Search

The study aims to present the results of paper compression under an axial load. Different heights of samples subjected to compression were taken into account. The main goal of the analysis was to determine experimentally the maximum compression load. In addition, numerical models based on the finite element method (FEM) were validated to refer to empirical results. The performed numerical simulations were founded on Green–Lagrangian nonlinear equations for large displacements and strains. The progressive failure of the compressed orthotropic material after exceeding maximum stresses was based on Hill's anisotropy theory. Nonlinear calculations were conducted by using a typical Newton–Raphson algorithm for achieving a sequence convergence. The accuracy of the developed model was confirmed experimentally in compression tests. The technique of analysing the shape of the compressed paper sample on the basis of images recorded during the measurement was used. The obtained test results are directly applicable in practice, especially in the calculation of the mechanical properties of corrugated cardboard and in determining the load capacity of cardboard packaging. Knowing the maximum compressive stress that packaging paper can withstand allows packaging to be properly designed and its strength assessed in the context of the transport and storage of goods. [ABSTRACT FROM AUTHOR]

Poly (p -phenylene benzoisoxazole) (abbreviation: PBO) paper honeycomb core (PPHC) is gradually being used as a novel honeycomb material for lightweight structures in high temperature environment. However, compressive properties of PBO paper can hardly be obtained accurately due to the thin thickness and easy-to-buckling of the paper. Therefore, the Short Span Test Method is applied to obtain the compressive strength of PBO paper. The compressive strength and failure of PBO paper are characterized experimentally for the first time. The strength of compression is then used in theoretical formula to study the compressive behaviors of PPHC and the reasonable agreement with the experimental results indicates the validity of the compressive strength. Furthermore, the failure mode of PPHC subjected to compressive loads is obtained, which presents the importance of the accurate characterization on the compressive strength of PBO paper. [ABSTRACT FROM AUTHOR]

The use of ultrasonic tools in paper forming results in highly dynamic mechanical alternating stress, which causes a changed material load. This work aimed to determine the influence of the ultrasonic process parameters of amplitude, ultrasonic time, and static contact pressure and to characterize the material compression during the ultrasonic-assisted forming of paperboard. To achieve this, a method was developed to determine the static, dynamic, and irreversible material compression during the gap-controlled forming of paper. The results showed that the ultrasonic amplitude, the gap pressure, and their second-order interactions had an important influence on the irreversible material compression. With the new method, the irreversible material compression could be increased up to 480% compared to the equivalent static load case. [ABSTRACT FROM AUTHOR]

The objective of this work was to examine opportunities for reducing the overall cost of lignocellulose hydrolysis to fermentable sugars. Primary sludge (PS), a negative cost lignocellulosic feedstock, was hydrolyzed sludge using a commercial cellulase preparation (Cellic® CTec2) in presence of non-ionic surfactants. Polyethylene glycol (PEG) 4000 facilitated the highest hydrolysis yield of 74.4% which represented a 2-fold increase over the control without surfactant. Response surface methodological analysis at four variables (hydrolysis time, solids, enzyme, and surfactant loadings) revealed that enzymatic hydrolysis was significantly enhanced by the interactive effect of all factors with solids and enzyme loadings as the most significant parameters (p < 0.05). Using ultrafiltration, 40% of the cellulase enzyme was recovered from the enzymatic hydrolysate and reused on fresh PS substrate. The hydrolysate fermentabilty was evaluated in production of 9.7 g/L bioethanol at 92% ethanol yield using Saccharomyces cerevisiae , and in production of 37.8% biolipids by the oleaginous yeast Cutaneotrichosporon oleaginosum at a carbon to nitrogen ratio of 40. The compression load of a sample prepared from the unhydrolyzed PS solids was 102% higher than Portland cement. The potential for valorization of the unhydrolyzed solids as reinforcement material warrants further investigations. • Enzymatic hydrolysis of primary sludge was optimized using statistical methods. • Surfactants increased the enzymatic hydrolysis efficiency and yield. • About a third of the enzyme activity was recovered and recycled. • Enzymatic hydrolysate was evaluated in bioethanol and biolipid production. • Unhydrolyzed solids from sludge hydrolysis was assesses as reinforcement material. [ABSTRACT FROM AUTHOR]

