Flexural Rigidity Research Articles

In this paper, a series of 1-g shaking table model tests were carried out to investigate the seismic behavior of a relatively stiff rectangular tunnel structure installed in soft clay bed, accounting for different ground motions with varying peak accelerations. Using a validated numerical analysis procedure, a suite of three-dimensional (3D) finite element (FE) analyses was performed to systematically study the factors of tunnel burial depth, seismic intensity, flexural rigidity of the middle column and tunnel wall thickness on the seismic response of rectangular tunnel structures installed in clayey ground. It was found that, with the increasing burial depth, the seismic response of rectangular tunnel structure became more intense due to the increased inertial force arising from the overlying clay; in terms of improving the seismic performance of tunnel structure, increasing tunnel wall thickness seemed more effective than increasing flexural rigidity of the middle column. Furthermore, it was found that the existing simplified approaches generally tended to overestimate the earthquake-induced racking distortions of rectangular tunnels installed in clayey ground. A new semi-empirical relationship was derived for better correlating the racking ratio with flexibility ratio for rectangular tunnels embedded in soft clays, which could provide a useful reference for the seismic design and risk assessment of similar clay-tunnel systems.

It is well-known that membrane deformation and water pores contribute to the spontaneous translocation of arginine-rich cell-penetrating peptides (CPPs). We confirm this through the observation of the spontaneous translocation of single R9 (nona-arginine) and Tat (48-60) peptides across a model membrane using the weighted ensemble (WE) method within all-atom molecular dynamics (MD) simulations. Furthermore, we demonstrate that membrane deformation and the presence of a water pore reduce the effective charge of the CPP and the bending rigidity of the model membrane during translocation. We find that R9 disturbs the model membrane more than Tat (48-60), leading to more efficient translocation of R9 across the model membrane.

The biological function of membranes is closely related to their softness, which is often studied through the membranes' thermally driven fluctuations. Typically, the analysis assumes that the relaxation rate of a pure bending deformation is determined by the competition between membrane bending rigidity and viscous dissipation in the surrounding medium. Here, we reexamine this assumption and demonstrate that viscous flows within the membrane dominate the dynamics of bending fluctuations of nonplanar membranes with a radius of curvature smaller than the Saffman-Delbrück length. Using flickering spectroscopy of giant vesicles made of dipalmitoylphosphatidylcholine, DPPC:cholesterol mixtures and pure diblock-copolymer membranes, we experimentally detect the signature of membrane dissipation in curvature fluctuations. We show that membrane viscosity can be reliably obtained from the short time behavior of the shape time correlations. The results indicate that the DPPC:cholesterol membranes behave as a Newtonian fluid, while the polymer membranes exhibit more complex rheology. Our study provides physical insights into the time scales of curvature remodeling of biological and synthetic membranes.

A very interesting technical objective for the improvement of the mechanical performance of cold formed profiles is to avoid its instability or even to reduce its effect. Among the proposed solutions, the reinforcement of the section with struts offers an optimal alternative. Positioned parallel to the web and fixed to the edges of the flanges, the struts perfectly counteract local instability and delay global instability. This study is a component of an experimental and numerical strategy to determine how much of an impact this kind of reinforcement will have on the overall strength of a bent C-beam.Two profile sizes and various variants of strut reinforcement are proposed. Experimentally, the profile is progressively braced between its flanges with square pieces, the side of which is equal to the height of the web. Thus, blocking their warping, at defined spacing, one could judge the contribution of the device added to the flexural rigidity. Following a finites elements modelling (ABAQUS) andthen a characterization of the cross-section according to Eurocode 3, the article proposes a prediction model that can estimate the contribution of the struts to the flexural rigidity of these profiles. The results were encouraging, as the flexural inertia can double at certain strut spacing, with almost no change in weight.

