Search Results (10)

The frame-unit bamboo culm structure system offers a novel approach to bamboo structure, combining advantages like reduced construction times and simplified joint designs. Despite its benefits, there is limited research on its mechanical properties and computational methodologies. This study conducted bending performance tests on simply supported frame-unit bamboo culm structures, revealing that the bending stiffness of the structure increases with the number of bolts in the edge joints, though with diminishing efficiency. Based on the experimental observations, a calculation model for this type of structure was established, proposing formulas to describe the stiffness relationships between the corner joints, edge joint, and the overall structure. Numerical simulations calculated the stiffness of the edge joint as a function of the number and placement of bolts, indicating that positioning bolts closer to the outer side enhances edge joint stiffness. By inputting the various rotational stiffness values of corner joints into the simulations and stiffness formulas, consistent total stiffness values were obtained, validating the proposed stiffness relationship formulas. The average stiffness values of the corner joints were derived from these formulas and experimental data, and the rotational stiffness of other types of corner points can also be obtained using this method. Furthermore, a finite element computational method tailored for this structural system was introduced, converting the actual structure into a beam element model for calculation. The equivalent joint forces can be distributed to various components of the actual structure, resulting in the internal force distribution of bamboo culms and bolts in the actual structure, thus achieving the design of the components. The calculated displacement values obtained from this method are close to the displacement values in the experiment, proving the feasibility of this method. Full article

In shear wall-frame systems, the foundation rotation that may occur under the shear walls changes the displacements and interstory drift ratios and changes the internal force distribution. This study investigates the effect of foundation rotations under shear walls on internal force distribution in shear-frame systems. The originality of the study lies in considering parabolic loads and dynamic analysis (first mode), in addition to static uniform or triangular distributed loads, when determining the shear wall moment contribution ratio under the influence of foundation rotation. The shear wall contribution ratio, a key parameter in many earthquake codes, is defined as the ratio of the sum of bending moments taken by the shear walls at the base to the overturning moment. It plays a crucial role in determining the building’s behavior. Depending on this ratio, the load-reduction coefficient is changed. This study investigates the effect of foundation rotation on the moment distribution at the base for three different static load cases and the first mode in the dynamic analysis. The multi-story building is modeled as an equivalent sandwich beam. The moment contribution ratio (MCR) was calculated with the help of analytical solutions of the differential equations written for three different load cases in static conditions, and graphs were created for practical use directly calculating the MCR. In the methodology of the study, the initial step involves the calculation of the equivalent sandwich beam stiffness parameters and the foundational rotational spring. Subsequent to these calculations, the MCR values can be directly obtained with the help of graphs. This approach facilitates the rapid and practical determination of the MCR and can be used in the preliminary sizing phase to eliminate possible errors in the data entry of software that performs detailed analysis. In addition, in the presented study, it has been shown that taking a single mode into account is sufficient when calculating MCR values in dynamic analysis. Full article

The intricate and highly complex morphologies of diatom frustules have long captured the attention of biomimetic researchers, initiating innovation in engineering solutions. This study investigates the potential of diatom-inspired surface stiffeners to determine whether the introduced innovative strategy is a viable alternative for addressing engineering challenges demanding enhanced stiffness. This interdisciplinary study focuses on the computer-aided generation of stress-adaptive lightweight structures aimed at optimizing bending stiffness. Through a comprehensive microscopical analysis, morphological characteristics of diatom frustules were identified and abstracted to be applied to a reference model using computer-aided methods and simulated to analyze their mechanical behavior under load-bearing conditions. Afterwards, the models are compared against a conventional engineering approach. The most promising biomimetic approach is successfully automated, extending its applicability to non-planar surfaces and diverse boundary conditions. It yields notable improvement in bending stiffness, which manifests in a decrease of displacement by approximately 93% in comparison to the reference model with an equivalent total mass. Nonetheless, for the specific load case considered, the engineering approach yields the least displacement. Although certain applications may favor conventional methods, the presented approach holds promise for scenarios subjected to varying stresses, necessitating lightweight and robust solutions. Full article

