Long-span roofs have a span greater than or equal to 12 metres. Long-span roofs can minimise substructure expenses and construction times while creating flexible, column-free interior areas. In various structures, such as factories, warehouses, buildings, hangars, huge shops, community centres, gyms, and arenas, they are frequently seen in large numbers.
Like traditional roofs, its principal functions are weather protection, fire prevention, sound and thermal insulation. It’s also possible that they’ll be the only structural element other than the outer walls, which means they’ll provide support for buildings amenities like elevators, lighting, etc.
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Materials
Common materials used to construct long-span roofs are reinforced concrete, prestressed concrete, wood, and aluminium alloys. Steel is popular because of its tremendous strength and does not spread fire when ignited. The design of long-span steel and composite bridges usually is done in conformity.
The roof serves as a structure.
The framing around the doorway
A beam (and rafter) is supported at both ends by columns in a portal frame, but the connections between the bar and columns are “rigid” such that the deflection is passed from the beam to the columns. As a result, the sectional size of the beams can be lowered, allowing them to traverse huge distances.
By adding a haunch, brace, or deepening the portion at the joints, the connection between the frame and the pillars is referred to as “stiff.” Steel, strengthened precast concrete, or glulam, a type of laminated wood, are the most common materials used to construct portal frames.
Pitch-roofed beam
Triangulated plane frames spread at appropriate centres make up pitched trusses. A tie member connects the truss’s top-edge rafters at their feet to keep them from expanding. Using struts and ties, the basic triangle can be strengthened. To attach a roof covering, purlins must be installed between the trusses.
Rooflights and the triangulated style of pitched rafters allow for good rainfall-runoff, adequate daylight spreads, and high roof volume.
They are frequently constructed from steel pieces bolted or welded together using shaped plates known as gussets. Angle sections are commonly used in steel truss members because they are inexpensive and can withstand both tension and compression pressures. With screws and timber connectors, timber members can be utilised instead.
Saw-toothed roofing
There are two distinct pitches in saw-tooth roofs, which are comparable in shape to the tooth of a saw. They make building a pitched roof over a broad area possible without creating a very tall apex. Because the steeper slopes face north, they’re known as “north light roofs” for the natural light they allow into deep plan buildings or factories.
In the absence of electric lighting, they were commonly utilised in industrial and production industries to maximise the utilisation of natural light. As a result of their ecological sustainability and shape, architects have introduced them well to solar panel installation.
The rafter with trusses
These structures can cover as much as 15-45 metres, depending on how they’re created. To carry purlins, they are typically made of wood or steel and are placed at a proper distance from each other. Most have a tinny sound to allow for adequate precipitation runoff, and roof lights can provide a considerable amount of daylight. Despite their reduced roof volume, their depth and volume grow with the span.
A spaceship’s hull
A simple pyramid unit is used as the basis for a modular roofing system typically welded to a forming tray and an apex boss. Large clear expanses of up to 22 m may be achieved with single-span designs, while methods may achieve up to 33 m.
The spacious deck can be built at ground level and then hoisted on top of surrounding supports using components carried to the site for assembly into beams. As a roof covering, any structural decking material that is both light and strong is ideal. The square upper space deck units can also be fitted with roof lights.
Frame of reference
Like a spaceship deck, but with more freedom to customise the design and layout, the chords and bracing elements of space frames are connected by several connectors, making them a lightweight, rigid roofing system. With each chord transmitting tension and compression stresses throughout its length as it flexes, their strength is derived from the triangle’s stiffness. Steel structure or aluminium tubes are used to construct most space frames.
For his pre-engineered constructions, Buckminster Full pioneered the 1960s utilisation of space frames.
Structure of textiles
High-tensile strength architectural fabrics like PTFE glass or PVC polyester allow for long spans with minimal use of material. A variety of steps for putting tension on them, including using supporting structures, structural cables, or air pressure. They’re usually translucent, which means they allow for a lot of natural light to pass through.
Inspect the roofs
‘Monitors’ refers to the raised glass sections of a monitor roof with a flat surface. Despite the building’s orientation, they provide even dispersion of illumination from the monitor lights. Light long-span girders or a precast concrete entrance frame can support the monitor frames.
Arch with a long arc of span
No trusses, frameworks, supports or purlins are required for long-span arches. Shell roofs are another name for them. Essentially, they’re curved skin covering a specific plan form and area with compressive and tensile forces acting on each other.
Structures for suspension
A suspended structure is one where the major load-bearing elements, such as cables, wires and chains, are only subject to extension forces. Suspended details in-plane (horizontal) structures are held by a wire tied to supports. Bridges and roofs are the primary applications for them.
Structures with cable stays
A flat roof system comprises overhead steel cables extending down from masts that stand above the roof level in this structural arrangement adapted from the bridge-building. The wires act as essential suspension elements for load resistance, whereas the roof structure is subject to moments, shears, and other forms of action effects. Due to the roof’s dead weight, it is envisaged that the suspending parts will remain in tension even in wind uplift.
