publications

2024

1. The Effect of Geometric Tiling Parameters on the Stiffness of a Rotational Kirigami System

   Isabel M. de Oliveira, Emily Baker , and Sigrid Adriaenssens

   In IASS 2024: Redefining the Art of Structural Design , Aug 2024
2. Numerical Modeling of the Deployment Mechanism of a Metallic Plate-Lattice Space Frame

   Isabel M. de Oliveira, Eduardo M. Sosa , and Sigrid Adriaenssens

   In Engineering Mechanics Institute Conference and Probabilistic Mechanics & Reliability Conference (EMI/PMC 2024) , May 2024

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   From folded furniture and stairs to corrugated roofs and composite steel decks, cut and folded sheet metal arises in different civil construction settings to take load-carrying functions. Origami and kirigami-inspired structural components have the potential to enable more efficient production of load-bearing systems while reducing waste and transportation costs. To design these systems, it is essential to understand their behavior during the reconfiguration from their flat to their deployed state. The present work focuses on understanding the deployment mechanics of a kirigami system fabricated from a single sheet of metal. Once adjacent unit cells are deployed from a periodic cut pattern, they connect side by side to form a plate-lattice space frame. The product has a primary surface consisting of the original flat sheet with cuts, a secondary surface of adjacently deployed and connected cells, and the legs that connect both surfaces. Like expanded metal, reduced cross-sections at the legs concentrate the deformations produced by deploying the system, forming localized hinges near the primary and secondary surfaces. We use nonlinear finite element analysis with sequential quasi-static steps and beam elements to simulate the deployment mechanism of a sheet with a square grid cut pattern. The simulations are performed using Abaqus/Standard. We first deploy the central portions of unit cells called hubs using out-of-plane prescribed displacements. Then, we use axial connector elements to reduce the distance between vertices of adjacent units to form a fully connected secondary surface. We identify and present the scaling laws of the deployment loads for different metal sheet thicknesses and corroborate load-displacement simulation results with experiments from previous work [1]. The developed study aims to be used to foster the design of high-performance load-carrying kirigami structures.

2023

1. Characterization of the Rotational Hinge Stiffness for Metallic Kirigami Space Frame

   Isabel M. de Oliveira, Eduardo M. Sosa , and Sigrid Adriaenssens

   In IASS 2023: Integration of Design and Fabrication , Jul 2023
2. Effect of Stamped Dimples on the Stiffness of Plates under Uniaxial Compression

   Isabel M. de Oliveira, Jun Sato , and Sigrid Adriaenssens

   In EMI 2023: Engineering Mechanics Institute Conference , Jul 2023
3. Experimental and Numerical Investigation of a Rotational Kirigami System

   Isabel M. de Oliveira, Eduardo M. Sosa , Emily Baker , and Sigrid Adriaenssens

   Thin-Walled Structures, Nov 2023

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   Engineered kirigami strategies enable structural systems that reduce cost and energy through flat-packing and rapid assembly. We studied the effect of the polygonal shape and cut pattern on the structural behavior of rotational kirigami units under tension and compression loads. Multi-step finite element models were developed, compared to experiments, and shown to predict experimental results robustly in the decimeter scale. We evaluate buckling-to-deployment load ratios, showing the load-carrying capacity of the system, and present a sensitivity analysis on localized geometric imperfections. These verified models can be used to further develop the system for load-carrying applications at larger scales.

4. An Exploratory Analysis of a Crowd-Sourcing Tool: Building Terminological Consensus in Civil Engineering

   Isabel M de Oliveira , Scott McClellan , Chris Rauch , Sigrid Adriaenssens , and Jane Greenberg

   Nov 2023

2022

1. Out-of-Plane Compressive Stiffness of Spin-Valence Kirigami Units

   Isabel M. de Oliveira, and Sigrid Adriaenssens

   In EMI 2022: Engineering Mechanics Institute Conference , Nov 2022

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   Kirigami spin-valence is a deployable system where patterned cuts are made in sheet material so that the sheet becomes vertically extensible [1]. Cut patterns are designed with units composed of a polygonal hub nested within another polygon (original polygon) where thin elements (legs) connect both geometries. The hubs can be popped out of the plane of the sheet material when they rotate with respect to the original polygon. The deployed hub vertices can be connected to adjacent hub vertices to form a space frame configuration. Examples of applications of origami and kirigami-inspired structures go from building façades and deployable bridges to metamaterials with tunable properties [2]. The fabrication of stiffer structures from flat sheet material is of interest to the construction industry for many reasons, including flat packaging and shipping the material to the construction site and rapid deployment and assembly of the structure. These features provide possible reduction of cost, construction material, and transportation resources. A metallic spin-valence kirigami with quadrilateral units was modeled with shell finite elements to characterize the structural system in [3]. That characterization concluded that this system could be used for façade and sculptural work, but the system should be stiffened for loadbearing applications. Considerable gains in stiffness should be achieved if changes in the geometry and cut pattern were provided for the space frame configuration. To study how additional stiffness can be achieved in this system, we first develop a simplified finite element model with beam elements and rotational hinge stiffness that is calibrated with previous work [3]. Then we use the simplified model to study different polygonal configurations under out-of-plane compressive loading. These configurations vary with respect to leg length to width ratio, and deployment height to polygon radius ratio. After finding configurations that present higher stiffness and global buckling multipliers, we perform a more detailed numerical model with shell elements to compare and verify results. References [1] M. Ramirez, E. Baker, E. Harriss, and G. Herning, “Double-Curved Spin-Valence: Geometric and Computational Basis,” pp. 408–425, 2020. [2] P. M. Reis, F. López Jiménez, and J. Marthelot, “Transforming architectures inspired by origami,” Proc Natl Acad Sci USA, vol. 112, no. 40, pp. 12234–12235, Oct. 2015, doi: 10.1073/pnas.1516974112. [3] N. Sherrow-Groves and E. Baker, “Structural finite-element analysis of steel kirigami space frame to characterize global behavior,” p. 8, 2019.