By deliberately designing microscopic internal mechanisms, architected materials can achieve a variety of material properties without changing constituent materials. Integration of the architected materials into a structure as substructures has a good potential to enhance structural performance and realize wide design freedom. This paper explores the capabilities of multiscale approaches for lattice structures, which is a major mechanism in architected materials. The objectives of this paper are (1) to demonstrate the capabilities of the framework to evaluate stiffness characteristics of lattice structures with two different two-scale analysis approaches and (2) to assess the accuracies and validity ranges of both approaches for appropriate evaluations of lattice structures. The two-scale analysis framework consists of the computational homogenizations for the generalized stiffness (ABD) and 3D stiffness (C) matrices. Equivalent stiffness characteristics of the unit cell are obtained by computational homogenizations to effectively capture the macroscopic responses of lattice structures. This study provides a comprehensive correlation study between the prediction accuracies of the two-scale analysis approaches in terms of tensile, bending, and torsional stiffness characteristics for practical modeling and development of lattice structures. The study will contribute a guideline for effective designs of high-performance structures with architected materials. Full article

Plantar plate positioning has been demonstrated as biomechanically superior. However, some operators remain resentful about the morbidity of the surgical approach. To provide improved plate fixation for first tarsometatarsal joint arthrodesis with respect to the tibialis anterior tendon, a medio-plantar plate was developed. The purpose of this biomechanical study was to compare its construct stability to that of a plantar plate construct. Twelve pairs of fresh frozen human specimens were used in a matched pair test. Each pair was fixed with a 4 mm compression screw and either a plantar locking plate or a medio-plantar locking plate. A cantilever beam test was performed in dorsiflexion. Before and after cyclic loading (5000 cycles; 40 N), bending stiffness and relative movements at the joint space were monitored in a quasi-static test including optical motion tracking. Maximum load and bending moment to failure were investigated in a load-to-failure ramp test. The bending stiffness of both groups did not significantly differ before (plantar 49.9 N/mm ± 19.2; medio-plantar 53.9 N/mm ± 25.4, p = 0.43) or after (plantar 24.4 N/mm ± 9.7; medio-plantar 35.3 N/mm ± 22.0, p = 0.08) cyclic loading but decreased significantly in both groups (p < 0.01) after cyclic loading. Relative movement increased significantly during cyclic testing in both groups (p < 0.01) but did not differ significantly between the groups before (p = 0.29) or after (p = 0.16) cyclic loading. Neither load nor bending moment to failure were significantly different (plantar 225 N ± 78, 10.8 Nm; medio-plantar 210 N ± 86, 10.1 Nm, p = 0.61). Both plate constructs provided equivalent construct stability, both being well suited for Lapidus arthrodesis. Full article

The objective of this paper is to present the application of equivalent single layer (ESL) approach for the ultimate strength assessment of ship hull girder in the context of numerical finite element (FE) simulations. In the ESL approach, the stiffened panel is replaced with a single plate, which has the equivalent stiffness of the original panel. Removal of tertiary stiffening elements from the numerical model facilitates time-savings in pre-processing and FE analysis stage. The applicability of ESL approach is demonstrated with two case studies, one compartment model and full-sized double hull tanker model in intact and damaged conditions. The damage extents are determined based on the international association of classification societies from common structural rules (IACS-CSR) for oil tanker. Ship hull girder is exposed to distributed pressure with the sinusoidal shape that bends the hull girder. This pressure load is applied separately to bottom and side structures to obtain the vertical and horizontal bending moments of the hull girder, respectively. Ultimate strength predictions obtained from ESL approach are compared to full three-dimensional finite element method (3D FEM) and IACS incremental-iterative method. The comparison between different methods is provided in terms of longitudinal bending moment and cross sectional stress distribution. Overall, ESL approach yields good agreement compared to the 3D FEM results in predicting the ultimate strength of ship hull girder while providing up to 3 times computational efficiency and ease of modeling. Full article

