Detailed explanation of superstructure construction technology of suspension bridge
Detailed explanation of the superstructure construction technology of the suspension bridge : Compared with the two-tower suspension bridge, we fully understand the bottlenecks encountered by the superstructure of the suspension bridge in the specific construction process. Analyze the equipment, equipment and construction plans used in the specific construction process, and explain the core construction links in the superstructure of the suspension bridge, mainly to make the superstructure of the suspension bridge better in design and construction .
1 construction case
The main bridge is a three-tower two-span suspension bridge, of which the bridge span is 390 + 1080 + 1080 + 390) m. A comparison between the three-tower two-span suspension bridge and the traditional two-tower suspension bridge reveals that during the construction of the three-tower two-span suspension bridge, the superstructure has difficulties.
(1) During the design of the main cable frame, it is necessary to cross the top of the tower multiple times, making the cable strand very easy to break, so new requirements are imposed on the quality of the traction equipment.
(2) The position where the catwalk crosses will be affected by the structure of the steel tower.
(3) The middle tower will be affected by factors such as temperature and natural environment, which makes it more difficult to control the main cable.
(4) The assembly of steel box suspenders encountered difficulties. The three-tower and two-span suspension bridge required the middle tower to be hoisted, so its control difficulty was greatly enhanced.
2 construction process
(1) Install the cable saddle
The cantilever lifting system of the tower mast lifts the main span of the main saddle of the side tower. In order to reduce the weight of transportation and lifting better, the saddle body needs to be divided into two parts for lifting, and then high-strength bolts are used for integration at the top of the tower. The main saddle in the middle uses a combination of cast and welded shells. The saddle does not need to be equipped with sliding wheels, etc., and the saddle body is manufactured separately, and then integrated with high-strength bolts at the top of the tower.
(2) Install catwalk system
When installing a catwalk system, a lighter, higher-strength fiber fly is used to tow the pilot cable on the water. Subsequently, the two main crossings crossed the river in an orderly manner, and the storage channel could be used normally. The use of the bracket method for erection of load-bearing cables will not affect normal navigation.
(3) Install the main cable
When installing the main cable, the traction system is towed from the north shore to the south shore by means of a door paddle pull, and the cable strand is adjusted appropriately using the reference cable method.
(4) Tight cable
Tighten the cables in the order of the primary and secondary spans. The way to tighten the cables in the main span is from the span to the middle tower, and the way to tighten the cables in the side span is from the anchor to the tower.
(5) Install the cable clip
When installing the cable clamp, it is necessary to install the cable clamp from low to high by means of a cable hoist, and in the specific construction process, the stud of the cable clamp needs to be tightened in multiple times.
(6) Install the sling
When installing a sling, you need to choose to install the sling vertically at the position of the clip.
(7) Installation of steel box girder
When installing a steel box girder, it needs to be installed with the help of a full hydraulic span cable crane. The entire suspension bridge has approximately 136 lifting beam sections, which need to be symmetrically installed from the main span body to both sides, following the smooth progress of the middle tower and the side tower.
(8) Main cable winding protection
The main cable needs to be wound from top to bottom. Wrapping is performed from the top of the tower to the anchor, and simultaneously at the up and down positions. After the side span is finished, the main span needs to be wound, in the same way. After all the cross-body wrapping is completed, it needs to be painted.
3 main construction equipment
(1) Tightening machine
Intelligent control of the main cable tensioner is suitable for the diameter range of 700-1000mm, and the fastening capacity of the main cable is about 6 × 2000kN. Intelligent control of the main cable tensioner consists of fastening equipment, mobile equipment and hydraulic equipment. It is manufactured in a modular way and is lightweight, easy to use and operate.
(2) Winding machine
The main cable winding machine is mainly applicable to the winding of round steel wire and s-shaped steel wire, and has a strong ability of continuous winding up and down. The tension of the main cable winding machine is 3kN, and the inclination angle can reach 30. , The speed of winding silk is extremely fast.
(3) Span cable crane
The hoisting force of the cable hoist is about 3700-3800kN, and the hoisting speed is 34-36m / h. The cable hoist is a large-scale mechanical equipment composed of multiple main parts, and the cable hoist can be installed and disassembled at the top of the tower and the center of the span at the same time, which greatly shortens the construction period and reduces the construction interference .
