Abstract
The LATTICE project addresses the limited use of automation and additive manufacturing (AM) in the construction sector by exploring the potential of Wire-and-Arc Additive Manufacturing (WAAM) for the production of efficient steel structural elements. WAAM offers the possibility to manufacture complex geometries while reducing material use and production constraints, thus enabling a new generation of lightweight and structurally efficient components. The project focuses on lattice structures, which are widely used because of their high stiffness- and strength-to-weight ratios. While lattice systems are well established at the micro scale and in large-scale truss structures, their application at the scale of individual structural elements (meso-scale), such as beams and columns, has been limited by the complexity and cost of conventional connections between bars. LATTICE aims to overcome this limitation by exploiting WAAM, and in particular the dot-by-dot deposition strategy, to manufacture lattice elements as continuous components. In this way, intersections between bars are produced through a continuous flow of material and the conventional physical node is replaced by a geometrical intersection. This concept leads to a new class of “node-free” lattice meso-elements. Lattice meso-elements are defined as structural components at the scale of a single beam or column, composed of straight bars with nominally constant cross-sections and different inclinations, continuously connected at their intersections. Their development requires the integration of expertise from three main research fields: Structural Design, Manufacturing & Technology, and Computational Mechanics. The project pursued four main objectives: (a) developing a comprehensive understanding of the WAAM manufacturing process for lattice meso-elements; (b) assessing the mechanical properties of their basic components, including straight bars and bar intersections; (c) developing a computational design procedure capable of generating efficient lattice geometries while accounting for manufacturing, mechanical and structural constraints; and (d) establishing design-oriented guidelines for the structural application of WAAM-produced lattice meso-elements. LATTICE was organised into three main phases: BASIC, DESIGN and MESO. During the BASIC phase, the WAAM dot-by-dot manufacturing process was investigated and optimized. Process parameters were calibrated through a Design of Experiments campaign, and an extensive series of specimens was fabricated, including individual bars and bar intersections produced at different build angles. These specimens were mechanically characterized under tensile and compressive loading. Particular attention was given to typical features of WAAM products, including surface roughness, mechanical anisotropy and the influence of printing parameters. The experimental campaign provided effective material properties, manufacturing constraints and preliminary design values for subsequent project activities. The DESIGN phase focused on the development of a computational framework for the generative design and optimization of lattice meso-elements. The procedure combines the force density method with multi-constrained structural optimization and explicitly incorporates WAAM manufacturing requirements, anisotropic mechanical properties, geometrical limitations and structural checks. Strength and buckling verifications are performed at the level of each individual bar. The resulting tool enables the automated form-finding of lattice structural elements that are both structurally efficient and compatible with the constraints of the selected manufacturing process. The MESO phase addressed the design, fabrication and experimental validation of full lattice meso-elements. Different optimized lattice column configurations, including geometries with three, four and six faces and different slenderness ratios, were manufactured using WAAM and tested under compression. Their structural response was investigated through analytical formulations, experimental campaigns and numerical modelling at different levels of refinement, ranging from simplified beam-line finite-element models to detailed solid models based on tomography data.
Results achieved
All the main project objectives have been addressed according to the original workplan, without major deviations. Within the BASIC phase, WAAM dot‑by‑dot process parameters were optimized through a Design of Experiment campaign, and an extensive series of specimens (single bars and bar intersections, at different build angles) was fabricated and mechanically characterized in tension and compression, leading to effective material parameters, process constraints and preliminary design values. In the DESIGN phase, a computational framework for the generative design of lattice meso‑elements was implemented, based on the force density method and multi‑constrained optimization, explicitly including WAAM manufacturing constraints, anisotropic mechanical properties, and strength and buckling checks for each bar. In the MESO phase, optimized lattice column geometries (with three, four and six faces and different slenderness) were fabricated via WAAM and tested under compression; analytical formulations, finite‑element models (from beam‑line to tomography‑based solid models) and experimental campaigns were developed to describe their structural behaviour and to support future design rules. The project has also produced tangible results such as: a WAAM printing protocol for lattice meso‑elements, technical datasets on basic components and lattice columns, a generative design tool, demonstrator columns, and a first set of design‑oriented guidelines currently being refined for publication. The project has successfully demonstrated the feasibility and potential of WAAM‑produced lattice meso‑elements as efficient structural components for lightweight steel structures, by combining manufacturing, structural design and computational mechanics in an integrated framework. Beyond the specific demonstrator columns, the main legacy of LATTICE lies in the datasets, tools and methods developed: WAAM protocols, mechanical characterizations, optimization‑based design procedures, multiscale numerical models and experimentally validated understanding of lattice behaviour. These outcomes support structural engineers and manufacturers interested in exploiting additive manufacturing for innovative steel structures, and they open new research directions on architected lattice materials, infilled configurations, and performance‑driven design for sustainable construction.Dettagli del progetto
Responsabile scientifico: Tomaso Trombetti
Strutture Unibo coinvolte:
Dipartimento di Ingegneria Civile, Chimica, Ambientale e dei Materiali
Coordinatore:
ALMA MATER STUDIORUM - Università di Bologna(Italy)
Contributo totale di progetto: Euro (EUR) 197.048,00
Contributo totale Unibo: Euro (EUR) 94.000,00
Durata del progetto in mesi: 24
Data di inizio
28/09/2023
Data di fine:
28/02/2026
