In the current building structure type, light housing steel structure has a very wide range of applications, in recent years has gained good development, especially in civil and industrial buildings are widely used, has become a trend in the development of residential nonindustrial. In the process of application and development over a long period of time, the light steel structure building type has become more diverse, for example, the portal steel structure system has now been more perfect, also formed some patented products, and gradually achieve standardisation and factory. Based on the many advantages of modern light steel structure buildings, attention should be paid to the study of light steel structure and the application skills and points of light steel structure, in order to promote the better development of the construction industry.
1、 Portal frame steel structure system
As early as 1999, portal frame light house steel structure was widely used, and has gained good development in the subsequent time, and is currently the fastest growing new light steel structure. In terms of the characteristics of the portal frame steel system, the main load bearing structure is the portal frame and the envelope is the pressed steel plate. In the design, the web is allowed to be partially destabilised to take advantage of the post-buckling strength of the web, and the height of the web can also be changed, and the beams and columns of the rigid frame can be made into variable section forms, which can be well adapted to the distribution of internal forces in the structural moment. At this stage, China’s portal frame structure has accumulated more successful experience in both design and production and installation, and can be widely used in sports stadiums, industrial plants, entertainment venues, storage and transportation facilities.
The current typical portal frame structural system consists of a variety of components, mainly wall panels, foundations, wall beams, wind columns, roof panels, main rigid frame, roof supports, purlins and inter-column supports. There are various options for designing the structure, including high and low span, multiple ridge, single ridge, single span, single slope, gentle slope, flat slope, multiple span, and even single or multiple swaying columns within the span. Rigid frame structures are mainly welded I-beam solid web sections, with plate thicknesses usually controlled to less than 16mm, as the height and thickness of the webs are large enough to allow for local instability, although variations in section can be achieved by changing the height of the webs using variable section members. When splicing beam-column nodes and diagonal beams of rigid frames, high-strength bolted end plates can be used, either flush or extended, with the flush end plates being less rigid in comparison, so the extended end plate connection should be preferred and the thickness of the end plate should be controlled to 20mm or more. If the wind load at the construction site is high, the stability of the purlins and wall beams under specific actions should be analysed, mainly to evaluate the stability under wind suction. Flexible supports consisting of tensioned round steel can be used for roof and inter-column supports, or if the plant has crane facilities, the lower column supports should be designed as rigid supports. In addition to this, sandwich panels and composite panels can be used for roof and wall panels. Sandwich panels and composite panels can be either single-layer or double-layer, and if single-layer panels are to be used, an insulation layer should be added. In general, the portal frame is a planar force-bearing system, suitable for application in buildings with narrow plan dimensions, column spacing of 7-9m and span of 18-36m, so it is widely used in modern industrial plant buildings.
2、 Steel systems for multi-storey building
Compared to reinforced concrete structures, multi-storey building steel systems are less labour intensive and faster to construct, and currently light steel frame structures are mainly used in public and residential buildings of 2 to 8 storeys. In the use of frame columns and beams, currently mainly H-beams or round steel pipes are used, in either hot-rolled or welded form, and usually the whole structure will use up to 40-50kg/m2 of steel, resulting in better economic indicators than concrete structures. In general, multi-storey housing steel systems are widely used in public buildings, such as schools, entertainment venues, hospitals, offices, industrial plants and also in commercial buildings.
The design of multi-storey building steel structure system, mainly relies on the “light house steel structure design regulations” “steel structure design code”, the typical effective multi-storey steel structure system by the column support, wall beam, frame beam column, compression steel plate floor cover, wall panel, roof support, floor level beam, purlin, foundation is composed of, usually load-bearing structure of the column distance in 6 ~ 12m, both in accordance with the space frame design, but also It can be designed either as a space frame or as a flat frame. In order to ensure the overall stability of the structure and to reduce lateral displacement, inter-column supports should be arranged in conjunction with the actual situation. In the design and construction of the floor, prefabricated slabs with cast-in-place slabs can be used, or a combination of primary and secondary beam systems and pressed steel plates can be used, requiring good contact between the primary beams and the columns, with hinged connections between the primary and secondary beams being preferred. In connecting between the floor slab and the steel beam, shear pegs can be used, which can greatly improve the bearing capacity and stiffness of the beam, if the floor beam is to be designed in accordance with the combined beam, it must be scientifically arranged pegs according to the force requirements, if the combined effect is not considered, the arrangement of pegs and other shear resistant parts can focus on the construction requirements. If the roof of a multi-storey housing steel structure building is not occupied, pressed steel plates and purlins can be used, internal walls should achieve light partitions, and external walls should use other light wall structures, which can also use pressed steel plates. In general, multi-storey housing steel structure system will be more widely used in the future, especially in multi-storey factory buildings and supermarkets, so there is a large potential market. Figure 1 shows a multi-storey house steel structure building.
Fig. 1 Steel structure of a multi-storey building
3、 Cold-formed thin-walled structural steel systems
The cold-formed thin-walled steel sections used today are cold-formed from ordinary or galvanized steel sheets, usually with a thickness of 0.5 to 3.5 mm, and are available in Z-shaped, C-shaped and square tube shapes, which can be formed into various patterns of folds and rolled edges. The cold-formed thin-walled steel structural system, which is currently in widespread use, mainly uses cold-formed thin-walled steel as a load-bearing skeleton structure and can be used in both multi-storey and single-storey housing.
In the current cold-formed thin-walled structural steel systems, the frame beams and columns are usually of I- or T-section, and are mostly composed of four C-channels or double C-channels. The load-bearing skeleton is usually a flat frame, and in order to ensure overall stability, inter-column bracing needs to be arranged scientifically. The cold-formed thin-walled structural steel system is usually small, so that the members are connected by bolts and only small lifting equipment is required on site.
At present, some galvanized cold-formed thin-walled steel buildings can usually be installed within a week, with good insulation, temperature and humidity, sound insulation performance, and gradually achieve batch commercial production. Overall, although the current phase of the cold-formed thin-walled steel structure system in China has gained good development, but both the design and construction are a little deficient, there is a need for further research, the follow-up in the cold-formed thin-walled steel structure technology research efforts, master more technical points to improve the physical properties of the building.