Transverse Layer Research Articles

Hybrid-Vlasov Modelling of Ion Velocity Distribution Functions Associated with the Kelvin–Helmholtz Instability with a Density and Temperature Asymmetry

The Kelvin–Helmholtz instability (KHI), characterized by vortices forming at a perturbed velocity shear layer, is a prominent candidate mechanism for mass, momentum, and energy transport across boundaries with velocity shear in various space plasma environments. It is of particular interest at the flanks of Earth’s magnetopause, which separates the plasma of the magnetosphere from the adjacent shocked solar wind flow in the magnetosheath. In the present study, we use local hybrid-Vlasov simulations to investigate the ion velocity distribution functions (VDFs) associated with KHI in a magnetopause-like, transverse velocity shear layer setting (magnetic field perpendicular to the shear plane). We look for signatures of ion finite Larmor radius (FLR) effects, which could be utilized in spacecraft measurements to recognize when such effects are active, influencing KHI evolution and driving plasma mixing. We show that when a density/temperature asymmetry exists across the shear layer, FLR effects produce a heat flux along the vortex edges. With a magnitude (≳0.1 mW m−2) that is a significant fraction of the total magnetosheath energy flux, the heat flux provides a distinct signature that could be measured with a single spacecraft. During the late nonlinear stage of KHI, mixed non-Maxwellian ion VDFs are additionally found within the vortices. Our results are also valid in the presence of a small magnetic shear across the magnetopause.

Behavior of CFRP confined rectangular high-strength concrete-filled steel tubular columns under eccentric compression

This paper presents an experimental study on the eccentric compression behavior of rectangular high-strength concrete-filled steel tubular columns confined with carbon fiber reinforced polymer (CFRP- CFST). Seventeen specimens were tested under eccentric compression, examining key parameters involving eccentricity, number of transverse CFRP layers, slenderness ratio, corner radius, CFRP partial wrapping scheme, and CFRP orientation. The effects of these parameters on failure mode, load-displacement relationship, strain development, and ultimate mechanical properties were analyzed and discussed. The ultimate bearing capacity (Nu) of CFRP-CFST columns improved with an increase in transverse CFRP layers, corner radius, and CFRP wrapping proportion, while it decreased with increasing eccentricity and slenderness ratio. Partial wrapping schemes reduced the effectiveness of CFRP confinement, with the outward local buckling of the steel tube primarily occurring in areas without CFRP confinement. Longitudinal CFRP provided less improvement to Nu compared to transverse CFRP under small eccentricity conditions. A theoretical model based on the fiber element method was developed to predict the ultimate bearing capacity and implemented through a custom program to facilitate calculations. The model was validated using a test database comprising results from this study and previous research. Additionally, axial force-bending moment (N-M) interaction curves were rapidly generated, providing a theoretical basis for the design and practical application of CFRP-CFST columns in practical engineering.

Multipurpose Impacts of Silver Nitrate on Direct Organogenesis of Begonia rex cv. DS-EYWA via Transverse Thin Cell Layering (tTCL) Technique

Begonia rex cv. DS-EYWA is an important plant for indoor and outdoor cultivation, and cv. DS-EYWA is a rare unique cultivar with curly, colorful leaves. Due to their importance, applying plant tissue culture techniques for mass and healthy production in a short period of time without seasonal limitation is of immense economic value. Applying several concentrations of silver nitrate (AgNO3) in combination with varied concentrations of cytokinins including 6-benzylaminopurine (BAP), thidiazuron (TDZ) (0, 0.5, 1, 1.5 mgL−1), and 1-naphthaleneacetic acid (NAA) auxin (0, 0.5, 1 mgL−1) via focusing on transverse thin cell layer (tTCL) petiole explants for high-scale production was used to establish an efficient in vitro propagation protocol. Our results showed that even low concentrations (25 mgL−1) can control internal bacterial infection and increase shoot direct regeneration efficiency. A combination of 1.5 mgL−1 BAP, 0.5 mgL−1 NAA, and 25 mgL−1 AgNO3 was the best treatment to increase the number of direct regenerated shoots, and a lower concentration of BAP (0.5 mgL−1) can be suggested for shoot elongation. Elongated shoots were successfully rooted in MS basal medium and acclimatized in a 1:1 peat moss/perlite sterilized pot mixture.

