Calculation Method For Characteristic Value Of Vehicle Load Of Highway Bridges

The rationality of highway bridge designing load is directly related to the bridge's security,economic and durability.The design vehicle load must be suitable for road traffic characteristics,the flow of traffic, transport conditions and future trends.Since 1988, the reliability of highway engineering has undergone nearly 20 years of development, the vehicle and traffic situation have changed a lot. Some factors that affect vehicle load mode characteristics have changed significantly such as the vehicle's load capacity,The proportion of vehicles,traffic characteristics.The design living load of Chinese highway bridge which based on limited measured data previously and refering specification is incompatible with the current condition of the actual operating load, which are obvious nowadays.The construction of many long span bridges which cross river also need new requirement to load patterns and standards of bridge designing.Therefore,a new round research of highway bridge designing vehicle load become urgent.As an important part of the the western transport projects (2008 318 494 04) "bridge designing load and identificated load of security",the paper focused on the outstanding issue of Chinese highway bridge vehicle load,considering domestic and international highway bridge vehicle load specifications and situation of research in order to model highway bridge design vehicle loads and vehicle loads of safety assessment,the paper investigated the vehicle operating conditions of highway bridges and load characteristics, and absorpted of domestic and foreign scientific research and technological achievements,then proposed four methods to calculate vehicle loads standard value of highway bridge:chain method,statistical method,empirical method,and regulation method. Chain method is to consult the load pattern and methods of foreign code,and determine the reasonable position of Chinese in the world through analysis and comparison,and meet the requirements of the development of transportation.Statistical method is to take the vehicle load as random variables,based on the actual number of statistical analysis and to determine the load standard value.Empirical method is based on our highway bridges'drafting process,to investigated of vehicle loads of traffic, taking full account of the load standard and reflecting the actual load conditions.Regulation method relys on traffic management policies to determin the design load under policies and regulations.Finally, the integral two-lane 20-metre simply-supported- beam were loaded by the four methods to get the load effect of different methods, and the load effect value were compared with each other.The methods and conclusions can give reference to revision of code.