泸州市沱江四桥总体设计

Overall Design of the Fourth Tuojiang River Bridge in Luzhou

泸州市沱江四桥是一座主跨200m的单塔斜拉桥,采用市政道路与远期规划轨道交通平层布置形式。桥塔为钢-混凝土组合塔,顺桥向呈觚(古代饮酒器具)形。主跨和城西新城侧边跨采用左右分离式钢箱梁,为减小结构内部约束作用,在斜拉索、塔、墩处双箱之间设置横隔梁,通过螺栓将横隔梁与钢箱梁连接。城北新城侧边跨与南、北引桥主梁采用预应力混凝土连续箱梁。混凝土箱梁和钢箱梁之间通过2m长钢-混结合段连接。该桥桥面宽49m,为减小混凝土收缩应力,在桥梁中线处桥面板和横梁上设置宽100cm混凝土后浇段,纵向分4个浇筑节段逐段施工混凝土箱梁。由于引桥梁端支反力比主桥梁端支反力大,为减小支反力差值产生的桥墩附加弯矩,将交接墩中心线朝远离桥塔方向偏移,同时将桥墩的顺桥向壁厚设置成不等厚。

The Fourth Tuojiang River Bridge is a single pylon cable-stayed bridge with a main span of 200 m and the vehicle lanes and the future light transit rails are designed to position on the same deck. The pylon, like a ＂gu＂ （a kind of liquor utensil in ancient China）, is a steel-concrete composite structure. The girders in the main span and the side spans connecting the new district in west part of the city are left and right separated steel box girders. To reduce the constraint effect inside the structure, diaphragm beams are installed between the two steel boxes at the stay cables, the pylon and the piers, and are connected to the steel boxes with bolts. The main girders in the side spans on the side of new district in the north of the city and both the south and north approa- ches are prestressed concrete continuous box girders. The concrete box girder and the steel box girder are connected by a 2-m long steel-concrete joint section. To reduce the concrete shrinking stress, a 100-cm wide post-cast concrete section is set on the deck slabs along the bridge central line and over the cross beams. Along the bridge length, the concrete box girder was cast in situ in four segments. Due to that the support reaction force at the approach ends is greater than that at the main bridge girder ends, the central line of the turning pier is made offset away from the py- lon, and makes the wall thickness of the piers along the bridge length variable, so as to avoid the occurrence of additional bending moment in the piers because of the existence of the support reaction force difference.