Identifying significant factors affecting plate stiffness of innovative CLT using Random Forest analysis

Abstract Innovative cross-laminated timber (CLT) is a relatively new engineered timber product. It is a new version of CLT having large gaps between lateral lamellas. Since it is a new material, the mechanical performance of this innovative material is not studied yet despite these advantages. This paper explores the factors that influence membrane, bending, shear, and torsional stiffness in innovative CLT and their implications, acknowledging the significance of knowing the plate stiffness of these innovative materials in predicting their behaviour and promoting their use in construction as bio-based materials. Using a large database of plate stiffness moduli derived from finite element computations and incorporating microstructural characteristics such as layer thicknesses, board width, gap width, longitudinal modulus of elasticity, longitudinal shear modulus, and rolling shear modulus of timber, Random Forest analysis was employed to study the significance of factors affecting plate stiffness in innovative CLT. Our results show that the gap affects the membrane, shear, and torsional stiffness for innovative CLT. However, the trans-versal layer thickness primarily controls the bending stiffness.

Rapid stress prediction of additively manufactured sandwich panels with lattice cores in thermal environments

Lattice-core sandwich panels (LCSPs) with fabricated by additive manufacturing have attracted extensive interest stemming from their exceptional mechanical properties and multi-functionalities. Nevertheless, the direct correlation among stress distributions in sandwiches, external loads, and ambient environments remains unclear. This study develops an analytical predictive model capable of efficiently capturing the mechanical response of LCSPs under various temperatures. The equivalent elastic modulus of lattice cores with different unit-cell aspect ratios is first determined according to finite element (FE) results. Subsequently, the thermo-mechanical field of the homogenized sandwich in various ambient temperatures is analytically predicted based on the higher-order shear deformation theory. Finally, truss stresses within lattice cores are directly calculated using an effective displacement transition method. The prediction exhibits outstanding consistency with FE simulations. Furthermore, the impact of several key variables on the truss stress distribution is demonstrated based on parametric analysis. The results reveal that the vertical truss is the main object of bearing the major uniaxial compressive load within the body-centered cubic (BCCZ) and vertically reinforced face-centered cubic (F2CCZ) lattice cores. The increased transverse layer number/power index and/or the smaller length-to-thickness ratio contribute to a significant reduction in inclined/vertical truss stresses. In contrast, the elevated longitudinal layer number, ambient temperature, and thermal expansion of face sheets result in stress accumulation. Furthermore, the stress distributions in BCCZ LCSPs are commonly higher than those within F2CCZ LCSPs. These results can provide a useful path for the design and fabrication of additively manufactured sandwich panels with desired mechanical properties.

Bending performance of cross-laminated timber constructed from fibre-managed Eucalyptus nitens under short-term and long-term serviceability loads

AbstractCross-laminated timber (CLT) has become a notable building material due to its structural efficiency, reliability and sustainability. In this study, the bending performance of three-layered CLT constructed from fibre-managed Eucalyptus nitens (E. nitens) was investigated under short-term and long-term loadings. Linear-elastic four-point bending testing was used to determine the maximum serviceability loading capacity before they reached the suggested deflection limits. A pilot study was conducted to investigate the creep behaviour of E. nitens CLT through long-term bending tests in a controlled environmental room. The study suggested that E. nitens CLT has higher serviceability loading capacity and lower creep ratio compared to CLT made from strength-class C24 spruce. The investigations of various configurations of E. nitens CLT panels based on structural grades implemented in top, cross, and bottom layers have revealed different short-term and long-term bending performances. The grade of transverse layers has been found to be the most important factor in improving the bending creep performance of E. nitens CLT. Two modelling equations were employed to perform curve fitting on the experimental creep ratio with time. The conventional power-law modelling tends to underestimate the longer-term creep ratio when compared to a recently developed nonlinear regression modelling equation that takes environmental conditions into account. The mean estimated creep ratio after 50 years was 1.77 for E. nitens CLT, and 1.89 for the C24 spruce CLT. The present study is a pilot investigation to increase the understanding of performance of the newly developed CLT made from fibre-managed plantations E. nitens, with particular emphasis on its creep behaviour. The results of this study provide valuable contributions for future research in this field, and ongoing commercial production of E. nitens CLT.

