Xirong analyzes modern steel structure buildings and their application in China

Steel structure is the fastest application and development of the new structural type at home and abroad, widely used in all kinds of industrial, public and residential buildings, with fast construction speed, beautiful building shape, less steel consumption, low cost and other advantages. This paper reviews and summarizes the development status of steel structures at home and abroad, and puts forward suggestions for the main problems in analysis, design and application.

In addition, steel structures can also replace masonry or wood structures, which can be recycled and comply with the principles of environmental protection and sustainable development. However, as a high-tech and new application, the quality of design and construction personnel is high, and special training is required. Processing and production need to establish professional production lines, invest in the people's congress in advance, and the anti-corrosion and fire prevention problems of the structure also need to be specially handled.

The commonly used steel structure load-bearing system in China includes: welded portal steel frame structure system, cold-formed thin-walled steel structure system, multi-layer frame structure system, thin-walled folded arch shell roof system. For industrial and civil buildings without cranes, the amount of steel used in steel structures is generally 20~50kg/m2, mainly depending on the size of the structural form, span, column spacing and live load.

The prefabricated steel house building system was born at the beginning of this century, mainly used in garages, using steel corrugated board roofing and walls, and in the 20s there was a stereotyped production of factory buildings. During World War II, steel house construction developed rapidly, mostly used for rapid construction of field hangars, and the large demand for industrial plants for post-war reconstruction further stimulated the development of steel houses. In the 40s, the portal rigid frame structure appeared, and in the 60s, a large number of colored profiled panels, Z-shaped purlins, thermal insulation wall panels and roof panels began to be used. At present, steel structure has become the main building structure type in developed countries, for example, 90% of single-storey and 60% multi-storey houses in the United Kingdom are steel structures.

In 1995, metal houses accounted for 65% of single- and double-storey buildings with a single area of 15,000m2 or less, and a total area of 35 million m2 was newly built, mainly used for various factories, commercial buildings, public buildings, agricultural buildings, etc. The main form of the steel structure system in the United States is the portal rigid frame, which has been very perfect in analysis, design theory and methods and manufacturing processes, and has developed a variety of patented products, and its special design software can complete the design, drawing, quantity statistics and engineering quotation in a short time, and has also achieved a high degree of standardization and factory production in manufacturing.

Despite the decline of the European construction market, the amount of steel structure construction engineering has shown a trend of increasing year by year, and the annual engineering volume has exceeded 7 million tons. China's large-scale application of steel structure from the Baosteel project, the introduction of the use of profiled steel plate enclosure structure, hot rolled H-beam as the main load-bearing structure of the new industrial plant, in the 80s metallurgical building research institute and other units researched and developed a complete set of construction technology, as well as H-beam, purlin, wall beam, profiled plate, sandwich panel, insulation board and other supporting production lines. In the 90s, foreign steel manufacturers pushed the whole set of structural systems to the domestic market, and domestic steel manufacturers and design units also began to promote the application of steel structures on a large scale. At present, China's steel production has reached 100 million tons, ordinary carbon steel quality is reliable, stable price, sufficient supply, galvanized and color steel plate performance is excellent, in the design, production and installation of steel structure has accumulated successful experience, all kinds of welding, cold forming, profile plate and other steel production line 100, has been formulated portal rigid frame house steel structure technical regulations (CECS102:98) and corresponding design manual 26, and developed some steel structure design professional software. The most widely used steel structure in China is the portal rigid frame system building and arch corrugated roof, the completed Beijing western suburb hangar and Dalian reserve grain depot single-storey portal rigid frame span has reached 72m, Wuhu Auto Parts Company's other plant monomer covers an area of more than 75,000 m2.

The main application fields of steel structure in China are: 1. New technology development zone projects, especially high-tech enterprises, in order to establish a corporate image, steel structure is mostly used; 2. Warehousing (grain and cotton warehouse, garage, reserve warehouse), distribution and transshipment center (industrial, commercial); 3. All kinds of (small tonnage crane) light industrial plants; 4. Shopping malls, exhibition halls, gymnasiums, waiting rooms, hangars, studios and other large-span public buildings; 5. Multi-storey residence, multi-storey industrial plant; 6. Multi-storey public buildings such as schools, hospitals, offices, and entertainment; 7. Commercial buildings such as supermarkets, retail, and department stores; 8. Renovation, expansion, renovation and addition of old buildings.

　　Second, the steel structure system and characteristics of the portal steel frame house steel structure system adopts the portal rigid frame as the main load-bearing structure, the profiled steel plate enclosure structure, the analysis design and production and installation technology is mature, widely used, and there are a variety of stereotyped complete systems. The scope of application includes all kinds of industrial plants, stadiums, entertainment venues, public buildings, warehouses and storage and transportation facilities, supermarkets, retail and commercial services, etc., and its reasonable span is generally between 18~36m.

