4020大桥是座公、铁两用桥,全长877.52米。正桥钢梁是四孔一联跨度为128米的米字型连续桁梁,桁高20米,主桁间距10米。铁路桥面为双轨道,两侧各有5米宽的公路桥面和1.5米宽的人行道(图1)。用钢量共7000多吨。在伟大领袖毛主席“备战、备荒、为人民” 4020 Bridge is a public and railway dual-use bridge, a total length of 877.52 meters. Zhengqiao steel beam is a four-hole a span of 128 meters of continuous-shaped truss girder, truss 20 meters high, the main girder spacing of 10 meters. The railway deck is a double track, with a 5-meter-wide road deck on both sides and a 1.5-meter-wide sidewalk (Figure 1). A total of more than 7000 tons of steel. In the great leader Chairman Mao “preparing for war, preparing for the people, for the people”