The concept of precast construction includes those buildings that are majorly made of components that are standardized and produced in a factory environment that is usually located away the site of construction. These materials are then transported to the site for assembly. They are manufactured by industrial methods of mass production that can help build a large number of buildings in a short time and at a low cost. The main features of this construction process are as follows:
- This includes the use of standardized tools, machinery and other equipment that is usually automated and can produce standard, interchangeable parts and products.
- The division and specialization of human work force is an essential part of this process.
The entire conventional construction process is restructured to enable the interaction between the design phase and production planning. This helps improve the speed of construction. It is hence important to design buildings that have a regular configuration in plan and elevation.
Precast building systems are known to be more economical when compared to conventional multi-family residential construction.
Depending on the load bearing structure, precast construction systems can be divided into the following categories:
- Large panel systems
- Frame systems
- Slab-column systems with walls
Large panel systems
This refers to the multi-story structures that are composed of large wall and floor concrete panels connected in the vertical and horizontal direction. These panels enclose appropriate spaces for the rooms within a building by forming a box like structure.
Precast frames can be constructed using either linear elements or spatial beam column sub-assemblages. Precast beam column sub-assemblages have the advantage that the connecting faces can be placed away from the critical frame regions. Linear elements are generally preferred because of the difficulties associated with forming
Slab-Column Systems with Shear Walls
These type of systems rely on shear walls to sustain lateral load effects and the slab column structure resists the gravity loads. There are basically two main systems in this category. First, the lift slab system with walls where the load bearing structure consists of precast reinforced concrete columns and slabs.
All the precast structural elements are assembled by means of special joints. Reinforced concrete slabs are poured on the ground in forms one on top of the other. They are lifted from the ground up to the final height by lifting cranes. They are then moved to their final positions. Temporary supports are used to keep them in place until the connection with the columns has been achieved.
Pre-stressed slab column system
This type of precast system is a slab column system that uses horizontal pre-stressing in two orthogonal directions to achieve continuity. The reinforced concrete floor slabs fit the clear span between columns and after erecting the slabs and columns of one story, the columns and floor slabs are pre-stressed. The gap between the slabs is filled with in situ concrete and the tendons become bonded with spans.
The use of precast structures in construction will definitely revolutionize the way the construction industry works.