Preliminary Planning of Steel Roof Space Trusses

During the preliminary plan phase of designing a steel roof space truss, a number of parameters must be considered and evaluated. These include the geometry of the framing system, the possible use of a proprietary system, the type of nodal joint, grid spacing, method of support, and depth of truss. Twelve types of truss framing systems that have been used for actual structures are presented. These systems are developed from basic elements of either rectangular or triangular prisms or from pyramids with either rectangular or triangular bases. Eleven different proprietary systems are briefly described. These proprietary systems are adaptable to closely spaced grids and shallow trusses and result in low weights per square area of structural material. Alternatively, a space truss can be developed utilizing a fabricated joint. Two examples are presented. These types of structures are usually deeper in depth with a larger module size. The weight of the structure is generally higher than that obtained by using a proprietary system. The actual weight of the truss is a secondary cost consideration. Three methods of analyses for preliminary designs are referenced. The review highlights some of the important factors that must be considered during the planning state of a steel roof space truss design.