The bridge was built by the Second Highway Engineering Bureau of China Communications Group (formerly the Second Highway Bureau of the Ministry of Communications, with special general contracting qualification). The construction time is as long as 3 years.
This bridge is the largest bridge in the southern section of expressway, the first composite beam cable-stayed bridge with the longest span and widest deck, and the only "typical demonstration and scientific demonstration" expressway under construction by the Ministry of Communications. 20 15 won the top ten most beautiful bridges.
work progress
Guanyinyan Yangtze River Bridge in Jiangjin is a control project around the southwest section of expressway. The main bridge is 879 meters, with a main span of 436 meters and a bridge width of 36.2 meters. It belongs to a five-span continuous steel-concrete composite beam cable-stayed bridge with twin towers and double cable planes. The maximum cable force of stay cables is 820 tons, and the bridge deck width is the widest among similar bridges in China, with a total length of 1 172 meters, both directions.
bridgework
The main girder is a 3.2m-high double-section steel-concrete composite beam. The length of the main girder in the standard section is 12m, and the end of the side span is gradually shortened to 8m and 4m. There is no fixed bearing in the longitudinal direction of the whole bridge, an oil damper is arranged between the lower beam of the cable tower and the beam body, and a limit bearing is adopted in the transverse direction. There are ***68 pairs of stay cables in the whole bridge, which are fan-shaped and have double cable planes.
Main tower and foundation
The bridge tower adopts a-shaped tower. The tower height of Dripping Rock Bank is 167.29m, the tower height of Nanpeng Bank is 172.79m, and the height above the bridge deck is about110 m. The lower beam is set below the bridge deck, and the upper beam is set about 60m above the bridge deck. Two beams divide the bridge tower into three parts: upper tower column, middle tower column and lower tower column. The upper tower column has a longitudinal width of 6.0m, a transverse width of 4.4m, a longitudinal thickness of 0.8m and a transverse thickness of1.3m.. The longitudinal width of the middle tower column is 6.0m, the transverse width is 4.4m, the longitudinal thickness is 0.8m, and the transverse thickness is1.0m. The vertical dimension of the tower column under the drip rock bank bridge gradually changes from 6.0m to 10.56m at the bottom of the tower, and the transverse dimension of the tower bottom gradually changes from 4.4m to 9.5m, The vertical dimension of the tower bottom gradually changes from 6.0m to 1 1.0m, and the inner wall of the tower is wrapped with Q235B steel plate, with the thickness of 10 mm ... In order to resist the tensile stress caused by cable tension on the box section of the bridge tower, longitudinal and transverse prestressing forces are arranged in the cable anchorage zone of the bridge tower, and φ S 15.24 steel strand is ".
The upper and lower beams of the main tower adopt prestressed concrete structure, and the prestress is anchored on the outer side wall of the bridge tower, and the two ends are tensioned. 20 φ2.5m rock-socketed bored piles were used for the foundation of the main tower on the Dripping Rock Bank, and an island cofferdam was built. The foundation of Nanpeng 'an main tower is located in the deep water area, and the water depth in dry season is 12m. Twenty φ2.5m rock-socketed bored piles are set, and φ32m double-walled steel cofferdam is used for construction.
bridge type
The main beam is a composite beam with the same stress as the steel main beam and the concrete slab, and the shear studs is used to combine them in the middle. The cable-stayed anchorage height of the composite beam is 3.2m, the mid-span height is 3.542m, the steel beam section is a compound section, the transverse center distance between the two steel beams is 35.2m, the concrete slab on the bridge deck is 26cm thick, the top of the steel beam is thickened by 40cm, and the total width of the main girder is 36.2m. The main longitudinal beam of I-beam is 2.8m high. The main longitudinal beam is divided into eight beam sections, with the standard beam length 12m, the standard diaphragm spacing 4m, the top section of the standard beam section 50mm× 1000mm, the bottom plate 80m×1000mm, the web thickness 28mm, and the three longitudinal stiffening ribs 22mm×260mm. The beam section near the bridge tower and auxiliary pier is widened and thickened. At the bridge tower, the cross section of the top plate of the main girder beam section is 50mm× 1000mm, the bottom plate is 60mm× 1200mm, and the web thickness is 28 mm.. The section of the top plate and the bottom plate of the main girder beam section at the auxiliary pier are 50mm× 1000mm and 80mm× 1200mm, and a reinforced steel plate with a web thickness of 28 mm is added near the fulcrum ... The length of the G beam section (transition beam section) near the connecting pier is 24.496 meters, and the end is locally raised by 4.0 meters ... The weight of the standard single beam is about/ A small longitudinal beam is set in the transverse span of the bridge deck, and two small longitudinal beams are set on both sides. The top and bottom plates of the small longitudinal beam are 500mm wide. Among them, the small longitudinal beams at the center line of the bridge deck are permanent structures, and the small longitudinal beams at both sides are temporary structures for construction. During construction, pedestrian passages are provided as templates for pouring wet joints. There is no shear studs between the permanent small longitudinal beam and the concrete slab, and the bridge deck is simply supported in the transverse direction of the bridge. The standard spacing of clapboards is 4.0m, the top plate of clapboards is 700mm wide and 28mm thick, the bottom plate is 700mm wide and 32mm thick, and the web plate is 16mm thick. The reinforcing ribs are arranged along the longitudinal and transverse directions of the partition plate. The diaphragm is reinforced in the weight section of the main girder, and the connection between the diaphragm and the main girder adopts shear joints. The steel main beam, diaphragm and small longitudinal beam of the whole bridge are all welded in the factory and transported to the bridge site, and all of them are connected by high-strength bolts on site. The main longitudinal beam steel plate adopts Q370qE and the cross beam steel plate adopts Q345qC. Because the top plate of steel plate beam needs to be directly connected with the anchor plate, the steel plate is required to be Z-direction steel plate, and its thickness (Z-direction) performance should meet Z35. Ensure that the steel meets the designed mechanical properties.
