Nanlongzong Steel Structure Processing is an integrated steel and processing enterprise. It achieves an annual processing capacity of 100,000 tons. Although our country achieved great success in iron structures early on, due to over two millennia of feudal restrictions, scientific development was not advanced, and it remained at the level of iron buildings for a long time. It wasn't until the end of the 19th century that modern steel structures were adopted in our country. After the founding of the People's Republic of China, the application of steel structures saw significant development, far surpassing past levels in both quantity and quality. In terms of design, manufacturing, and installation, we've reached a high level, mastering the design and construction techniques for various complex buildings. Across the country, we have built numerous large-scale and structurally complex steel structures, including industrial buildings, large-span civil steel structures, and railway bridges. Our steel trusses, such as those in Beijing and Shanghai's stadiums, the three-hinged steel arches at the Shaanxi秦始皇兵马俑 Exhibition Hall, and the "Bird's Nest" in Beijing.
Structural steelwork engineering
1. Structural steel has a lighter self-weight.
2. Structural steelwork has a high reliability.
3. Good vibration and impact resistance of steel
4. Steel structure manufacturing has a high degree of industrialization.
5. Steel structures can be assembled accurately and quickly.
6. Large steel structure indoor space
7. Easy to form a sealed structure
8. Structural steel is prone to corrosion.
9. Poor fire resistance of steel structure
Seismic Resistance: The roofs of most low-rise villas are sloped, thus the roof structure generally employs a triangular truss system made of cold-formed steel components. After the structural boards and gypsum boards are sealed, the light steel components form a very sturdy "plate rib structure system." This structural system boasts enhanced seismic resistance and the ability to withstand horizontal loads, making it suitable for areas with seismic intensity of 8 degrees or higher.
Wind resistance: The lightweight, high-strength, good overall rigidity, and strong anti-deformation capability of the structural steel building allow it to withstand hurricanes with wind speeds of up to 70 meters per second, ensuring protection for life and property.
Durability: The light steel frame residential structure is composed entirely of cold-formed thin-walled steel components. The steel frames are made from corrosion-resistant, high-strength cold-rolled galvanized sheets, effectively preventing rust from affecting the steel plates during construction and use, thereby extending the service life of the light steel components. The structural lifespan can reach 100 years.
Thermal Insulation: The main material used for thermal insulation is glass fiber cotton, offering excellent thermal insulation properties. The insulation boards used for exterior walls prevent the "cold bridge" phenomenon, achieving superior thermal insulation. A thermal resistance value of R15 in about 100mm thick insulation cotton is equivalent to that of a 1m thick brick wall.
Soundproofing: Sound insulation is a crucial factor in evaluating residential properties. Windows installed in light steel systems are made with double-glazed glass, offering excellent soundproofing, reaching over 40 decibels. Walls composed of light steel studs, insulating materials, and gypsum boards can achieve a soundproofing effect of up to 60 decibels.
Healthiness: Dry construction method minimizes environmental pollution from waste, with steel structural materials and most auxiliary materials being recyclable, aligning with current environmental awareness; all materials are green building materials, meeting ecological and environmental requirements, and conducive to health.
Comfort: The light steel wall system features a breathable function, allowing for adjustable indoor air humidity and dryness; the roof is equipped with ventilation, creating a circulating air space above the interior, addressing the roof's ventilation and heat dissipation needs.
Quick: All dry construction work, unaffected by environmental seasons. A building of about 300 square meters can be completed in 30 working days with just 5 workers, from foundation to decoration.
Eco-friendly: Materials are recyclable, truly achieving green environmental protection.
Energy-saving: Walls provide excellent insulation, heat retention, and soundproofing, achieving up to 50% energy-saving standards.
Steel structure design
In the construction of civil engineering projects, the application of steel structure engineering in design not only allows for greater span space in the buildings but also offers the advantages of easy installation and lower costs, thus broadening its application in civil engineering. As China's urbanization progresses further, the number of high-rise buildings will sharply increase, demanding higher standards for the design of steel structure engineering.
In recent years, the application of steel structures in construction projects has become increasingly significant, yielding very good results. However, due to inadequate design work in steel structure projects, issues with insufficient stability in the constructed buildings have arisen, severely impacting users' safety and property. To ensure higher quality in the construction of steel structure projects, it is crucial to design strictly in accordance with relevant specifications and standards, and to meticulously address key design aspects, thereby providing users with safer and more reliable steel structure buildings.
Structure
The detection and calculation of the slenderness ratio of steel structural members, as per regulations, can determine the member dimensions. The slenderness ratio should be calculated based on the actual dimensions.
