Precast Beam

What is a precast beam?

A precast beam is a horizontal load-bearing member produced in the plant and placed on site onto column corbels or column heads. Beams tie the columns together, complete the structural frame and carry the loads above them down to the columns.

Its role in an industrial building

In an industrial building, a beam's job depends on where it sits and what it carries. The industry typically groups beams by function as follows:

Which beam types your project needs, and the scope of production, are confirmed together during the project review.

Section options

Precast beams can be designed with rectangular, I, T, inverted T or L sections. Inverted T and L sections are common where floor units will bear on the beam. Across the industry, beams are produced either as conventionally reinforced or as prestressed members. In pre-tensioned production, steel strands are tensioned before casting and released once the concrete has gained sufficient strength, pre-compressing the member so that longer spans and slimmer sections become possible. The method, section dimensions and reinforcement layout are set by the structural design.

Production and quality

Beams are cast in project-specific molds once reinforcement, connection sleeves and cast-in parts are in place. The plant environment allows concrete mix, cover and dimensions to be checked with the same care on every element. Each element is marked according to its position in the erection plan before dispatch.

Erection and connections

On site, beams are lifted by crane and set onto the column corbels. An elastomeric (neoprene) bearing pad is usually placed at the support; the beam is located by dowels projecting from the column, and the dowel holes are grouted to complete the connection. Connection details are designed to the rules the earthquake code sets for precast reinforced concrete buildings.

Choosing the right beam

The main factors in beam selection are the span to be covered, the loads to be carried, column spacing, building height and transport conditions. Very long, heavy beams may call for larger cranes and special transport, so spans and column grids are planned together with production and erection constraints in mind. If there will be an overhead crane, a mezzanine or heavy services, flagging them at the start lets the beams be designed for those loads and avoids the need for strengthening later.