What Is a Concrete Panel?

Reinforced concrete slabs, made of reinforced concrete materials, are the basic structure or component in house construction and various engineering structures. They are often used as roofs, floors, platforms, walls, retaining walls, foundations, floors, and pavements. , Pool, etc., the application range is extremely wide. Reinforced concrete slabs are divided into square slabs, circular slabs, and special slabs according to the plane shape. It is divided into unidirectional board and bidirectional board according to the structure's force acting mode. The most common are unidirectional plates, bidirectional plates supported on four sides, and beamless flat plates supported by columns. The thickness of the plate shall meet the requirements of strength and stiffness.

Reinforced concrete slab

Unidirectional boards are available in cast and precast. Cast-in-place slabs are usually integrated with reinforced concrete beams and form a multi-span continuous structure. Prefabricated panels are widely used as roofs and floors in industrial and civil buildings. Commonly used prefabricated panels include solid panels, hollow panels and trough panels.

When the ratio of the long side to the short side of a slab supported along four sides is not greater than 2, the load on the slab will be transmitted to the supporting structure (beam or wall) in both long and short span directions.

Internal force analysis and design of bidirectional plates with four sides supported, elastic analysis method and limit analysis method. The elastic analysis method regards the reinforced concrete slab as a homogeneous elastic body, and performs the elastic mechanics method. The elastic analysis of a bidirectional plate with four sides supported is a very complicated problem. In general structural static calculation manuals, there are ready-made calculation forms for designers to check. The limit analysis method considers the plasticity of reinforced concrete, can reasonably use the effectiveness of the reinforcement, and can save 20-25% of the reinforcement compared with the elastic analysis method. The limit analysis method for reinforced concrete slabs, the most commonly used is the yield line method, the main point of which is to determine the simplified diagram of the slab failure based on theoretical reasoning or model tests (see figure), and then apply

For calculation of beamless slabs, the total bending moment distribution method (empirical coefficient method) and the equivalent frame method are commonly used.

The total bending moment distribution method considers the flat plate as a multi-span continuous unidirectional plate in the longitudinal and transverse directions. First, the total bending moment of the simply supported plate generated by the uniformly distributed load is calculated. Supports and spans for mid-span strips. The empirical distribution coefficient is determined based on experimental research and practical experience, and due consideration is given to the redistribution characteristics of the internal force of reinforced concrete slabs, which can be found in relevant codes. This method is widely used for its simple calculation.

The equivalent frame method divides the entire structure into vertical and horizontal frames with "frame columns" and "frame beams" along the columns of the vertical and horizontal columns, and calculates according to the general structural mechanics method. Then the bending moment is proportioned according to the relevant specifications. , Distribute on the column plate and span plate. The width of the equivalent frame beam is: when the vertical load is applied, it is equal to the distance between the centerlines of the plates; when the horizontal load is applied, it is equal to half the distance between the centerlines of the plates.

The reinforcement of beamless slabs is composed of a two-way reinforcing mesh parallel to the axis of the column network. The positive and negative steel bars on the column strips and mid-span strips in the longitudinal and horizontal directions are arranged like unidirectional multi-span continuous plates. When the span is large, non-bonded post-tensioned prestressed steel wire bundles can be configured. The construction methods of beamless slabs include a layer-by-layer cast-in-place method and a layer-up construction method in which the floor is prefabricated on the site and then elevated to a predetermined level.