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2023
Conference article
Open Access
A geometry-preserving shape optimization tool based on deep learning
Favilli A, Laccone F, Cignoni P, Malomo L, Giorgi D
In free-form architecture, computational design tools have made it easy to create geometric models. However, obtaining good structural performance is difficult and requires further steps, such as shape optimization, to enhance system efficiency and material savings. This paper provides a user interface for form-finding and shape optimization of triangular grid shells. Users can minimize structural compliance, while ensuring small changes in their original design. A graph neural network learns to update the nodal coordinates of the grid shell to reduce a loss function based on strain energy. The interface can manage complex shapes and irregular tessellations. A variety of examples prove the effectiveness of the tool.Source: LECTURE NOTES IN CIVIL ENGINEERING, vol. 437, pp. 549-558. Torino, Italy, 26-28/06/2023
Project(s): Future Artificial Intelligence Research
Favilli A, Laccone F, Cignoni P, Malomo L, Giorgi D
In free-form architecture, computational design tools have made it easy to create geometric models. However, obtaining good structural performance is difficult and requires further steps, such as shape optimization, to enhance system efficiency and material savings. This paper provides a user interface for form-finding and shape optimization of triangular grid shells. Users can minimize structural compliance, while ensuring small changes in their original design. A graph neural network learns to update the nodal coordinates of the grid shell to reduce a loss function based on strain energy. The interface can manage complex shapes and irregular tessellations. A variety of examples prove the effectiveness of the tool.Source: LECTURE NOTES IN CIVIL ENGINEERING, vol. 437, pp. 549-558. Torino, Italy, 26-28/06/2023
Project(s): Future Artificial Intelligence Research
See at:
CNR IRIS 
| link.springer.com | CNR IRIS 
| CNR IRIS
2023
Conference article
Open Access
FreeGrid: a benchmark on design and optimisation of free-edge gridshells
Bruno L, Cignoni P, Gabriele S, Grande E, Imbimbo M, Laccone F, Marmo F, Mele E, Raffaele L, Tomei V, Venuti F
FreeGrid is meant to offer a common benchmark to test and compare different approaches to the design and optimization of steel gridshells, from man-based heuristic design to AI-based one. FreeGrid sets three design baseline problems: a barrel vault, a paraboloidal dome, and a hyperbolic paraboloid, having their spring line partially not constrained (free-edge) and subjected to symmetric and asymmetric load conditions. Participants are called to modify the baseline gridshell(s) in order to improve their structural performances, buildability, and sustainability, all three of them weighted in a single, bulk quantitative performance metric. Participants shall comply with a limited number of design constraints, while any other design solution is allowed. Baseline setups, performance metrics and design constraints will be fully detailed in technical specifications made publicly available. The full data of the baseline structures will be offered to participants according to an Open Data policy, together with postprocessing utilities intended to align the procedure to obtain the performance metrics. The FreeGrid benchmark will be launched within the IASS Symposium 2023 in Melbourne.
Bruno L, Cignoni P, Gabriele S, Grande E, Imbimbo M, Laccone F, Marmo F, Mele E, Raffaele L, Tomei V, Venuti F
FreeGrid is meant to offer a common benchmark to test and compare different approaches to the design and optimization of steel gridshells, from man-based heuristic design to AI-based one. FreeGrid sets three design baseline problems: a barrel vault, a paraboloidal dome, and a hyperbolic paraboloid, having their spring line partially not constrained (free-edge) and subjected to symmetric and asymmetric load conditions. Participants are called to modify the baseline gridshell(s) in order to improve their structural performances, buildability, and sustainability, all three of them weighted in a single, bulk quantitative performance metric. Participants shall comply with a limited number of design constraints, while any other design solution is allowed. Baseline setups, performance metrics and design constraints will be fully detailed in technical specifications made publicly available. The full data of the baseline structures will be offered to participants according to an Open Data policy, together with postprocessing utilities intended to align the procedure to obtain the performance metrics. The FreeGrid benchmark will be launched within the IASS Symposium 2023 in Melbourne.
