.25 mm and a strength grade of 1770 MPa, which was the same product as those used in the main cables of Xihoumen Bridge, a suspension bridge in China with a 1650 m central span
Summary
In companion papers [10, 11], an accelerated corrosion test was conducted on high-strength steel (HSS) wires to investigate the effect of strain levels and corrosion time. e HSS wires had a nominal diameter of 5.25 mm and a strength grade of 1770 MPa, which was the same product as those used in the main cables of Xihoumen Bridge, a suspension bridge in China with a 1650 m central span. E yield stress and tensile strength were related to the minimum diameter of steel wires through regression analysis of test results of the accelerated corrosion tests: Py 7.191dmin + 0.855,. 3. Resistance of Cables considering Corrosion Effects e main cables of Xihoumen Bridge were erected by the Prefabricated Parallel Wire Strand (PPWS) method. E multiscale model, including the scale of wire, the scale of strand, and the scale of cable, proposed by Elachachi et al [8] was adopted to evaluate the long-term resistance of the main cables considering corrosion effects. By incorporating the wire scale, strand-scale, and cable-scale models discussed in the previous sections, a probability model for the resistance of the main cables in service after operation for different years can be obtained (see Figure 4)
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