1、 Implementation of mandatory provisions This bridge construction drawing design does not violate the Compulsory Provisions of Engineering Construction Standards of the People's Republic of China. 2、 Technical standards and basis for design (I) Specifications, standards 1, General Code for Design of Highway Bridges and Culverts JTG D60-2004 2, Code for Design of Highway Masonry Bridges and Culverts (JTG D6l-2005) 3, Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts JTG D62-2004 4, Technical Standards for Highway Engineering JTG B01-2003 5, Code for Design of Subgrade and Foundation of Highway Bridges and Culverts (JTJ024-85) 6, Technical Code for Construction of Highway Bridges and Culverts (JTJ041-2000) 7, Code for Seismic Design of Highway Engineering (JTJ004-89) (II) Technical Standard 1, Design Load: Automobile: Highway Class II 2 Design seismic intensity The basic seismic intensity within the scope of this project is VII degree, and the seismic peak acceleration is 0.10g. According to the specifications, the seismic fortification of highway bridge structures shall be based on the design intensity VII as the starting point. In combination with relevant regulations, this bridge shall be fortified based on the structure of VIII. 3. Bridge deck width: double side crash barrier+net 7m (roadway)+horizontal curve widening (including geometric widening)=9m 3. General layout of the bridge The plane of the bridge is located on the R=27.5m circular curve, straight line and R=91.41m curve, and the longitudinal plane is located on the 2.0% uphill section, which is controlled by terrain, river, geological conditions, etc, The bridge span is arranged as 1-60m constant cross-section catenary open web concrete box arch, with a total length of 84.62m. The foundation of 0 # and 1 # abutments adopts well digging foundation and open web abutment. 4、 Overview of bridge site engineering geology 1. Overview of bridge site This bridge is located at the downstream of the confluence area of XX and XX River (Bhote Koshi). XX bridge is located at the upstream of the old bridge, about 1km away from XX. The left bank of the bridge site area is 5-8m high. The slope close to the river bank is 30~45 degrees. The river bank is composed of boulder, cobble and small cobble layer colluvium. The river bank is covered with grass and shrubs. The right bank slope faces east and extends south-north, with a gradient of 20~30 degrees. The river bank is composed of colluvial soil, which is mainly composed of large boulders, large cobbles, small cobbles and fine mineral powder. The extra large boulder with soil is more than 6m thick. The river bank suspended rock bed is schist rock bed. 2. Main engineering characteristics The stratum structure of the bridge site area is basically composed of sand gravel and large boulder mixed with medium coarse sand, except for the thin layer of coal slag on the surface of the left bank. Although the medium coarse sand layer is found within a certain depth of underground, it does not extend horizontally. The particle size of large boulder in soil layer reaches 1.2m. The sand gravel and boulder layer is composed of gneiss. Large boulders with quartzite composition are also found between the sand gravel and boulder layers. There is groundwater at the depth of 10.9m on the left bank and 3.55m on the right bank. 5、 Key points of bridge design (I) Main features of superstructure 1. Main arch ring This bridge is a 60m reinforced concrete box arch bridge with one hole, L0=60m， f0=10m，f0/L0 =1/6， Arch axis coefficient m=2.514. The main arch ring is composed of six arch boxes, each of which is installed in three sections. The fabrication of each section of arch box is to combine the web plate and diaphragm plate divided in advance on the reinforcement skeleton of the bottom plate, then cast the bottom plate and joints in situ, and finally cast the top plate to form a closed arch box component. After installation, only the vertical and horizontal connection and reinforcement between the box sections and the concrete pouring of the longitudinal joints shall be carried out. The total height of the arch ring is 1.3 meters. The two arch boxes outside the arch ring are side boxes, and the middle ones are middle boxes. The thickness of the outer web of the side box is large, and the formwork must be erected and poured at the same time with the bottom plate. The thickness of the top and bottom plates is the same regardless of the middle box or the side box, and the center distance of the box axis is 1.5 meters. The bottom plate of each box is 1.46 meters wide, and the top plate is 1.32 meters wide for the middle box, considering the need of pouring concrete for longitudinal joints. In addition to meeting the full width condition of the arch ring, the top plate of the side box should also consider the need to erect the model plates of the side wall and cross wall on the arch. The width of the outside of the box top should be 5 cm, 1.46 m practical. In order to increase the joint strength, both sides of the arch box joint section shall adopt the 18-20 cm thick wall cast in the workshop. The box top plate shall be cast only to the end diaphragm. The joint section shall not be cast to form an open section so that workers can enter the box for operation. Finally, the transverse tie beam shall be filled when pouring.
