Category: SITECAST CONCRETE FRAMING SYSTEMS

Concrete is a shapeless material that must be given form by the designer. For economy, the designer can adopt a standard system of concrete framing. For excitement, one can invent new shapes and textures, a route taken by many of the leading architects. Some have pursued its sculptural possibilities, others its surface patterns and textures,…

The cost of a concrete building frame can be broken down into the costs of the concrete, the reinforcing steel, and the formwork. Of the three, the cost of concrete is usually the least significant in North America and the cost of formwork is the most significant. Accordingly, simplification and standardization of formwork are the…

The ancient Romans built unreinforced concrete vaults and domes as roofs for temples, baths, palaces, and basilicas (Figure 13.2). Impressive spans were constructed, including a dome over the Pantheon in Rome, still standing, that approaches 150 feet (45 m) in diameter. Today, the arch, dome, and vault remain favorite devices for spanning long distances in…

Concrete that is intended as finished interior or exterior surfaces, and is specified with highly prescribed finish characteristics, is known as architectural concrete. Most formed concrete surfaces, although structurally sound, have too many blemishes and irregularities to be visually attractive. A vast amount of thought and effort has been expended to develop handsome surface finishes for…

The development of sitecast concrete construction continues along several lines. The basic materials, concrete and steel, continue to undergo innovations, as described in Chapter 13. The continuing evolution of high-strength, high-stiffness concrete, along with improvements in concrete forming systems and concrete pumping technology, have enabled sitecast concrete construction to remain economically competitive with structural steel for…

Preliminary factors to be considered in the selection of a sitecast concrete framing system for a building include the following (Figures 14.43 and 14.44): 1. Are the bays of the building square or nearly square? If so, a two-way system will probably be more economical than a one-way system. 2. How long are the spans? Spans up…

Posttensioning can be applied to any of the sitecast concrete framing systems. It is used in beams, girders, and slabs, both one-way and two-way, to reduce member sizes, reduce deflection, and extend spanning capability. Two-way flat plate structures are very commonly posttensioned, especially when spans are long or zoning restrictions on the height of the…

A concrete stair (Figure 14.40) may be thought of as an inclined one-way solid slab with additional concrete added to make risers and treads. The underside of the formwork is planar. The top is built with riser forms, which are usually inclined to provide greater toe space and make the stair more comfortable to users.…

Two-way concrete framing systems are generally more economical than one-way systems in buildings where the columns can be spaced in bays that are square or nearly square in proportion. A two-way solid slab is a rarely seen system, occasionally used for very heavily loaded industrial floors, in which the slab is supported by a grid of beams…

One-Way Solid Slab System A one-way solid slab (Figures 14.16–14.19) spans across parallel lines of support furnished by walls and/or beams. The walls and columns are poured prior to erecting the formwork for a one-way slab, but the forms for the girders and beams are nearly always built continuously with those for the slab, and girders, beams,…