The mechanical response of three different structural core sandwich panels in out-of-plane compression and shear has been analyzed. Specific core shapes examined are arc-tangent, wavy trapezoidal and hemispherical. Unit cells consisting of representative elements of the core attached to face sheets were selected for analysis. Both face sheets and core were assumed made from paper. Finite element analysis employing large deformation and rotations and orthotropic elastic–plastic behavior was used. The results show that the arc-tangent and trapezoidal cores are prone to collapse by extensive bending and buckling, whereas the hemispherical core behaved more stably in compression and shear. Core sheets with a hemispherical shape were prepared from copy paper sheets in a specially designed forming machine. Sandwich test specimens were prepared from this core and tested in out-of-plane compression, and the load-displacement response was compared to predictions from finite element simulations. The experimental and finite element results were consistent. [ABSTRACT FROM AUTHOR]

Gas diffusion layers (GDLs) are the most rigid layers in a 5‐layer or 7‐layer membrane electrode assembly (MEA) of a proton exchange membrane fuel cell. Therefore, in the fuel cell analysis, the mechanical properties of GDLs have a great impact on the stress distribution of the membrane as well as the performance of the whole cell. However, the mechanical properties of GDLs are not sufficiently studied. Nonlinear behavior of GDLs under cyclic compression is discussed rarely in literature. The existing model takes both constraints into consideration, but due to a geometrical oversimplification of the carbon paper microstructure, it shows some deviation, which cannot be overcome by selecting appropriate parameters. In this paper, the geometry of carbon paper microstructure has been reanalyzed. Based on the improved geometry formula, a modified model of carbon paper GDL is presented and verified by experimental data. Furthermore, both the experimental mechanical characteristics are achieved as support data for the improved model. [ABSTRACT FROM AUTHOR]

The early studies on mechanical model of paper honeycomb structures were always concentrated on static situation, however, paper honeycomb would meet some random events of impacting and vibration during the process of transportation. Considering the virtual working circumstance, dynamic experiments under medium and low strain rates were undertaken and corresponding models of mechanical properties were derived. There exists a certain strain-rate effect which leads to the difference of mechanical properties between dynamic and static condition. A mechanical model was given to estimate plateau stress and yield stress at different strain rates based on experimental data by employing the methods of Cowper–Symonds model and piecewise function. The conclusion can be applied to characterise and improve the compressive properties of paper honeycomb structure efficiency. [ABSTRACT FROM AUTHOR]

This paper proposes a meso-structural model for the discrete fibrous network of paper, which is able to upscale the irreversible phenomena from the underlying hygro-mechanics towards the effective behaviour at the macro-scale. The swelling of individual fibres, induced by moisture content variations, is transmitted to the network through inter-fibre bonds and governs the resulting effective material response. The present approach is based on a recently developed discrete meso-structural model for the reversible part of the response, which distinguishes between the influence on the hygroscopic behaviour of free-standing fibre segments and inter-fibre bonds. The network structure, fibre and bond geometries and hygro-elastic properties are explicitly incorporated. The major novelty of this contribution is the extended fibre constitutive model, enabling to describe some typical irreversible mechanisms and instability effects related to the history of the manufacturing. This extension strongly affects the effective material behaviour beyond the elastic range. Despite the valuable work in the literature, no papers can be found dedicated to meso-structural models including these phenomena. Using an appropriate homogenization strategy, the unit-cell is solved analytically, capturing irreversible shrinkage in restrained dried paper and the occurrence of local buckling within the bond for freely dried material. The proposed scale transition offers a deeper insight into the complex relation between the events occurring at the different length scales. The potential of the proposed methodology is demonstrated through the convincing agreement with experimental data obtained from the literature. [ABSTRACT FROM AUTHOR]

