Which system features open-web steel joists that span between beams or bearing walls, with typical spans from 60 to 144 ft?

The open-web steel joist system is designed specifically for spanning long distances between beams or load-bearing walls, with spans commonly varying from 60 to 144 feet. This system utilizes a series of interconnected steel members forming a web-like structure, allowing it to support significant loads while minimizing material use and weight.

Open-web steel joists are favored in commercial and industrial applications due to their efficiency in providing unobstructed spaces for mechanical, electrical, and plumbing systems above the ceiling. This flexibility in ceiling design is a key advantage, enhancing the overall functionality of spaces in various building types.

The other options do not fit the criteria specified in the question. Flat slabs involve a thick, solid concrete slab without any supporting beams, which is not conducive to the specified span range or system design. Trussed wood joists are typically used for shorter spans compared to steel options and are often not capable of matching the spanning capabilities of open-web steel joists. Waffle slabs, characterized by their grid-like structure, are primarily used for their rigidity and strength but do not function in the same way as open-web steel joists and do not meet the span requirements outlined.

Thus, the open-web steel joist system is the correct choice, as it is