美国由于公路造价猛涨,公路税收又普遍下降,给公路建设带来了严重的影响。在这种情况下,要求工程师们寻求一种经济的桥梁体系,如许多采用预制构件组成的桥梁那样,减少现场工作费用,获得最大的节约。而节约首先要在计划中体现,如要求合理的设计和安全标准等内容。在低交通量道路上也要求按高坚固体系进行有潜力的设计是不妥当的。在美国西北地区和一部分其他 In the United States, due to the soaring cost of the highway, the tax revenue of the highway has generally dropped, which has seriously affected the highway construction. Under these circumstances, engineers are asked to find an economical bridge system that, like many bridges made of prefabricated components, reduces field work costs and maximizes savings. Savings must first be reflected in the plan, such as requiring reasonable design and safety standards. It is also inappropriate to require promising designs based on high strength systems on low traffic roads. In the northwestern United States and part of others