This paper deals with fatigue behavior of paper-based friction materials under cyclic compression to tension loading and damage behavior under cyclic compressive loading. The fatigue tests under out-of-plane compressive stress to slight tensile stress loading are conducted to evaluate fatigue strength of friction materials. The tests under cyclic out-of-plane compressive loading are also conducted to investigate influence of compressive stress and load cycles on damage behavior. Two kinds of friction materials are composed of aramid-based fiber and phenolic resin, and cellulose fiber and phenolic resin. Their fatigue strengths decrease with increasing load cycles. The damage density in both materials increases with increasing compressive stress and load cycles. [ABSTRACT FROM AUTHOR]

Dewatering on the paper machine takes place by gravity, suction, pressing, and evaporation. Optimizing the operation of the vacuum system is important, since the electricity consumption of the vacuum pumps might be one-fifth of the total electricity consumption of the paper machine. Vacuum dewatering involves large volumes of air penetrating the web. The present study presents four sets of measured air flow rates useful for designing industrial equipment. The mass flux of air increases with increasing applied vacuum and decreases with increasing basis weight. Paper technological parameters, such as fiber size and fiber flexibility, also influence the mass flux. [ABSTRACT FROM AUTHOR]

This paper presents 2 mathematical models to predict the initial peak stress and the plateau stress of corrugated paperboard which is simplified and regarded as the orthotropic plate under longitudinal compression. The resultant stress‐strain curve exhibits initial stiffening stage and a long plateau stage, where the initial peak stress determining the edgewise crush resistance of the board and most impact energy will be absorbed by the long plateau stage. By analyzing the elastic buckling of the board wall, a model of predicting the initial peak stress was obtained, while the plateau stress model was developed based on the gradual process of compression for corrugated board and energy conservation principle. Moreover, experiments were carried out to corroborate the presented model by comparing the predicted value with that by experiments, showing overall good agreement. It can be concluded that the proposed models can be applied for design of corrugated containers and cushioning packaging by corrugated paperboard. [ABSTRACT FROM AUTHOR]

This paper conducts the analytical investigation on the buckling of cylindrical shells with axially variable elastic modulus subjected to axial compressive load for the first time. First, it proves that the axially distributed elastic modulus can be expressed as the combination of constant and variable component. Then, governing differential equations for buckling analysis are derived and exactly solved by the combined perturbation method and Fourier analysis. Accordingly, the closed analytical solutions for the cylinder with arbitrarily variable elastic modulus are obtained, which reveal the explicit relations among buckling load, shell sizes and elastic modulus functions. Based on the presented analytical formulas, four types of elastic modulus variations for shell material which are uniform, periodic, linear and combined are studied in detail, and the results are also well verified. The derived analytical solutions in this paper can serve as benchmarks for buckling analyses of thin-walled cylinders with elastic modulus variations resulted from design, material manufacturing process, material imperfections and so on. [ABSTRACT FROM AUTHOR]

Copyright of Materials Science / Medziagotyra is the property of Kaunas University of Technology, represented by Prof. Rymantas Jonas Kazys and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• The shear properties of aramid paper are characterized for the first time.. • Characterizing shear properties of paper makes the prediction of honeycombs better. • The failure mode map of paper honeycombs subjected to complex loads is obtained. Aramid paper honeycomb cores have been widely used in lightweight structures. However, shear properties of aramid paper can hardly be obtained accurately due to the shear buckling of the paper. Therefore, we make the paper into a laminate to prevent buckling and apply the v-notched beam test method to the laminate to obtain the in-plane shear properties of aramid paper. The shear strength and failure strain of aramid paper are characterized experimentally for the first time. The properties are then used in finite element simulations to study the shear behaviors of paper honeycombs and the good agreement with the experimental results indicates the validity of the shear properties. Furthermore, the failure mode map of the paper honeycomb subjected to combined shear and compressive loads is obtained, which presents the importance of the accurate characterization on the shear properties of the paper. This characterization method can also be applied to other types of paper. [ABSTRACT FROM AUTHOR]

