Application and seismic design of Xinjiang steel structures in earthquake areas

Xinjiang steel structures have shown significant advantages in construction projects in earthquake zones due to their lightweight, high strength, excellent ductility, and convenient construction. The core of its seismic performance lies in the elastic-plastic deformation ability of the material, which can absorb and dissipate seismic energy through a reasonable structural system, thereby effectively reducing the damage to buildings caused by earthquakes. In recent years, with the deepening of seismic theory and the advancement of engineering technology, steel structures have been widely used in high-rise, super-high-rise buildings and important public facilities in high-severity earthquake areas, becoming a key technical path to improve the seismic safety of buildings.

1. Application characteristics and advantages of steel structures in earthquake areas

Material properties and seismic suitability

Steel has high strength and good ductility. It can still maintain large plastic deformation after yielding without breaking immediately. This characteristic enables the steel structure to form an energy dissipation mechanism through the plastic hinges of the components under earthquake action, converting seismic energy into structural deformation energy. Xinjiang steel structure manufacturers said that in contrast, concrete structures are prone to brittle failure under strong earthquakes, and the "softness to overcome rigidity" mechanism of steel structures is more in line with the three-level requirements of seismic design of "not damaged by small earthquakes, repairable by moderate earthquakes, and not collapsed by large earthquakes." For example, after the Hanshin Earthquake in Japan (1995), a large number of steel structure buildings deformed but did not collapse, proving their ability to survive high-intensity earthquakes.

Seismic Optimization of Structural Systems

Commonly used systems for steel structures in earthquake zones include steel frames, steel frame-support structures, steel-concrete composite structures, etc. Xinjiang steel structure manufacturers say that steel frame structures transmit seismic forces through the rigid connection of beam-column nodes and are suitable for mid- and low-rise buildings; support structures (such as central supports and eccentric supports) enhance the overall stiffness through the yield energy dissipation of diagonal bracing. The eccentric support sets an energy-dissipating section at the intersection of the support and the beam. During an earthquake, shear or bending yielding occurs first, protecting the main structure from damage. In high-rise structures, the steel frame-shear wall (or core tube) combined system combines the flexibility of the steel structure with the rigidity of the concrete shear wall, which can effectively control the lateral movement of the structure. For example, the Shenzhen Ping An Financial Center (600 meters) adopts a steel-concrete hybrid structure, which achieves an excellent balance of lateral stiffness and ductility in the 7-degree seismic fortification intensity zone.

Lightweight and foundation anti-seismic benefits

The self-weight of the steel structure is only 1/3~1/2 of the concrete structure, which can significantly reduce the inertia force under earthquake action (seismic force is proportional to the mass), thus reducing the foundation load and foundation stress. In weak foundations or seismic liquefaction areas, lightweight features make the foundation design of steel structure buildings more flexible. For example, pile foundations or raft foundations can meet seismic requirements and reduce project costs and construction difficulties.

2. Key technical points of seismic design of steel structures

Performance-based seismic design approach

Xinjiang Steel Structure Factory Direct Sales said that traditional seismic design is mainly based on "strength control", while modern steel structure design pays more attention to the "performance target" orientation. By setting the structural performance under different earthquake levels (such as elasticity, non-yield, allowable plastic deformation, etc.), nonlinear analysis methods (such as push-over analysis, dynamic time history analysis) are used to verify the energy dissipation capacity of the structure. For example, for lifeline projects such as hospitals and fire command centers, it is required to maintain structural integrity and normal functions under major earthquakes. Performance goals need to be achieved by increasing the ductility coefficient and ultimate bearing capacity of key components (such as columns and nodes), or by setting up shock-absorbing devices (such as viscous dampers, buckling restraint supports).

Ductility design of nodal connections

Nodes are the weak link in the seismic resistance of steel structures. "Strong nodes and weak components" is the core design principle - that is, ensuring that the bearing capacity of nodes is higher than that of components, so that plastic hinges first appear at the beam ends or support energy-consuming sections, rather than node damage. Bolted-welded hybrid connections (beam flange welding, web bolted connections) are commonly used. Low-hydrogen welding rods must be used and non-destructive testing must be performed during welding to avoid brittle fractures caused by welding defects; In addition, the joint structure needs to avoid stress concentration, such as setting stiffeners at the beam ends and using thick plates or haunches in the joint area to improve its rotational capacity and energy consumption potential.