See at:
CNR IRIS | iass2023.org.au | CNR IRIS
2023
Conference article
Open Access
Static- and fabrication-aware segmented concrete shells made of post-tensioned precast flat tiles
Laccone F, Menicagli S, Cignoni P, Malomo L
This paper introduces a novel structural concept for freeform shells, in which the shape is decomposed into flat tiles to be assembled sequentially with the help of falseworks. Once the structure is completed, the tiles are post-tensioned to minimize the tension forces and avoid detachment. The entire design process, from an input shape to fabrication, is managed by an automatic pipeline. The input shape is segmented into a field-aligned quad mesh, computed from the principal stress of the thin shell. The flat tiles are obtained by extruding each face along the normal of the best-fitting plane per face. The contact between adjacent tiles is ensured only at their edge midpoints so the forces can mainly flow along the cross directions. The best configuration of cable paths and pre-loads is found by solving a constrained optimization problem exploiting a reduced beam model of the shell. All tiles can be prefabricated in the shop with an adaptable and reusable molding system. Once the structure is completed, the top surface is finally completed with an in situ cast that fills the gaps and activates the entire shell behavior. In contrast, the bottom surface maintains its jagged aesthetics.Source: LECTURE NOTES IN CIVIL ENGINEERING, vol. 437, pp. 1-10. Turin, Italy, 26-28/06/2023
Laccone F, Menicagli S, Cignoni P, Malomo L
This paper introduces a novel structural concept for freeform shells, in which the shape is decomposed into flat tiles to be assembled sequentially with the help of falseworks. Once the structure is completed, the tiles are post-tensioned to minimize the tension forces and avoid detachment. The entire design process, from an input shape to fabrication, is managed by an automatic pipeline. The input shape is segmented into a field-aligned quad mesh, computed from the principal stress of the thin shell. The flat tiles are obtained by extruding each face along the normal of the best-fitting plane per face. The contact between adjacent tiles is ensured only at their edge midpoints so the forces can mainly flow along the cross directions. The best configuration of cable paths and pre-loads is found by solving a constrained optimization problem exploiting a reduced beam model of the shell. All tiles can be prefabricated in the shop with an adaptable and reusable molding system. Once the structure is completed, the top surface is finally completed with an in situ cast that fills the gaps and activates the entire shell behavior. In contrast, the bottom surface maintains its jagged aesthetics.Source: LECTURE NOTES IN CIVIL ENGINEERING, vol. 437, pp. 1-10. Turin, Italy, 26-28/06/2023
See at:
CNR IRIS | link.springer.com | ISTI Repository | CNR IRIS | CNR IRIS
2023
Conference article
Open Access
Statics and stability of bending-optimized double-layer grid shell
Laccone F, Pietroni N, Froli M, Cignoni P, Malomo L
Grid shell structures are optimal when considering their aesthetics and lightness, but their efficiency is highly reduced when their shape deviates from a pure membrane. Many contemporary architectures possess a freeform shape, conceived mostly on aesthetics and functional criteria. In these cases, finding an efficient grid shell often requires substantial shape modifications. This work addresses a new kind of doublelayer structure that aims to preserve the desired shape design. The structural system comprises a quad-meshed grid shell aligned to the target shape and enriched with an additional reinforcement layer that adds bending stiffness. This additional layer, going inward and outward of the main surface, presents variable height and discontinuous elements based on the required bending strength. The obtained structural system differs from both grid shells, as these latter may be very deformable in this setup, and from classic double-layer structures (space frames), which are heavier and redundant. In this paper, we show how the presented system compares with grid shell and double-layer competitors in terms of statics and stability. We highlight the pros and cons based on a systematic comparative analysis run on selected freeform shapes.Source: LECTURE NOTES IN CIVIL ENGINEERING, pp. 569-578. Turin, Italy, 26-28/06/2023
Laccone F, Pietroni N, Froli M, Cignoni P, Malomo L
Grid shell structures are optimal when considering their aesthetics and lightness, but their efficiency is highly reduced when their shape deviates from a pure membrane. Many contemporary architectures possess a freeform shape, conceived mostly on aesthetics and functional criteria. In these cases, finding an efficient grid shell often requires substantial shape modifications. This work addresses a new kind of doublelayer structure that aims to preserve the desired shape design. The structural system comprises a quad-meshed grid shell aligned to the target shape and enriched with an additional reinforcement layer that adds bending stiffness. This additional layer, going inward and outward of the main surface, presents variable height and discontinuous elements based on the required bending strength. The obtained structural system differs from both grid shells, as these latter may be very deformable in this setup, and from classic double-layer structures (space frames), which are heavier and redundant. In this paper, we show how the presented system compares with grid shell and double-layer competitors in terms of statics and stability. We highlight the pros and cons based on a systematic comparative analysis run on selected freeform shapes.Source: LECTURE NOTES IN CIVIL ENGINEERING, pp. 569-578. Turin, Italy, 26-28/06/2023
See at:
CNR IRIS | link.springer.com | ISTI Repository | CNR IRIS | CNR IRIS
2023
Conference article
Open Access
Computational design of fabricable geometric patterns
Scandurra E, Laccone F, Malomo L, Callieri M, Cignoni P, Giorgi D
This paper addresses the design of surfaces as assemblies of geometric patterns with predictable performance in response to mechanical stimuli. We design a family of tileable and fabricable patterns represented as triangle meshes, which can be assembled for creating surface tessellations. First, a regular recursive subdivision of the planar space generates different geometric configurations for candidate patterns, having interesting and varied aesthetic properties. Then, a refinement step addresses manufacturability by solving for non-manifold configurations and sharp angles which would produce disconnected or fragile patterns. We simulate our patterns to evaluate their mechanical response when loaded in different scenarios targeting out-of-plane bending. Through a simple browsing interface, we show that our patterns span a variety of different bending behaviors. The result is a library of patterns with varied aesthetics and predefined mechanical behavior, to use for the direct design of mechanical metamaterials. To assess the feasibility of our approach, we show a pair of fabricated 3D objects with different curvatures.
