Experimental testing and numerical modelling of the behaviour of intermeshed steel connections

  • Pantelis Matis

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

This thesis presents the development of a new form of steel connection known as the "Intermeshed Steel Connection" for the resistance of gravity loads in frame structures. The thesis investigates the efficacy of the connection system via physical testing, numerical simulation, and design techniques. This research establishes the groundwork for revolutionising the steel building construction industry by advancing the fundamental science and engineering principles for intermeshed (interlocking) connections formed by advanced, automated, precise, volumetric cutting.

In steel fabrication, advanced techniques like high-definition plasma, water jet, and laser cutting enable fast, computer-controlled operations with exact finishes. Historically, such sophisticated machinery has been primarily utilized to expedite conventional tasks like cutting sheet metal or other standard fabrication procedures, such as cutting instead of drilling holes, without fully exploiting their capabilities. The intermeshed steel connection aims to harness this underused potential by using these cutting-edge technologies for the volumetric cutting of open steel sections, producing precisely interlocking steel pieces that form a robust connection. This method predominantly transfers loads through direct contact and bearing within the connection components, bypassing traditional fastening methods like welding or bolting. This approach facilitates the rapid assembly and disassembly of steel structures and promotes the reuse of materials.

If fully automated, the intermeshed connection system can enhance design, fabrication, and installation integration. Although the intermeshed steel connection has a number of appealing characteristics, the concept of cutting open steel sections presents difficulties in terms of load transfer mechanisms and failure modes. For example, implementing the cuts would result in a break in the beam continuity and/or the formation of sharp corners in the specimen. The former may interfere with load paths, whereas the latter may increase stress concentrations. Before introducing the intermeshed connection system into engineering practise, the structural behaviour of these connections must be thoroughly comprehended and adequate performance under axial and gravity loads must be demonstrated.
The purpose of this research is to provide a comprehensive understanding of the behaviour and performance of intermeshed steel connections at both global and local levels, as well as to investigate suitable design methods. In order to reach this objective, numerous connection-specific details were considered, experimental testing was conducted, and the connections were analysed using ABAQUS structural analysis software. The intermeshed steel connections subjected to direct tension, compression, and flexural loading were the subject of this thorough investigation. The load-displacement behaviour, yield and ultimate capacities of these connections, stress and strain concentrations and failure modes, were determined.

For the front intermeshed steel connections, connection geometry CON3 was recommended for adoption of both tensile and compressive zones due to its more desirable, simple and practical geometry than CON1 and CON2 although it is weaker in tension than the others. In order to accommodate higher tolerances the side intermeshed steel connections were designed and tested in tension and compression. The performance of these connections in axial loading was satisfactory and design recommendations were made in order to avoid an undesirable failure mode observed in the lower flange area from the experiments in tension. In compression the eccentricity of loading should be avoided because it reduces the compressive resistance of the side intermeshed connection as it was observed by the numerical analyses performed. For pure flexural loading the side intermeshed steel connections were tested and were found to have sufficient load carrying capacity and ductility according to the design calculations. Based on the interaction between various parts (through contact bearing and friction), the intermeshed steel connection exhibited sufficient load carrying capacity, rigidity, and ductility to meet the design specifications. This connection is very advantageous because it is safe, robust, demountable, and reusable at the end of a structure's life, and it can significantly reduce the cost and time required to erect a building.

Thesis is embargoed until 31 July 2025.


Date of AwardJul 2024
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsNorthern Ireland Department for the Economy & Invest Northern Ireland
SupervisorSu Taylor (Supervisor), Gerard Hamill (Supervisor) & Patrick McGetrick (Supervisor)

Keywords

  • intermeshed steel connections
  • advanced manufacturing techniques
  • digital image correlation
  • experimental testing
  • finite element analysis
  • finite element modelling
  • reuse of structural steel
  • axial loading
  • structural analysis
  • ABAQUS
  • four point bending test
  • digital fabrication
  • material tensile testing
  • new steel connections
  • nonlinear structural analysis
  • contact theory

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