Restricted by the existing construction technology, there are a lot of disconnections in the angle steel components of transmission towers. At present, there are more studies on single angle steel or cross bracing, but less on the main member containing disconnection joints. According to the disconnection position in the main member, an upper end disconnection, middle end disconnection, and lower end disconnection were designed in this paper. At the same time, a tower section model of a connected main member and a tower section model of a disconnected main member were established and analyzed by finite element analysis. Considering the loadings acting on transmission towers, the two load conditions of axial loading and tension–compression coupling are set. Considering the loadings acting on transmission towers, the influences of the combination form of the inner and outer steel cladding and the steel cladding area ratio on the ultimate bearing capacity of the main member were studied under 72 groups of different tower sections applied with axial loadings. The influence of the disconnection joints on the stability of the tower section was studied under 24 groups of different tower sections applied with tension and compression coupled loading conditions. Referring to the specifications, the slenderness ratio correction factor formula of the disconnect main member can be derived. The results indicate that when designing the disconnection joint in the main member, it is recommended to choose a middle end disconnection with a steel cladding area ratio of 1.0. [ABSTRACT FROM AUTHOR]

Past research efforts have developed several self-centering beam-to-column connections for minimizing structural damage in steel moment frames after severe earthquakes. However, less focus has been on low-damage column base connections. Severe damage at the base of columns in conventional steel structures with moment frames is likely during an intense earthquake, rendering the building nonresilient. This paper evaluates the application of a recently developed viscoplastic damper in low-damage column base connections. The proposed viscoplastic damper is a rubber-steel core damper (RSCD), which consists of a high-damping rubber layer and several ductile steel bolts. The proposed column base connections prevent damage and inelastic deformations in the steel column and its base plate by allowing a rocking mechanism at the base of the column and limiting damage to easily replaceable steel bolts in the dampers. The paper discusses the design and behavior of the column base connections equipped with RSCDs. Continuum finite element models of RSCD dampers were developed and validated using experimental results. The rocking response was validated using experimental results for rocking columns with a silt damper. A total of 21 finite element models of rocking columns with RSCD were used to numerically examine the column response to combined axial loading and cyclic lateral loading. The influence of different parameters on the cyclic response of the proposed column base connections was also evaluated. These parameters are steel bolt diameter-to-length ratio (d/h), rubber thickness, column axial compressive load, number of bolts, and steel material type. The results confirmed the effectiveness of the proposed column base connection for minimizing damage to the steel column and its base plate. An optimal d/h ratio of 0.4 was found for the design of RSCDs. In addition, analytical formulas are presented to evaluate the yield and ultimate strength of the proposed column base connection, and the comparison with FEM results indicates that the presented mechanism has sufficient accuracy. [ABSTRACT FROM AUTHOR]

Numerical modelling of corrugated paperboard is quite challenging due to its waved geometry and material non-linearity which is affected by the material properties of the individual paper sheets. Because of the complex geometry and material behaviour of the board, there is still scope to enhance the accuracy of current modelling techniques as well as gain a better understanding of the structural performance of corrugated paperboard packaging for improved packaging design. In this study, four-point bending tests were carried out to determine the bending stiffness of un-creased samples in the machine direction (MD) and cross direction (CD). Bending tests were also carried out on creased samples with the fluting oriented in the CD with the crease at the centre. Inverse analysis was applied using the results from the bending tests to determine the material properties that accurately predict the bending stiffness of the horizontal creases, vertical creases, and panels of a box under compression loading. The finite element model of the box was divided into three sections, the horizontal creases, vertical creases, and the box panels. Each of these sections is described using different material properties. The box edges/corners are described using the optimal material properties from bending and compression tests conducted on creased samples, while the box panels are described using the optimal material properties obtained from four-point bending tests conducted on samples without creases. A homogenised finite element (FE) model of a box was simulated using the obtained material properties and validated using experimental results. The developed FE model accurately predicted the failure load of a corrugated paperboard box under compression with a variation of 0.1% when compared to the experimental results. [ABSTRACT FROM AUTHOR]

