Wusu Bridge, located in Wusu Town, Fuyuan County, Heilongjiang Province, is an important port bridge between China and Russia. Located in the border, it is inconvenient to organize manpower and material resources, and it is inconvenient for mechanical materials to enter the market. Long winter time and short construction time.

The main bridge of Wusu Bridge is a cable-stayed bridge with single tower and single cable plane, and the large cantilever steel box is combined with the deck section. Steel boxes are manufactured in sections in the factory and welded integrally on site.

The main girder is 280 meters long, 26.5 meters wide and 3.55 meters high. It is divided into 365,438+0 segments along the longitudinal direction. The consolidation section (0#) of the middle tower beam is 15m long, which is a reinforced concrete structure, and the rest is a composite beam structure of steel box beam and reinforced concrete slab. The steel box girder * * * is divided into 30 sections, of which 26 standard sections (Z2 ~ Z 14) are 9m long and weigh about 95.4t, and two side span cableless sections (Z 15) are1.9m long and weigh about/kloc. The cable-free section of the tower column (Z 1) is 3.5m long and weighs about 37.5t

Figure 1 Section Layout (unit: m)

2 Scheme comparison and selection

According to the geographical location of the project and previous construction experience, two main girder erection schemes are preliminarily drawn up: bracket method and cantilever erection method.

2. 1 Support method

Steel box girder is installed by bracket method. The support is arranged at the main span 12m, and the support forms are steel pipe piles and Bailey beams. The steel box girder segment is hoisted to the support by a 500t floating crane. Temporary connection after adjustment, then welding construction, lifting the bridge deck.

The scheme has the characteristics of fast construction speed, parallel operation with the main tower construction, large floating crane cooperation construction, difficult erection of water support and high cost. The construction speed is fast, but according to the progress, the support needs to cross the ice at one time, and the structural safety risk is great.

2.2 Cantilever erection method

Design a special bridge deck hanger to lift the steel box girder and bridge deck as a whole. After the steel box girder is welded, install the bridge deck.

The scheme is characterized by symmetrical cantilever installation, suspension welding instead of large floating crane, difficult bridge deck installation and long construction period, and the main girder can not be constructed until the tower column is completed. The winter vacation season is not affected by the weather.

Considering the special geographical location of this project, it is more reasonable to adopt the hanger method for construction. In the design of hanger, the functions of steel beam welding and bridge deck installation are considered comprehensively.

3 hanger design

There are two general hanger forms: (1) diamond or triangle, which is composed of welded steel; (2) Flat chord type composed of box girder or Bailey beam. In view of the fact that the hanger is also used as bridge deck installation equipment, and there is no operating platform at the back end of diamond or triangle, the flat chord hanger composed of Bailey beam is selected.

The flat chord suspender is mainly composed of the following parts: main truss system, walking system, lifting system and deck installation system.

The main truss system includes Bailey truss, parallel connection, cross beam and rear anchor beam. The walking system includes a walking beam, front and rear walking legs and a temporary jack. The lifting system includes lifting top beam and a full set of SLD hydraulic lifting system provided by OVM company. The deck installation system includes deck lifting equipment and running slideway. Its overall layout is shown in Figure 2.

Fig. 2 Overall layout of hanger (unit: mm)

3. 1 main truss system

The main truss adopts double-layer reinforced Bailey beam, and all components can meet the requirements.

Table 1 Calculation Results of Bailey Beam after Reinforcement

3.2 Walking system

The slideway consists of two 6m long steel beams, which are completed in two steps. After the slideway is laid, the main girder should be laid first. After the main girder is laid for 4.5m, lift it, and lift it with temporary jack. The slideway is anchored 4.5m forward, and the main girder is laid 4.5m backward.

3.3 lifting system

The lifting system needs to lift the steel box girder, steel cantilever and upper bridge deck from the water surface to the installation position, and the lifting weight is 260t t. The lifting equipment adopts a full set of SLD hydraulic lifting system provided by OVM Company. The lifting platform is located at the front end of the cantilever of the main girder, and the lifting platform moves back and forth on the main girder through the longitudinal moving device, which is convenient for the contraposition installation of the steel girder. A special spreader is designed to hoist the main girder, and the position of the hoisting point can be adjusted to meet the hoisting needs of different sections and different centers of gravity.

3.4 Deck Installation System

Because the concrete bridge deck is located at the joint of the steel beam, it is necessary to weld the steel beam before installing the bridge deck. Walkway beams are set on both sides of the main girder to realize the extraction, movement and installation of the concrete bridge deck lifting system.

4 construction points

Hanger can meet the cantilever erection of main girder, but it is necessary to use crane boat or fixed hanger to complete the initial block. In the process of using the hanger, strong wind operation must be avoided. In order to ensure the stability and synchronization of walking, two groups of main trusses are connected into a whole through beams.

5 abstract

In the design of modern cable-stayed bridges, steel-concrete composite beams are becoming more and more common. In the construction process, the scheme of lifting the composite beam as a whole before installing the bridge deck can effectively reduce the cost and risk. The design of the bridge deck installation system on the main girder breaks the conventional practice of installing the bridge deck with truck cranes, which makes the construction process connect smoothly and obviously reduces the construction cost. This technology has universal reference significance in the future construction of cable-stayed bridges.

The above are collected and sorted by Zhong Da Consulting Company.

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