4 Key Techniques for Suspension Bridge Superstructure Construction
(1) Catwalk construction
Three-span and two-tower suspension bridges have different types of structures, and compare these different Lou structures with the connection processing part of the tower top. Finally, four-span continuous is selected as the main structural form, mainly because it has the following four Aspects:
a. The cat wall structure is not designed at the tower wall position of the middle tower, which can protect the middle tower beneficially.
b. When using a 4-span continuous method for construction, no unbalanced force will be generated, which will greatly reduce the impact on the span body, which will greatly reduce the difficulty of adjusting and installation.
c. The construction is carried out in a 4-span continuous manner, so that the top position of the catwalk and the main cable are more parallel, which is convenient for future operations.
d. Construction is carried out in a 4-span continuous manner, which greatly reduces the impact on the channel.
In order to greatly increase the erection speed of catwalk load cables, it is necessary to erection in two sections at a position of 30 cables. The catwalk load cables with the middle tower as the north-south direction of the dividing line are erected with four sets of traction systems. The two sections of the catwalk into the center, under the traction of the north and the south, the front anchor head first passed the side tower and then approached the middle tower, and the rear anchor head was pulled back to the anchorage by anchoring with the pulley of the hoist, thereby forming 4 consecutive catwalk load cables.
The catwalk load-bearing element of the main span needs to be indirectly erected by means of an aerial bracket. The distance between the brackets is controlled at about 100M. The weight of the catwalk load cable side tower can provide a certain back tension. Therefore, when the aerial bracket method is used for erection, the catway load cable will not affect the normal Sailing makes an impact. After the erection of the load line is completed, it needs to be adjusted.
(2) Main cable erection
The parallel cable strands used in the main cable erection are composed of 169 cable strands, and each cable strand is composed of 91 galvanized steel wires with a diameter of 5.2mm. The length of a single cable strand is about 3100m and the weight is about It is 475kg. During the main cable erection, the cable strands need to be numbered smoothly and used in ascending order.
The erection of cable strands generally consists of multiple procedures including traction and plastic surgery. The front Yin anchor head of the strand is connected with the puller, and then the winch is turned on to pull the strand, and the two winches are tightened and released at the same speed. In this way, the pulling speed of the strands and the speed of releasing the strands can be kept consistent, and the reverse tension of the strands can be controlled within a certain range, which effectively reduces the occurrence of loosening of the strands.
A torpedo fixture is set within a fixed distance. When traction is performed, a special person needs to be arranged to observe it, timely find the problems encountered, and solve them in time. After the cable anchor's rear anchor head is lowered from the cable tray, it needs to be placed at the anchor span position by means of a tower crane. When pulling the cable strand, it is necessary to mark the midpoint of the main tower saddle of the middle tower and the midpoint of the cable strand, and observe its heavy platform point. After the heavy platform is pulled, it is necessary to stop pulling the cable strand.
Before the cable strand enters the saddle, the cross section of the cable strand needs to be adjusted to a rectangular cross section. After the adjustment of the cable strand sections at the positions of the main cable saddle and the scattered saddle is completed, the cable strand needs to be placed in the corresponding saddle groove. In order to prevent the upper strands from squeezing the lower strands, the sag of the strands needs to be adjusted accordingly when entering the saddle. The adjustment position of the main span body center is controlled at 300-400m, and the adjustment position of the side span center is controlled at 100-200m.
After the strands are put into the saddle, the anchor heads of the strands need to be locked by means of a winch in the anchor chamber, and the anchor heads of the two sections of the strands must be fixed. When adjusting the sag, first adjust the main span, and then adjust the side span. Generally, the adjustment of the standard cable stock sag and the general cable stock sag is appropriately adjusted, and the others do not need to be adjusted.
Basic cable stock adjustment is generally adjusted by elevation method, and the general cable stock sag adjustment is corresponding to the basic cable stock adjustment. After adjusting the sag of the cable strand, you need to use a jack to tighten the nut to control its tension within the specified range.
4.3 Steel Box Girder Installation
When installing steel box beams, in addition to treating the slings as a whole, other sections of the lifting beams need to be hoisted in sections. The three-tower two-span suspension bridge has a total of 134 lifting stages, and the length of each lifting stage is 16m. When installing steel box beams, it is necessary to install them from the north-south direction to the middle direction. Each side of the middle tower and the position of the side tower need to set up a closing section, with a total of four.
- Previous: No more;
- Next: Some important links in the installation of suspension bridges in scenic spots
Contact: Manager Sun / Manager Du
Mailing address: Zhonglian Road, Xiaoji Town, Xinxiang County