Homogenization of two-dimensional materials integrating monolayer bending and surface layer effects

Abstract The glulam-cross laminated timber (CLT) composite floor is a type of prefabricated composite floor that integrates glulam beams and CLT slab into a unified structure using shear connectors. To investigate the bending performance of the glulam-CLT composite floor, the bending test was conducted on a full-scale composite floor under static load. The study comprehensively analyzed the failure mechanism, load–deflection behavior, interface slip and strain distribution of the glulam-CLT composite floor. The test results of the composite floor indicated that the failure mode was tensile fracture of the wood beam at the bottom. As the load increased, the deflection deformation of the mid-span beam exceeded that of the edge beam. When the load reached its ultimate limit, the deflection deformation of the mid-span beam increased by 14.4% compared to the edge beam. In the early loading phase, the strain distribution of the composite section satisfied the assumption of a plane section. However, the strain distribution deviated from this assumption with the increased load due to the relative slips between the glulam beam and CLT flange. To calculate the bending performance of the composite floor, the M-shaped section of the glulam-CLT composite floor was simplified as T-section composite beams. The linear-elastic method for determining the flexural rigidity and ultimate bearing capacity of the glulam-CLT composite floors was proved to be accurate and reliable. The findings provided valuable insights into the bending behavior of the CLT flange under load and emphasized the non-uniform stress distribution caused by shear lag effects.

Elastic properties of 3D printed clavicles are closer to cadaveric bones of elderly donors than commercial synthetic bones

Abstract The truss‐confined buckling‐restrained brace (TC‐BRB) with a varying or constant section truss confining system was proposed for applications of long span and large force capacities. Their feasibility and hysteresis behavior were examined through experimental investigations. This paper presents an original formulation of the elastic buckling resistance of the novel restraining system, considering the shear reduction effect. The findings indicate that the chord predominantly contributes to the flexural rigidity in the restraining system, while the post primarily contributes to the overall shear rigidity. Subsequently, the ultimate compressive strength of a TC‐BRB is evaluated, incorporating the effects of chord residual stress, length differences between the restrainer and entire brace, and initial in‐plane flexural deformation, based on available experimental data. A numerical procedure employing finite element model (FEM) analysis is introduced to simulate the mechanical characteristics of TC‐BRBs. The critical loads are verified through FEM analyses and test results. The failure mode observed in the numerical models is the instability of the chords near the midspan, as expected. A simplified approach for determining the ultimate compressive strength and design recommendations for TC‐BRBs are provided for engineering practice.

This study explores the flexural behavior of continuous fiber-reinforced composite sandwich structures built entirely using material extrusion additive manufacturing. The continuous fiber additive manufacturing system used in this study works sequentially, thus enabling the addition of fiber reinforcement just in the face sheets, where it is most effective. Three-point bending tests were carried out on sandwich panel specimens built using thermoplastic reinforced with continuous glass fiber to quantify the effect of fiber reinforcement and infill density in the flexural properties and failure mode. Sandwich structures containing continuous fiber reinforcement had higher flexural strength and rigidity than unreinforced sandwiches. On the other hand, an increase in the lattice core density did not improve the flexural strength and rigidity. The elastic modulus of fiber-reinforced 3D-printed sandwich panels exceeded the predictions of the analytical models; the equivalent homogeneous model had the best performance, with a 15% relative error. However, analytical models could not correctly predict the failure mode: wrinkle failure occurs at 75% and 30% of the critical load in fiber-reinforced sandwiches with low- and high-density cores, respectively. Furthermore, no model is currently available to predict interlayer debonding between the matrix and the thermoplastic coating of fiber layers. Divergences between analytical models and experimental results could be attributed to the simplifications in the models that do not consider defects inherent to additive manufacturing, such as air gaps and poor interlaminar bonding.

Endovascular procedures rely on navigating guidewires, catheters and other devices through tortuous vasculature to treat disease. A critical challenge in these procedures is catheter herniation, in which the device deviates from its intended path, often irrecoverably. To elucidate the mechanics of herniation, we developed a physical flow model of the aortic arch that enables direct measurement of device curvature during experimentally simulated neuroendovascular procedures conducted from an upper arterial access. Combined with measurements of initial, unstressed device shapes and flexural rigidities, the method enables the experimental estimation of the device bending energies during these simulated procedures. Characteristic energy profiles revealed distinct stages in both herniation and successful navigation, governed by the interplay between device properties and vascular anatomy. A deterministic progression from successful navigation to herniation was identified, with catheter systems following paths determined by measurable energy barriers. Increasing guidewire stiffness or decreasing catheter stiffness reduced the energy barrier for successful navigation while increasing that for herniation. This framework enables the prediction of endovascular herniation risk and offers unique insight into improved device design and clinical decision-making.

