A Case Study of Traffic Load for Long-Span Suspension Bridges

The structural Eurocodes have been given the status of National Standards since 2007 and all conflicting National Standards previously used in member states of the European Union were withdrawn in 2010. The Eurocode has also been adopted in the design of long-span suspension bridges. However, the traffic load models in Eurocode EN 1991-2:2003 are only valid for bridge spans of less than 200 m. Traffic load models for loaded lengths greater than 200 m may be defined in the National Annexes or on a project-specific basis. This paper discusses the traffic loads for long-span bridges defined in BS5400, AASHTO LRFD,(1) Sweden TK BRO, Great Belt (East) Bridge Design Basis, the Superstructure Design of Honshu-Shikoku Bridge of Japan, and the Highway Bridge Design Code of China. Together, these codes have been adopted in the design of more than 20 long-span suspension bridges. This article proposes a traffic load model for long-span suspension bridges in the framework of Eurocode Load Model 1, in which multiple lane factors and impact factors are also taken into account. The recommended traffic load model was utilized in the design of a suspension bridge with a main span of 1550 m. According to the design load partial factors and resistance partial factor of the main cable, the margin of safety for the main cable was calculated. The results indicate that the recommended traffic load model for long-span suspension bridges is reasonable.