The main bridge structure of Hongshanmiao Bridge is a cable-stayed bridge with inclined tower without backstays, with a main span of 206 meters and a bridge width of 33.2 meters. There are no piers under the bridge. The vertical height of the bridge tower is136.8m. If the steel shell base is added, it will exceed 150m, which is equivalent to a 50-story building. Tower foundation adopts enlarged foundation. The plane size of the foundation is 3 1m, 30m, the height of the foundation is 1 1m, and there are 25 anti-slide piles with depths of 2m and 5m respectively. The inclination of this tower is 58 degrees. The tower and deck are completely inclined 13 parallel steel wire with harp. The tower adopts hollow reinforced concrete structure with equal cross section and thin wall, which is consolidated with the tower foundation. The tower is a fully prestressed concrete box structure, the main beam is a steel-concrete composite structure, and the parent material of some steel structures is 16Mnq. The stay cables are made of high-strength and low-relaxation galvanized steel wires with a diameter of 7mm, which are bundled and twisted into finished cables. The auxiliary holes of pier 2 #-3 # on the south bank are prestressed reinforced concrete box girders with a span of 30.305 meters. Prestressed reinforced concrete box girder is used as the cross beam of the special-shaped block ramp of the main tower/pier KLOC-0/# on the north bank, with a width of10m and a height of1.25m, and it is single box and three rooms. In order to ensure the construction safety of the main bridge, the concrete leaning tower method with steel main girder is adopted. The steel beam is constructed by multi-point continuous incremental launching method, and the installation of the steel beam is completed by setting temporary piers and guide beams. During the design and construction of the bridge, a series of new technologies were boldly adopted, including the balance construction technology of the main beam of the leaning tower, the adjustment construction technology of the double stress cables of the beam tower, the design and construction of the super-long steel-concrete cantilever beam of 14m, and the torsion design and construction of the large hexagonal steel box beam. The application of these technologies breaks through the traditional design and construction organization scheme, enriches the international bridge construction theory and fills the gap in the history of bridge construction in China. The project was undertaken by the Fifth Company of China Railway Bridge Bureau Group under China Railway Engineering Corporation. Overall design and key technology research of Changsha Hongshan Bridge (cable-stayed bridge with inclined tower without backstays) 1. Geographical location of the bridge Changsha Hongshan Bridge is a super-large bridge on the North Second Ring Road of Changsha, which spans Liuyang River and is one of the key projects in the ring road construction. Hongshan Bridge connects Sifangping Interchange in the south and Laodaohe Bridge in the north. The bridge is located in Hongshan Temple Leisure Resort, which is less than 2 kilometers away from the airport expressway in the east and less than 3 kilometers away from Changsha Window of the World in the north. Because the geographical location of the bridge is very important, the owner unit Changsha Huancheng Road Construction Headquarters decided to build the bridge into a landmark landscape building in Changsha from the requirements of improving the grade of the provincial capital city. Later, Hunan University put forward the plan of harp cable-stayed bridge with leaning tower without backstays, which was submitted to the municipal government office meeting for discussion and approval. Hongshan Bridge, with a main span of 206 meters, will become the largest bridge in the world. This paper briefly introduces the overall design and key technology research of the bridge. 2. Geological conditions and other natural conditions are briefly described as follows: the bedrock of the bridge site is shallow, most of which is exposed, and the lithology is slate of Lengjiaxi Group in Mesoproterozoic. The characteristics of slate in each layer from top to bottom are as follows: ① Strongly weathered slate, brownish yellow, silty slate and argillaceous slate, with soft and strongly weathered rocks, extremely developed joints and fissures, broken rocks and low core recovery rate. ② Weakly weathered slate, yellowish gray, grayish yellow and gray, with silty slate and argillaceous slate, brittle lithology, developed joints and cracks, slow drilling speed, layer thickness of 2.5 ~ 1 