Nowadays, the trend to benefit from environmentally friendly waste and recycle it instead of incineration processes that can cause pollution in the environment to have a clean and green environment that is free from pollution and can work for a long time without consumption and damage. This study is designed to manufacture prosthetics limbs from PMMA (polymethyl methacrylate) reinforced with different weight percentages of waste paper layers (0%, 3%, 6%, 9%, and 12%) by the "hand lay" method. The tensile, flexural, impact, compression, and hardness of these composites are tested before and after adding weight percentages waste paper layers to determine the mechanical properties behavior. The average values of all the samples are collected and analyzed by one-way analysis of variance (ANOVA) to interpret the results. When discussing the results of mechanical tests, it is found that the addition (12%-waste paper layers) to (PMMA) increased the average values (tensile, flexural, impact, compression, and hardness) by 142.1%, 532.3%, 146%, 99.2%, and 6.37%; respectively, compared to the mean values of other samples. It is clear from this work there is an improvement in the properties of PMMA after strengthening with waste paper layers. [ABSTRACT FROM AUTHOR]

An increased demand for sustainable materials has led to intensive research in the field of three-dimensional paperboard forming. To date, this work has focused on forming processes with shape-giving tools. However, individual shapes are often required, especially for largeformat products. Incremental forming can be used in metal processing for small batches. In this article, the technology of incremental forming is transferred to paperboard. The results showed that elevated moisture content and a superimposed counter pressure significantly increased the forming limits. In addition, the use of polymer layers increased the shape accuracy. An extended understanding of the underlying mechanisms was achieved by analyzing the forming behavior. In uniaxial and biaxial characterization tests the influence of the moisture content on the forming behavior was investigated with conditions relevant for incremental forming. It was found that the bulge test is suitable to determine the most suitable moisture content regarding the forming limits and the spring back behavior in incremental forming. In addition, it was observed that the bearable elongations during the incremental forming of paperboard are significantly higher than in the established characterization tests. The reason for this is a compression of the fiber network during forming. [ABSTRACT FROM AUTHOR]

This paper presents the results of experimental testing of block masonry prisms and wallettes under uniaxial compression. The compressive load was applied in a direction perpendicular or parallel to the bed joints. Masonry prisms and wallettes were tested in the former direction, whereas only wallettes were tested in the latter direction. No influence of mortar strength or block thickness was observed on the cracking and failure patterns of specimens of similar type, although material crushing and spalling was marginally influenced by block strength. The cracking load for the assemblages tested normal to the bed joint was nearly 90% of the peak load capacity and higher as compared to 70% of the peak load capacity for the wallettes tested parallel to the bed joints. Similar load capacity and elastic modulus were observed for the prisms and wallettes tested normal to the bed joints. Whereas the strength for the wallettes tested parallel to the bed joints was 49%–83% less compared to those tested normal to the bed joints, their elastic modulus was nearly 25% higher. The experimental strength and strain values were compared with the existing analytical methods, which correlated well. [ABSTRACT FROM AUTHOR]

Origami-inspired design has recently emerged as a major thrust area of research in the fields of science and engineering. One such design utilizes Kresling-pattern origami to construct nonlinear springs that can act as mechanical bit memory switches, wave guides, fluidic muscles, and vibration isolators. The main objective of this work is to characterize the static equilibria of such springs, their stability, and bifurcations as the geometric parameters of the Kresling pattern are varied. To this end, a mathematical model which assumes that the different panels can be represented by axially deformable truss elements is adopted. The adopted model demonstrates that the shape of the potential energy of the spring is very sensitive to changes in its geometric parameters. This causes the static configuration to undergo several bifurcations as one or more of the geometrical parameters are varied. In particular, it is shown that the geometric parameter space of the Kresling pattern can be divided into five regions, each of which results in a qualitatively different spring behavior. Results of the axial truss model are verified experimentally demonstrating that, for the most part, the model is capable of predicting the loci and bifurcations of the spring's equilibria. Nevertheless, it is also observed that, away from the equilibrium points, the quasistatic behavior of the spring is not well-approximated by the axial truss model. To overcome this issue, a modified model is developed which accounts for (i) the rotary stiffness of the creases, (ii) self avoidance due to panel contact at small angles between the panels, and (iii) buckling of the creases under compressive loads. It is shown that the modified model is capable of providing a better overall qualitative approximation of the quasistatic behavior. [ABSTRACT FROM AUTHOR]

