Portal Frame Roof Structure

It is the primary framing.

Portal frame roof structure.

Roof purlins and wall girt not only support the roof and walls but also provide lateral support for the main structural beams and columns which form the secondary framing of portal steel frame buildings. These include steel reinforced concrete and laminated timber such as glulam the connections between the columns and the rafters. Portal frame structures are designed to span between supports and rely on fixed joints with moment resisting capacity where vertical supports connect to horizontal beams or trusses. As such this type of structure is used for depots warehouses and out of town shopping.

Steel portal frames usually have pinned bases and moment connections at the column rafter interface and mid span apex splice in the rafter. Portal frames are generally low rise structures comprising columns and horizontal or pitched rafters connected by moment resisting connections resistance to lateral and vertical actions is provided by the rigidity of the connections and the bending stiffness of the members which is increased by a suitable haunch or deepening of the rafter sections. Steel columns roof beams and bracing systems constitute the primary force skeleton of the portal steel frame. Portal frames are often constructed out of steel i sections with solid webs or latticed members made of angles or tubes.

Portal frame structures can be constructed using a variety of materials and methods. Their most widespread applications lie in warehouses barns and other large single story industrial structures. Steel portal frame structures provide an efficient and cost effective means of creating large column free spaces.