A small expansion bolt caused a major accident
Thread Content
Investigation report on the collapse of the cooling water pipeline in the Changshu Wanda underground garage: The direct cause was incorrect selection and installation of expansion bolts, which resulted in insufficient strength of bracket No. 3; this led to the collapse of the air-conditioning cooling water pipeline, which struck a car that was entering the parking lot as well as the \"Legend Track\" car wash located beneath the pipeline. As a result, 3 people died – 2 passengers in the car and 1 employee from the car wash. Indirect cause 1: Jiangsu Qianan Construction Engineering Co., Ltd. provided a calculation sheet for the expansion bolts of the supports and hangers, but the sheet was not signed by any relevant personnel from the company; it was not reviewed and approved by the supervision unit, nor was it submitted to the general contractor, nor was it approved by the design unit ； The calculation sheet specifies that expansion bolts with a diameter of 12 mm should be used for the supports and hangers; however, in practice, expansion bolts with a diameter of 10.8 mm were used for those pipe sections (according to the \"Code for Construction of Ventilation and Air Conditioning Projects\", expansion bolts with a diameter of 20 mm should be used when the pipe diameter is greater than 300 mm, and the actual diameter of the cooling pipes is 700 mm) ； Without the written consent of the design unit, two of the expansion bolt heads on the steel panels of the supports and hangers (out of a total of 6 expansion bolts) were cut to be level with the surface of the steel plate ； Without the written consent of the design unit, two of the expansion bolt heads on the steel panels of the supports and hangers (out of a total of 6 expansion bolts) were cut to be level with the surface of the steel plate ； Another 2 bolts are not properly connected to the beam.
2. Shanghai Jianhao Engineering Consulting Co., Ltd. failed to review the contractor’s calculation documents in accordance with the regulations； No violations of code requirements were found in the bolts used for supports and hangers. Failing to promptly identify and prevent specialized subcontractors from lowering construction technical standards in violation of regulations such as the Regulations on Quality Management of Construction Projects. 3. China State Construction Shanghai Design and Research Institute Co., Ltd. set out only principle-based requirements in the \"Design Instructions\" regarding the spacing of supports and hangers, as well as seismic considerations and application diagrams; it did not provide specific calculation requirements for professional subcontractors in cases where the diameter of the cooling pipes (which is actually 700 mm) exceeds the scope applicable to those diagrams, thereby violating relevant regulations.
4. Changshu Wanda Investment Co., Ltd. violated the provisions of the \"Administrative Measures for the Subcontracting of Construction Projects in Housing Construction and Municipal Infrastructure\", by directly designating the subcontractor for HVAC system construction. 5. The Second Engineering Bureau of China State Construction Engineering Group failed to report to the local housing and construction authorities the situation in which the project owner directly designated a subcontractor for HVAC installation work. The general contractor’s obligations were not fulfilled properly, as no unified management was implemented over the construction units responsible for the HVAC work. 6. The Changshu Municipal Housing and Urban-Rural Development Bureau does not provide sufficient supervision and guidance to the quality inspection stations and construction management departments under its jurisdiction with regard to quality oversight and market management tasks; furthermore, there is no mechanism for sharing relevant supervision information, which results in inadequate, untimely, and ineffective oversight.
4. Changshu Wanda Investment Co., Ltd. violated the provisions of the \"Administrative Measures for the Subcontracting of Construction Projects in Housing Construction and Municipal Infrastructure\", by directly designating the subcontractor for HVAC system construction. 5. The Second Engineering Bureau of China State Construction Engineering Group failed to report to the local housing and construction authorities the situation in which the project owner directly designated a subcontractor for HVAC installation work. The general contractor’s obligations were not fulfilled properly, as no unified management was implemented over the construction units responsible for the HVAC work. 6. The Changshu Municipal Housing and Urban-Rural Development Bureau does not provide sufficient supervision and guidance to the quality inspection stations and construction management departments under its jurisdiction with regard to quality oversight and market management tasks; furthermore, there is no mechanism for sharing relevant supervision information, which results in inadequate, untimely, and ineffective oversight.
7. As the quality supervision department for housing construction projects, the Quality Supervision Station of the Changshu Municipal Housing and Urban-Rural Development Bureau fails to provide adequate supervision over the quality of the actual construction works, as well as over the quality-related practices of the construction and supervision units. Although 15 quality inspections were carried out over time, the work was not thorough enough, and no inspections were conducted on the piping in the HVAC system ； No cases of HVAC project managers or project supervisors being absent from their posts for extended periods were found ； It was found that the professional supervisor responsible for installation under the project was not present, yet no effective measures were taken to address this issue.
8. After discovering during inspections that the Wanda Plaza project in Changshu had issues with subcontracting that were not registered, the Construction Management Department of the Changshu Housing and Urban-Rural Development Bureau issued a \"Rectification Notice\" requiring corrective action. The construction party responded in writing stating that the rectifications had been completed, but in reality this was not the case; yet no follow-up checks were carried out promptly； During the special inspection of supervision, it was found that the supervisors were not on site, and points were deducted as a result. However, no further follow-up checks were conducted to verify whether the supervisors showed up later on, so the process did not form a closed loop.
Sometimes it’s these small details that lead to big problems