The aim of this paper is to refine a scientific solution to the problem of automated or semi-automated efficient and practical design of 3D printed chainmails of exoskeletons with pre-programmed properties (variable stiffness/flexibility depending on direction) reflecting individual user needs, including different types and degrees of deficit. We demonstrate this with the example of using chainmail in a hand exoskeleton, where 3D printed chainmail components can be arranged in a single-layer structure with adjustable one- or two-way bending modulus. The novelty of the proposed approach consists in combining the use of real data from research on the exoskeleton of the hand, new methods of their analysis using deep neural networks, with a clear and scalable design of a 3D printed fabric product that can be personalized (mechanical parameters such as stiffness and bend angles in various directions) to the needs and goals of therapy in a particular patient. So far, this approach is unique, having no equivalent in the literature. This paves the way for a wider implementation of adaptive chainmails based on machine learning, more efficient for more complex chainmail designs. Full article

With railway interoperability, new trains are allowed to move on the French railway network. These trains may present different designs from standard trains. This work aims to complete the current approach for vehicle admission on the railway network, which is defined in technical baselines. Historically, computation rules for traffic conditions are based on simplified analytical works, which are considerably qualitative. They have evolved through feedback and experimental campaigns to comply with the track structure evolution. An efficient methodology based on numerical simulation is needed to evaluate railway vehicle admission to answer this issue. A perspective to update these computation rules is to evaluate the structural fatigue in the rail. That is to say, fatigue is caused by bending and shear stresses. The complexity of the railway system has led to an investigation at first of the vertical response of the railway track and quantifying its contribution to the rail’s stress response. In that sense, this paper investigates the vertical track response to a moving railway vehicle at low frequencies. For this purpose, a lightweight numerical model for the track, a multi-body model for the vehicle, and a random vertical track irregularity are proposed. More explicitly, the track model consists of a two-layer discrete support model in which the rail is considered as a beam and sleepers are point masses. The rail pads and ballast layer are modelled as spring/damper couples. Numerical results show a negligible effect of track inertia forces due to high track stiffness and damping. Nevertheless, this assumption is valid for normal rail stresses but not for ballast loading, especially in the case of sleeper voids or unsupported sleepers. Hence, the prediction of the mechanical stress state in the rail for fatigue issues is achieved through a static track model where the equivalent loading is obtained from a dynamic study of a simplified vehicle model. A statistical analysis shows that the variability of the vertical track irregularity does not influence the output variabilities like the maximum in time and space of the normal and shear stress. Full article

Stability analysis of a corrugated ring subjected to uniform external pressure is under consideration. Two main approaches to solving this problem are analyzed. The equivalent bending stiffness approach is often used in engineering practice. It is based on some plausible assumptions about the behavior of a structure. Its advantage is the simplicity of the obtained relations; the disadvantage is the difficulty in estimating the area of applicability. In this paper, we developed an asymptotic homogenization method for calculating the critical pressure for a corrugated ring, which made it possible to mathematically substantiate and refine the equivalent bending stiffness approach. To evaluate the results obtained using the equivalent stiffness approach and asymptotic homogenization method, the imperfection method is used. The influence of the corrugation parameters on buckling pressure is analyzed. Full article

The current work presents a study on hollow cylinder composite beams, since hollow cylinder cross-sections are one of the principal geometry in many engineering fields. In particular, the present study considers the use of these profiles for scaffold design in offshore engineering. Composite beams cannot be treated as isotropic ones due to couplings mainly present among traction, torsion, bending and shear coefficients. This research aims to present a simple approach to study composite beams as they behave like isotropic ones by removing most complexities related to composite material design (e.g., avoid the use of 2D and 3D finite element modeling). The work aims to obtain the stiffness matrix of the equivalent beam through an analytical approach which is valid for most of the laminated composite configurations present in engineering applications. The 3D Euler–Bernoulli beam theory is considered for obtaining the correspondent isotropic elastic coefficients. The outcomes show that negligible errors occur for some equivalent composite configurations by allowing designers to continue using commercial finite element codes that implement the classical isotropic beam model. Full article