I. Equipment structure
1. Tower and tower foundation. The tower foundation is made of C25 concrete, embedded with steel bars and welded with the tower foundation. This tower is assembled from universal bars. The top of the tower is equipped with 4? Eight-character rope wind belt vertebra 37.5, tower waist setting 4? Lumbar cord wind 37.5.
2. Main cable. The main cableway adopts 4? Spine wire rope is 37.5, left bridge span is 280 meters, working sag is 30.6 meters, right bridge span is 300 meters, working sag is 32.7 meters, and they are anchored on the ground anchors on both sides.
3. Lifting rope. The sling is wound on the antenna pulley block, one end of which is fixed on the tower, and the other end passes through the antenna pulley block and the hoist to carry the hoisted object. Choose soft, wear-resistant and knotty steel wire rope.
4. Traction rope. The traction rope is an endless rope that drags the antenna pulley back and forth along the main rope without tension. Choose flexible wire rope.
5. Buckle system. Fastener system consists of fastener rope, fastener frame, machinery, pulley, hoist and ground anchor.
6. Wind power cable. Wind cables are divided into side wind cables and opposite wind cables. Lateral wind cables are used to stabilize box girder and adjust the axis of arch box; One end of the opposite wind cable is fixed on the ground anchor, led to the other end through the tower and fastened on the ground anchor.
7. Antenna pulley. Antenna block is a device for running and lifting heavy objects on the main ropeway. It consists of wheels, lifting pulley blocks and a traction system.
8. saddle. Generally, the cable saddle is fixed on the center line of the cable tower, and it is arc-shaped, and its radius should be >: cable diameter 12 times or more; 300 times the diameter of steel wire.
Second, the cable crane system layout (see figure 1)
1. Cable TV system. According to the weight and structural form of the steel arch rib segment of the bridge, the cable span of the bridge hoisting system is 440 m, the length of the main cable is about 1 200 m, and two groups of main cables are adopted. A single group of main cables consists of 7 +50 sealed steel wires, and the designed lifting weight of the single group of main cables is 100 t, and the total lifting weight of the two groups of main cable systems is 200 t ... Two groups of working ropeways are arranged upstream and downstream of the main cables of this bridge. It is used for hoisting cross-supporting structures and other auxiliary building installation projects, and hoisting and transporting construction machinery and materials below 5 t.
2. Fastening system. The design of fastener system is influenced by many factors, such as topography, geology, segment weight and so on. The stress calculation results will determine the design of fastening point structure, fastening saddle, fastening ground anchor and fastening end beam, and also affect the installation sequence and construction period of arch rib segments and cross brace structures, which is closely related to the installation accuracy and construction safety of steel arch ribs of this bridge. 1 860 MPa+ 15.24 mm high strength and low relaxation steel strand is used for the buckle cable, and the anchorage end of the buckle point structure near the end of the hoisting steel arch rib segment is treated with pier head. The steel strand turns to the tensioning end of the ground anchor through the buckle saddle, and the tensioning end adopts the clip anchorage, and the cable force is adjusted by the jack. By loosening the lifting cable, tightening the jack and closing the fastening cable, the vertical force of the arch rib is lifted by the cable.
3. Tower system. The main tower on the left bank is placed on the main pier, and the middle column of the tower needs to be provided with an enlarged foundation between two separated piers; The main tower on the right bank is erected on the subgrade behind the abutment of the approach bridge. The left bank tower height108m, and the right bank tower height is 94m. In addition, the width of the two ribs at the arch foot is about 36 m, considering that the cable saddle flat cars of a group of ropeways at the top of the tower occupy about 3 m on both sides of the tower, the width of the top of the main tower is 48 m, and the width of the bridge along the tower is 4 m. According to the actual terrain of the construction site and the preliminary cable force calculation results, the leaning towers on both sides are arranged in front of the main tower, and the elevation of the top of the leaning tower is controlled so that the horizontal included angle between the last stay cable and the arch rib is not less than 6o.
