Open-Web Steel Joists for Roofs and Floors

Open-web steel joists are light trusses made of top and bottom chords connected by a web of diagonal members. They are used to support roof deck or floor deck, spanning between beams, walls or frames. Their open web allows ducts, pipes and cables to pass through, which is useful in offices, retail buildings and mezzanines.

Compared with solid beams of similar depth, joists use less steel for long spans with uniform loads. They are also light to handle and quick to erect. Chords and webs are typically formed from angles, rods or cold-formed sections and welded together in the shop.

Joist depth and member sizes are selected by the project engineer for the span, loads and deflection limits. Bridging is installed between joists to brace them during erection and in service, and it is an essential part of the system. Concentrated loads from equipment or hangers need to be identified so that joists can be designed for them.

In pre-engineered buildings, joists are used for mezzanine floors, low-slope roofs of offices and commercial annexes, and as part of hybrid systems where joists span between primary frames. Where joists are used in floors, vibration performance is considered along with strength.

World Steel supplies open-web steel joists designed to the code specified for the project, coordinated with the supporting frames, deck and bridging, and shown on erection drawings with bearing details.

When specifying joists, provide the span, roof or floor use, uniform and concentrated loads, deflection criteria, deck type and any openings for services. The project engineer selects the joist profile and bridging layout and confirms them on the design drawings.