Built-up sections, hot rolled sections, and cold formed elements offer the basic steel frame work, with a choice of single skin sheeting with additional insulation or insulated sandwich panels for roofing and wall cladding. The goal is to deliver a comprehensive building envelope system that is airtight, energy efficient, light and cost effective, and, most importantly, engineered to fit user requirements like a well-fitting glove.
Mezzanine levels, canopies, fascias, interior partitions, crane systems, and other structural accessories can be added to these Pre-Engineered Steel Buildings. Special mastic beads, filler strips, and trims are used to make the structure watertight. This is a very versatile construction structure that can be finished on the inside to fulfil any function and decorated on the outside to generate attractive and distinct architectural styles. It is ideal for any low-rise structure and has various advantages over traditional structures.
Pre-engineered structures are typically low-rise structures with maximum eave heights of 25 to 30 metres. Low-rise structures are useful for offices, homes, showrooms, and storefronts, among other purposes. It is particularly cost-effective and quick to apply the pre-engineered approach to low-rise buildings. Buildings can be created in less than half the time they normally take, especially when additional engineered sub-systems are used.
A building with a ground floor, two intermediary storeys, and a roof is the most popular and cost-effective style of low-rise structure. A low-rise building’s roof might be flat or sloping. Mezzanine systems are used to provide intermediate floors in low-rise buildings. Single-story dwelling houses take the least amount of time to build and may be built in any type of geographic location, including extreme cold hilly hills, high rain-prone areas, plain land, and extreme hot climatic zones.
A pre-engineered building consists of nine primary components, including: Vertical columns or main framework completing the wall framework Purlins, girts, and eave struts are all types of purlins. Prefabricated panels or sheeting with insulation craning system.
Main Framing
The rigid steel frames of the building are referred to as main framing. Tapered columns and tapered rafters make up the PEB rigid frame (the fabricated tapered sections are referred to as built-up members). The tapered parts are made with cutting-edge technique that involves welding the flanges to the web. The ends of the tapered pieces are welded with splice plates. Bolting the splice plates of connected sections together creates the frame. The major framing columns in conventional housing are of the ISMC group.
End Wall Framing
A pre-engineered building’s endwall frame can be either a primary rigid frame (identical to the interior structure) or a post and beam frame. The decision is made based on the customer’s needs (namely, whether he wants to go in for future expansion or not) and/or the building’s needs (is the endwall open for access).
Columns (posts) with pinned ends support horizontal beams known as endwall rafters in the post and beam end wall framing system. To give lateral stability and a tidy look, girts are flush framed between posts. Because of the diaphragm effect of the wall sheeting, post and beam endwalls are expected to be laterally stiff. The diaphragm movement has been shown to be sufficient to.
Purlins, girts and eave struts
Secondary cold-formed parts include purlins, girts, and eave struts. Their preparation does not include any welding. They are made by simply bending a steel coil into the desired shape (Z-shape for purlins and girts, and C-shape for eave struts).
Purlins: Purlins support the roof panels as supplementary elements. Pre-engineered structures use Z-shaped purlins, which have the advantage of being lapped at support points and nested together to increase rigidity. This capability gives greater strength and lowers deflection. C-shaped purlins, on the other hand, lack this capability and are therefore not employed as purlins or girts.
The following loads are applied to the purlins:–
Loads of gravity (dead + alive)Uplift (suction) load caused by the wind Longitudinal wind loads cause axial force (especially for the strut purlins)
Girts: Girts are used to provide a framework for sidewall and endwall cladding. By-framed (by-pass) construction is used for sidewalls to take advantage of lapped girts, and flush construction is used for endwall girts to effectively exploit diaphragm action. Endwall girts that are flush with the endwall column web are simply supported members.
The following loads are applied to the girts:–the force of gravity (dead)Suction and wind pressure
Eave Struts: Cold formed C sections are used for all eave struts. These are simply members who help others (180mm in depth and 2.0mm or 2.5mm in thickness). At the corners, eave struts are an excellent choice.