Portal rigid frame structure types are diverse, can be single ridge, multi-ridge, single span, multi-span, high and low span, or single slope, double slope, steep slope, gentle slope, flat slope, curved roof, and single or multiple swinging columns can also be provided in the span. The components are mostly I-section, and equal section, variable section, armpit, solid belly, fasting, lattice beam and column members can be used. The typical structural system is mainly composed of foundation, main rigid frame, wall beam, purlin, roof panel, wall panel, wind-resistant column, roof support, intercolumn support, etc.

The main basis for the design of portal rigid frame structure is the steel structure design code (GB17-88), the technical code for cold-formed thin-walled steel structure (GB17-87) and the steel structure technical regulations for portal rigid frame houses (CECS102:98). Beam and column members mostly adopt welded I-shaped solid abdominal section, plate thickness is generally below 16mm, web height is large, by changing the web height to achieve variable section, can use the buckling strength of the web, according to the effective section characteristics to calculate the strength and stability of the component. The shape of the beam and column members is simple, which is convenient for the use of factory processing technology.

Portal rigid frame structure beam and column joints and inclined beam site splicing joints often use the strength bolt end plate connection, can be extended or flush type, considering that the rigidity of the flat end plate connection is small, in view of the semi-rigid connection in China there is no suitable calculation method, it is recommended to use the extension end plate connection, and there should be enough end plate thickness (more than 20mm) to ensure the stiffness of the node 21, 22 portal rigid frame can be rigid or articulated column feet, there are crane workshops should use rigid joint column feet.

The purlin or wall beam adopts C or Z shaped cold-formed thin-walled steel galvanized purlins or black purlins, the purlin (beam) distance is 1.5~2.5m, and ordinary bolts are mostly used to connect with the main rigid frame, and simple support or continuous system can be used, and the end of the purlin (wall beam) can be braced, which can not only improve the bearing capacity of the purlin (wall beam), increase the span of the purlin (wall beam), but also strengthen the lateral stability of the beam (column). For open (semi-open) buildings in areas with large wind loads, the lateral stability of beams (columns) can also be strengthened. For open (semi-open) buildings in areas with large wind loads, the negative wind pressure (reverse bending) working conditions of purlins and wall beams should be considered to calculate = The layout principle of support is similar to that of Pugang plant (roof truss), and the roof and inter-column support often use round steel tie rods, and the lower column support of the crane workshop should be designed by pressing the rod. Wall panels and roof panels can be single-layer or double-layer sandwich panels, composite or single-layer panels plus thermal insulation layer, and self-tapping bolts or fasteners are used.

Multi-storey house steel structure system Multi-storey house steel structure system adopts welded or hot-rolled H-beam steel as the main load-bearing frame structure, profiled steel plate composite building cover, enclosure structure and inner partition, and if necessary, support should be set to improve lateral stability. The main structural form of two-to-eight-story office, public or residential buildings in Europe, the United States and Japan is the frame, profiled steel plate composite building cover system, the amount of steel used is about 40~50kg/m2, mainly using hot-rolled or welded H-shaped steel beam columns or square, round pipe components M. The structural frame has the advantage of faster construction speed than reinforced concrete, and the use of composite building covers can ensure the overall stability of the steel beam, the stiffness and bearing capacity of the beam, but the construction and installation technology requirements are high, and the support may have a certain impact on the use.

Multi-storey house steel structure is mainly used in residential, multi-storey industrial plants, schools, hospitals, offices, entertainment and other public buildings, as well as supermarkets, retail, department stores and other commercial buildings, old buildings to add floors, renovation and expansion, etc. The column spacing is between 6~12m, and the typical multi-storey house steel structure system is composed of foundation, frame beam column, wall beam, purlin, roof panel, wall panel, roof support, intercolumn support, floor secondary beam, profiled steel plate cover, etc. The load-bearing structure is designed according to the plane frame or space frame, if necessary, the inter-column support is arranged to ensure the overall stability, reduce the lateral displacement, the floor adopts the main and secondary beam system, the profiled steel plate combined building cover or prefabricated plate plus cast-in-place plate superimposed building cover, the non-human roof can use purlins and profiled steel plates, the internal wall is partitioned, and the exterior wall adopts profiled steel plate or other wall structures. At present, some domestic multi-storey factories have begun to adopt the above structure, and the development of multi-storey housing system provides a huge potential market for the application of multi-storey house steel structure. The use of composite beams can realize the rigidity of the structure, reduce the size of the structure, and increase the space used in the building. The web opening beam can provide passage space for the equipment pipeline, but stiffeners should be provided around the hole to improve shear resistance. The secondary beam of the roof roof adopts round or hexagonal honeycomb beam, which can increase the beam height by 70% without increasing the amount of steel, and the combined truss can further increase the span.

