Steel structure, especially light steel structure building system, was born at the beginning of the 20th century and developed rapidly during World War II.It is mainly used for military building facilities with high construction speed requirements; in the 1940s, portal frame structure appeared; in 1960s, a large number of light-weight enclosure systems composed of color profiled panels and cold-formed thin-walled steel sandalwood strips have been widely used.In recent years, with the increase of the world’s total steel production and the decline of international military steel consumption, some large steel producing countries and economically and technologically developed countries, such as Europe, North America, Japan and Australia, continue to expand the scope of the use of steel structures and build various steel structure houses. According to their living habits, they mainly build low rise independent houses with 1-3 floors.With the decrease of resources and the increase of population in North America and Europe, the research and development of multi-storey light steel structure residence began.The proportion of construction steel consumption in the total steel consumption in various countries has been significantly increased, and the proportion in Japan is about 50%.The steel consumption of steel structure in America, Sweden, Japan and other countries has accounted for more than 30% of the steel production, and the steel structure area accounts for more than 40% of the total building area.

1. Europe

     20In the 1950s, due to the severe trauma of World War II, Europe had a great demand for housing. In order to solve the problem of housing shortage, some European countries adopted the steel structure building system with high degree of industrialization, built a large number of houses, and formed a batch of complete and standard steel structure residential systems, which have continued to this day.In Finland, Sweden, Denmark, France and other countries, all kinds of steel structure building systems have become very popular. Among them, Sweden’s steel structure, especially the light steel structure, is the most developed. Prefabricated components of light steel structure residential buildings account for 95%. At the same time, it is also the largest light steel structure residential building manufacturing country in the world, with production supply to European countries.

2. North America and Australia

In the United States, Canada and Australia, galvanized light steel keel has been used to replace the traditional wood structure of light steel residential building system, which has been developed for more than 30 years.In 1996, the proportion of light steel structure residential buildings in the United States reached 20%, that in Canada was about 30%, and that in Australia was about 50%.However, this kind of structure is mainly used in low rise small houses.Since the late 1990s, the multi-storey light steel keel residence has developed rapidly in North America, and has been completed about 3 million square meters.In addition to residential buildings, this system is also used in nursing homes, holiday hotels, primary schools and other buildings.

Light steel structure residential building system is made of galvanized cold-formed thin-walled steel profiles as the structural load-bearing part, which is commonly used to build 2-3-story low-rise residential buildings.The yield strength of the material used for galvanized cold-formed thin-walled steel is Q235 or Q345.The steel keel of the wall is arranged according to a certain modulus, and the center distance is generally 400mm or 600mm; the section of cold-formed thin-walled steel is between 93-200 mm, and the thickness of steel plate is between 0.84-1.91mm.The steel keel section of the floor structure is generally 150-300 mm, the steel plate thickness is 0.84-2.56 mm, and the maximum floor span is up to 8-9 m at present.The roof truss can be directly overlapped with light steel ribs.

The exterior wall of light steel structure residence usually adopts energy-saving and light-weight composite sandwich wall, and the interior wall can adopt gypsum board; the wall of kitchen and toilet adopts waterproof gypsum board or cement plus pressing plate; the floor adopts light structural plate; the roof can adopt colorful tile, color board tile and other roof materials.

(1) Light steel structure residential system in Canada

Light steel members in Canada are usually formed by cold bending and rolling of galvanized or aluminized zinc alloy sheet. The cross-section shape is usually C-type and groove type. The thickness of steel plate can be changed according to the requirements of structure, and the length of components can be determined as required.Although the bearing capacity of a thin steel plate itself is not high, its bending and compression resistance capacity will be doubled after cold bending into different shapes (e.g. type C).Therefore, the bearing capacity of light steel members mainly depends on the cross-section shape rather than the thickness of the plate.This constitutes its characteristics of light weight and high strength.

Low rise housing:

structural system

Residential structure is usually composed of floor, wall and roof system.The structural form of light steel residence usually adopts the plate rib system supported in the line. The light steel components can be applied to different building components. The use of light steel components can greatly simplify the structural system, and at the same time, it can provide effective use of the bearing capacity of the structural system and components, design flexibility and construction convenience.

Floor system

As a floor joist, the light steel keel has a section height of 150-300 mm, and its steel plate thickness is about 0.84-2.56 mm. The common support form of floor joist is simply supported or continuous beam. Multi span continuous beam can be in the form of single component or multi-component overlapping.Generally speaking, the form of multi member overlapping is more flexible than that of single component, and it is also convenient in transportation.The web of joist keel of floor is usually punched with equal spacing to facilitate the crossing of water and electricity pipelines.