Connections in the steel structural support system can be inspected as per regulations; dimensions of the support system components can be measured as per regulations; they should be verified or evaluated according to the design drawings or corresponding design specifications.
The width-to-thickness ratio of steel structural members can be determined according to regulations, and the relevant dimensions of the member cross-section can be calculated. Evaluation should be conducted in accordance with the design drawings and relevant specifications.
Coating
The quality of steel structure protective coatings shall be tested in accordance with the current national product standards for coating quality.
The rust removal grade on the steel surface can be determined by comparing and observing the images specified in the current*** "Steel Surface Rust and Rust Removal Grade for Pre-Painting" GB8923 standard.
The coating thickness of different types of paints should be tested using the following methods:
Film thickness, which can be measured using a film thickness gauge, should be inspected on a random sample of components, the number of which should not be less than the minimum capacity specified for Class A samples in the standard table, nor less than 3 pieces; measure 5 locations per piece, with each location's value being the average thickness of the dry film at 3 measurement points spaced 50mm apart.
2. The coating thickness of thin-type fire-retardant coatings can be measured using a coating thickness gauge, and the measurement method should comply with the provisions of CECS24 in the "Technical Code for Application of Fire-Retardant Coatings on Steel Structures."
3. For the thickness of thick-type fire-resistant coating, the coating thickness should be measured using a probe and a steel ruler, with the measurement method in accordance with the provisions of CECS24, "Technical Code for Application of Fire-Resistant Coating for Steel Structures." The thickness and deviation values of the coating should be evaluated according to the provisions of GB50205, "Code for Acceptance of Construction Quality of Steel Structure Engineering." The appearance quality of the coating should be inspected and evaluated according to the provisions of GB50205 for different materials.
Steel truss
The inspection of steel grid structures can be divided into items such as the bearing capacity of nodes, welds, dimensions and deviations, the non-straightness of rods, and the deflection of the steel grid structure.
The inspection of the bearing capacity of steel truss welding ball joints and bolt ball joints should be conducted according to the requirements of the "Quality Inspection and Appraisal Standard for Grid Structure Engineering" JGJ78. For existing bolt ball joint trusses, nodes can be extracted from the structure for ultimate bearing capacity testing of the joints. When cutting bolt ball joints, measures should be taken to ensure structural safety.
Weld seams in steel grid structures can be inspected using ultrasonic testing methods. The inspection and evaluation procedures should comply with the requirements of either "Ultrasonic Testing and Quality Grading Method for Welded Steel Grid Structures with Ball Nodes" JG/T3034.1 or "Ultrasonic Testing and Quality Grading Method for Welded Steel Grid Structures with Bolt Nodes" JG/T3034.2.
The appearance quality of the welds in the steel truss should be inspected in accordance with the requirements of the "Code for Acceptance of Construction Quality of Steel Structures" GB50205.
Welded ball, bolted ball, high-tensile bolts, and bar deviation inspections should be conducted in accordance with the provisions of the "Quality Inspection and Evaluation Standard for Grid Structure Engineering" JGJ78, with specified inspection methods and allowable deviation values.
The wall thickness of steel grid tube members can be measured using an ultrasonic thickness gauge, and the surface coating should be removed prior to measurement.
The non-straightness of the steel truss member axes can be measured by the pull-line method, and its non-straightness must not exceed one thousandth of the member's length.
The deflection of the steel truss can be measured using a laser distance meter or a level instrument. The number of measuring points within each half-span should not be less than 3, and there should be 1 measuring point at the midpoint of the span. The distance from the measuring point at the end to the end support should not exceed 1m.
Structural Performance Load Testing and Dynamic Measurement
For large and complex steel structural systems, in-situ non-destructive load tests can be conducted to directly assess structural performance. Load tests for structural performance can be carried out according to the standard specifications. Load factors and judgment principles can be determined as per regulations, and may also be appropriately adjusted based on specific circumstances.
When in doubt about the load-bearing capacity of structures or components, prototype or full-scale model load tests can be conducted. The tests should be entrusted to an institution with adequate equipment capabilities. A detailed test plan should be developed before the test, including the test objectives, selection or fabrication of specimens, loading devices, placement of measurement points and testing instruments, loading steps, and the evaluation method for test results. The test plan can be formulated according to standards and should be agreed upon by all relevant parties prior to the test.
For large-scale, significant, and steel structural systems, it is advisable to conduct actual structural dynamic testing to determine the natural vibration period and other dynamic parameters. The structural dynamic testing should comply with standard regulations.
The stress of steel structural rods can be measured using resistance strain gauges or other methods, based on actual conditions.
