我国公路桥梁总数已达 2 8万座 ,计 10 0 0万延米 (即 1万km)。除大量的中小跨径桥梁外 ,为适应高等级公路向高原山区延伸和跨越江河湖海的需要 ,各种类型的大跨度桥梁得到发展。在这些桥梁中 ,主跨在 40 0m以上的桥梁建成 3 5座 ,在建6座 ;主跨在 60 0m以上的桥梁建成 13座 ,? The total number of road bridges in our country has reached 28,000, accounting for 10 million linear meters (or 10,000 km). In addition to a large number of small and medium-sized bridges, various types of long-span bridges have been developed to meet the needs of high-grade highways extending to the plateau and mountains and across rivers, lakes and seas. Among these bridges, 35 bridges with main span of more than 40m are built and 6 are under construction; 13 bridges with main span of 60m above ground are completed;