The safety risks of complicated suspension bridge construction are divided into several parts, such as anchorage construction, main tower construction, cable saddle hoisting, catwalk erection, main cable erection, sling and cable clamp installation and steel box girder hoisting, so as to prepare for construction safety management.
A, anchorage construction safety risk analysis
Anchorage is an important structure for transmission and bearing of main cables of suspension bridges. From the local construction of anchorage, there are a lot of excavation, drilling, milling, chiseling, hammering and other construction operations, such as steel bar production, steel cage transportation, steel cage hoisting and so on. Template transportation, assembly, installation and removal, concrete pouring and maintenance, anchoring system construction. These working environments are characterized by narrow workplaces, mixed workers, diverse construction equipment and more temporary electricity consumption. A little carelessness in the construction process will easily lead to falling from a height, object hitting, lifting injury, electric shock and collapse accidents.
Second, the main tower construction safety risk analysis
The construction of main tower includes the construction of foundation, cap, tie beam, tower foundation, tower column, cross beam, tower body and bridge infrastructure. In these partial construction links, due to the existence and influence of many factors, such as the design of construction scheme and construction safety technical measures, the safety of the construction process, the construction working environment, the construction climate conditions and the implementation of various construction safety measures, negligence in the construction process will inevitably lead to safety accidents such as falling from a height, hitting objects, lifting injuries and electric shock.
Third, the cable saddle hoisting construction safety risk analysis
Suspension bridge cable saddle hoisting includes the hoisting construction of main cable saddle and loose cable saddle. Because the main cable saddle and loose cable saddle of suspension bridge are large components, these components are the main cable support and positioning components of suspension bridge beam, which are heavy. The saddles of the main cable saddle and the loose cable saddle weigh tens of tons or even nearly a hundred tons, and the components are huge, with the maximum length and width up to nearly 10 meter and the width and height up to 4 ~ 100 meter. Therefore, the hoisting construction of large components such as cable saddles is prone to safety production accidents such as lifting injury (even serious accidents that lead to machine crash and death), falling from a height, object strike and electric shock death.
Four. Safety Risk Analysis of Erection and Demolition of River-crossing (Sea-crossing) Diversion Cable and Catwalk
After the construction of the anchorage, pylon and saddle of the suspension bridge is completed, the erection of the main cable will begin immediately. Before the erection of the main cable, construction procedures such as crossing the river (sea) and catwalk erection must be carried out. In the towing process of the guide cable, the ships used, the hoisting system and the operators directing the towing construction must be carried out in accordance with the requirements of the standardized, reliable and feasible construction scheme, and can be successfully completed with the cooperation of the strict navigation closure measures of the maritime department. In ropeway traction, catwalk erection and demolition, long-term aerial and water work can be successfully completed only on the premise of rigorous and feasible construction scheme and safety technical disclosure before construction. These operations are often easy to happen: vehicle injury, drowning, object strike, falling from a height, electric shock accident.
Five, the main cable erection construction safety risk analysis
The traction of the main cable strand of suspension bridge beam depends on the traction system, and the main cable erection of bridge generally adopts the gantry single-line reciprocating traction system. The main traction winch is arranged behind the anchorages on both banks, and the cable releasing mechanism is arranged on the ground behind one of the anchorages. Traction system consists of main traction and auxiliary traction. The main traction part is the traction between the rear anchorage surface of one anchorage and the other anchorage, and two winches are used for traction. The auxiliary traction part is the short-distance traction between the cable bracket behind the anchor and the anchor surface, and the winch equipped with the anchor block is directly used as the power. For the main traction and auxiliary traction, installing cables and brackets between steep anchor surfaces and installing traction ropes on the anchor surfaces directly affects the safety of construction operations, such as the leveling and compaction of the ground supported by brackets on the anchor surfaces, the standing stability of overhead welding operations, the safety and reliability of steel wire ropes, the wearing of safety protection articles by construction workers, the safety and reliability of cranes, chain chains and other facilities, and the influence of weather conditions on catwalk overhead and water operations.
Six, sling and cable clamp installation construction safety risk analysis
Dozens or even hundreds of pairs of main cable clamps and slings on suspension bridges are important structures that transfer the dead load of steel box girder and deck system and the live load of steel box girder to the main cables, while maintaining the shape of the main cables and making the steel wires more evenly stressed. In the process of installing the main cable clamp and sling, the cable clamp is transported to the bottom and anchorage of the tower by flat trucks and barges, and installed to the top of the tower one by one. When lifting the cable clamp, it is necessary to dismantle the cat gantry, keep the crane load-bearing cable fixed between the loose saddle gantry and the tower gantry, and install a simple crane beam. In order to ensure the technological requirements of the main cable of suspension bridge, the temperature stability of the cable clamp installation process must be ensured. Therefore, when installing slings and cable clamps, there are construction safety risks such as lifting injury, object strike, drowning and electric shock.
Seven, steel box girder hoisting construction safety risk analysis
The hoisting of steel box girder focuses on multi-level three-dimensional operations such as water, land and high altitude. It is a suspension bridge construction with high operational risk, complex construction conditions, many working procedures, long construction period and numerous equipment. Because the hoisting construction of steel box girder generally adopts cable-crossing machine, hoist, pulley block, tugboat, flat-bottomed boat and other equipment, the construction process is affected by the construction period, tide, weather change, construction environment and other aspects, and it is easy to have serious or major safety accidents such as falling from high altitude, object strike, lifting injury, drowning in water, mechanical injury, ship collision and so on.
Eight. conclusion
Suspension bridge construction has the characteristics of long construction period, great difficulty, many equipments, rapid change, poor environment and high risk. However, before construction, the possible major risks should be reasonably evaluated, so as to formulate perfect safety management measures in the construction organization design and construction scheme, establish a reasonable and complete safety organization in the basic management of construction safety, implement effective safety education and safety supervision for construction personnel, and implement standardized management in the management of construction equipment, so as to truly achieve full, all-round and whole-process safety control. Effectively control safety risks, so as to effectively reduce lifting injuries, object strikes, falling from a height, electric shock and other safety accidents. In order to meet the requirements of efficient construction and safe and low-risk management of suspension bridge and ensure the smooth construction of suspension bridge.
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