Wall system

The light steel keel used for wall can be divided into load-bearing and non load-bearing. The section height of load-bearing C-shaped keel is generally between 93 and 200 mm, and the thickness of steel plate is usually between 0.80 and 1.91 mm; the section height of non load-bearing keel is 41-150 mm, and the thickness of steel plate is 0.45-0.84 mm, which is a very economical and practical wall system,This kind of rib wall is also widely used in high-rise residential buildings, which is composed of light steel keel and gypsum board (if it is used as external wall, structural plate should be added).

roof truss

Light steel members with different cross-section forms and thicknesses can be widely used for various roof forms and systems.The roof truss can be directly composed of light steel rafters or light steel trusses.Light steel truss can not only be made on site, but also suitable for large-scale integrated production in factories.

Medium and low rise housing:

Light steel plate rib structure system is usually suitable for residential buildings with six floors or less, but there are also examples of eight story hotel buildings.The thickness of the light steel keel of the first floor of the middle-level residential building can reach 2.6 mm, and the keel spacing is usually 305 mm.According to the length of the floor structure, the following systems can be selected: light steel floor system, steel bearing composite floor composed of profiled steel sheet and concrete, prefabricated or cast-in-place reinforced concrete floor.The composite floor composed of light-weight open web steel truss, profiled steel sheet and concrete can be used for extra large bay. The anti lateral load system is usually composed of X-type inclined support system composed of light steel brace, or shear wall system composed of shear plate and light steel keel.Roof trusses are mostly made of light steel rafters or trusses.

High-rise residential:

In Canada, light steel structure has been widely used in all kinds of high-rise buildings, including residential buildings. It is mainly used for internal and external infill walls, partition walls, curtain walls, external retaining walls, roof trusses and roof systems. The bearing structure of high-rise buildings is often composed of H-shaped steel or reinforced concrete frame system,The light-weight internal and external wall system composed of light-weight steel members is very easy to integrate with the frame system of load-bearing structure.

(2) Light steel structure residence in America

Like other Western European countries, light steel structure is mainly used for low rise residential buildings in the United States. In recent years, the United States has begun to carry out research and development of multi-storey light steel structure residential system. The earliest multi-storey light steel residential building was designed in 1990, and the total area has developed to about 300000 square meters.And obtained a lot of mature technology and experience.

The multi-storey light steel structure residential technology in the United States is a comprehensive technology, which integrates light steel structure, building energy conservation and heat preservation, building fire prevention, building sound insulation, new building materials, design and construction. The socialized division of labor is clear, and the manufacturers, constructors and designers of various products cooperate closely to develop multi-storey light steel structure residential technology. The most critical problem is its structureFor its own performance, the floor structure should have a suitable span and be as light as possible, and hope to have a better floor in-plane stiffness. The wall structure should bear the vertical load (self weight and floor live load) and lateral load (wind load and horizontal earthquake action) at the same time.

The characteristics of American multi story light steel structure residence are as follows

The light floor system consists of C-type light steel joists and thin plates laid on the joists.The general span of joists is 3.6m-4.8m, the height of joists is 254MM (the maximum span of joists can reach 11m), and the spacing between joists is 600mm.The joist has large holes on the web, which is very convenient for pipeline crossing and layout.There are three methods for the floor: high density wood fiber cement board; full laying profiled steel plate and then pouring 20 mm ceramsite lightweight aggregate concrete; fully paving directional wood fiber board or high-density laminated plywood.On these light-weight floors, a load of 316-365 kg per square meter can be carried.The weight of the floor structure system is only one fourth to one sixth of the traditional concrete floor system in China, but the structural height of the floor will be 100 ~ 120mm higher than that of the ordinary concrete slab.

The vertical wall structure generally takes the inner transverse wall as the load-bearing wall of the structure. The wall column is a C-shaped light steel component. The wall thickness is usually 0.84-2 mm, and the wall column spacing is generally 400-600 mm. The lower end of the wall column is the bottom channel beam with U-shaped opening upward. The top end of the wall column is the top channel beam with U-shaped opening downward, 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 braces are set up within the height range of the wall column.This kind of wall structure layout can effectively bear and reliably transfer vertical load, and the layout is convenient, but the wall structure can not bear horizontal load.In order to resist horizontal wind load and earthquake action, there are two ways in American multi-storey light steel structure residential system, which are light steel shear wall or ordinary steel frame structure with cross bracing.Generally, the light steel shear wall is arranged in the household wall. The 0.5mm galvanized steel sheet is covered with gypsum board and then fixed on the light steel wall column to form a shear wall similar to the stress skin diaphragm structure. A special member is connected between each floor to connect the shear wall of the upper and lower floors, so as to effectively transfer the horizontal shear force and the tensile force generated by the horizontal force on the wall column.In the earthquake area, in order to ensure the safety of the structure, the ordinary steel frame with cross bracing is used as the lateral force resisting structure, and a hybrid structure system with light steel bearing vertical load and ordinary steel bearing horizontal load is formed.

