House Structure: Prefabricated Panel
Prefabricated panels are commonly used floor components in early 20th-century construction, classified as engineering modules or sections, produced in prefabrication yards and installed on-site.
Structural Types and Manufacturing Process
Prefabricated panels come in two types: solid and hollow. The hollow structure achieves lightweighting by reducing non-load-bearing concrete, lowering material consumption. During manufacturing, a hollow mold is first created using wooden planks. Reinforcing bars are placed inside the mold, followed by pouring cement. After drying, the wooden planks are removed to obtain the finished product. This industrial production method improves construction efficiency but, limited by early technology, results in weaker overall structural integrity.
Common Specifications and Load Standards
The dimensions of prefabricated panels are constrained by transportation and installation conditions. The maximum common span is 4.2 meters (for residential use), with widths primarily 500mm and 600mm, and thicknesses mostly 120mm or 150mm. Regarding live load ratings, general residential buildings use Grade 1 panels (1kN/m²) or Grade 2 panels (2kN/m²), while the southwest region, due to special geological conditions, mandates a minimum of Grade 4 panels (4kN/m²) to enhance safety.
Architectural Characteristics and Limitations
Prefabricated panel buildings are mainly brick-concrete structures, with walls mostly consisting of load-bearing brick walls and floors using prefabricated concrete panels. This structure results in lower overall stiffness, with floor plans limited by panel dimensions, fixed户型 designs, typical room spans of 3-4 meters, poor north-south ventilation, and floor heights mostly between 2.6-2.8 meters. Existing prefabricated panel buildings commonly face the following issues:
- Weak earthquake resistance: Rigid connections at joints are prone to cracking or even collapse during earthquakes;
- Poor sound and thermal insulation: Hollow structures or thin panel designs lead to insufficient insulation and significant sound transmission through concrete;
- Short service life: Designed for approximately 30-50 years, much shorter than the over 70 years for cast-in-place concrete structures;
- Difficult renovation: Internal structures are hard to adjust, with high risks of water leakage and increasing maintenance costs over time.
Policies and Replacement Trends
With advancements in construction technology, cast-in-place concrete and prefabricated buildings have gradually replaced traditional prefabricated panel houses due to their superior overall performance and earthquake resistance. Since 2022, China has implemented renovation policies focusing on repair and upgrading of prefabricated panel houses, demolishing only those meeting hazardous building standards, with a focus on addressing structural safety, water leakage, and energy efficiency to extend their service life.
