Simulation and behaviour of single-span steel portal frames
File(s)
Author(s)
Ahmed, Aya
Type
Thesis
Abstract
Portal frames are a common structural system in single-storey industrial and commercial buildings. In recent decades, the design of portal frames has evolved towards larger structures with stiffer cladding systems, introducing structural challenges such as increased frame flexibility and higher demand on connections. These concerns were highlighted by a SCOSS alert in 2018 (SCOSS, 2018), emphasising the need to reevaluate the current design recommendations. The effect of scale on the overall behaviour of steel portal frames and their connecting elements and fasteners is therefore investigated in this study.
Finite element models were employed to conduct the investigation. The modelling approaches for typical components of steel portal frames are described and validated. These models account for the nonlinear material stress-strain responses, the load-displacement characteristics of portal frame connections and the behaviour of portal frame cladding systems. The validated key components were utilised to develop a full portal frame FE model, which was then validated and used in a parametric study to investigate the effect of scale of single-span portal frames. Wind sway was found to be the most critical load case, resulting in substantial shear displacements of the cladding screw connectors, reaching up to 20 mm at 1.5 times the serviceability load levels. As for the effect of scale, the increase in height was found to exacerbate the shear displacements of the cladding screw connectors under wind sway load. In contrast, the increase in span increased the shear displacements of the cladding screw connectors under both gravity load and thermal action. However, the change in frame length had a minimal effect. Overall, the demand on the connector elements in modern steel portal frames have been shown to be high under some realistic loading scenarios, particularly in the end bays, prompting the need to consider suitable means of mitigation in future research.
Finite element models were employed to conduct the investigation. The modelling approaches for typical components of steel portal frames are described and validated. These models account for the nonlinear material stress-strain responses, the load-displacement characteristics of portal frame connections and the behaviour of portal frame cladding systems. The validated key components were utilised to develop a full portal frame FE model, which was then validated and used in a parametric study to investigate the effect of scale of single-span portal frames. Wind sway was found to be the most critical load case, resulting in substantial shear displacements of the cladding screw connectors, reaching up to 20 mm at 1.5 times the serviceability load levels. As for the effect of scale, the increase in height was found to exacerbate the shear displacements of the cladding screw connectors under wind sway load. In contrast, the increase in span increased the shear displacements of the cladding screw connectors under both gravity load and thermal action. However, the change in frame length had a minimal effect. Overall, the demand on the connector elements in modern steel portal frames have been shown to be high under some realistic loading scenarios, particularly in the end bays, prompting the need to consider suitable means of mitigation in future research.
Version
Open Access
Date Issued
2023-09-27
Date Awarded
01/12/2023
License URL
Advisor
Gardner, Leroy
Walport, Fiona
Sponsor
Schlumberger Limited
British Constructional Steelwork Association
Publisher Department
Civil and Environmental Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)