Nansan separated overpass is located in the KJ-7 bid section (K439+300~K454+900) K449+151 of the reconstruction and expansion project of Shi 'an, Hebei Province, the design load: highway - classⅠ (widening and new bridge); Bridge deck width: double width 2× net -21m; Design flood frequency: 1/100; Environment category: ClassⅠ; Peak acceleration coefficient of ground motion: 0.15g (seismic intensityⅦ).
The upper part adopts 3×30.1m prestressed concrete composite box girder oblique bridge with an oblique Angle of 25°. The lower part adopts column pier, column platform and bored pile foundation. The azimuth of the bridge is 30° north by east. The superstructure consists of 7 main beams, each of which is constructed separately and simply supported in the longitudinal direction, forming 3 span continuous beams, and then connected to each box beam through the diaphragm. The main beam concrete design label is C50, and the bridge deck pavement layer is 12cm thick C50 concrete cast-in-place layer + waterproof layer +10cm thick asphalt pavement layer.
The construction cost of the seamless transformation of the South Third Road separated overpass increases by 101,000 yuan, but the durability of the bridge can be improved after the transformation, and the maintenance and maintenance cost of the expansion joint can be reduced by 4,701,600 yuan. It avoids the repair, maintenance and replacement of expansion joints, improves the capacity of highways, avoids traffic jams, brings convenience to the travel of residents, and indirectly drives the prosperity of the local economy.
The construction unit of the South Third Road separated overpass is Hebei Highway Administration (Group), and the design unit is China Communications First Highway Survey and Design Research Institute Co., LTD., Hebei Transportation Planning and Design Institute. The College of Civil Engineering of Fuzhou University is responsible for the scientific research project based on the bridge. The design of the bridge has been guided and the structure of the bridge has been studied. It was completed and opened to traffic in 2015.
（a）Side view of bridge
（b）Bridge deck photos