Study on the Bending-Shear Properties of Concrete-Filled Circular Carbon Fibre Reinforced Plastic Steel Tubes.

In order to study the bending-shear performance of CFRP concrete-filled steel tubes, static tests were conducted on 15 circular concrete-filled CFRP steel tube bending-shear specimens. For all specimens, Ds was 120 mm, ts was 2 mm, and ml was 1. The shear displacement (V-Δ) curve of the specimen and the collaborative work between the steel tube and CFRP are discussed. ABAQUS was applied to simulate the V-Δ curve and failure mode of the specimen. We explored the effects of CFRP layers, material strength, the steel ratio, and the shear span ratio on the bending-shear performance of components. The experimental results show that a steel tube and CFRP can work together. As the shear span ratio increased, the bearing capacity and stiffness of the specimen decreased. An increase in the number of transverse CFRP layers could improve the bearing capacity of the specimen, but it had no significant effect on the stiffness. Calculating the elastic stage stiffness and bearing capacity of 15 short columns of test and FE curves revealed an average error of 6.71% and a mean square error of 0.83 for the elastic stage stiffness. The simulation results of the established finite element model are in good agreement with the experimental results. The average error of the bearing capacity was 3.88%, with a mean square error of 0.94. Based on experimental and finite element results, the moment shear correlation equation for concrete-filled CFRP steel tube bending-shear members is presented.

An impact of Richardson number on the inclined MHD mixed convective flow with heat and mass transfer

AbstractThe two‐dimensional mixed convective MHD flow with heat and mass transfer is investigated for its behavior with Dufour and Soret mechanisms over the porous sheet. The copper–alumina (Cu–Al2O3) hybrid nanoparticles are used in the base fluid water. The governing system of partial differential equations is converted into a system of ordinary differential equations via similarity transformations, obtaining the solution for velocity, temperature, and concentration fields in exponential form. The problem is demonstrated in the Darcy–Brinkman model, the impact of included parameters such as Richardson number, magnetic field, and Dufour numbers are studied for the obtained solution with the help of graphs. Increasing the magnetic field decreases both transverse and axial velocity profiles. Increasing the magnetic field and Richardson's number decreases the solution (Al2O3–H2O). Increasing the values magnetic field and Richardson's number decreases both transverse and axial velocity profiles. Increasing the values of the Dufour effect increases the axial and transverse velocity boundary layer. The magnetohydrodynamic hybrid nanofluid flow over porous media works efficiently in liquid cooling and, therefore, has significant applications in industrial heating and cooling systems, solar energy, magnetohydrodynamic flow meters and pumps, manufacturing, regenerative heat exchange, thermal energy storage, solar power collectors, geothermal recovery, and chemical catalytic reactors.

Radially transverse isotropic inclusions in isotropic elastic media: Local fields, neutral inclusions, effective elastic properties

Radially transverse isotropic inclusions in homogeneous isotropic elastic host media are considered. Mellin transform method is used for solution of the volume integral equation of the problem for an isolated inclusion subjected to a constant external stress (strain) field. The tensor structure of the solution is revealed with precision to three scalar functions of the radial coordinate, and the system of ordinary differential equations for these functions is derived. For multilayered radially transverse isotropic inclusions with constant elastic coefficients inside layers, explicit solution of these equations is obtained. An efficient numerical algorithm of solution for inclusions with an arbitrary number of the layers is proposed. Neutral inclusions that do not disturb homogeneous external fields applied to the medium are considered. It is shown that an inclusion with an isotropic core and radially transverse isotropic external layer can be weak neutral by appropriate choice of the layer elastic constants. The effective field method is used for determination of the effective elastic stiffness tensor of a homogeneous isotropic medium containing a random set of radially transverse isotropic inclusions.

