Prefabricated Floor Slab Accident in Zhongxian

At around 12:00 PM on April 11, 2024, a three-story prefabricated floor slab house in Fengshou Community, Guanba Town, Zhongxian County, Chongqing City, experienced a floor slab fracture accident, resulting in 2 deaths and 3 injuries. It was initially determined that the brittle fracture was caused by excessive temporary loading on the second floor.

Direct Cause of the Accident: Overloading Leading to Brittle Fracture

In the accident, the floor slab on the second floor fractured and fell due to the temporary accumulation of goods, with the load exceeding the design bearing capacity of the prefabricated slab. Prefabricated slabs are brittle materials with weak impact resistance. When the local load exceeds their ultimate bearing capacity, they are prone to sudden fracture rather than plastic deformation. In this accident, the second floor was used as a goods warehouse, and there may have been concentrated loading or dynamic loads (such as handling impacts), further exacerbating the structural risk.

Typical Characteristics and Historical Background of Prefabricated Floor Slab Houses

Prefabricated floor slab houses were mostly built in the 1980s, using prefabricated concrete floor slabs spliced together for construction. They are commonly found in residential or public buildings of up to six stories. Their characteristics include:

• Material and Process Limitations: Due to the technical conditions at the time, the concrete strength and steel bar configuration of the prefabricated slabs were relatively low, and there were often gaps at the splicing points, resulting in poor integrity.
• Short Service Life: They were usually designed with a service life of less than 20 years. After long-term use, concrete carbonation and steel bar corrosion significantly reduce the bearing capacity.
• Obvious Functional Defects: They have poor seismic performance (mostly brick-concrete structures lacking seismic construction measures), insufficient thermal and sound insulation, and indoor layouts that are difficult to meet modern needs.

Safety Hazards and Countermeasures for Old Prefabricated Floor Slab Houses

Currently, a large number of prefabricated floor slab houses have entered the "advanced age" stage and face the following risks:

• Structural Aging: Concrete spalling and exposed and corroded steel bars weaken the bearing capacity of the floor slabs, increasing the risk of fracture.
• Changes in Usage Functions: For example, converting residential buildings into warehouses or chess and card rooms, resulting in increased loads or crowded personnel, exceeding the original design standards.
• Lack of Maintenance and Management: Some houses have not undergone regular safety appraisals, and hidden dangers have not been promptly identified.

Suggested Measures:

1. Regular Safety Appraisals: Conduct structural inspections on old prefabricated floor slab houses, evaluate indicators such as bearing capacity and crack width, and reinforce or demolish them if necessary.
2. Regulate Usage Behaviors: Avoid concentrating heavy loads on the floor slabs, especially dynamic loads (such as machine vibrations and frequent handling).
3. Policy-Guided Renovation: Local governments can promote the renovation of dilapidated houses through subsidies and resettlement to improve living safety.

This accident once again serves as a warning that strict management of the usage scenarios of old prefabricated floor slab houses is necessary to avoid tragedies caused by overloading or structural aging.