| Abstract: |
This report summarizes a NIST study aimed at assessing the safety of parallel wire suspension bridge cables under thermal effects. Both low temperatures, potentially embrittling the bridge wires, and high temperatures, potentially softening the wires, are considered. Recommended thermal and mechanical properties of suspension bridge wire are developed based on published data and on tensile testing carried out as part of this study. These recommended properties are incorporated in a computational model developed to analyze the thermal and mechanical response of a parallel wire suspension bridge cable subjected to prescribed surface temperatures. The analysis results indicate that embrittlement due to low temperatures does not significantly reduce the ultimate capacity of the cable. Exposure to high temperatures, on the other hand, could lead to failure of the cable, due to thermal softening of the steel wires and thermal expansion, which causes the heated outer wires to shed load. Reducing the surface area exposed to high temperatures is found to increase the exposure time required to produce failure. To obtain a copy of this report, contact Joe Main, joseph.main@nist.gov. |