The effect of the pitch of the boards in the transverse layer on the deformability and stress distribution in a threelayer CLT panel rigidly clamped on both sides

CLT panels are made by gluing several layers of boards crosswise, which provides them with high load-bearing capacity and bending resistance. In addition to the number of layers in the panel, the deformability and bearing capacity are influenced by the geometric parameters of the plate, the way the layers are attached to each other, the way the structure is supported, etc. Due to the fact that the material has recently been used in construction, many issues remain poorly understood, and therefore there is an opportunity and need to optimize some aspects both in the CLT panels themselves and in the way they interact with other building structures.In this article, the influence of the pitch of boards in the transverse layer on the deformability and stress distribution in a three-layer CLT panel rigidly pinched on both sides was studied. Numerical studies of the finite element method (FEM) were carried out using the computing complex SCAD+. The computational model of the plate in this study is a composite orthotropic plate with rigid connections between the layers. The result of the study is numerical data reflecting the dependence of the distribution of normal stresses OX and OY and the transverse deformation of the plate on the pitch of the lamellae (boards) in the bottom layer. Projections of the computational model with normal stress isofields on the stretched and compressed plate layer are also obtained. This makes it possible to identify general patterns of stress distribution and deformation changes with variations in geometric parameters for this type of support for their use in the design of building structures using CLT panels as well as in the optimization of the structure in order to increase the cost efficiency of resources.

Efficient mechanical modeling of sandwich panels with functionally graded lattice cores under thermal environments

3D-printed sandwich panels with functionally graded (FG) lattice cores have garnered widespread attention owing to their outstanding mechanical performance. However, the straightforward interplay between the service environment, strut structure, and their mechanical behavior has not been systematically explored. In this study, an analytical two-step prediction modeling is developed to efficiently obtain the mechanical response of 3D printed sandwich panels with FG lattice cores. Initially, the effective elastic moduli of FG lattice cores are identified based on finite element (FE) analysis. The stress and deformation of the core-homogenized sandwiches in thermal environments are predicted using the higher-order shear deformation theory. Subsequently, the de-homogenization is employed to calculate strut stresses. The prediction shows excellent agreement with the FE results in the literature. Furthermore, parametric analysis is performed to uncover the impact of crucial variables on the strut stresses within the FG lattice cores. The results show that the strut stress decreases with the increased transverse layer number and power index, while increasing with the higher ambient temperature, length-to-thickness ratio, and thermal expansion of the sandwich panels. The proposed model can serve as an efficient tool for the design and printing of high-performance lattice-core sandwich panels.

Study on the Quasi-Ductile Fracture Behavior of Glubam: The Role of Fiber Distribution.

Cracking in fibrous composites is inevitable, and the fracture pattern is influenced by its fiber distribution. Bamboo fibrous composites have a distinct fiber distribution, which makes them an excellent material for studng the relationship between fiber distribution and fracture mode. Glued laminated bamboo is a bi-directional bamboo fibrous composite, which is called glubam for short. Its vertical thickness is about 28 mm, and the ratio of the number of longitudinal fiber layers to the number of transverse fiber layers is 4:1. This study conducted three-point bending fracture tests on single-edge notched specimens of glubam to investigate its mode-I fracture characteristics in the transverse vertical direction. The deformation curves show that the specimens still have the load-carrying capacity after reaching the maximum load, and the load shows a trend of step-like decrease, exhibiting a quasi-ductile fracture behavior. Overall, the fracture process can be divided into four stages, including linear, softening, quasi-ductile, and failure stages. In this study, based on certain assumptions, the prefabricated notch length a0 was adjusted according to the position of the transverse fibers. Subsequently, the non-linear elastic fracture mechanics method was employed to calculate the fracture parameters of glubam during the softening and quasi-ductile stages, including the fracture toughness KIC* and fiber tensile strength ft. The deviation of the fracture parameters between the two stages is within 10%, indicating that the correction of the a0 is correct. This indirectly proves that the staggered structure formed by longitudinal and transverse fibers is responsible for the quasi-toughness fracture of glubam. Finally, this study summarized and analyzed the quasi-ductile fracture behavior and found that materials or structures exhibiting quasi-ductile fracture behavior often possess a staggered structure. This staggered structure makes the crack in the form of semi-stable propagation, while the load decreases in a step-like manner.

