Portal frames are commonly used to create wide-span enclosures such as; warehouses, agricultural buildings, hangars, entertainment and sport venues, factories, large retail units, and so on, where a clear space is required uninterrupted by intermediary columns.
They are originally used because of their structural efficiency, meaning that large spaces could be enclosed with little use of materials and for a low cost.
Portal frames are a type of structural frame, that, in their simplest form, are characterized by a beam or rafter (or) supported at either end by columns, however, the joints between the beam and columns are ‘rigid’ so that the bending moment in the beam is transferred to the columns. This means that the beam can be reduced in sectional size and can span large distances. Typically, the joint between the beam and the columns is made ‘rigid’ by the addition of a haunch, bracket, or by a deepening of the section at the joints
Where a pitch is required, portal-frames can have a mono pitch, or can have a double pitch with a rigid joint at the apex. Other forms include; tied portal frames, propped portal frames and multi-span portal frames which can cover very large areas. Where the portal frame includes a pitch, the wider the span of the frame, the higher the apex.
Our portal frame design includes the design of the portal frames and the purlins and cladding rails. It also includes the design of the gable framing, and stability bracing. It also includes the design of the foundations.
We need the following information for a portal frame design:
Architectural layouts showing the span and centres of the frames and elevations showing the eaves and ridge height of the portal frames.
The type of roof cladding.
The type of wall cladding.
The building location.
Details of any service loading which will be supported by the steel-work.
The position of any doors.
Site investigation report.