The under-supported CFST tie arch is a statically indeterminate structure. The upper and lower parts of the bridge are integrated into the foundation and even the foundation. The structure is more statically static and the force is complicated. Because the stiffness of the tie rod is much smaller than the stiffness of the tie beam of the arch-girder combination system, especially for long-span bridges, the tension of the tie rod will be greatly deformed, while the rib, tie and pier are consolidated. At the same time, according to the displacement deformation coordination condition, the increase of the horizontal thrust of the arch is mainly taken up by the pier and the arch rib itself, and thus it is considered to have a thrust structure after the deformation of the tie bar. It is precisely because of the structural characteristics of the under-supported CFST tie rod arch, and the difficulty of the arch rib in the construction, it is necessary to strengthen the quality control of the construction.
1 Arch bridge arch rib construction scheme Arch bridge scheme The arch rib is constructed by cable hoisting. According to the hoisting capacity of the cable hoist, the arch ribs are prefabricated in sections, and the two arch legs are first hoisted in place by the cable hoist and fixed by the buckle Then, hoist the remaining sections in turn and dock with the first hanging section until the lifting is completed. During the entire hanging process, the cable tension should not be adjusted frequently. Therefore, before each section of the rib hoisting construction, an accurate estimation should be made for the pre-lifting value of the hanging point label and the cable force of the buckle. It is built by cable hoisting method.
The air inlet device with air filter should be installed in the cool and clean place of the main wind direction as much as possible. The air exhaust device should be installed on the top of the wall opposite the air inlet device to form the wind as far as possible. The delivery device can be evenly distributed as soon as possible without leaving a dead angle.
In addition, the air inlet should be as low as possible, and the danger of winter covered with snow should be avoided; the risk of dust, explosive or corrosive substances entering the air compressor station must also be considered.
According to the actual operation of the existing air compressor station, the air-cooled air compressor station is very beneficial to reduce the temperature inside the air compressor station after installing the ventilation duct. Therefore, when the air-cooled air compressor and dryer should be installed with the air duct, The number of arch ribs is large, the single-piece lifting stage is large in volume and complex in structure, which is likely to cause the actual line shape of the arch to deviate from the ideal line shape during the construction process. For the long-span arch bridge with cable hoisting and cable-stayed construction, the key technology of construction control is the determination of the cable force and the determination of the arch and beam positioning elevation. Especially when the buckle and the back cable are constructed with steel strands, it is objectively required that the buckles and the back cables should be reduced as much as possible, and the elevations are not allowed to be repeatedly adjusted. Otherwise, it is easy to cause the loss of the cable due to slack of the steel wire, or even slippage. Quality accident.
The hanging tower is placed at the top of the buckle tower, and the hoisting crane tower and the buckle tower are hinged to minimize the interference to the buckle anchor system. When the cable hoisting system is designed, the hoisting main cable system is divided into two groups, which can be conveniently combined.
The hoisting stage is the most unfavorable stage of stress. The difficulty of arch rib lifting and overhanging construction has the following aspects: 1) The maximum weight of the arch rib is large, and its lifting is difficult. How to formulate reasonable lifting conditions, how to cable the lifting system Design, there are many problems that need to be solved.
2) The arch rib cantilever length is large, and the stability risk during the hoisting process is large. As the span increases, the stability factor will decrease and the road will decrease. When designing the ventilation duct, pay attention to whether the wind pressure of the self-contained fan of the calibration equipment is greater than the resistance loss of the air duct. When the wind pressure is less than the loss of the air duct resistance, the fan should be installed. When designing the air duct, do not use a ventilator, it should be m/s; when using a ventilator, it should be 6~10m/s.
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