Harnessing the potential of transverse thin cell layer culture for high-frequency micropropagation of Thai ginseng (Kaempferia parviflora Wall. Ex Baker)

In vitro plant propagation techniques play an important role in modern agriculture and horticulture, offering efficient methods for the accelerated multiplication of high-value plant species. Thin cell layer (TCL) culture technique has emerged as a promising approach for large-scale in vitro plantlets production. This study explores the potential of TCL culture as a cutting-edge strategy to enhance the efficiency of multiple shoots formation in Kaempferia parviflora. An attempt was also made to look into the synergistic effects of cytokinin and auxin [6-benzyladenine (BA) - indole-3-acetic acid (IAA)] during micropropagation. Shoot tip explants (from rhizome sprouts) were cultured onto Murashige and Skoog (MS) medium enriched with BA (2.0–8.0 mg/L) and IAA (0.2–0.8 mg/L) in combination where the highest shoot number (7.3 shoots/explant) and length (5.9 cm) was obtained in 8.0 mg/L BA and 0.8 mg/L IAA. Subsequently, the transverse thin cell layer (tTCL) culture system was successfully utilized whereby the shoot tip explants were individually sliced from tips at the meristem and cultured onto MS medium supplemented with BA (2.0–8.0 mg/L) and IAA (0.2–0.8 mg/L) in combination. The regenerated tTCLs exhibited the highest shoot multiplication (9.3 shoots/tTCL; 28 shoots/shoot tip) and length (5.3 cm) in 4.0 mg/L BA + 0.8 mg/L IAA, thus significantly increased number of plantlets were obtained from tTCL culture (953.0 plantlets) compared to shoot tip culture (527.7 plantlets) after six sub-culture cycles. The tTCL regenerants were successfully acclimatized (with 90% survival) and displayed active growth. Genetic fidelity assessment via inter-simple sequence repeats, conserved DNA-derived polymorphism, directed amplification of minisatellite-region DNA, and start codon targeted polymorphism marker systems suggested that a very low level (5.8%; 148 out of 2572 scorable bands) of polymorphism was detected whereas the ploidy level remained unchanged, confirmed by flow cytometry analysis. The implementation of tTCL culture, coupled with a controlled sub-culture regimen, holds significant potential for the efficient commercial-scale production of K. parviflora.

Bending and Vibration Behaviour of CLT-Steel Composite Beams

A strengthening of cross-laminated timber (CLT) by a composite effect with steel girders can widen the application of CLT ceilings to spans over 8 m. Most possible shear connectors are not stiff enough to ensure a completely rigid composite. At present, it has not been sufficiently clarified how the elastic bending behaviour is affected by the influences of the flexibility of continuously and discontinuously shear connectors, the number of transverse layers of the CLT and the span width. Thus, 4-point bending tests and vibration tests were performed with different cross-section configurations and two different shear connectors in continuous and discontinuous spacing in spans of 8.10 and 10.80 m. To date, no comparable bending tests have been carried out in these spans, with more than five CLT-layers and discontinuously arranged shear connectors. The composite beams deformed linear-elastically until the yield strength of the steel was reached. The composite effect increased the elastic bending stiffness up to twofold compared to no composite. Increasing the span resulted in a higher bending stiffnesses. The elastic bending stiffness of the composite beams with shear studs was significantly lower than with fully threaded screws. For a worthwhile composite effect, both materials should contribute a balanced share of the stiffness. A larger share of the CLT in the bending stiffness compared to the steel girder created a higher elastic limit load capacity but an equivalent bending stiffness. It is necessary to discuss which cross-sectional configurations are appropriate in terms of load bearing capacity, economic efficiency and sustainability. To assess the practical application potential in spans between 8 and 12 m, the tests were additionally evaluated for the equivalent load level for the serviceability limit state of office or industrial buildings. For spans of 8.10 m, the limits according to EC5 for the initial deflection of L/300 and fundamental frequency of 8 Hz can be met. For spans of 10.80 m, only less strict deflection limits are achieved. However, by increasing the degree of composite through more shear connectors, compliance with the limit values mentioned could already be possible with the cross-sections tested. In case of fire, it may be sufficient to consider only the CLT with the reduced cross-section method (EN 1995-1-2) for load transfer, even for longer fire durations.