Scandurra E, Laccone F, Malomo L, Callieri M, Cignoni P, Giorgi D
This paper addresses the design of surfaces as assemblies of geometric patterns with predictable performance in response to mechanical stimuli. We design a family of tileable and fabricable patterns represented as triangle meshes, which can be assembled for creating surface tessellations. First, a regular recursive subdivision of the planar space generates different geometric configurations for candidate patterns, having interesting and varied aesthetic properties. Then, a refinement step addresses manufacturability by solving for non-manifold configurations and sharp angles which would produce disconnected or fragile patterns. We simulate our patterns to evaluate their mechanical response when loaded in different scenarios targeting out-of-plane bending. Through a simple browsing interface, we show that our patterns span a variety of different bending behaviors. The result is a library of patterns with varied aesthetics and predefined mechanical behavior, to use for the direct design of mechanical metamaterials. To assess the feasibility of our approach, we show a pair of fabricated 3D objects with different curvatures.
See at:
diglib.eg.org | CNR IRIS | ISTI Repository | CNR IRIS
2023
Journal article
Open Access
Geometric deep learning for statics-aware grid shells
Favilli A, Laccone F, Cignoni P, Malomo L, Giorgi D
This paper introduces a novel method for shape optimization and form-finding of free-form, triangular grid shells, based on geometric deep learning. We define an architecture which consumes a 3D mesh representing the initial design of a free-form grid shell, and outputs vertex displacements to get an optimized grid shell that minimizes structural compliance, while preserving design intent. The main ingredients of the architecture are layers that produce deep vertex embeddings from geometric input features, and a differentiable loss implementing structural analysis. We evaluate the method performance on a benchmark of eighteen free-form grid shell structures characterized by various size, geometry, and tessellation. Our results demonstrate that our approach can solve the shape optimization and form finding problem for a diverse range of structures, more effectively and efficiently than existing common tools.Source: COMPUTERS & STRUCTURES, vol. 292
Project(s): Future Artificial Intelligence Research, SUN
Favilli A, Laccone F, Cignoni P, Malomo L, Giorgi D
This paper introduces a novel method for shape optimization and form-finding of free-form, triangular grid shells, based on geometric deep learning. We define an architecture which consumes a 3D mesh representing the initial design of a free-form grid shell, and outputs vertex displacements to get an optimized grid shell that minimizes structural compliance, while preserving design intent. The main ingredients of the architecture are layers that produce deep vertex embeddings from geometric input features, and a differentiable loss implementing structural analysis. We evaluate the method performance on a benchmark of eighteen free-form grid shell structures characterized by various size, geometry, and tessellation. Our results demonstrate that our approach can solve the shape optimization and form finding problem for a diverse range of structures, more effectively and efficiently than existing common tools.Source: COMPUTERS & STRUCTURES, vol. 292
Project(s): Future Artificial Intelligence Research, SUN
See at:
CNR IRIS | ISTI Repository | www.sciencedirect.com | CNR IRIS
2023
Contribution to conference
Open Access
Static- and fabrication-aware concrete shells segmented into flat tiles
Laccone F, Menicagli S
The design of freeform concrete shells has gained popularity recently, pushed by computational tools that allow manipulating and exploring complex shapes interactively. However, their actual fabrication, even on a small scale, still poses challenges of feasibility and cost. Continuous shells require accurate and dense formworks, while segmented shells offer a low prefabrication rate, especially in the case of variable curvature. We propose a novel structural concept for freeform shells, in which the shape is decomposed into flat tiles, touching each other at the midpoint of the edges. Once assembled, the tiles are post-tensioned to minimize the resulting tension on the structure under service load. The outer surface is finally completed with an in situ cast that fills the gaps and activates the entire shell behavior. The bottom surface presents a jagged aesthetic due to gaps and misalignments at the seams. We developed an automatic pipeline to manage the design process from a general input shape to fabrication. The input shape is segmented based on a field-aligned quad mesh computed from the principal stress of the thin shell. The flat tiles are obtained by extruding each face along the normal of the associated checkerboard mesh, i.e., a mesh whose 'solid' parts are the planar rhomboids with vertices on each quad edge's midpoint. The contact between adjacent tiles is ensured only at their edge midpoints so that forces can flow along the cross directions, namely the principal directions. Candidate post-tensioning paths are found by clustering the segments linking pairs of opposite midpoints of the tiles' edges. We discard paths that do not terminate on the boundary, closed loops, or paths with significant kinks, to avoid localized shear on the surface.
