Structural design of steel pitched portal frames by GMNIA with strain limits
File(s)
Published version
Author(s)
Chan, HU
Tsang, A
Walport, F
Gardner, L
Type
Journal Article
Abstract
A new structural design framework for steel pitched portal frames based on geometrically and materially nonlinear analysis with imperfections (GMNIA), in line with the provisions of EN 1993-1-14 is presented herein. The framework is implemented using beam finite elements, with the effects of instability at the member and system levels directly captured in the analysis, and the effects of local buckling accounted for by the application of strain limits, defined by the Continuous Strength Method (CSM). The accuracy of the design method is assessed against the results obtained from benchmark shell finite element models of pitched portal frames with a range of cross-section slendernesses. Particular focus is placed on evaluating the ability of the proposed framework to capture the system-level structural behaviour, the influence and response of the haunch regions and the cross-sectional slenderness-dependent levels of plastic moment redistribution that are characteristic of steel portal frames. Comparisons are also made against the traditional design approach according to EN 1993-1-1. The results show that traditional EN 1993-1-1 design can lead to unsafe or overly conservative capacity predictions at cross-section class boundaries, with the adoption of the elasto-plastic moment resistance Mep largely mitigating this variability at the Class 2–3 boundary, reducing conservatism by up to 17% for relatively stocky Class 3 sections. In contrast, the GMNIA + CSM framework yields consistently safe-sided designs, with improved capacity predictions by up to 12% across the examined frames compared to the EN 1993-1-1 framework.
Date Issued
2026-11-01
Date Acceptance
2026-04-21
Citation
Thin-Walled Structures, 2026, 230, Part A
ISSN
0263-8231
Publisher
Elsevier BV
Journal / Book Title
Thin-Walled Structures
Volume
230, Part A
Copyright Statement
© 2026 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
License URL
Publication Status
Published
Article Number
115022
Date Publish Online
2026-05-01