Structural Mechanics Characterization of Steel Intermeshed Connections

Abstract

This thesis presents the efforts to develop a new class of steel connection named the “Intermeshed Connection” for gravity load resistance in frame structures. The thesis investigates the performance of the connection system using physical testing and numerical simulation, as well as methods for its design. The project herein lays the groundwork to transform the steel building construction industry by advancing the underlying science and engineering precepts for intermeshed connections created from precise, volumetric cutting. Advanced manufacturing techniques, such as high-definition plasma, water jet, and laser cutting, are powerful tools that offer fast operation and precise finish in the process of steel fabrication. To date, this class of advanced manufacturing equipment has only been used to accelerate traditional processes for cutting sheet metal or other conventional fabrication activities (e.g. cutting instead of drilling holes). Such approaches have not capitalized on the equipment’s full potential. The intermeshed connection is intended to exploit this potential by harnessing advanced cutting technologies for volumetric cutting open steel sections, which results in precise steel pieces that can intermesh (i.e. interlock) with each other and form a connection. In such connections, loads transfer mainly through direct contact of the connection components rather than by traditional means through welds or bolts, which facilitates fast assembly and disassembly of steel structures and material reuse. The intermeshed system, if fully automated, can enhance the integration between design, fabrication, and installation. Although the intermeshed connection has multiple interesting features to offer, the idea of cutting of open steel sections poses challenges regarding the load-transfer mechanisms and failure modes for intermeshed connections. For instance, implementation of the cuts would cause discontinuity in the beam or formation of sharp corners in the specimen. The former could interrupt load paths, and the latter could increase stress concentrations. Therefore, to introduce the intermeshed connection system to engineering practice, the structural behavior of these connections needs to be fully understood and adequate performance under gravity loads needs to be demonstrated. The aim of the present study is to provide insight on the structural performance of the intermeshed connection at both global and local levels, and to investigate appropriate design methods. To reach this goal, numerous details of the intermeshed connection were considered, a design procedure was developed, physical specimens were designed and tested, and beams with intermeshed connections were analyzed using sophisticated numerical procedures. This investigation was conducted in a step-by-step state assessment of the intermeshed connection subjected to multiple scenarios of gravity loading and various support conditions. Load resistance and design of these connections were explored to evaluate the mechanics of intermeshed connections including stress and strain concentrations, effective material utilization, failure modes, and connection geometry optimization. Relying on the interaction of individual components, the intermeshed connection demonstrates ample load carrying capacity, stiffness, and ductility, which fulfilled the design requirements. This connection promises to be robust, secure, dismountable and offers the ability to be manufactured within current industrial tolerances and be erected quickly.