We report a computational study of the bending deformation of two-dimensional nanoribbons by classical molecular dynamics methods. Two-dimensional double transition metal carbides, together with monometallic ones, belong to the family of novel nanomaterials, so-called MXenes. Recently, it was reported that within molecular dynamics simulations, Ti4C3 MXene nanoribbons demonstrated higher resistance to bending deformation than thinner Ti2C MXene and other two-dimensional materials, such as graphene and molybdenum disulfide. Here, we apply a similar method to that used in a previous study to investigate the behavior of Mo2Ti2C3 nanoribbon under bending deformation, in comparison to the Ti4C3 sample that has a similar structure. Our calculations show that Mo2Ti2C3 is characterized by higher bending rigidity at DTi2Mo2C3≈92.15 eV than monometallic Ti4C3 nanoribbon at DTi4C3≈72.01 eV, which has a similar thickness. Moreover, approximately the same magnitude of critical central deflection of the nanoribbon before fracture was observed for both Mo2Ti2C3 and Ti4C3 samples, wc≈1.7 nm, while Mo2Ti2C3 MXene is characterized by almost two times higher critical value of related external force.

Paper-based materials are being alternative candidates to build load-bearing components for the high demanding building sector to be committed to the green transition, but more knowledge of structural mechanics of such components is needed. In this work, three categories of innovative load-bearing sandwich beams with cup-box core fully made of different paper materials were produced, tested and analyzed in four-point bending. The first failure mode was observed at the top facesheets due to the low compressive strength of paper materials; Beams with thin facesheets had premature buckling failure, whereas those with thicker facesheets exhibited ductility reaching higher deflection before the compressive failure. The developed finite element model, calibrated with the experiments for the equivalent bending and shear rigidities, provided figures of the modulus of the facesheet as well as the properties of the core. Furthermore, the compressive plasticity behavior of the facesheets was assessed by fitting the model with load-deflection curves from the tests. Using the model for the structural optimization of the thickness and height of the core, the work suggests optimal values 3 times higher than the original ones.

This study investigates the incorporation of boron carbide (B4C) filler particulates into a kenaf fiber-reinforced epoxy matrix to explore its potential in lightweight applications, focusing on antimicrobial effectiveness, mechanical integrity, thermal properties, and microstructural characteristics. The composite material was formulated by blending varying seven different concentrations of boron carbide (0–50 g) and kenaf fibers (KFs) with an epoxy resin, aiming to achieve a balance between mechanical strength and minimal weight. Antimicrobial test revealed that the composite material, consisting of kenaf fiber reinforced with B4C particulates, exhibited significant antibacterial activity against common pathogens. Mechanical testing indicated that the addition of boron carbide and kenaf fibers significantly improved the tensile strength and flexural rigidity of the composites. Specifically, enhancements in tensile strength and flexural modulus were quantitatively analyzed, showing notable increases compared to the base epoxy resin. Scanning Electron Microscopy (SEM) was employed to examine the fracture surfaces following mechanical testing, revealing improved interfacial bonding between the kenaf fibers and the epoxy matrix due to the presence of boron carbide. This microscopic analysis also highlighted areas where stress distribution was optimized, contributing to the composite's enhanced mechanical properties.

Nylon fabric has poor moisture management properties due to the absence of hydroxyl groups. In this work, an attempt has been made to enhance the moisture management properties of nylon fabric using sodium lignosulfonate (SLS). SLS is an essential by-product of the wood pulping industry. Various concentrations of the SLS were prepared in an aqueous medium, and the nylon fabric was treated with them using the exhaust method. The effects of the parameters of the treatment process are analyzed using Box–Behnken response surface design of experiment and analysis of variance (ANOVA). Upon testing the water vapour transmittance rate (WVTR), it was found that the SLS treatment is efficacious in improving moisture management. Water contact angle is reduced to 10.6° from 105.3° after the coating, which proves the achievement of hydrophilic surface. The average wetting time of nylon fabrics decreased by 78% after the SLS treatment. A significant increase in the bending modulus, flexural rigidity, and coefficient of the SLS-treated fabrics is observed when SLS concentration is high. After the SLS treatment, wetting time decreases, absorption rate increases, spreading speed increases, and overall moisture management capacity (OMMC) increases significantly. The SLS coating over the nylon surface is found to be durable with excellent rating for light and washing fastness.

