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Creator:	Kalač, Šemso
Title:	Experimental and theoretical research of the planar Aluminium lattice structure joints
Copyright date:	2025
Trajni link:	https://phaidra.ucg.ac.me/detail_object/o:1971?tab=0#mda
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Select license:	Autorstvo-Nekomercijalno 3.0 Srbija (CC BY-NC 3.0)

Academic metadata

Theses Type:	Phd. theses
Academic Expertise :	Tehnicko-tehnološke nauke
Academic Title:	doktor nauka - gradevinarstvo
University:	Univerzitet Crne Gore
Faculty:	Građevinski fakultet
Group:	Studijski program Građevinarstvo

Other Theses Metadata

Title translated:	Eksperimentalno i teorijsko ispitivanje ravanskih veza aluminijumskih rešetkastih konstrukcija
Format:	PDF/A (pages)
Abstract:	The growing demand for lightweight, corrosion-resistant, and sustainable construction materials has led to the increased use of aluminum alloys in civil engineering. Among the structural applications, aluminum truss systems offer significant advantages in terms of reduced self-weight, durability, and simplified installation processes. However, the adoption of aluminum structures in construction sector remains limited due to a lack of comprehensive understanding of welded joint behavior—particularly in the heat-affected zone (HAZ), where significant material degradation occurs as a result of welding. This doctoral research aims to systematically investigate the mechanical performance of welded planar joints in aluminum truss structures, with a focus on quantifying the strength reduction within the HAZ and developing reliable predictive models. The study integrates experimental, numerical, and analytical approaches to assess the structural behavior of welded joints composed of square (SHS) and circular (CHS) hollow section profiles. Particular attention is given to evaluating joint configurations commonly encountered in lattice girders, such as X and K joints. The experimental component of this research was conducted in collaboration with the Faculty of Civil Engineering at the University of Montenegro and the Chair of Metal Structures at the Technical University of Munich. It involved the fabrication, instrumentation, and testing of full-scale welded aluminum truss specimens using EN AW-6082 T6 alloy. Mechanical characterization included tensile testing, Vickers hardness testing, and Digital Image Correlation (DIC) to capture localized strain distributions and identify plastification in the HAZ. In parallel, finite element models were developed using ANSYS software to simulate joint behavior under realistic loading conditions. These models were calibrated and validated using the experimental data. Analytically, the research builds on and extends existing steel-based design provisions found in EN 1993-1-8, adapting them to the context of aluminum welded joints by incorporating reduction factors for the HAZ, modified yield-line models, and deformation-based limit states. The study examines chord face plastification failure mechanisms, and correlates them with geometric parameters including the brace-to- chord width ratio (β) and thickness-to-width ratio. 17 The results demonstrate that conventional design approaches underestimate the effects of welding in aluminum structures and may lead to unconservative predictions if HAZ softening is not accounted for. Experimental findings show up to 50% reduction in yield strength within the HAZ compared to the base material, consistent with previous studies yet quantitatively refined through extensive testing. Numerical simulations and analytical models presented herein provide improved predictive accuracy and design reliability. This research contributes to the body of knowledge by proposing practical design recommendations and validated analytical expressions tailored to welded aluminum joints. These findings support the enhancement of Eurocode 9 (EN 1999-1-1) and promote safer, more efficient utilization of aluminum in structural engineering. The work is particularly relevant for applications involving long-span roofs, transport infrastructure, offshore platforms, and prefabricated systems in corrosive or hard-to- access environments. Ultimately, the study offers a pathway for integrating aluminum more confidently into modern load-bearing structural systems.
Language:	English

Abstract:

The growing demand for lightweight, corrosion-resistant, and sustainable construction materials has led to the increased use of aluminum alloys in civil engineering. Among the structural applications, aluminum truss systems offer significant advantages in terms of reduced self-weight, durability, and simplified installation processes. However, the adoption of aluminum structures in construction sector remains limited due to a lack of comprehensive understanding of welded joint behavior—particularly in the heat-affected zone (HAZ), where significant material degradation occurs as a result of welding. This doctoral research aims to systematically investigate the mechanical performance of welded planar joints in aluminum truss structures, with a focus on quantifying the strength reduction within the HAZ and developing reliable predictive models. The study integrates experimental, numerical, and analytical approaches to assess the structural behavior of welded joints composed of square (SHS) and circular (CHS) hollow section profiles. Particular attention is given to evaluating joint configurations commonly encountered in lattice girders, such as X and K joints. The experimental component of this research was conducted in collaboration with the Faculty of Civil Engineering at the University of Montenegro and the Chair of Metal Structures at the Technical University of Munich. It involved the fabrication, instrumentation, and testing of full-scale welded aluminum truss specimens using EN AW-6082 T6 alloy. Mechanical characterization included tensile testing, Vickers hardness testing, and Digital Image Correlation (DIC) to capture localized strain distributions and identify plastification in the HAZ. In parallel, finite element models were developed using ANSYS software to simulate joint behavior under realistic loading conditions. These models were calibrated and validated using the experimental data. Analytically, the research builds on and extends existing steel-based design provisions found in EN 1993-1-8, adapting them to the context of aluminum welded joints by incorporating reduction factors for the HAZ, modified yield-line models, and deformation-based limit states. The study examines chord face plastification failure mechanisms, and correlates them with geometric parameters including the brace-to- chord width ratio (β) and thickness-to-width ratio. 17 The results demonstrate that conventional design approaches underestimate the effects of welding in aluminum structures and may lead to unconservative predictions if HAZ softening is not accounted for. Experimental findings show up to 50% reduction in yield strength within the HAZ compared to the base material, consistent with previous studies yet quantitatively refined through extensive testing. Numerical simulations and analytical models presented herein provide improved predictive accuracy and design reliability. This research contributes to the body of knowledge by proposing practical design recommendations and validated analytical expressions tailored to welded aluminum joints. These findings support the enhancement of Eurocode 9 (EN 1999-1-1) and promote safer, more efficient utilization of aluminum in structural engineering. The work is particularly relevant for applications involving long-span roofs, transport infrastructure, offshore platforms, and prefabricated systems in corrosive or hard-to- access environments. Ultimately, the study offers a pathway for integrating aluminum more confidently into modern load-bearing structural systems.