House with Hollow Prefabricated Slab Structure

Houses with hollow prefabricated slab structures are constructed using components such as prefabricated hollow floor slabs, featuring unique structural characteristics, a wide range of application scenarios, as well as common issues and corresponding reinforcement methods.

Structural Characteristics

A hollow prefabricated slab refers to a concrete slab with a hollow cross-section. Compared to solid slabs of the same span, it is lighter in weight, has a lower building height, is easier to transport and install, and is an efficient prestressed component. It can reduce the load-bearing structure and increase the freedom of architectural and structural design. The overall structure is composed of components such as prefabricated hollow floor slabs and hollow brick masonry (especially non-reinforced masonry).

Application Scenarios

In construction engineering, it is widely used in multi-story residential, commercial, educational, medical, and industrial buildings. In bridge engineering, it is one of the earliest-applied prefabricated structures and is extensively used in bridges of various highway grades in China, accounting for a significant proportion of currently operational beam bridges. For example, the original superstructure of the Jinma River Bridge in the Chengdu-Wenjiang-Qionglai Expressway expansion project adopted prestressed concrete simply-supported hollow slabs.

Common Issues

1. Floor slab cracking and deflection: This usually occurs due to improper span settings, insufficient material thickness, construction process deviations, or overloading, leading to a decrease in load-bearing capacity. Additionally, uneven foundation settlement can cause increased structural displacement and tensile stress, resulting in cracks in the web of the prefabricated hollow floor slab, affecting aesthetics and comfort.
2. Wall cracking: Hollow blocks and their connections may have insufficient ductility and tensile strength. If the walls are not reinforced and no steel reinforcement bands are provided under beams, under the combined effects of seismic shear and uneven foundation settlement, they often exhibit X-shaped cross-cracks on the exterior longitudinal walls and horizontal cracks at a 45-degree angle around door and window openings, weakening the integrity of the building enclosure.
3. Weak overall integrity due to joint failure: In traditional hollow brick houses, the connection details between the bottom of concrete beams, wall panels, and slab-to-slab joints are not properly handled, and no reinforcing steel bars pass through the joint areas for reinforcement. This makes them prone to fracture, slippage, and separation at the junctions of new and old layers, resulting in poor seismic energy dissipation performance and a higher risk of overall collapse during disasters.
4. Moisture erosion and aging failure: Hollow cavities form "flow channels." If external waterproofing is inadequate, it may lead to electrochemical corrosion of steel bars or tie rods, generating new rust-induced expansion cracks. Under the influence of hot-cold and dry-wet climatic conditions, the shrinkage or expansion of walls along capillary pores can also cause the concrete layer on the inner walls of hollow components to peel off, affecting durability and service life.

Reinforcement Methods

The fiber-reinforced reinforcement method (CFRP, GFRM) - wrapping method is suitable for scenarios where the slab surface bears heavy loads, resulting in severe deflection and small cracks but still has some degree of repairability. The core process steps include first inspecting the structural cracks and sealing them if necessary; milling and cleaning the base layer of the铺设面 (laying surface); spraying an immersion adhesive; laying the cut and designed-length carbon fiber sheets with staggered layers after the adhesive has slightly dried, pressing to remove air at the bottom and excess adhesive; and applying a protective paint coating on the surface. If necessary, pre-tensioning can be applied based on calculations to enhance the coupling effect between the composite and the structure.