In recent years, light steel structure has been widely used in workshops, small exhibition halls and office buildings because of its low steel consumption, short design and installation time and high degree of industrialized production. This has promoted the development of steel structure enclosure systems from single to diversified, which has led to the change of new design ideas and new construction methods.
The envelope system of light steel structure mainly includes wall system, roof system, light belt, wrapping and flooding, gutter and insulation wool. The envelope system is one of the main components of the light steel structure, which determines the ornamental appearance of the building and the waterproof and thermal insulation effect of the building.
1. Design and construction of roofing and wall system
1.1 Classification of color plate enclosure system
According to the composition of the color board enclosure is divided into: single-layer board, EPS sandwich panel, BHP color steel plate, GRC wall panel, polyurethane sandwich panel, glass wool field composite sandwich panel, and rock wool sandwich panel.
According to the construction method, there are finished composite panels and on-site composite panels. On-site composite panels are divided into lap panels, nibbled panels, and concealed buckle panels.
According to the material: galvanized color steel plate, titanium plate, aluminum galvanized color steel plate, aluminum alloy plate pressure plate, stainless steel plate pressure plate, copper plate.
1.2 Design considerations
The site composite board is widely used in light steel structure because of its low processing cost and more mature construction technology. The colorful roofing board is made of 0.376t and 0.5t thick galvanized baked paint color board.
Roof slope affects the discharge of rainwater on the roof, in the design of the roof slope should be taken 1/8-1/20, in the area of more rainwater should take the larger value (see CECS102:98), in addition to the roof slope and the type of roof panels used, the general exposed nail type plate using the slope requirements are larger, hidden type requirements are smaller.
Large span steel structure roof panel should adopt concealed buckle type color steel plate. In a large number of engineering applications, the concealed buckle type color steel plate shows the following advantages: (1) to avoid the temperature difference caused by the roof panel deformation is too large, self-tapping screws are cut off. (2) In rainy areas, typhoon areas, exposed self-tapping screws in temperature deformation, wind load vibration, rubber pad aging, very easy to cause corrosion and leakage of the plate, the use of concealed buckle picking steel plate can avoid the above situation. For roofs with single slope length more than 60 meters, it is necessary to process two plates to form expansion joints between plates, and connect them with Taitai cover sheets, which can slide with each other between color plates and can solve the problem of temperature deformation.
1.3 Construction precautions
In the construction, for the roof of large span, the color board needs to be a whole piece of molding board, because the crane lifting board is easy to cause deformation of the board, so the installation generally does not use the crane, colorful winch semi-slanting type lifting.
2. Design and construction of light-emitting panels
According to the material, the light board is divided into glass fiber reinforced polyester light board, honeycomb or solid board made of polycarbonate, etc. According to the shape, it can be divided into glass fiber reinforced polyester light board (referred to as FRP light tile) and other flat or curved light board with the same waveform as the roof panel.
Different light panels have different fixing methods, polycarbonate light panels are fixed with aluminum fasteners, waveform light panels are fixed with light panel brackets and self-tapping screws, and then sealed with glue. The position of the light board is generally set in the span. Light plate and self-tapping screw connection, there must be a cover plate. Sunlight board cold and hot deformation is larger, easy to be self-tapping nail shear, so the sunlight board in playing self-tapping nail should open a larger hole. The expansion and contraction of the light board should be considered when installing the light board.
The lap of the light board is not needed within 12m, more than 12m, the lap is needed, the lap length is 200-400mm, the lap is coated with two sealants, the horizontal lap does not need to close the edge, the lap of longitudinal color steel plate needs to see the plate type, ordinary pressure type steel plate, generally do not test the false edge, directly fix it with the color plate with self-tapping nails, and apply sealant, the bite plate needs to do the edge.
The longitudinal length direction lap should be set near the sandal, roofing waterproof treatment shall be used sealant inside the coating, the sealant surface is easy to age; lap with two water mud middle sandwich a white or colorless sealant.
Lightboard lateral color plate lap: bright screw roof panel or dark buckle roof panel, light board should be reserved for the effective width of the board, in the light board crest with long self-tapping screws fixed, taking into account the light board thermal expansion and contraction is not the same, the light board should be pre-punched processing (8mm hole is appropriate), self-tapping screws need to be placed under the reinforced waterproof gasket, to prevent the light board thermal expansion and contraction in the screw cracking.