1.0m, and layer top elevation of19.55438+0 ~ 25.66mm. ③ Weathered slate, bluish gray, gray, silty slate and argillaceous slate, fresh and hard, with well-developed foliation. The drilling speed is slow, and the cores are mostly blocky, columnar and broken. The buried depth of the top layer is 13.5 ~ 22.0 m, and the elevation of the top plate is12.8 ~19.93 m. Geological exploration has not revealed this distribution, and the allowable bearing capacity [σ 0] = 2700 kPa. The once-in-a-century height of the bridge site is 10min, the average maximum wind speed is 28 m/s, and the dominant wind direction is northwest wind. The basic intensity of Changsha earthquake is ⅵ degree, and this bridge is fortified at ⅶ degree, and the bridge site is on Class II site. Meteorologically, Changsha is located in the subtropical zone, affected by the monsoon, with abundant rainfall. The highest temperature over the years is 40.6℃, the lowest temperature is-1 1.4℃, and the annual average temperature is 17. 1℃. Three. Main technical standards and span 1. Road grade: urban expressway grade 2. Design load: six-lane car-class 20, trailer-120; The crowd load is 3.5kN//m2, and a 3000kN overweight vehicle is used as the check load. 3. Bridge width and road width constitute the whole bridge width: 33.2m Road width: 2 * [0.5m crash barrier +0.5 safety belt +2*3.75+3.5 roadway +0.5 safety belt +2. 1 guardrail and anchor cable area 14.0/2 pedestrian walkway] = 33.2m4 Calculation span: 206m 4. Main bridge design points L. The cable tower and foundation cable tower adopt prestressed concrete box structure. The profile of the section is 12m (along the bridge) * 8.2m (across the bridge), the horizontal inclination of the tower body is 58, and the height of the tower (above the bridge deck) is 135m. For cable-stayed bridges with inclined towers without backstays, the self-weight design of towers is one of the key issues. In order to ensure that Suo Wenhua is in a good stress state, we determine the self-weight of the tower according to the following principles. That is, when all dead loads and semi-live loads act on the beam, the tower is in an axial compression state, as shown in Figure 2. According to the geometry and balance relationship (cables are arranged in parallel), it can be concluded that the center of gravity of cable tower segment is determined in principle according to the above formula, and the C value of Hongshan Bridge is 2.432, and the concrete volume of tower body is relatively large. Finally, in order to reduce the center of gravity, the cable tower is designed in the form of variable wall thickness (lower thickness and upper thickness), and the concrete volume of the whole cable tower is about 6700 cubic meters. The sidewalk of Hongshan Bridge is located between two cable planes in the center of the bridge, which is about 2m higher than the carriageway. In order to facilitate pedestrians and ensure smooth traffic, a pedestrian hole with a height of 9m and a width of 3m was opened at the root of the tower (Figure 3). There is also a sightseeing elevator in the tower, and there is a viewing platform at the top. Due to the good geological conditions of the bridge site, the bedrock is outcropped, and the wall foundation adopts 3 1m (horizontal) *30m (horizontal) * 9m (high) to expand the foundation, and the eccentricity of the basement is less than 0.5m under the most unfavorable combined load. 2. The main girder of the main girder is a steel-concrete composite structure. A rectangular closed steel box beam with a height of 44m *7.0m (width) is set in the center of the bridge (box wall thickness is 28mm), and a box steel cantilever beam with a length of 12.9m is set every 4m along the bridge to form a spine frame structure system. Part of the base material of the steel structure is 16Mnq steel, and the steel cantilever beam is covered with a concrete bridge deck with a thickness of 2 10mm, and the bridge deck and the steel cantilever beam are connected by a φ22mm shear studs with a spacing of 120mm. Compared with the conventional cable-stayed bridge, the cable-stayed bridge without backstays can provide less stiffness, so under the live load, the internal force amplitude of the main girder is relatively large, so it is difficult for the ordinary reinforced concrete structure to bear this large internal force amplitude and it is easy to crack. Therefore, the concrete deck of Hongshan Bridge is placed near the neutral axis of the main girder. From the overall stress, the bridge deck only bears axial force, while the steel box girder bears axial force, bending moment and torque. In order to prevent the steel box girder from