Loadbearing Architectural Precast Concrete Wall Panels

Architectural precast concrete wall panels that act as loadbearing elements in a building are both a structurally efficient and economical means of transferring floor and roof loads through the structure and into the foundation. In many cases, this integration can also simplify construction and reduce costs. This article presents the many benefits that can be derived from using loadbearing architectural precast concrete walls in buildings. Discussed herein are the various shapes and sizes of wall panels, major design considerations, and when loadbearing or shear wall units should be the first design choice. The role of connections, shear walls, and the use of precast concrete as forms for cast-in-place concrete is explained. In general, the design methods and techniques presented in this article apply to buildings in both seismic and non-seismic areas.

The latter part of this article shows how these design principles can be applied in practice in a variety of buildings. These examples illustrate the use of window wall panels, spandrels, and solid or sandwich wall panels as the loadbearing wall members. When all the advantages of using architectural precast concrete as loadbearing walls are added up, it makes good sense to use this structural form in building applications.

Loadbearing facades have both an a esthetic and structural function.In building practice, the most
economical application of architectural precast concrete is as loadbearing structural elements. Loadbearing units become an integral part of the structure, taking the vertical and horizontal floor and roof loads, and/ or transferring horizontal loads into shear wallscor service cores. Such an arrangement can be economical, not only from a structural design standpoint, but also from the viewpoint of overall construction. In some cases, the loadbearing elements also can contribute to the horizontal stability of the building. Architectural precast concrete cladding is noted for its diversity of expression, as well as its desirable thermal, acoustic and fire-resistant properties. Commonly overlooked is the fact that concrete elements normally used for cladding applications, such as solid wall panels, window wall or spandrel panels, have considerable inherent structural capability.

 

In the case of low- or mid-rise structures, the amount of reinforcement required to handle and erect a precast component is often more than necessary for carrying imposed loads. Thus, with relatively few modifications,
many cladding panels can function as loadbearing members. For taller buildings, additional reinforcement may be necessary for the lower level panels. The slight increases in loadbearing wall panel cost (due to reinforcement and connection requirements) can usually be more than offset by the elimination of a separate perimeter structural frame. Depending upon the application, the loadbearing panels also may reduce or eliminate a structural core or interior shear walls, particularily in buildings with a large
ratio of wall-to-floor area. The increase in interior floor space gained by eliminating columns can be substantial
and, depending on the floor plan, partition layout flexibility can be enhanced.

To take maximum advantage of loadbearing units, decisions as to their functions should be made before structural design has progressed to a stage where revisions become costly. Cost savings tend to be greatest in low- to mid-rise structures of three to ten stories. As with all precast concrete applications, further economies can be realized if the panels are repetitive. Besides minimizing the number of casting forms necessary, repetitive panel designs enable repetitive connections. Architectural loadbearing panels can be used effectively to renovate and rehabilitate old deteriorated structures. These panels can be used not only in all-precast structures but also in structural steel framed structures and castin- place concrete structures.