近年来,由于铁路、公路的发展,很多既有铁路城市繁忙遭口将有步骤地改成立体交叉,则大跨度的三孔连续框构作为立交形式采用者日渐见多。这种带有封闭式底版的框构桥,其整体性强,基底设计应力小,可避免桩基或沉井等人工深基础。例如,1974年我们在某新线即因地基承载力较低而设计了两座较大跨度的框构立交桥, In recent years, due to the development of railways and highways, many existing railway cities have been gradually replaced by three-dimensional intersections. As a result, the long-span three-hole continuous frame has become increasingly popular as an overpass user. This kind of frame-type bridge with a closed bottom plate has the advantages of strong integrity and less stress on the base design, so as to avoid artificial deep foundation such as pile foundation or caisson. For example, in 1974, we designed two large span overpass structures at a new site due to the low foundation bearing capacity.