Date of Award

Spring 2024

Document Type


Degree Name

Doctor of Philosophy (PhD)


Civil & Environmental Engineering


Civil Engineering

Committee Director

Zia Razzaq

Committee Member

Mojtaba B. Sirjani

Committee Member

Shahin N. Amiri

Committee Member

Mamadou Konate

Committee Member

Gene W. Hou


Presented herein is an experimental and theoretical study of biaxially loaded hollow rectangular section steel beam-columns with applied torsion at elevated temperatures. The theoretical analysis is based on a system of simultaneous materially nonlinear differential equations of equilibrium for which an iterative semi-analytic solution approach is formulated. Although the primary goal of this research is to study the influence of elevated temperatures on the steel member with the complex loading, rigorous analysis is also conducted of the member at ambient temperature for comparison. The experimental part of the study involves conducting tests on the members at both ambient and high temperatures. A biaxial bending apparatus with a pair of gimbals and means to apply an axial load as well as torsion is used to perform the experiments. The elevated temperatures are introduced by means of a heat chamber surrounding each test specimen. The theory is validated by a comparison to the experimentally observed behavior and strength. A set of general dimensionless interaction expressions are developed that can be used for determining the ultimate strength of biaxially loaded beam-columns with applied torsion at elevated temperatures. The substantial reduction of the member strength due to temperature dependent nonlinear material properties and second-order effects is also quantified..


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