Taxonomy of Structural Systems: Frames

A frame is a bulk active structural system composed of individual members and serves to support a structure or building. The rigid linear elements, columns and beams, act in tension or compression. This system can be made out of concrete, steel or wood.

Columns, which are loaded axially and act in compression, can also be made out of masonry. The columns take the load of the beams and anything supported by the beams and transfers the load safely to the ground. Beams, loaded transversely, act in bending which includes both tension and compression. Beam loads are a result of floor plates and anything supported by those plates (permanent inner structures such as walls, and immpernant loads like people and furniture). The columns and beams can be arranged in a variety of manners, two of which are single and continuous spans. A single span is made up of a singular beam supported by two columns on either end. A continuous span consists of a much longer beam stretching across multiple columns. In addition to this, there are braced frames, rigid frames, and shear walls. Braced frames are susceptible to dangerous movement. To fix this, the frame can be braced in one or two ways. If braced in one way, the frame can still bend in one direction as the tension will only work in one direction. If braced in two ways, the frame will not move. A rigid frame cannot rotate and is often welded at the corners. Shear walls occur between columns and beams and cannot move at all.

Each of the three principle materials available for framing have their advantages and disadvantages. Concrete is an inherently rigid material; it is cast in place and provides more safety based on basic material characteristics out of the three options. It is fireproof without added materials. As a result of its bulk, it is also highly wind resistant. Unfortunately, the upfront cost of concrete framing is far more than the other two as it requires more onsite work. Design wise, concrete framing offers a wide variety of shapes not previously able to be built. With reinforcement, developers are finding that the material lowers floor to floor heights, yielding “more rentable space” (Madsen).

Steel bends well, making it an advantage in seismic zones. Like concrete, it can resist high wind loads; in steels case, however, its ability to move is what makes this possible. In addition to wind resistance, steel frames are also able to “span greater distances carry heavier loads than timber construction” (Ching). In terms of design, innovations in steel are also allowing floor to floor heights to lower.

Wood framing comes in two forms: light wood framing and heavy wood framing. Light wood framing uses “relatively small, closely spaced members to form assemblies that perform as structural units” (Ching). A light wood frame lowers cost of construction as it takes little to no heavy machinery to construct, materials can be carried by hand, and the components of the system are easily manipulated to form a variety of geometric shapes. That being said, it is not fireproof and does not withstand high wind loads well. Heavy wood framing traditionally features often rough hewn heavy timber joined in a “traditional mortise and tenon joinery” or “modern metal joinery”, unlike those of the light