Publications

Abstract: Mass timber compartments exhibit fire dynamics that differ significantly from noncombustible enclosures due to timber fuel contribution, charring, and ventilation interactions. This study presents a single-zone, Python-based compartment fire model developed for mass timber applications. The model builds upon the RISE framework and integrates transient one-dimensional heat transfer, oxygen-limited combustion, timber charring, char oxidation, and gypsum fall-off within a unified solver. The current formulation accounts for exposed timber fuel contribution but does not yet include additional CLT fuel contribution following protective layer fall-off. This feature is currently under development and will be added in future work. The model is validated against six full- scale experiments, including three RISE tests [1], two tests reported by McNamee et al. [2], and one National Research Council of Canada test [3]. These cases primarily represent ventilation- controlled fire behavior. In addition, a parametric study was conducted on key model coefficients, to evaluate how variations in these parameters influence predicted gas temperatures and heat release rate evolution. This analysis identifies the parameters that most significantly affect peak temperatures and decay behavior and establishes practical ranges for their application. These insights provide rapid guidance on expected compartment response and help inform parameter selection and calibration in more detailed CFD-based fire simulations.

Keywords: Mass timber; Compartment fires; Single-zone fire model; Timber charring; Performance-based fire engineering

Abstract: Trusses are valued for their simple design principles and efficient load-bearing capability. However, their slow assembly process and static topology restrict rapid deployment and reconfiguration for functional use. Mechanical linkages, in contrast, offer rapid deployability and reconfigurability but are challenging to apply as large-scale civil structures. These challenges raise the question: Can the design versatility of trusses be combined with the kinematic advantages of mechanical linkages to create structurally efficient, deployable, and reconfigurable large-scale systems? To that end, we present a method inspired by flat-foldable quadrilateral linkages to transform static trusses into compactly stowable, reconfigurable systems. An additional node is introduced on the tensile members of triangular units based on Grashof linkage principles. This node converts triangles into flat-foldable quadrilateral linkages, enabling system-level reconfigurability while preserving the load capacity, stiffness and stability of the structure. We show that the Fink, Scissor, and Warren trusses can be transformed into reconfigurable systems, achieving up to 93% and 60% reduction in convex hull area and maximum length, respectively, upon actuation of all degrees of freedom. Our method also extends to topology-optimized trusses, enabling the design of functional, shape-morphing trusses for arbitrary geometries, loads, and support conditions. Proof-of-concept prototypes, including a reconfigurable cantilever and a three-meter Warren truss bridge, validate feasibility while demonstrating load capacities and stiffness comparable to their static counterparts. We believe the proposed method will advance the design, analysis and fabrication of sophisticated bar-linked reconfigurable structures with potential applications in deployable infrastructure, aerospace systems, robotic components, consumer devices, metamaterials, and more.

Keywords: Reconfigurable trusses; Shape-morphing trusses; Foldable trusses; Four-bar linkages

Abstract: This technical note presents the derivation, validation, and application of a three-node torsional spring (3NTS) element for the analysis of bar-linked, reconfigurable structures. The 3NTS element assigns rotational stiffness to a joint (node) of two axial force members (bars) in truss-like assemblies. This element avoids the use of rotational degrees of freedom in the model by recasting its resisting moment into equivalent nodal forces, which are consistent with global equilibrium, thereby keeping the model size compact and computationally efficient. The 3NTS is integrated into standard non-linear solvers to simulate large-displacement response and validated against analytical solutions of two benchmark examples: the simplest 3NTS structure and the buckling of a vertical column. We further apply the framework to a reconfigurable truss structure from our previous work to illustrate potential functional use cases and outline its broader applicability to metamaterials, kirigami systems, and biomechanical assemblies. An open-source matrix structural analysis tool implementing the 3NTS and axial force members is made available with this note.