Wear on the surface of the femoral head increases the risk of hip and femur fractures. Biomechanical experiments conducted on the femur are based on its bending and torsional rigidities. Studies regarding the deflection of the femur bone when the femoral head is coated with microfilms composed of durable and compatible biomaterials are poor. This study aimed to investigate the effects of different biomaterial microfilm coatings over the femoral head on the deflection of the human femur. We utilized 2023 R1 finite element analysis (FEA) software to model the directional deformation on the femoral head and examine the femur's deflection with varying microfilm thicknesses. The deflection of the femur bone was reported when the femoral head was uncoated and coated with titanium, stainless steel, and pure gold microfilms of different thicknesses (namely, 50, 75, and 100 μm). Our results show that the femur's minimum and maximum deflection occurred for stainless steel and gold, respectively. The deformation of the femur was lower when the femoral head was coated with a 50-micrometer microfilm of stainless steel, compared to the deformation obtained with gold and titanium. When the thickness of the microfilm for each of the materials was increased, the deformation continued to decrease. The minimum deformation of the femur occurred for a thickness of 100 μm with stainless steel, followed by titanium and gold. The difference in the directional deformation of the femur between the materials was more significant when the coating was 100 μm, compared to the thicknesses of 50 and 75 μm. The findings of this study are expected to significantly contribute to the development of advanced medical techniques to enhance the quality of life for patients with femur bone-related issues. This information can be used to develop more resilient coatings that can withstand wear and tear.

Finite element analysis of square hollow section steel braces incorporating different infill materials under cyclic loading

Tunnelling-induced nonlinear responses of continuous pipelines resting on tensionless Winkler foundation

This study performs mechanical analysis for Al/Foam composite sandwich panels under 3-point bending using numerically and experimentally. The flexural rigidity, elastic deflections, and normal, shear stresses are obtained by analytical calculations of the Timoshenko beam equation and compared finite element (FE) models for 3-point bending loading conditions. The FE models are constructed using 2D single-layer shell and 3D solid discrete-layer models. The validity of FE models at the analysis is evaluated for Al/PVC Foam sandwich composites for the elastic state. The experimental bending results of Al/XPS Foam sandwich composites are compared with numerical models at elastic and elastoplastic states. The elastic results indicate that the out-of-plane deflection results agree well across numerical and analytical models. Normal stresses at the core are higher in 3D discrete-layer solid models compared to laminated shell theory-based models for thick plates, due to the more accurate characteristics of the discrete-layer solid models. The Timoshenko beam theory-based analytical bending results show a good correlation with the results from laminated shell theory-based finite element method (FEM) analyses. Elastoplastic FEM analysis indicates that discrete-layer-based 3D solid FEM models effectively predict local effects dependent on indentation failure.

As a core component of biological and synthetic membranes, lipid bilayers are key to compartmentalizing chemical processes. Bilayer morphology and mechanical properties are heavily influenced by electric fields, such as those caused by biological ion concentration gradients. We present atomistic simulations exploring the effects of electric fields applied normally and laterally to lipid bilayers. We find that normal fields decrease membrane tension, while lateral fields increase it. Free energy perturbation calculations indicate the importance of dipole-dipole interactions to these tension changes, especially for lateral fields. We additionally show that membrane area compressibilities can be related to their cohesive energies, allowing us to estimate changes in membrane bending rigidity under applied fields. We find that normal and lateral fields decrease and increase bending rigidity, respectively. These results point to the use of directed electric fields to locally control membrane stiffness, thereby modulating associated cellular processes.

Exploring the influence of flexural rigidity variability of aquatic plants on stem deflection geometry and flow characteristics