Why Structure Assessment Matters: Design Versus Reality
A structure designed to stand still behaves very differently when it is lifted. What works in theory on paper does not always work in motion. This fundamental reality underscores why a comprehensive structure assessment is essential before any lifting operation commences.
When engineers design mining structures such as conveyor trusses, pipe racks, or equipment modules, they optimise these components for their final installed condition. The calculations account for dead loads, live loads, wind forces, and seismic considerations that the structure will experience during its operational lifetime. However, these design parameters rarely consider the transient yet critical phase of lifting and transport.
This oversight creates a significant gap between design intent and real-world execution. A structure assessment specifically focused on lifting conditions addresses this gap by analysing how the structure will perform under an entirely different set of loading scenarios.
Structure Assessment in Practice: The 24-Metre Conveyor Example
Consider a 24-metre conveyor truss, a common element in mining operations across Australia. When installed on its permanent supports, this structure distributes loads predictably along its length. The design accounts for conveyor belt tension, material loads, and environmental factors acting on a fully supported frame.
However, when this same truss is lifted by a crane at two or four discrete points, the load distribution changes dramatically. The structure that performed admirably in its installed state suddenly experiences stress concentrations, deflection patterns, and dynamic forces that were never part of the original structure assessment.
Large, long, and inherently flexible structures like conveyor trusses are particularly susceptible to these transitional stresses. Without proper structure assessment for lifting conditions, what appears to be a straightforward operation can result in permanent deformation, connection failures, or catastrophic structural compromise.
Structure Assessment for New Load Cases
Lifting introduces a range of load cases that differ substantially from in-place conditions. These include:
Bending moments at lift points: Concentrated forces at crane attachment locations create localised stresses that may exceed the capacity of members designed for distributed loading.
Torsional forces: Uneven lifting, wind gusts, or slight misalignments between lift points can induce twisting forces that the original design never anticipated.
Dynamic amplification: The act of lifting introduces acceleration and deceleration forces, requiring structure assessment to account for dynamic load factors that increase effective loads beyond static calculations.
Structure Assessment for Deflection Control
A thorough structure assessment recognises that lifting safety goes beyond strength verification alone. While ensuring that stresses remain within allowable limits is fundamental, it is equally important to evaluate how the structure behaves under load in terms of displacement and deformation. Deflection control is particularly critical for precision fitted components, where even small movements can have significant consequences.
Excessive movement during lifting can lead not only to temporary distortion but also to permanent damage. For conveyor structures, this deflection may result in misalignment of idler frames, distortion of stringers, damage to bearings or other mechanical components, and increased difficulty during final installation and commissioning. In some cases, excessive deflection can also introduce residual stresses that compromise long term performance and reliability.
Structure assessment for lifting must therefore establish acceptable deflection limits based on both functional and structural requirements. It should also verify that the proposed lifting arrangements, such as lifting points, rigging configuration, and load distribution, maintain deformations within tolerable bounds throughout all stages of the lift. Considering both strength and serviceability ensures that the structure remains fit for purpose not only during lifting, but also in its final installed condition.
The Yenem Approach to Structure Assessment
Yenem Engineering bridges the gap between design intent and real-world execution through rigorous structure assessment services. Our engineers analyse structures not merely for their ultimate installed condition but for every stage of their journey from fabrication yard to final position.
Ensure your lifting operations are underpinned by rigorous engineering analysis. Contact Yenem Engineering today to schedule a complimentary consultation with our structural specialists.
Before you lift, reassess. Yenem ensures your structures perform beyond the drawing board.