The steel structure design of multi-storey houses is based on the steel structure design code (GB17-88), the housing steel structure design regulations organized by the China Engineering Building Standards Association are being approved, according to the space rigid frame analysis design, no column support according to the side shift frame design, column section using H-shaped or box-shaped, beam for I-shaped solid belly beam, the main beam and the column are just connected or hinged, the main beam and the column should be articulated; The composite building cover can be stacked with profiled steel plates or prefabricated plates. The floor beam should be designed according to the composite beam, and the number and size of anti-shear parts such as bolts should be arranged according to the force requirements, if the combined role is not considered, the anti-shear parts such as bolt nails can be placed according to the structural requirements. The use of honeycomb beam can not only improve the utilization rate of the cross-section, but also provide passage space for the equipment pipeline, there are no clear regulations on the design and calculation of honeycomb beam, but there are experimental research data at home and abroad for design. Inter-column supports, wall supports and roof supports transmit the longitudinal force of the crane and should be designed according to wind, seismic and structural requirements. The new profiled steel plate rib composite building cover is supported in the widened lower flange (Slimdek) of the beam, and the equipment pipeline can be arranged between the beam ribs, and the overall structural height of the beam plate is only 300mm, which also improves the fire performance of the beam, but it is necessary to solve the torsional design problem of the beam.

Cold-formed thin-walled steel used to be mostly used as single components of roofing, partitions and enclosure structures, such as purlins, wall beams, gable frames, steel roof trusses, trusses, etc., and only a small number of structural components were promoted and applied in medium and small span portal rigid frames (no cranes), single and multi-storey houses, villas, shelves and other buildings. Because the cold-formed thin-walled steel structure system mostly adopts composite building cover, enclosure and partition, on-site construction dry operation, full bolt assembly, it has the advantages of easy installation, light handling weight, only small lifting equipment, etc., and has great development potential in low-rise housing. A number of four~six-storey residential buildings have been built in Hong Kong, all using high-strength galvanized cold-formed thin-walled steel, with extremely light weight and easy installation (2). The galvanized cold-formed thin-walled steel villa produced in the United Kingdom is completely installed by hand, and the construction takes only one week, and the long-term observation of building physical properties such as heat preservation, sound insulation, temperature and humidity, and energy consumption in the three-story residential demonstration house built in Oxford is carried out to prove its superiority. The research on cold-formed thin-walled steel residential construction has been included in the key research projects in Europe, and various sample houses have been developed successively, and have entered the stage of mass commercial production.

Steel plate or galvanized steel plate is cold-pressed or cold-bent, the basic shape is C-shaped, Z-shaped and square (moment) tube type, and can form a variety of folds and crimps, I or T shape to improve section stiffness and bearing capacity. Frame (rigid) frame beams and columns can be composed of double C or four C channel steel to form I, T-shaped sections. The load-bearing structure is a flat frame, and the support between columns is arranged to ensure the overall stability, and the floor adopts the main and secondary beam system and combines the building cover. The roof is made of purlins and profiled steel plates, the interior walls are lightweight partitions, and the exterior walls are made of lightweight insulation panels.

The design of cold-formed thin-walled steel structure is based on the technical specification for cold-formed thin-walled steel structure (GB18-87), according to the analysis of plane or space frame structure, the portal rigid frame mostly adopts articulated column feet, the frame beam and column connection is mostly hinged or semi-rigid joint, and the secondary beam is mostly C-shaped or Z-shaped steel.

The application of cold-formed thin-walled steel in residential buildings has developed rapidly at home and abroad, mainly using galvanized C-shaped steel, and carried out structural tests under various load conditions, through the construction of sample rooms, the building (roof) cover and wall panel vibration and sound insulation, thermal insulation and condensation and other building physical properties were comprehensively tested.

Thin-walled steel plate arch shell roof structure system long-span metal folded arch roof is a new type of building structure introduced from the United States in the early 90s, is a roof structure system using colored steel plate on-site roll forming, with no beams, no columns, no rivet bolts, fast construction speed, saving the amount of steel, set load-bearing and envelope structure in one of the advantages, widely used in plant, warehousing, commercial, agricultural and hangar construction, the maximum span can exceed 40m. Problems with fire protection and node connection of steel structures. Foreign countries in public buildings a large number of steel structure, the application of exposed arc components, honeycomb beams and steel pipe structure to express architectural art, a large area of thermal insulation glass enclosure to enhance the permeability and natural lighting rate of the building, in line with the principle of energy conservation and environmental protection.