Keywords: Torsional spring element; Joint rotational stiffness; Reconfigurable bar-linked structures

Abstract: Trusses are valued for their simple design principles and efficient load-bearing capability. However, slow member-by-member assembly and static topology restrict rapid deployment and reconfiguration of trusses for functional use. While mechanical linkages offer rapid deployability and reconfigurability, their scalability for large-scale civil structures is often constrained by the characteristics of their unit cells. These limitations raise the question: Can the design versatility of trusses be combined with the kinematic advantages of mechanical linkages to create structurally efficient, force-stable, scalable, deployable, and reconfigurable systems? To that end, we present a method inspired by flat-foldable quadrilateral linkages to transform static trusses into compactly stowable, reconfigurable systems. An additional node is introduced on the tensile members of triangular units with the help of Grashof linkage principles. This node converts triangles into flat-foldable quadrilateral linkages, enabling system-level reconfigurability while preserving the structure’s load capacity, stiffness and stability. We show that the Fink, Scissor, and Warren trusses can be transformed into reconfigurable systems, achieving up to 93% and 60% reduction in convex hull area and maximum length, respectively, upon actuation of all degrees of freedom. Proof-of-concept prototypes, including a reconfigurable cantilever and a three-meter Warren truss bridge, validate feasibility while demonstrating load capacities and stiffness comparable to their static counterparts. We believe the proposed method will advance the design, analysis and fabrication of sophisticated bar-linked reconfigurable structures with potential applications in deployable infrastructure for aerospace systems, robotic components, metamaterials, and more.

Keywords: Reconfigurable trusses; Four-bar linkages; Shape-morphing trusses; Force-stable trusses

Abstract: Trusses are valued for their simple design principles and efficient load-bearing capability. However, slow member-by-member assembly and static topology restrict rapid deployment and reconfiguration of trusses for functional use. While mechanical linkages offer rapid deployability and reconfigurability, their scalability for large-scale civil structures is often constrained by the characteristics of their unit cells. These limitations raise the question: Can the design versatility of trusses be combined with the kinematic advantages of mechanical linkages to create structurally efficient, force-stable, scalable, deployable, and reconfigurable systems? To that end, we present a method inspired by flat-foldable quadrilateral linkages to transform static trusses into compactly stowable, reconfigurable systems. An additional node is introduced on the tensile members of triangular units with the help of Grashof linkage principles. This node converts triangles into flat-foldable quadrilateral linkages, enabling system-level reconfigurability while preserving the structure’s load capacity, stiffness and stability. We show that the Fink, Scissor, and Warren trusses can be transformed into reconfigurable systems, achieving up to 93% and 60% reduction in convex hull area and maximum length, respectively, upon actuation of all degrees of freedom. Proof-of-concept prototypes, including a reconfigurable cantilever and a three-meter Warren truss bridge, validate feasibility while demonstrating load capacities and stiffness comparable to their static counterparts. We believe the proposed method will advance the design, analysis and fabrication of sophisticated bar-linked reconfigurable structures with potential applications in deployable infrastructure for aerospace systems, robotic components, metamaterials, and more.

Keywords: Reconfigurable trusses; Four-bar linkages; Shape-morphing trusses; Force-stable trusses

Abstract: Traditional hull fabrication relies on labor- and time-intensive methods to generate smooth, curved surfaces. These conventional methods often lead to hull surface topologies that are static in design with hydrodynamics aimed at handling a broad range of sea conditions but not optimized for any specific scenario. In this paper, we introduce a method of rapidly fabricating planing hulls using the principles of curved-crease origami. Starting from a flat-folded state, the curved-crease origami hulls can be deployed to match traditional planing hull shapes like the VPS (deep-V, Planing hull with Straight face) and the GPPH (General Purpose Planing Hull). By extension of the ability to conform to a desired shape, we show that the curved-crease origami hulls can emulate desired hydrodynamic characteristics in still as well as wavy water conditions. Furthermore, we demonstrate the shape-morphing ability of curved-crease origami hulls, enabling them to switch between low and high deadrise configurations. This ability allows for on-demand tuning of the hull hydrodynamic performance. We present proof-of-concept origami hulls to demonstrate the practical feasibility of our method. Hulls fabricated using the curved-crease origami principles can adapt to different sea states, and their flat foldability and deployability facilitate easy transport and deployment for rapid response naval operations such as rescue missions and the launch of crewless aquatic vehicles.