Integration of energy-consuming components and shock-absorbing technology

In high-intensity areas (such as 8 degrees and above), relying solely on the ductility of the structure may be difficult to meet the seismic requirements, and shock-absorbing technology needs to be introduced:

Buckling restrained brace (BRB): It consists of a core material (low yield point steel) and an outer sleeve. The core material yields and dissipates energy during an earthquake, and the outer sleeve restrains its buckling, avoiding the problem of compression instability of traditional supports and increasing the structural damping ratio by 2 to 3 times;

Viscoelastic damper: dissipates energy through shear deformation of polymer materials, suitable for controlling wind vibration and comfort under small earthquakes;

Seismic isolation bearings: Rubber isolation pads or friction pendulum bearings are installed between the foundation and the superstructure to change the dynamic characteristics of the structure and reduce the upward transmission of seismic energy. For example, after a steel structure teaching building in Dali, Yunnan adopted seismic isolation technology, the structure's seismic response was reduced by more than 60%.

Component Sections and Stability Control

Xinjiang Steel Structure Manufacturer Direct Sales said that steel columns need to avoid instability caused by excessive slenderness ratio. The slenderness ratio limit of axial compression columns is 150 (seismic level one). The in-plane and external stability of the compression bending members need to be checked; the cross-section design of the beam should meet the "strong shear and weak bending", that is, the shear force design value takes the larger value of the shear force corresponding to the bending moment design value and the earthquake shear force to ensure that the bending yield of the beam end precedes the shear failure. In addition, the width-thickness ratio of the component plate must meet the limit value (such as the I-shaped beam flange width-thickness ratio ≤ 13√235/fy) to prevent local buckling from reducing the ductility of the component.

3. Engineering Practice and Challenges

There are an increasing number of successful applications of steel structures in earthquake zones. For example, in the 2011 Tohoku earthquake in Japan (magnitude 9.0), steel-structured residences using eccentric supports experienced only slight deformation and no collapse cases; after the Wenchuan earthquake in my country (2008), a rebuilt community in Mianyang adopted a steel frame-support structure and withstood the test of many aftershocks in a seismic fortification intensity area of ​​8 degrees. However, there are still challenges in design and construction:

Steel quality control: The production accuracy and welding process of low yield point steel (such as LY100) have a significant impact on the ductility of components, and it is necessary to strengthen the incoming material inspection;

Complexity of nonlinear analysis: Dynamic time history analysis requires selecting appropriate seismic waves (at least 3 sets of natural waves + 1 set of artificial waves), and considering parameters such as initial defects of components, residual stress, etc., which requires high technical requirements for designers;

Economic balance: Xinjiang Steel Structure Factory Direct Sales said that the application of shock-absorbing devices may increase the cost (about 5% to 10%), and the cost needs to be reduced by optimizing the structural system (such as reasonable arrangement of supports) and material selection (such as Q355ND weathering steel).

4. Future development trends

With the integration of AI technology and BIM, the seismic design of steel structures is becoming intelligent: component sections are optimized through parametric modeling and machine learning, and digital twin technology is used to simulate the structural response under earthquake action; at the same time, the application of new materials such as high-performance steel (Q690, Q960) and fiber-reinforced composite materials (FRP) will further enhance the strength and durability of steel structures. In addition, modular steel structures (factory prefabricated components assembled on site) have broad prospects in post-earthquake reconstruction due to their fast construction speed and controllable quality. For example, Japan's "Emergency Housing Module" can be completed within 72 hours and meets earthquake resistance requirements.

Conclusion

Xinjiang steel structure has become an ideal choice for earthquake-resistant buildings in earthquake areas due to its ductility, lightweight and system flexibility. In the design, it is necessary to achieve a "safe, economical and efficient" seismic solution through performance-based target setting, node ductility optimization, energy-consuming technology integration and other means. With the accumulation of technological innovation and engineering experience, steel structures will play an increasingly important role in improving the city's earthquake resilience and ensuring the safety of people's lives and property.