Rigid Frame & Roof Truss Alternative – AS 4100 / AS 1170
Project Overview
Designed and analysed alternative structural systems for a large industrial warehouse located in South-West Sydney. The project involved evaluating a rigid portal frame and a roof truss alternative, including load assessment, preliminary sizing, and stability verification in accordance with Australian Standards.
Engineering Scope
Evaluation of dead, live, and wind loads in accordance with AS 1170
Development of load combinations for ultimate and serviceability limit states
Preliminary sizing of structural members
Tension and compression member design for roof truss alternative
Beam–column combined action checks for rigid frame system
Second-order (P–Δ) stability assessment
Comparative evaluation of structural system efficiency and cost implications
Figure 1. Wind load distribution along portal frame elevation showing varying pressure intensities and tributary spans for lateral analysis.
Figure 2. Critical flange identification under sagging and hogging moments, highlighting compression zones and lateral restraint requirements.
Structural System Considered
Industrial warehouse frame
Steel portal frame alternative.
Roof truss replacement option
Braced system with cold-formed steel purlins and girts
Typical internal frame analysiss
Tools & Analysis
Microstran structural modelling
Excel-based load and capacity calculations
Australian Standards compliance checks (AS 4100, AS 1170)
Figure 3. Finite element modelling and bending moment distribution of steel portal frame analysed in Strand7.
Figure 4. Member capacity verification for axial compression and bending in accordance with AS 4100.
Key Engineering Outcomes
Verified structural adequacy under combined bending and axial actions
Assessed stability effects under wind loading
Compared rigid frame and truss solutions for structural efficiency
Integrated load evaluation with practical constructability considerations
Figure 5. Member selection and capacity checks for critical column and mid-rafter regions based on Microstran analysis results.
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