How to calculate and evaluate the load-bearing capacity and structural stability of Steel Truss?

In modern construction and bridge engineering, Steel Truss has become the preferred solution for large-span structures due to its advantages such as high strength, light weight, flexible span and high degree of industrialization. However, the scientific evaluation of its load-bearing capacity and stability is the core link to ensure the safety of the project.
1. Static analysis: mechanical deconstruction from nodes to the whole
The calculation of the load-bearing capacity of steel trusses begins with static analysis. By establishing a three-dimensional mechanical model, engineers need to decompose the forces of truss nodes and members. The internal force equilibrium equation at the node (such as ∑Fx=0, ∑Fy=0) is the basis, and the axial force calculation of the member needs to be combined with Hooke's law (σ=Eε) and Euler's formula (critical load P_cr=π²EI/(KL)²) in material mechanics. For example, in the design of railway bridges, the cross-sectional dimensions of the main truss members must meet the strength condition of N/(φA) ≤ f, where φ is the stability coefficient and f is the yield strength of the steel.
It is worth noting that the stiffness of the node connection directly affects the internal force distribution. When using finite element software (such as ANSYS or ABAQUS) for nonlinear analysis, it is necessary to consider the bolt preload, weld strength and local buckling effect. The case of a 120-meter-span steel truss in a gymnasium shows that through refined modeling, the stress concentration factor of the node domain can be reduced from 3.2 to 1.8, significantly improving the safety reserve.
2. Dynamic characteristics and stability evaluation
The stability of steel trusses not only involves static failure, but also needs to prevent dynamic instability. Eigenvalue buckling analysis can determine the critical load corresponding to the first-order buckling mode, but in actual engineering, initial defects (such as initial bending of the rod at L/1000) need to be introduced for nonlinear buckling analysis. Taking a steel truss of a cross-sea bridge as an example, after considering the wind vibration effect, the overall stability factor of the structure needs to be increased from 2.5 to above 3.0.
Dynamic response analysis is also critical. The natural frequency of the structure is obtained through modal analysis (usually controlled at 3-8Hz to avoid the traffic load frequency band), and the displacement response under earthquake or wind load is evaluated in combination with the time history analysis method. In the design of a high-rise corridor steel truss, the wind-induced acceleration is reduced by 40% after the TMD tuned mass damper is used, meeting the human comfort requirements.
3. Intelligent monitoring and full life cycle management
With the development of Internet of Things technology, steel truss evaluation is shifting from static calculation to dynamic monitoring. Fiber Bragg grating sensors can monitor the strain of rods in real time, and BIM models combined with machine learning algorithms can predict the degradation of structural performance. For example, 200 monitoring points are installed on the steel truss of an airport terminal, and the data is updated every 5 minutes, achieving a second-level warning of stress overlimit.
The safety assessment of steel trusses is a precise combination of mechanical theory and engineering practice. From the classic material strength formula to the intelligent monitoring system, each link requires rigorous scientific verification. In the future, with the popularization of parametric design and digital twin technology, the performance optimization of steel trusses will enter a new stage with higher precision. Only by adhering to computing principles and integrating innovative technologies can we build a steel backbone that spans time and space.