4. Ground anchor system. The ground anchor of the cable hoisting system of the bridge adopts gravity ground anchor and pile anchor, and the ground anchor is composed of concrete and mortar rubble. In order to ensure the stability of the tower and adjust the verticality of the tower, according to the calculation, cables and wind cables must be set in the front, back, left and right directions of the tower. In the process of arch rib installation, cables and wind cables must be arranged in the upstream and downstream direction of arch rib to adjust the axis of arch rib during installation and ensure the stability of arch rib installation. Generally speaking, the cable wind rope ground anchor is not stressed, and Wolong ground anchor can be used according to the topographic and geological conditions. In order to reduce the stress of cable wind rope, the plane intersection angle between cable wind rope and arch rib should not be less than 45o.
Third, the cable hoisting construction
1. Arch box hoisting. The lifting sequence of arch box is arch foot section → secondary arch section → arch foot section → secondary arch section → vault closure section. After the inner single-rib two-span arch box is completed, the outer arch box is hoisted and closed, and then the main cable is moved laterally to complete the hoisting of the inner arch rib and the outer arch rib on the other side. After lifting it to the installation position, adjust it horizontally with the crosswind cable, at the same time, accurately reach the designated position, control the change of axis and elevation, the axis deviation shall be ≤ 10mm, the elevation of the upper joint shall be pre-raised 150 ~ 200 mm, and then fasten the crosswind cable and fix it.
2. Hoist the secondary arch. After the secondary arch joint is hoisted to the installation position, it will be moved in place by using the crosswind cable, the elevation of the upper and lower ends will be adjusted to make the joint elevation relative, and the joint bolt will be installed. At the same time, the upper and lower ends will be observed with two levels to control the elevation change. At this point, the connecting bolt should not be screwed too tightly, and a certain gap should be left. Tighten the secondary arch buckle first, then loosen the lifting rope once, and so on for many times until the lifting rope is loosened. Close the fastening rope every time, loosen the hanging rope, and observe with a spirit level. The lifting range of the upper joint shall be controlled at ≤ 5 ~ 10 cm.
3. Hoist the vault part. According to the order of the arch foot buckle first and then the second arch buckle, the two sides are symmetrical, and the buckle is relaxed evenly, and the cycle is repeated. The elevation change is controlled at the upper end of the secondary arch segment △y, which is about twice as much as the lower end of the secondary arch segment, that is, when △y = 2 △ y, the elevation change is limited to ≤ 10mm until the elevation of the upper and lower ends of the secondary arch segment is equal to the design elevation.
4. Rib smell tie beam hoisting. After the oven is hoisted, 4? The main cable of vertebra 47.5 is arranged in the form of 2×247.5 along the axis of two ribs, so as to facilitate the hoisting of inter-rib tie beams and other arch buildings and speed up the construction progress.
5. Hoisting the capping beam. The cableway crown block slowly transports the capping beam to a position about 50cm away from the upper end of the support, and then bolts the transverse cable wind rope. At the same time, release the short brake at one command and adjust the wind rope of the transverse cable, so that both ends of the capping beam are slowly in place at the same time. Observe the verticality of the installation with theodolite and hanging ball, and observe the elevation of the top of the capping beam with level. After meeting the design requirements, weld the joint immediately, cool it 1 ~ 2h after welding, unhook and dismantle the cable, and plaster the joint with high-grade cement mortar.
By summarizing the construction experience, this paper introduces the structural composition of cable hoisting equipment, which is different from the main arch concrete filled steel tubular arch bridge. Because the arch rib is inclined at a certain angle, only through full preparation, scientific analysis and reasonable calculation can the whole process be ensured to be safe and smooth. Practice has proved that the cable hoisting technology adopted is very successful, and its achievements have comprehensively improved the unsupported cable hoisting system of long-span bridges, which can be used for reference by similar bridges.
The detailed information of "Bridge Cable Hoisting Construction Technology" can be found in the link of Zhong Da Consulting Design, and all relevant building construction information you want is available.
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