fatigue damage due to excessive stress amplitude, Hongshan Bridge, like Alamiro Bridge in Spain, has a beam height of 4.4m, and the section size of the steel box girder is designed by torsion control, including the first kind of torsional stability and lateral torsional stiffness. For the local stability of the bearing plate of steel box girder, because there is no highway bridge calculation code in China at present, we use the design standard and description of the superstructure of Shikoku Bridge in Honshu, Japan (1989) and the design code of highway bridge in America (1994) to calculate the local stability, and the results are basically the same. 3. The cable-stayed Hongshan Bridge is a single cable plane structure, with the distance between two rows of cables across the bridge of 6m and the distance between cables along the bridge of 12m. *** 13 has 26 pairs of cables, all of which have a horizontal inclination of 25. The cables are arranged in parallel, with a length of 65.9~289.8m The cables are made of φ7 high-strength low-relaxation galvanized high-strength steel wire, which is corrosion-resistant. Hongshan Bridge is a cable-stayed bridge with inclined tower and single cable, which is obviously different from the conventional cable-stayed bridge. Therefore, the anchorage mode of stay cables on tower beams (especially towers) deserves careful consideration. After many times of analysis and calculation, the cable is finally anchored on the neutral axis of the tower, which is one of the differences from the ordinary cable-stayed bridge. If the cable is anchored to the front box wall, the concentrated force at the anchorage point will produce a large additional couple on the section of the tower box, and the bending moment generated in the tower can account for more than 30% of the total bending short, resulting in poor stress of the tower under long-term load. Therefore, it is necessary to place the anchor point on the neutral axis. The maximum stress amplitude δ σ of the cable is 90MPa, which is small, so the fatigue of the cable is not controlled. 5. In the modal analysis and calculation results in the preliminary design stage, the mechanical characteristics of Hongshan Bridge are comprehensively analyzed and calculated, and the cable adjustment of the beam tower with double control stress is calculated by using the plane bar finite element method; Modal characteristics, stability and seismic performance are calculated by space bar finite element method. The torsion of the main girder is calculated by the plate-shell element method. The eight-node hexahedral element method is used to calculate the local stress of the anchorage point of tower cable and the bond between tower and beam. The Alamiro Bridge in Seville, Spain, was built at 1992 and designed by Santiago Calatrava. This is the world's first long-span cable-stayed bridge with leaning tower without backstays. Alamiro Bridge has a main span of 200 meters and a width of 32 meters, which is slightly smaller than the construction scale of Hongshan Bridge. Through the spatial calculation of the dynamic modal characteristics of Hongshan Bridge, it is found that the calculated and measured results are basically consistent with those of Alamiro Bridge, as shown in Table 65438+. Scientific research on intransitive verbs In order to ensure the construction safety of Hongshan Bridge, after the preliminary design of the bridge was completed, the following three problems were specially studied: (1) 1:30 full-bridge similar model test. The main purpose of the test is to investigate the overall mechanical properties of the bridge during construction and operation, including stress, deformation, stability and effective distribution width of the bridge deck. (2) Tower-beam bond 1: 6 segment model test. The main purpose of the test is to investigate the distribution law of horizontal component after the cable reaches the tower root, and to investigate whether the bending and torsion stress characteristics of steel box girder meet the design. (3) Wind tunnel tests of segmental and full-bridge models. The aerodynamic parameters of each section, the wind speed of vortex-induced vibration, the maximum amplitude of buffeting and the critical wind speed of flutter instability are determined, and the results of the maximum wind-induced internal force are given Seven. Conclusion Hongshan Bridge broke ground on 1999 12.30 and was built by the Fifth Bridge Bureau of the Ministry of Railways. According to the plan, the bridge will be completed by the end of 200l, and the construction of Hongshan Bridge will contribute to the development of China's bridge industry.