Panels and insulation
Roof and wall sheeting, roof and wall liners, partition and soffit sheeting are all made from single skin profile steel sheets. Steel coils and aluminium coils are commonly used to make steel sheets. Steel coils with a minimum thickness of 0.5mm high tensile steel are used. The stiffness required, the governing loads (dead/live/wind), and other factors influence the profiles. The profile of the sheets, as well as the depth and number of ribs, determine their strength.
Steel sheets are usually zincalume or galvanised profiled sheets that are permanently colour coated either plain or with specific paints like PVF2 if superior anti-corrosion qualities are required.
Fibrous insulation slabs / rolls of non-combustible Rockwool, Aluminium foil laminated, laid over a metal mesh bed produced between the purlins, and then the roofing steel sheet fixed over it, can be used to appropriately insulate these structures. A double skin profile steel sheet wall cladding with a Rockwool Insulation slab sandwiched in between and kept in place using ‘Z’ spacers in between the two profile steel sheets can also be used to insulate siding walls. A double skin insulated roofing system can also be built in a similar arrangement.
When a nice finished appearance is desired, liner panels are utilised to conceal the roof purlins, wall girts, and Rockwool insulation on the inside of the building. Insulation of various thicknesses can be put beneath the panels if the temperature inside the building needs to be controlled. Another option is to provide prefabricated insulated panels, which are made up of two single skin panels (simple steel sheets zincalume colour coated) with polyurethane foam insulation sandwiched between them. These panels are designed to be used as thermally efficient roof and wall claddings for structures, such as cold storages and high altitude locations.
The wall panels for standard dwelling are made up of exterior contoured steel sheet that is fastened to the columns and purlins. Between the purlins, rockwool insulation is applied, and then a particle/rigid board inner sheet is bonded to the columns and purlins, completely hiding the steel construction. The roof is made of profile steel sheets with insulation adhered to the underside. Particle/rigid board false ceiling is attached to a steel frame work suspended from the trusses. Insulation can also be applied to the polythene-wrapped artificial ceiling. For protection, a two-foot-high brick wall must be built on the outside.A second option for wall construction is to weld metal mesh to the columns and purlins.
System of cranes
Cranes are utilised in industrial buildings to improve material handling productivity and allow for more effective space usage by decreasing or eliminating traffic caused by forklifts and other vehicles. The crane runway beams are simply supported by cap channels and built-up sections. It can also be tapered because it’s a built-up part, lowering beam costs over long spans.
Mezzanine system
For lateral stability, the mezzanine framing is usually attached to the main rigid frame columns. Simple span members are studied and designed for mezzanine beams and joists. Built-up beams (that may be tapered for wide spans or heavy loads) support built-up, hot-rolled or cold-formed mezzanine joists, which in turn support a metal deck in a standard mezzanine structure. As a final surface, a reinforced concrete slab is cast on the metal deck. The metal deck isn’t meant to support live loads on the floor; it’s just meant to support the reinforced concrete slab while it’s being poured. The floor loads must be carried by the reinforced concrete slab. Hot rolled tube parts or built-up sections are used for interior mezzanine stub columns.
Checkered plates or grating can sometimes be used in place of concrete flooring. A structural framing system is sometimes installed on top of the roof to support large roof accessories like HVAC units, water tanks, and other miscellaneous roof equipment. Roof platforms are what we call them. At occasion, a thin walkway known as a catwalk is built, which is used largely by maintenance staff to get access to mechanical equipment supported on roof platforms. Catwalks are typically installed alongside crane beams, hanging beneath rigid frame rafters, or elevated over the building’s roof line.
Bracing System
Longitudinal cross bracing consists of 7-strand twisted galvanised cables with an eye bolt and an adjusting nut at both ends, located near the outer flange of columns or rafters and attached at the web of the rigid frame to provide lateral stability to the structure against wind, seismic, or other forces. Crane longitudinal loads will be carried to the foundation utilising smooth round bars or hot rolled angles instead of wires in structures supporting cranes. Portal bracing is also offered when the sidewall must be open for access or other reasons. The fixed base column can be built in the minor axis direction to resist the lateral stresses applied along the length of the building for small width buildings with low eave heights.
Also Check