ВЛИЯНИЕ ТОЛЩИНЫ ПОПЕРЕЧНОГО И ПРОДОЛЬНЫХ СЛОЕВ НА ДЕФОРМАЦИИ И НАПРЯЖЕНИЯ В 3-СЛОЙНОЙ ПЛИТЕ ДПК (CLT), СМОДЕЛИРОВАННОЙ КАК СОСТАВНАЯ ПЛАСТИНА

The study examines the effect of the transverse and longitudinal layers thickness of a three-layer CLT panel on the deformations and distribution of the resulting tensile and compressive normal stresses in the layers. Due to the current lack of a unified methodology for the calculation of multilayer materials with orthotropic properties in layers at present, we carried out the study with the SCAD+ computing complex using the finite element method. The studied model was a composite orthotropic plate. The authors obtained, systematized and clearly showed the dependences of the values of the maximum deflection and normal stresses on the thickness variation of transverse and longitudinal lamellae in a three-layer CLT panel under different boundary conditions. As a result of the study, we found that the greatest influence on the deflection and normal stresses along the span was caused by the longitudinal slab layers. The results provide a better insight into the relationship between deformability and stress distributions and the variation of transverse and longitudinal layer thicknesses. The obtained patterns can be used in the design of building structures using CLT panel.

Electrochemical shock and transverse cracking in solid electrolytes

Ceramic solid electrolytes are crucial for electrochemical devices, including emerging solid-state batteries. However, they are susceptible to degradation and failure under harsh conditions, leading to dendrite growth, cracking and short circuits. While longitudinal lithium dendrites have been identified as a primary degradation mechanism, recent experiments have revealed transverse reduction fronts and bowl-shaped cracks that differ significantly from the longitudinal picture. We propose an electrochemical shock model to explain these transverse degradation modes in solid electrolytes (SE) and mixed ionic-electronic conductors (MIEC), where SE is taken to be the very weakly electronic leaking limit of MIEC. The model describes a transverse layer with an abrupt oxygen potential jump over a short distance, caused by the electronic transport bottleneck on the Brouwer diagram. Using Li7La3Zr2O12 as an example, we demonstrate that even minor nonuniform lithium distribution associated with an electrochemical shock can induce stress concentrations, resulting in electrolyte cracking and bowl-shaped cracks. The electrochemical shock model highlights the significance of finite electronic conductivity in the degradation of SE and MIEC, providing insights for the design of durable solid electrolytes.

Optimization of Different Auxin and Cytokinin Combination in Nutrient Medium for Establishment of Optimal in vitro Multiple Plantlet in Ficus carica L. cv Siyah Orak

Ficus carica Linnaeus is a flowering plant under the Moraceae family, usually propagated conventionally from cuttings due to the seeds being non-viable. However, this method is prone to diseases, and pests, time-consuming and space-intensive. Therefore, other methods are needed to overcome these issues. This study was conducted to induce callus and multiple shoots via plant tissue culture techniques enabling mass production of fig plants. Initially, leaf segments of Ficus carica L. cv Siyah Orak were cultured on different MS media strengths (¼, ½, ¾,1 MS) to induce callus. The highest callus means weight was observed on explant cultured in ¾ MS media (875±0.036). Callus was proliferated by subculturing explant into ¾ MS media supplemented with different concentrations of TDZ (0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 mg/L). MS media (3/4) supplemented with 2.0 mg/L TDZ (920±0.03) shows the best result for callus proliferation. Callus induction using transverse and longitudinal thin cell layers from nodal segments cultured on different MS media strengths (¼, ½, ¾,1 MS) shows ¼ MS as the optimum media for both tTCL (100±0) and lTCL (96.7±0.15). Friable callus (%) was observed the highest on ½ MS (63.33±0.55) and ¼ MS (76.67±0.50) media for both tTCL and lTCL, respectively. As for the number of leaves produced, both tTCL (0.83±0.0.28) and lTCL (1.00±0.33) explant showed the best results in ¼ MS media. Apical buds produced the highest mean for both the number of leaves and length of the shoot on 1MS media supplemented with 2.0 mg/L BAP (3.5±0.20, 13.73±0.66), respectively. For root formation (%) and number of roots, both show the best results in media supplemented with 2.5 mg/L IAA (10±0.31, 0.83±0.50). It can be concluded that the best shoot growth performance was observed from apical bud cultured on 1MS media supplemented with 2.0 mg/L BAP+ 2.5 mg/L IAA.

