Bearing Structure of Prefabricated Slab Houses

The bearing structure of prefabricated slab houses is formed by assembling prefabricated slabs as the main components and placing them on brick walls, with the load-bearing primarily relying on load-bearing walls and the performance of the prefabricated slabs themselves. The specific characteristics are as follows:

I. Construction Method and Structural Characteristics The floor slabs of prefabricated slab houses are cement components prefabricated in factories. During production, wooden models are nailed, steel bars are arranged, and cement is poured to form the slabs. During construction, the prefabricated slabs are transported to the site for assembly and directly placed on the brick walls. This type of structure was widely used from the 1960s to the early 1990s. Its advantages are fast construction speed and low cost, but its overall integrity is relatively poor. If a problem (such as cracking) occurs with a prefabricated slab, it may affect adjacent walls or other floors like dominoes, leading to a decrease in structural stability.

II. The Role and Identification Methods of Load-Bearing Walls Load-bearing walls are the core supporting structures of prefabricated slab houses, and their importance is reflected in:

1. Identification methods:
   • The thickness is usually more than 240mm;
   • In rectangular house types, the longer side walls are mostly load-bearing walls;
   • Although the exterior walls of the building do not directly bear the weight of the floor, they need to bear the weight of the walls on each floor and are also considered load-bearing walls;
   • The walls at both ends of the supporting beams are load-bearing walls.
2. Importance: Once a load-bearing wall is damaged (such as being removed during renovation), it will directly cause damage to the load-bearing structure of the building. For example, after an owner in a certain community removed a load-bearing wall, cracks appeared in the entire building, the walls tilted, and ultimately, the residents had to be urgently evacuated.

III. Load-Bearing Capacity of Prefabricated Slabs According to the "Building Structural Load Code", the load-bearing capacity of ordinary residential prefabricated slabs is about 200 kilograms per square meter (equivalent to the weight of 4 adults), but it is specifically divided into three levels:

• Class I slabs: with a load-bearing capacity of 100 kilograms (relatively rare);
• Class II slabs: with a load-bearing capacity of 200 kilograms (used in most residential buildings);
• Class IV slabs: with a load-bearing capacity of 400 kilograms (mostly used in old factories). The load-bearing capacity is affected by factors such as the concrete grade, steel bar model, slab thickness, room span, and whether there is beam support. It should be noted that 200 kilograms is a uniformly distributed load. If the weight is concentrated on a very small area (such as the size of a shoebox), the floor slab may crack even if the total weight does not exceed the limit.

IV. Existing Problems Prefabricated slab houses generally have the following defects:

• Weak earthquake resistance: Due to poor overall integrity, they are prone to collapse during earthquakes;
• Poor sound insulation and heat insulation: The gaps in the prefabricated slabs easily lead to the conduction of sound and heat;
• Limited service life: About 30-50 years. Some regions have already initiated demolition work.