Laccone F, Menicagli S
The design of freeform concrete shells has gained popularity recently, pushed by computational tools that allow manipulating and exploring complex shapes interactively. However, their actual fabrication, even on a small scale, still poses challenges of feasibility and cost. Continuous shells require accurate and dense formworks, while segmented shells offer a low prefabrication rate, especially in the case of variable curvature. We propose a novel structural concept for freeform shells, in which the shape is decomposed into flat tiles, touching each other at the midpoint of the edges. Once assembled, the tiles are post-tensioned to minimize the resulting tension on the structure under service load. The outer surface is finally completed with an in situ cast that fills the gaps and activates the entire shell behavior. The bottom surface presents a jagged aesthetic due to gaps and misalignments at the seams. We developed an automatic pipeline to manage the design process from a general input shape to fabrication. The input shape is segmented based on a field-aligned quad mesh computed from the principal stress of the thin shell. The flat tiles are obtained by extruding each face along the normal of the associated checkerboard mesh, i.e., a mesh whose 'solid' parts are the planar rhomboids with vertices on each quad edge's midpoint. The contact between adjacent tiles is ensured only at their edge midpoints so that forces can flow along the cross directions, namely the principal directions. Candidate post-tensioning paths are found by clustering the segments linking pairs of opposite midpoints of the tiles' edges. We discard paths that do not terminate on the boundary, closed loops, or paths with significant kinks, to avoid localized shear on the surface.
2023
Journal article
Open Access
Exploring new frontiers in gridshell design: the FreeGrid benchmark
Bruno L, Gabriele S, Grande E, Imbimbo M, Laccone F, Marmo F, Mele E, Raffaele L, Tomei V, Venuti F
Gridshell structures require an intricate design activity that shall comply with several design goals of diverse nature. This design phase can be approached with different methods and strategies and usually requires multiple competencies from different scientific fields. In this context, a common benchmark, called FreeGrid, is proposed to the scientific and practitioners' communities in order to test and compare different approaches to the design and optimization of steel gridshells on the bases of ad-hoc defined performance metrics. FreeGrid sets three design baseline problems: a barrel vault, a parabolic dome, and a hyperbolic paraboloid, having their spring line partially not constrained (free-edge) and subjected to uniform and piecewise uniform load conditions. Participants are called to modify the baseline gridshell(s), observing a limited number of design constraints (related to geometry, external constraints and material), in order to improve their structural, buildability, and sustainability performances through the maximization of a bulk quantitative performance metric. Specifically, the structural performance metric accounts for both ultimate and serviceability behavior, through the calculation of the critical Load Factor and maximum vertical displacement; the buildability performance metric includes the evaluation of face planarity, uniformity of structural joints and members; the sustainability performance metric is based on the structure embodied carbon. This paper describes the baseline gridshells setups, the proposed performance metrics and the recommended method for performance assessment. The complete data of the baseline structures are made available according to an Open Data policy, together with postprocessing utilities intended to align the procedure to obtain the performance metrics.Source: STRUCTURES, vol. 58
Bruno L, Gabriele S, Grande E, Imbimbo M, Laccone F, Marmo F, Mele E, Raffaele L, Tomei V, Venuti F
Gridshell structures require an intricate design activity that shall comply with several design goals of diverse nature. This design phase can be approached with different methods and strategies and usually requires multiple competencies from different scientific fields. In this context, a common benchmark, called FreeGrid, is proposed to the scientific and practitioners' communities in order to test and compare different approaches to the design and optimization of steel gridshells on the bases of ad-hoc defined performance metrics. FreeGrid sets three design baseline problems: a barrel vault, a parabolic dome, and a hyperbolic paraboloid, having their spring line partially not constrained (free-edge) and subjected to uniform and piecewise uniform load conditions. Participants are called to modify the baseline gridshell(s), observing a limited number of design constraints (related to geometry, external constraints and material), in order to improve their structural, buildability, and sustainability performances through the maximization of a bulk quantitative performance metric. Specifically, the structural performance metric accounts for both ultimate and serviceability behavior, through the calculation of the critical Load Factor and maximum vertical displacement; the buildability performance metric includes the evaluation of face planarity, uniformity of structural joints and members; the sustainability performance metric is based on the structure embodied carbon. This paper describes the baseline gridshells setups, the proposed performance metrics and the recommended method for performance assessment. The complete data of the baseline structures are made available according to an Open Data policy, together with postprocessing utilities intended to align the procedure to obtain the performance metrics.Source: STRUCTURES, vol. 58
See at:
CNR IRIS | ISTI Repository | www.sciencedirect.com | CNR IRIS