Flexural performance of 3D printed concrete structure with lattice infills

Large-scale 3D printed concrete structures with lattice infill will result in lightweight components with high mass-specific strength, and faster fabrication, compared to conventional casting methods. However, the effect of different infill patterns on mechanical performance is still not addressed clearly in many scientific publications. This study investigates the bending performance of 3D-printed concrete beams with four infill patterns such as lattice, triangular, lattice-triangular, and sinusoidal tested in vertical (layer deposition direction) and transverse (layer translation direction) loading directions. The load versus displacement curves and crack propagation patterns are investigated both via Finite Element (FE) simulations and experiments. The FE results corroborated by experiments indicated that the triangular patterns perform better than lattice-shaped infill counterparts particularly under the transverse loading direction exhibiting the highest flexural deformation resistance capacity. The findings of this study would be useful in latticing large-scale concrete structures for diverse applications.

ВЛИЯНИЕ ШАГА ДОСОК В ПОПЕРЕЧНОМ СЛОЕ НА ДЕФОРМАТИВНОСТЬ И РАСПРЕДЕЛЕНИЕ НАПРЯЖЕНИЙ В ТРЕХСЛОЙНОЙ CLT-ПАНЕЛИ, СМОДЕЛИРОВАННОЙ КАК СОСТАВНАЯ ПЛАСТИНА

Cross-laminated timber (CLT panel) and its structures are interesting for engineers and scientists due to its low installation weight, ease of fabrication, high strength and durability. However, many aspects remain under-researched. In particular, the issue of changes in deformability and bearing capacity of slabs under different variations of geometrical parameters in the layers of the structure had not been studied. We studied the effect of the pitch of the transverse layer in a three-layer CLT panel on the deformation and distribution of the resulting normal stresses. The model was a composite orthotropic plate. Because of the lack of a unified methodology for calculating layered materials with orthotropic properties in the layers, the studies were carried out by means of the SCAD+ computational complex using the finite element method. The article obtained, systematized and clearly showed the deflection and stress dependences of varying lamella pitch in the transverse layer of a three-layer CLT panel. The results provide a better understanding of the dependence of deformability and stress distributions on the variation of board pitch in the transverse layer of the slab. In the future, this will allow us to explore opportunities to optimize the design of the CLT panel in order to reduce its weight, cost, reduce resource consumption while maintaining the required characteristics.

Out-of-plane shear strength of cross-laminated timber made of Japanese Larch (Larix kaempferi) with various layups and spans

Cross-laminated timber (CLT) is a promising construction material. When CLT is used for horizontal applications, shear stress occurs in the out-of-plane direction and can fracture the transverse layers owing to the rolling shear. The out-of-plane shear strength of the CLT can be evaluated by an out-of-plane loading test and is affected by the CLT layups and/or span conditions. In this study, we conducted out-of-plane loading tests on 3-layer 4-ply, 5-layer 7-ply, 7-layer 7-ply, and 9-layer 9-ply CLT made of Japanese larch (Larix kaempferi) under various spans and investigated the effect of layups and spans on the out-of-shear strength. The fracture modes of the specimens were classified into three types: shear fracture, shear fracture accompanied by bending fracture, and bending fracture. The out-of-plane shear strength of the specimens except for the 9-layer 9-ply ones decreased as the span increased, and then converged to a constant value (1.0–1.5 kN/mm2). In addition, the shear strength decreased exponentially as the number of laminae in the transverse layers increased and then converged to a constant value (1.0–1.5 kN/mm2). The out-of-plane shear strength of the 9-layer 9-ply specimens decreased as the shear span increased; however, the converged value with a longer span could not be calculated because the tests were conducted under only three-span conditions. The shear strength of 3-layer 4-ply specimens was lower than that of the other layups. The results of the Monte Carlo simulation of the shear strength of the laminae in the transverse layers showed that a model, which assumed that the minimum shear strength of the laminae in the transverse layers determined the shear strength of a specimen, tended to correspond with the decreasing tendency of shear strength with longer spans. The results showed that the weakest link model for the out-of-plane shear fracture of the CLT would relate to a specimen with long span.