Behaviour and design of structural steel members under moment gradients
File(s)
Author(s)
YANG, Zichang
Type
Thesis
Abstract
Moment gradients are very common in structural engineering, and several experiments have shown that beams under moment gradients exhibit higher load-carrying capacities. However, to date, limited research has been carried out on the local behaviour of members under moment gradients, and there is a lack of design guidance that can capture the beneficial effect of moment gradients. Therefore, this study aims to systematically explore the local buckling behaviour of beams under moment gradients and to develop more accurate and reliable design approaches within the EC3 framework.
An experimental investigation on 20 full-scale high strength steel box section beams was first conducted, including three loading configurations: four-point bending, stiffened three-point bending and unstiffened three-point bending. The experiments confirmed that moment gradients have a beneficial effect on the ultimate moment resistance of beams. An approach for measuring the local buckling half-wavelength was proposed, and it was found that the half-wavelength of beams is shorter with higher magnitude or gradient of moments.
Finite element (FE) models were established and validated by the experimental results. The explicit modelling of residual stresses in shell and beam element models was discussed, along with a design recommendation based on the Continuous Strength Method (CSM). A comprehensive parametric study was carried out to expand the data pool of beams under moment gradients. Based on experimental and numerical data, the study found that the beneficial effect of moment gradients has a correlation with the presence of stiffeners, the cross-section slenderness and the aspect ratio of sections. Finally, modified EC3 design rules with a new local moment gradient parameter were proposed for beams under combined moment and shear, and shown to offer enhanced efficiency over existing methods.
An experimental investigation on 20 full-scale high strength steel box section beams was first conducted, including three loading configurations: four-point bending, stiffened three-point bending and unstiffened three-point bending. The experiments confirmed that moment gradients have a beneficial effect on the ultimate moment resistance of beams. An approach for measuring the local buckling half-wavelength was proposed, and it was found that the half-wavelength of beams is shorter with higher magnitude or gradient of moments.
Finite element (FE) models were established and validated by the experimental results. The explicit modelling of residual stresses in shell and beam element models was discussed, along with a design recommendation based on the Continuous Strength Method (CSM). A comprehensive parametric study was carried out to expand the data pool of beams under moment gradients. Based on experimental and numerical data, the study found that the beneficial effect of moment gradients has a correlation with the presence of stiffeners, the cross-section slenderness and the aspect ratio of sections. Finally, modified EC3 design rules with a new local moment gradient parameter were proposed for beams under combined moment and shear, and shown to offer enhanced efficiency over existing methods.
Version
Open Access
Date Issued
2024-01-31
Date Awarded
01/04/2024
License URL
Advisor
Gardner, Leroy
Publisher Department
Civil and Environmental Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)