What are the design features of American houses?

Multi-storey light steel structures in the United States are mainly used in multi-storey apartments and hotels. The earliest multi-storey light steel residence was designed in 1990. So far, the total area of multi-storey light steel structure has developed to about 300,000 square meters. Judging from the development situation, the United States has successfully carried out the research and development and engineering application of multi-storey light steel residential system, and there are many mature technologies that can be used as reference for the development of multi-storey light steel residential system in China.

Keywords: steel structure residential system

Multi-storey light steel structures in the United States are mainly used in multi-storey apartments and hotels. The earliest multi-storey light steel residence was designed in 1990. So far, the total area of multi-storey light steel structure has developed to about 300,000 square meters. Judging from the development situation, the United States has successfully carried out the research and development and engineering application of multi-storey light steel residential system, and there are many mature technologies that can be used as reference for the development of multi-storey light steel residential system in China.

Multi-storey light steel structure residential technology in the United States is a comprehensive technology integrating light steel structure, building energy conservation and thermal insulation, building fire prevention, building sound insulation, new building materials and design and construction. The socialized division of labor is clear, and the manufacturers, builders and designers of various products work closely together. Driven by the North American Metal Structure Association, relying on the newly compiled light steel structure design standards and extensive publicity, it has developed rapidly. It can be predicted that the construction of light steel structure will be a main structural development direction of multi-storey apartments and hotels in the United States.

The key problem of developing multi-storey light steel structure residential technology is the performance of the structure itself. The floor structure should have a suitable span and be as light as possible, and it is hoped that the floor has good in-plane stiffness. The wall structure should bear vertical load (dead weight and floor live load) and lateral load (wind load and horizontal earthquake). The characteristics of American multi-storey light steel residential buildings are as follows:

1. The light floor system consists of a C-shaped light steel keel and a thin plate laid on the keel. Generally, the joists span 3.6m ~ 4.8m, the joist height is 254mm (the maximum joist span can reach 1 1m), and the joist spacing is 600mm. The patented joist product developed by Dietrich Company in the United States has a big hole in the web, which is very convenient for pipeline crossing and layout. There are three methods for flooring, namely: high-density wood fiber cement board; Laying profiled steel plates and pouring 20mm ceramsite lightweight aggregate concrete; Unfolding oriented wood fiberboard or high-density laminated plywood. These lightweight floors can bear a load of 3 16 ~ 365 kg per square meter.

The weight of the floor slab structure system is only one quarter to one sixth of that of the traditional concrete floor slab system in China, but the structural height of the floor slab will be higher than that of the ordinary concrete slab 100 ~ 120 mm.

2. For the vertical wall structure, the internal transverse wall is generally used as the load-bearing wall, and the wall columns are C-shaped light steel members. The wall thickness is generally 0.84 ~ 2mm according to the load, and the spacing between the wall columns is generally 400 ~ 600mm. The lower end of the wall column is a bottom channel beam with an upward U-shaped opening, and the upper end of the wall column is a top channel beam with a downward U-shaped opening, and the joist is fixed on the side of the upper channel beam. In order to improve the stability of the wall column, three light steel supports are generally set within the height range of the wall column. This kind of wall structure arrangement can effectively bear and reliably transmit vertical load, which is convenient to arrange, but the wall structure cannot bear horizontal load.

In order to resist horizontal wind load and earthquake, there are two ways for American multi-storey light steel residential system, that is, adopting light steel shear wall or adopting general steel frame structure with cross braces. Light-weight steel shear walls are generally arranged in the residential walls, covered with 0.5 mm galvanized steel plates on gypsum boards, and then fixed on light-weight steel wall columns to form shear walls with similar stressed skin structures. Special members are arranged between each floor to connect the upper and lower shear walls, effectively transmitting horizontal shear force and tensile force caused by horizontal force acting on the wall column. In the earthquake area, in order to ensure the structural safety, steel frames with cross braces are generally used as lateral force resisting structures, forming a mixed structural system in which light steel bears vertical load and general steel bears horizontal load.

3. Building thermal insulation and energy-saving technology In the American light steel residential system, thermal insulation and energy-saving technology is highly valued. For the wall, in order to ensure the thermal insulation effect, in general, in addition to filling glass fiber between the wall columns, a layer of thermal insulation material is attached to the outside of the wall to effectively bridge the wall columns to the external wall panels; Joists between floors are filled with glass fiber to reduce heat transfer through floors; Glass fiber is filled between the wall columns of all interior walls to reduce the heat transfer between walls.

4. Building fire prevention technology

One of the most critical problems of light steel structure is the application of fire prevention technology. Fire-proof gypsum boards are pasted on both sides of the wall and the ceiling of the floor. The common firewall and the residential wall are protected by gypsum boards with a thickness of 25.4 mm (1 inch), which meets the fire protection requirements of 1 hour. In addition, the glass fiber filled between the wall column and the floor joist also plays an active role in fire prevention and heat transfer. These products have passed the testing and certification of UL certification laboratory in the United States. The requirement for fire resistance limit of American residence is lower than that of China, which is related to the fact that American residence design emphasizes the time needed to ensure escape, but does not overemphasize the requirement for fire resistance limit of residence itself.

5. Building sound insulation technology In light steel buildings, the research and development work in the United States has made great efforts in sound insulation treatment. Glass wool is filled between the inner and outer walls and the joists of the floor, which effectively prevents the audio part from spreading through the air. For the impact sound transmitted by solid, the American multi-storey light steel residence has been treated as follows: for the household wall, two wall columns are used to form two walls, leaving a gap in the middle; For the small keel of fixed gypsum board for ceiling, the elastic structure with small grooves is adopted to effectively reduce the transmission of solid sound between floors.