199918: 5010.4, the Rainbow Bridge in Qijiang County, Chongqing collapsed as a whole, causing 40 deaths and/kloc-0.4 injuries, resulting in a direct economic loss of 63 1 10,000 yuan.

Basic situation

Rainbow Bridge in Qijiang County is located on the Qijiang River in Gunan Town, Qijiang County. This is a footbridge across the river, connecting the old and new urban areas. The bridge is a half-through concrete-filled steel tubular basket arch bridge with a length of140m, a clear span of the main arch of120m, a total width of 6m and a clear width of 5.5m. The bridge started on19941.5,/kloc-0. During the construction, the original design of open caisson foundation was changed to enlarged foundation, and the foundation was embedded in the cornerstone. The main arch steel pipe is processed into 8-meter-long standard section by the Labor Department of Chongqing General Machinery Factory, and the full arch steel pipe is welded, assembled and closed without any quality assurance information in the standard section. After the steel pipe arch is formed, the pipe section in the pipe is filled with concrete. The bridge deck is supported by suspenders, beams and portal frames. The derrick is anchored by group anchors, and the anchorage model is YCMl5-3. 1March, 99615th, the bridge was put into use without the approval of the legal institution, and the project cost was 4180,000 yuan.

Accident process

1October 4th 1999 18: 50, more than 30 people walked on the rainbow bridge and 22 armed police soldiers were training. When they lined up to run about two-thirds of the bridge from west to east, the whole bridge suddenly collapsed and all the people on the bridge and the armed police soldiers fell into the river. After struggling to save them, they were saved.

Direct cause

The locking mode of the main arch steel strand is wrong, which can not guarantee the effective locking and uniform stress of the steel strand. Part or all of the steel strand at the anchor head slips out, which makes the anchorage of the steel strand of the boom invalid.

Welding problems of main arch steel pipe In the factory processing of main arch steel pipe, serious defects such as cracks, incomplete penetration, incomplete fusion, porosity and slag inclusion generally exist in butt weld, and the quality can not meet the acceptance standard of secondary weld stipulated in construction and acceptance specifications.

Concrete-filled steel tube problem The concrete-filled steel tube strength of the main steel tube can't meet the design requirements, and leakage occurs in some places, and even a cavity with a length exceeding 1 m appears at the main arch rib plate. There are also serious quality problems in grouting protection of suspenders.

The design problem is rough and can be changed at will. There are no clear requirements for the material, welding quality, joint position and anchor locking quality of the main arch steel structure during construction. The bearing capacity of the main arch can not meet the requirements of the corresponding code after the bridge is loaded with flower terrace and other loads.

Due to the poor management of the bridge, after the anchorage failure of suspenders and steel strands accelerated, the old failure cracks occurred in the arch steel pipe of the lower support at the west bridge head, and the stress of the main arch deteriorated sharply, which has become a dangerous bridge.

remote cause

The construction process seriously violates the basic construction procedures. Did not go through the formalities of project approval and plan approval, planning land acquisition, design review, construction bidding, construction permit, project completion acceptance, etc.

The qualification of design and construction subject is unqualified. Private design, illegal drawing; The construction contractor violates the law; This is a serious violation of the contract.

Management confusion. Individual leaders in Qijiang county have too much administrative intervention, and they are arbitrary about many problems in engineering construction, lacking restraint and supervision; The responsibilities of the construction owners and county construction administrative departments are confused, the responsibilities are not implemented, the project contracting is chaotic, and the management is seriously dereliction of duty; The general contracting project in the contractual relationship is chaotic, and the general contractor has seriously neglected his duties; Construction management is chaotic, design changes are arbitrary, procedures are incomplete, technical management is weak, responsibilities are not implemented, and construction quality of key processes and important parts is not checked; The management of materials and components in the site is out of control, and the test is not carried out as required. The main arch steel pipe processed by the external processing unit is delivered to the contractor for use without passing the welding quality inspection; The quality supervision department accepted the entrustment of quality supervision without strictly examining the construction conditions of the project, failed to perform its duties seriously, and failed to effectively stop the wrong practice of delivering the project without acceptance; The management of engineering archives is chaotic, and there is no special person to manage it; Forced use without acceptance.

In addition, the corruption of a few leading cadres in charge of project management is serious, which makes all the management systems stipulated by the state exist in name only.

Accident lesson

Carry out a major inspection of project quality. After the accident, all relevant units in Chongqing carried out a large-scale inspection of the quality of the dragnet project within the city, focusing on whether the qualifications are consistent, whether the procedures are legal and whether the quality is qualified. For the existing completed projects with quality and safety problems, find out one and thoroughly rectify one. The stopped projects must be resolutely stopped, the unqualified ones must be resolutely cancelled, and the responsible person should be replaced immediately. For the built buildings (structures) with potential quality and safety hazards,

Focus on rectifying the construction market in Qijiang County, and standardize the main behaviors of all parties involved in the construction. In view of the chaotic construction market in this county and the extremely irregular behavior of all parties involved in the construction, Chongqing helped the county solve the fundamental problems and weak links in management and urged the county construction Committee to rectify the construction market.

Further strengthen the management of the construction market and construction site. Chongqing strictly implements the project legal person responsibility system, bidding system, contract management system and project supervision system, insists on separating government from enterprise, and insists on collective decision-making on major issues. No one may interfere with the open, fair and just bidding of a project. For construction projects that do not meet the specified requirements, once found, the funding will be stopped immediately.