In the American light steel residential system, heat preservation and energy saving technology is attached great importance to. For the wall, in order to ensure the thermal insulation effect, in addition to filling the glass fiber between the wall columns, a layer of thermal insulation material is pasted on the outside of the wall to effectively isolate the heat bridge from the wall column to the outer wall panel; glass fiber is filled in the joist between the floors to reduce the heat transfer through the floor Glass fiber is filled between columns of all interior walls to reduce heat transfer between walls.

Building fire prevention technology, for the light steel structure, the most critical problem is the application of fire prevention technology. The two sides of the wall and the ceiling of the floor are pasted with fireproof gypsum board. For ordinary firewall and household wall, 25.4% is used Millimeter thick (1 inch) gypsum board protection to meet the fire protection requirements of one hour. In addition, glass fiber filled between wall column and floor joist also plays a positive role in fire protection and heat transfer.

Building sound insulation technology in light steel buildings, the research and development work in the United States has made great efforts to deal with the sound insulation. Glass wool is filled between the inner and outer walls and the joists of the floor, which effectively prevents the audio part transmitted through the air. For the impact sound transmitted through the solid, in the multi-storey light steel residential buildings in the United States, the following structural treatment has been made: for the household wall, two wall columns are used with the middleFor the small keel of fixed gypsum board for ceiling, elastic structure with small slot is used to effectively reduce the solid sound transmission between floors.

(3) Cold formed thin wall light steel structure residential system in Australia

Structural features:

The load-bearing structure adopts cold-formed thin-walled light steel framework, high-strength and anti-corrosion steel coil plate (yield strength 550MPa, zinc aluminum alloy coating thickness 270g / m2), steel thickness of 0.75mm, through computer-aided manufacturing special equipment, according to the design requirements, directly rolled into various types of structural members.The vertical load-bearing components are closely arranged columns with the maximum column center distance of 600mm.Plane load-bearing members: the roof adopts truss net, the grid size is 600x600mm, the floor (ground) surface adopts truss beam, the maximum middle distance is 1200mm, and the door and window lintel adopts small truss beam.

The wall enclosure structure is made of lightweight high-strength enclosure material or fiber cement board.

The roof, floor and internal and external walls are made of waterproof and thermal insulation materials.

The roof and floor system adopts waterproof glass fiber tile, waterproof membrane, thermal insulation material cotton, stringer and hanging fireproof gypsum board.

Construction features:

The production of steel structure adopts computer-aided manufacturing technology, and the whole process of production is completed by professional equipment controlled by computer software, so as to ensure that the accuracy error of component manufacturing is less than half millimeter which is difficult to achieve by manual work.In addition to the foundation construction, the rest are all dry construction and installation.

Design features:

Cold formed thin-walled light steel structure system is a mature technology in Australia.The special CAD technology light steel structure construction design software is used in the design. The design files generated from this software can be directly input into the processing equipment for automatic processing.

3Light steel structures in Asian countries:

Due to the economic expansion of Western European developed countries and the economic rise of Asian countries, India, Japan, South Korea and other countries began to study and develop steel structure residential buildings in the early 20th century. The steel structure buildings in Japan accounted for about 50% of the total construction amount, and the steel structure buildings in South Korea accounted for about 20% of the total construction amount, and H-beam steel accounted for about 50% – 60% of the total steel used for steel structure.

The history of steel structure building in Japan is about 100 years.At present, among all kinds of building structures in Japan, the number of steel structure buildings is the largest, accounting for about 20% of the total residential building area, and most of them are low rise independent houses.Low rise and small-scale residential buildings using light steel have been systematized. The completed light steel structure residential buildings account for 25% – 28% of the total number of residential buildings. of which the KC housing system of Nippon Steel is particularly prominent.

The steel plate structure is similar to the steel plate structure used in the shear wall system to resist the transverse load.Each floor is placed and installed on the wall panel of the floor. The wall panel is separated by each floor in the vertical direction, so the vertical wall can not form a continuous wall in structure.Therefore, it is technically necessary to connect the upper and lower wallboards as a whole through the anti pulling anchor bolts through the floor, and at the same time, the shear bolts are used to connect the wall panels and the floor slabs.

OSB (oriented particleboard), structural composite board, cement fiber laminate are generally used for structural board.This kind of board solves the defects of the original pure wood board in fire prevention, waterproof and structural overall strength. This kind of substitute product solves the deficiencies of the original wood board in fire prevention, waterproof and overall structural strength, and improves the overall performance of the building system.

The fire prevention uses the board with higher fire resistance performance, such as non combustible cement-based structure board, fire-resistant gypsum board and so on as the basic material.In order to prolong the fire resistance time of the wall and enhance the integrity of fire resistance.

The heat insulation measures increase the reflection effect of the wall on the radiant heat by adding a reflective layer in the composite external wall, which greatly reduces the influence of the radiant heat on the indoor thermal environment of the building. The test comparison and practice show that the energy saving effect is obvious, and the thermal stability is also improved.