Structural Analysis Considerations for Industrial Steel Structures

Industrial steel structures—such as pipe racks, material handling systems, transfer structures, and equipment supports—present a distinct set of challenges compared to conventional building design. These systems are often governed by heavy equipment loads, irregular geometry, non-building load combinations, and serviceability or constructability constraints that demand careful analytical judgment.

Unlike repetitive floor-framed buildings, industrial structures tend to be highly bespoke. Each project requires deliberate decisions around idealization, load application, boundary conditions, and analysis method to ensure the model reflects real structural behavior.

Industrial Steel Starts With Load Behavior, Not Geometry

Industrial structures are governed by:

• Concentrated equipment reactions
• Eccentric gravity loads
• Operational and thermal effects
• Wind and seismic loads applied to open frames, not diaphragms

RISA-3D modeling tip: Model loads where they physically act

• Apply equipment loads at true attachment points, not “clean” nodes
• Use point loads, line loads, and plate surface loads instead of smeared tributary assumptions
• For wind on open frames, use Open Structure Wind Loads so projected area — not member count — controls demand

If wind pressure varies around complex geometry, projected plate loads (PX, PY) allow RISA-3D to calculate realistic force reduction automatically — something that would be painful to do by hand.

Torsion Is Often the Real Design Driver 

Booms, cantilevered conveyors, bucket wheels, and offset equipment introduce torsion long before flexure governs.

If torsion matters and the model doesn’t show it, the model is lying to you.

RISA-3D modeling tip: Use plates when section assumptions break down

• Box booms, shells, and stiffened equipment supports can be modeled with plate elements
• Ensure plate meshes share nodes — forces only transfer through connected geometry
• Use templates (cylinders, cones, domes, discs) to generate complex shapes quickly and consistently

Plates are not overkill in industrial steel — they’re often the only way to see stress flow caused by rotating or eccentric equipment.

Tension-Only Members: Powerful, Dangerous, Necessary

Industrial structures routinely include:

• Hung framing
• Tie-downs
• Cables
• Members that are intended to go slack

RISA-3D modeling tip: Treat T/C-only members as behavioral assumptions

• Tension-only members remove compressive stiffness entirely
• During solution, RISA-3D iterates to determine which members are ON or OFF
• Non-convergence is often a modeling insight, not a software failure

If RISA-3D flags instability or convergence issues:

• Review which members are cycling on/off
• Confirm whether the structure relies on those members for stability
• Consider whether a “nearly tension-only” behavior is more realistic than absolute

For cable modeling:

• Use tension-only members
• Assign a weightless material
• Apply cable weight elsewhere as point loads
• Use thermal loads to simulate prestress when required

No real member is perfectly tension-only — but RISA-3D gives you visibility into when that assumption breaks.

Don’t Skip the Deflected Shape

Industrial models often “solve” even when:

• Boundary conditions are wrong
• Stability is artificial
• Load paths are unintentionally rerouted

RISA-3D modeling tip: Review deflected shapes by basic load case

• Look at uncombined dead, wind, seismic, and operational loads
• Increase deflection magnification to reveal subtle instability
• If the shape surprises you, trust the surprise 

Iteration Is the Design — Not a Failure of It

Industrial structures evolve:

• Equipment weights change
• Load cases get refined
• Geometry shifts late in design

RISA-3D supports this reality by allowing:

• Fast re-modeling
• Appended substructures
• Selection states to isolate dense regions
• Spreadsheet and graphical workflows to coexist

The goal isn’t a single “final” run — it’s a model that remains transparent and defensible as assumptions change.