Deck facilities
There are 24 kinds of precast concrete bridge decks, the maximum plane size is 3.4m×8.54m, and the top surface is painted with C60 high-strength concrete. The difference between different types of concrete bridge deck mainly lies in prestressed pipes and prestressed teeth, and the precast concrete slab is provided with micro-sawtooth shear keys in the longitudinal direction. In order to reduce the shrinkage and creep of concrete, the precast bridge deck must be stored for at least 6 months before installation. C60 micro-expansive concrete is poured between precast concrete bridge decks to form bridge decks. The concrete bridge deck is set with longitudinal prestress, with a side span of 82m and a middle span of 164m. The longitudinal prestressed steel beams on the roof of the main girder are all constructed by using 7φ S 15.24 steel strand, group anchor and SBG plastic corrugated pipe, and vacuum-assisted grouting method. The concrete bridge deck makes the shear studs on the steel main girder and the flange plate on the diaphragm bear the same force as the steel beam. The shear studs of the whole bridge is made of φ22mm round head welding nail and 260mm length of ML 15 steel, and the shear studs of the whole bridge is welded in the factory.
Maintenance facilities
The cable and the main girder are anchored by pulling plate, which is mainly composed of pulling anchor plate, four stiffening ribs, pulling anchor tube and anchor seat supporting plate. This anchorage structure was first seen in Anasis Bridge in Canada, and later used in Minjiang Bridge in Qingzhou, China. The anchor plate is divided into upper, middle and lower parts. Both sides of the upper anchor plate are welded to the outside of the anchor pipe, which directly transfers the cable force of the stay cable to the upper anchor plate. Hollow out the middle part and install the anchor. In order to compensate for the weakening of the hollowed-out part and enhance its lateral stiffness, reinforcing plates are welded on both sides. The lower part is directly welded on the top surface of the upper flange of the main beam. This structure has clear force transmission path, simple structure and convenient construction. The most important thing is that the whole anchorage system is above the bridge deck, which is convenient for future maintenance, but it also causes a large concentration of load stress and welding residual stress at the weld. Through the spatial nonlinear finite element analysis of the anchor plate structure, the fatigue resistance of the wing plate at the top of the main girder is studied experimentally. The anchor plate is safe and reliable, but the initial yield load is low. Under the design load, the bottom of the weld between the anchor plate and the anchor pipe, that is, the arc near the anchor pad, is a high stress area, and the plastic area appears first. The welds between the anchor plate and the anchor tube, and between the anchor plate and the upper wing plate of the main girder are the main force-transmitting welds, which require full penetration and strict flaw detection. The anchor plate is directly welded on the top plate of the main girder, and the top plate of the main girder bears tensile stress in Z direction. Z-direction performance of steel plate and welding heat affected zone are the two weakest links in the steel structure of the bridge, so the quality control of steel and welding construction is the focus of the whole steel structure manufacturing. Static and fatigue tests were carried out on the anchor plate.
The stay cable adopts parallel steel wire system, and the standard strength of steel wire is 1670MPa. The diameter of steel wire is 7mm, and there are seven specifications for stay cables (187,15,199,253,283,313,349). Finished cable 136(* *). The cable plane is a spatial cable plane, the distance between upstream and downstream of stay cables is 35.2m, the standard cable distance along the bridge direction is 12m, the tail cable near the end of the side span is encrypted, the cable distance is 4 m, and the vertical distance of stay cables on the tower is1.6m. The whole stay cables are protected by protective sleeves, and the outer surface of the protective sleeves is provided with spirals to suppress the occurrence of rain vibration.
Important significance
Jiangjin Guanyinyan Yangtze River Bridge is an important line connecting Xipeng in Jiulongpo District of Chongqing and Xianfeng Town in jiangjin district. The Chongqing Ring Expressway with a total length of 186 km will be completed and opened to traffic. After opening to traffic, it takes only about half an hour to drive from the main city of Chongqing to Jiangjin via Chengdu-Chongqing Expressway and Ring Expressway, with a mileage of about 50 kilometers in expressway. It takes only 40 minutes to reach Jiangjin city, saving about 30 minutes compared with the current running time.
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