Keywords: Curved-crease origami hulls; Tunable hydrodynamics; Shape morphing hulls; Deployable hulls

Abstract: Curved creasing of thin sheets differs from most other origami because the surface of the sheet bends globally as it is folded from a 2D to a 3D state. This global bending results in smooth surface structures with anisotropic stiffness and complex mechanistic behaviors. In this talk, we explore the mechanics of curved crease structures and highlight how these origami can be used for systems with shape-morphing and functional capabilities. We begin by discussing the theoretical principles governing curved crease folding and present a reduced-order ‘bar and hinge’ simulation tool suitable for capturing the folding and post-folding mechanical behavior of these structures. Next, we explore a unique behavior seen in curved creased sheets where localized changes in the folding (i.e., a pinch) results in global bending and twisting deformations. We show that these pinch-induced deformations are higher for patterns where the curvature of the crease is larger. Additionally, patterns with less creases and an even number creases will twist more than patterns with many or an odd numbers of creases. The number of creases have little effect on the pinch-induced bending of the origami. Based on the twisting and bending shape-morphing, we propose practical applications including a gripper mechanism, an adaptive façade system, and a beam with tunable bending stiffness. Finally, we present a practical scenario where curved crease origami are used to create a reconfigurable boat hull with adaptable hydrodynamic characteristics. The hull consists of four connected sheets where folding of the system changes the surface curvature and the overall hull topology. We explore the hydrodynamic characteristics of the adaptable hull in both calm and wavy water conditions. Results show that unfolding the origami hull results in a lower deadrise angle (flatter hull bottom) that has lower frictional drag and is well suited for calmer waters. On the other hand, reconfiguring the hull to have a higher deadrise angle allows for smoother sailing in wavy conditions. Moreover, the hull shape can be adapted based on the water surface wavelength to avoid resonant behaviors where high pitch and heave motions can make the hull particularly unstable.

Abstract: In shipbuilding, the topology of the hull surface plays an essential role in determining a hull’s hydrodynamic response. However, traditional methods of hull assembly generate static designs, where a hull can only perform well under a specific range of speeds or wavelengths. In this work, we introduce a novel technique of fabricating planing hulls following the principles of curved-crease origami, where active folding allows for shape morphing and adaptable hydrodynamic characteristics. These curved-crease origami structures offer additional advantages over conventional shipbuilding techniques like reduced joint complexity, improved structural stiffness, and rapid fabrication from a flat state. We use the Bar and Hinge model for the kinematic analysis of curved-crease origami patterns and a simplified mathematical model based on Low Aspect-ratio Strip Theory to study the hydrodynamic characteristics of morphing hull geometry in calm and wavy water conditions. Results show that active control of hull hydrodynamics is achieved as the extent of actuation determines the hull deadrise angle. Higher actuation means a lower deadrise and a flatter hull profile which is beneficial in reducing frictional drag. In contrast, lower actuation means a higher deadrise which is especially beneficial for cutting through waves and reducing heaving and pitching motion. Furthermore, we show that a passive control over hull hydrodynamics can be achieved by varying the length and curvature of the initial crease pattern. It is observed that the hulls show a resonant response for all hydrodynamic characteristics under specific wavelengths. Increasing the length and curvature of the hull typically results in lowering of the heave and pitch displacements and accelerations. This active and passive control allows us to steer clear of resonant behavior and ensure seakeeping fitness by reducing the possibility of motion sickness for passengers. In conclusion, this work extends the merits of curved crease origami to more practical applications like naval engineering. It opens avenues for novel structural design methods in fields requiring adaptable structural responses against varying fluid flow.

Keywords: Curved-crease origami hulls; Tunable hydrodynamic performance; Shape morphing surfaces

Abstract: Fabrication and assembly of smooth curved surfaces is a complex process. It makes applications like the manufacturing of ship hulls a time-intensive process. In contrast, the principles of origami allow rapid and efficient fabrication of surfaces from flat sheets. Sheets, when folded along curved creases, reduce joint complexity, improve overall structural stiffness, allow easy assembly, and only require a small initial footprint. To exploit these properties, we used the bar and hinge model to design and analyze curved-crease origami patterns which form planing hulls upon folding. This study shows that the hull geometry is sensitive to the crease pattern, and surfaces can morph moderately by changing the extent of folding. Further, we used a simplified mathematical model that predicts a planing boat's motion to study the hydrodynamic characteristics of curved origami surfaces, including drag force, natural frequency, heave, surge and pitch amplitudes, velocities, and acceleration. The results show that surface hydrodynamic characteristics depend significantly on the crease pattern, and the performance can be optimized with parametric changes to the initial crease pattern. This study highlights the potential for origami to create smooth curved surfaces by vastly reducing the fabrication time and paves the way for shape morphing origami structures in fields like aerospace, civil, marine, and mechanical engineering.

Keywords: Curved-crease origami hulls; Tunable hydrodynamic performance; Shape morphing surfaces