Structural Safety of Prefabricated Slab Houses

The structural safety of prefabricated slab houses presents multiple hazards, with overall safety being relatively low. Details are as follows:

I. Poor Earthquake Resistance
Prefabricated slab houses lack overall integrity, with rigid connections missing between components, resembling a "building-block" stacking. During earthquakes, horizontal forces can easily cause instant separation between floor slabs and walls, and the collapse process occurs without crack warnings or deformation buffers, with entire prefabricated slabs falling directly, leaving extremely short escape times. In historical earthquakes, such houses have had high collapse rates and severe casualties, representing a major flaw in earthquake-resistant design.

II. Vulnerable Connection Points
Prefabricated slabs are connected to walls and to each other only through simple overlaps or filling, lacking rigid framework support such as ring beams and structural columns. Foundation settlement, wall cracking, or long-term weathering and steel bar corrosion can continuously reduce connection strength. After two or three decades of use, some old houses may experience chain collapses of floor slabs due to minor external forces (such as stacking heavy objects or renovation wall demolition).

III. Material Issues
To reduce costs, early prefabricated slabs often suffered from material shortcomings:

• Poor Steel Bar Quality: Small workshops used thin steel wires instead of standard steel bars, with insufficient diameter and strength;
• Substandard Concrete: Low-grade, thin concrete prone to cracking;
• Brittle Failure Characteristics: Compared to cast-in-place floor slabs, prefabricated slabs lack toughness, breaking instantly under overload without warning periods. Daily use, stacking heavy objects, renovation, or aging can all trigger sudden collapses.

IV. Other Common Hazards

1. Crack Risks: Steel bar corrosion at joints can easily lead to cracking in large-span areas such as living rooms, with high risks of steel bar breakage.
2. Floor Slab Issues: Horizontal through-cracks may appear at the bottom of slabs, with joint cracking, or the middle of slabs may sink, with loose concrete and exposed, corroded steel bars at both ends.
3. Load-Bearing Wall Issues: Vertical/diagonal cracks, cracking and downward pressure on window and door lintels, weathering and peeling at the base of ground-floor walls; for houses of three stories or more without ring beams and structural columns, earthquake resistance is significantly reduced.
4. Node Connection Issues: Insufficient support length of prefabricated slabs (specification requires ≥80mm), wall corner disconnections or cracks.
5. Unauthorized Modifications and Usage Environments: Actions such as demolishing load-bearing walls, unauthorized additions (such as roof additions, stacking heavy objects on floor slabs), or changing purposes (residential to commercial) can significantly increase structural loads,极易 (extremely likely to) trigger safety accidents.