In structural engineering, a pre-engineered building (PEB) is designed by a PEB supplier or PEB manufacturer with a single design to be fabricated using various materials and methods to satisfy a wide range of structural and aesthetic design requirements. This is contrasted with a building built to a design that was created specifically for that building. Within some geographic industry sectors, pre-engineered buildings are also called pre-engineered metal buildings (PEMB) or, as is becoming increasingly common due to the reduced amount of pre-engineering involved in custom computer-aided designs, simply engineered metal buildings (EMB).
During the 1960s, standardized engineering designs for buildings were first marketed as PEBs. Historically, the primary framing structure of a pre-engineered building is an assembly of I-shaped members, often referred to as I-beams. In pre-engineered buildings, the I beams used are usually formed by welding together steel plates to form the I section. The I beams are then field-assembled (e.g. bolted connections) to form the entire frame of the pre-engineered building. Some manufacturers taper the framing members (varying in web depth) according to the local loading effects. Larger plate dimensions are used in areas of higher load effects.
Other forms of primary framing can include trusses, mill sections rather than three-plate welded, castellated beams, etc. The choice of economic form can vary depending on factors such as local capabilities (e.g. manufacturing, transportation, construction) and variations in material vs. labour costs.
Typically, primary frames are 2D-type frames (i.e. may be analyzed using two-dimensional techniques). Advances in computer-aided design technology, materials, and manufacturing capabilities have assisted a growth in alternate forms of pre-engineered building such as the tension fabric building and more sophisticated analysis (e.g. three-dimensional) as is required by some building codes.
Cold-formed Z- and C-shaped members may be used as secondary structural elements to fasten and support the external cladding.
Roll-formed profiled steel sheet, wood, tensioned fabric, precast concrete, masonry block, glass curtainwall or other materials may be used for the external cladding of the building.
In order to accurately design a pre-engineered building, engineers consider the clear span between bearing points, bay spacing, roof slope, live loads, dead loads, collateral loads, wind uplift, deflection criteria, internal crane system, and maximum practical size and weight of fabricated members. Historically, pre-engineered building manufacturers have developed pre-calculated tables for different structural elements in order to allow designers to select the most efficient I beam size for their projects. However, table selection procedures are becoming rare with the evolution in computer-aided custom designs.
While pre-engineered buildings can be adapted to suit a wide variety of structural applications, the greatest economy will be realized when utilizing standard details. An efficiently designed pre-engineered building can be lighter than the conventional steel buildings by up to 30%. Lighter weight equates to less steel and potential price savings in the structural framework.