The steel structure is composed of the main and secondary structures, roofing, wall maintenance structures, etc., and the current large ¥ in terms of building structure treatment and building accessories selection is handled by each manufacturer, and its project quality is often difficult to guarantee. Building structure treatment problems, not only involve the use of the building function, but also if not handled properly, but also affect the structural safety of the building, there has been an improper setting of support between columns, resulting in the structure collapse in the typhoon accident, should be as soon as possible to organize the compilation of a general steel structure standard atlas, to standardize the structural treatment of steel structure.

In terms of processing, production and installation, except for a few new production lines, most of the production lines have backward technology, low processing accuracy, uneven construction units, halfway out of home, lack of necessary special equipment and technical training, installation period and quality are difficult to guarantee, engineering accidents occur from time to time, and no FE reflects the advantages of fast structural speed. European countries have started the steel structure education plan, for higher education and vocational education, organized more than 400 steel structure experts from more than 20 countries to compile, for six years, more than 40 countries have introduced this set of teaching materials.

The design, production and installation of steel structure is a highly professional technical work, and the education level, professional level and operation skills of practitioners are quite high, not ordinary workers can be competent after simple training, and it takes years of engineering practice and experience accumulation to be competent. China's steel structure construction and acceptance specifications not only make clear provisions on the production and installation process and quality control, but also strictly stipulate the requirements for the assessment and qualification certification of welding personnel. Personnel and units engaged in the design, production and installation of steel structures must have qualification certificates issued by the national technical supervision department and qualification certification bodies to ensure the quality of the project and avoid engineering accidents.

Reducing the intermediate links of steel structure design, production and installation is an important measure to improve the quality of the project and ensure the construction period, and foreign companies provide customers with a full range of services from engineering feasibility study to post-project maintenance. There are many departments involved in steel structure engineering, and the management efficiency of a project directly affects the quality and efficiency of the project.

Therefore, the information exchange, process cooperation and technical coordination between various departments is the key to ensure the quality of the project, according to the customer's requirements for the planning, design, production, installation and maintenance of the steel structure to implement the project general contracting one-stop service, according to the actual situation of the project reasonable allocation of manpower and equipment resources, reasonable allocation of capital investors and interest recipients, the implementation of unified project management, in the premise of ensuring quality and construction period can also bring the best economic benefits to the company.

Fourth, the research and development trend of domestic steel structure China once advocated portal rigid frame steel structure in the 70s, but it was limited by steel and traditional design theory, and was not promoted. After the reform and opening up, Shenzhen and Shanghai took the lead in introducing portal rigid steel structures designed and manufactured abroad, and found that they were very light, much less steel than our traditional practice, thus gradually abandoning the concept of expensive steel structure.

Due to historical reasons, most of China's steel structures are used in heavy metallurgical plants, large-span bridges and large-span public buildings, and the centralized management department is also responsible for the former Ministry of Metallurgical Industry. With the large application of steel structure, especially steel structure in civil buildings, the Ministry of Construction as the competent construction also realized that it is necessary to regulate the building steel structure market and develop civil building steel structure, in 1996 under the China Building Metal Structure Association set up a building steel structure committee, encourage and promote the application of steel structure, organized the formulation of steel structure design regulations, in 2000 set up the Ministry of Construction and the Metallurgical Bureau of steel application coordination group to guide and coordinate the application of steel structure and steel in the project.

China's steel output has exceeded 100 million tons, and the supply of construction steel is sufficient. The state encourages the construction industry to actively adopt steel structures in terms of policies. To promote the healthy development of the construction market, alleviate the backlog of steel, and provide a product market for the metallurgical industry. In foreign construction industry to become the main consumption market of steel (20% in recent years, China's grain and cotton harvest, urgent need for storage space, the construction of steel structure warehouse is an effective way. Newly built high-tech production enterprises, such as modern food processing, light textile, electronic products, pharmaceuticals and high-tech agricultural projects, have high requirements for production and working environments, and basically tend to use steel structures. In addition, port and customs warehouses, freight warehouses along the railway, have also gradually adopted section steel structures.

Now that steel supply is sufficient and the price is low, steel structure is no longer a structural type that is more expensive than concrete. Its steel consumption is generally 20~50kg/m2, the comprehensive cost has been the same as the concrete structure, and in most cases it is lower than the traditional reinforced concrete structure, and has the competitive advantage of fast construction and beautiful architecture. More and more construction units have begun to recognize the superiority of steel structure, and gradually become a structural type of industrial buildings, and have also been recognized in multi-storey civil buildings.