2020

1. Connection System for Gridshell Structures Using Parametric Modeling and Digital Fabrication

   Isabel M. de Oliveira, Ruy Marcelo De Oliveira Pauletti , and Leila Cristina Meneghetti

   Automation in Construction, Jan 2020

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   Lightweight structures in grid form made of elements joined together with nodes are called reticulated shells, or gridshells. We propose a new connection system and method for gridshell structures. The connection system applies to grids that have a high variability of curvature and connection parameters. The connection uses standardized hub geometries and interconnecting parts. The elements of the structure connect to the hubs through these interconnecting parts, which absorb varying parameters of the connection, such as incidence, twist, and adjacency angles, and the fabrication tolerance of element lengths and bolted connections. The aim is to provide a system that can be assembled quickly, disassembled and reused. We use parametric modeling environment to model global and local geometry of meshes and nodes. Inputs for the programmed parametric definition include a discretized surface, geometry of the hub notch, and element cross-sections; outputs include element lengths, interconnecting parts geometries, and assembly information. We present a physical model that serves as a proof of the concept developed within the computational modeling environment. Finally, we discuss the scalability of the model and future work.

2018

1. Design and Construction of a Membrane-Tensegrity Sculpture

   Paula M. Bolelli , Karina B. Rocha , Isabel M. de Oliveira, Willyams B. Mello , Alfredo H. Haydamus , Luiza C. Boechat , Ruy M. O. Pauletti , and Vinicius F. Arcaro

   In IASS 2018: Creativity in Structural Design , Jan 2018

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   This work describes the design and the construction of a membrane-tensegrity sculpture, developed in the context of a graduate course on light structures at the University of São Paulo. The structure combines compressive struts and a continuous membrane, to shape an octahedral star, whose equilibrium conditions are much alike a tensegrity module. As initial geometry it was assumed the first stellation of the octahedron, which allowed the definition of a single type of fabric pattern, repeated 12 times. Alternative patterning and shape finding methods are also discussed in the paper. Since the cusps of the resulting surface have proportions beyond the Goldsmith limit, a minimal surface is in fact unachievable for the prescribed geometrical conditions, thus stress concentrations appear at each cusp. The resulting geometry was patterned suing a uniform strain compensation. That proved to be too much inaccurate, due to the intrinsic strain variations, which luckily were balanced by the flexibility of the selected fabric, finally resulting a pleasant sculpture, which was displayed at the hall of the Civil Engineering building at the Polytechnic School.

2. An Application of Structural Topology Optimization to Creative Staircase Design

   Isabel M. de Oliveira, Ruy M. O. Pauletti , and Arthur H. Lara

   In IASS 2018: Creativity in Structural Design , Jan 2018

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   This paper presents the details and key aspects of the application of structural topology optimization to the shape finding of an ultra-high performance concrete (UHPC) staircase. The choice of the mesh size, boundary conditions, material properties, and restrictions are some of the aspects discussed in this study. The optimized geometry is used as an inspiration for a final parametric model, seeking minimization of different formwork and reduction of production costs. Additional project aims are to use the least amount of supports and the slenderest cross-section possible. Selection of UHPC enables the definition of unusual geometries, that would be unfeasible with regular reinforced concrete. The methodology consists of choosing an initial geometry to apply the topology optimization, then, vary the optimization parameters and evaluate how the results differ. After that, we change the initial geometry and apply optimization again to evaluate if results differ. The total volume of material and distribution of voids in space are used to create a model with smooth geometry. This geometry is then simulated for stress analysis and adjusted to meet design criteria. Further steps needed for construction are discussed.

2017

1. Application of Structural Topology Optimization to the Design of a UHPC Staircase

   Isabel M. de Oliveira, Ruy M. O. Pauletti , and Arthur H. Lara

   In XXXVIII Iberian-Latin American Congress on Computational Methods in Engineering (CILAMCE) , Jan 2017

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   This paper presents an application of structural topology optimization to the shape finding of an ultra-high performance concrete (UHPC) staircase. In this project, the optimized geometry is used as an inspiration for a final parametric model, seeking minimization of different formwork and reduction of production costs. Therefore, the steps should have the same form, and the only different component should be the intermediate landing. Additional aims are the least amount of supports and the slenderest cross-section as possible. Selection of UHPC enables the definition of unusual geometries, that would be unfeasible with regular reinforced concrete. After the definition of the base geometry in the software, a first topology optimization is performed. Afterwards, the results are analyzed, the remaining parts are modeled with a smooth geometry, and the resulting geometry is simulated for stress analysis and adjusted until they meet design criteria.