Slurry-infiltrated fiber concrete (SIFCON) has excellent potential for application as a new material with good crack resistance, impact resistance, and seismic performance. In this paper, SIFCON blocks were cast in a single pour using the custom-made two-dimensional directional steel fiber placement device, followed by compressive testing. Based on the test results, the effects of fly ash substitution rate, steel fiber aspect ratio, and steel fiber volume fraction on the compressive bearing capacity and ductility of SIFCON blocks were investigated. The results indicate that the custom-made device in this paper effectively achieves the directional placement of steel fibers, offering a cost-effective solution that optimizes the construction process. Regarding the test results, it was observed that the compressive bearing capacity of SIFCON blocks decreases linearly with increasing fly ash substitution rate, while the addition of fly ash improves the ductility of the blocks. Notably, a 31% decrease in bearing capacity was noted when the fly ash substitution rate increases from 0% to 40%, whereas the ductility ratio increased by 99% for the same substitution rate range. Furthermore, the results revealed a positive correlation between the bearing capacity and ductility of SIFCON blocks with higher steel fiber aspect ratios and volume fractions. Specifically, the bearing capacity increased by 19% and 33% with steel fiber aspect ratio increments from 33 to 70 and volume fraction increases from 10% to 14%, respectively. Additionally, the ductility ratio of the test blocks increased by 104% when the aspect ratio of the steel fibers increased from 33 to 70, and by 37% when the volume fraction of steel fibers rose from 10% to 14%. [ABSTRACT FROM AUTHOR]

The methods employed to calculate the axial bearing capacity of a helical pile depend on the shear failure model around the pile, which is also influenced by the spacing and diameter of the helical plates. However, studies on the transition of the failure mode and the load transfer mechanism with the change of helical plate spacing and diameter in cohesionless soil subjected to axial compressive load were limited. Thus, this paper investigated the effects of helix diameter and spacing on the axial compressive load-bearing capacity, shear failure model, and load transfer mechanism of helical piles with two helical plates embedded in the homogeneous medium and dense sands, as well as in the stratified medium to very dense sand. Axial loading tests on helical piles with various helix diameters and spacings were simulated using a two-dimensional finite element program with axisymmetric modeling to obtain the load-settlement curve, which was later used to estimate the ultimate bearing capacity of the helical piles. The ultimate bearing capacity of the helical piles was also computed using the conventional methods, i.e., the individual bearing and cylindrical shear methods, and then compared to the numerical-based axial bearing capacity. The stress-strain behaviors of pile and soil were modeled using the Linear Elastic and Mohr-Coulomb material models, respectively. The results show that the numerical-based ultimate bearing capacity of a helical pile increased with increasing the diameter and spacing of the helix. However, the ultimate bearing capacity computed using conventional methods did not show this trend. Then, the transition from the cylindrical shear to the individual bearing failure mechanism occurred at a spacing ratio (i.e., helical plate spacing divided by its diameter) of about two. Ultimately, the load transfer curves indicate that the helical plates mainly supported the applied load. [ABSTRACT FROM AUTHOR]

The structural components inside power transformers are commonly made of high-density pressboard, due to its suitable mechanical and dielectric properties. Among these components are the spacers used in the windings of transformers, which are subjected to compressive loading during operation. The spacers are immersed in dielectric liquid and subjected to high temperatures and chemical reactions during the lifespan of the transformer, which result in the degradation of their dielectric and mechanical properties. The performance and reliability of the power transformer greatly depends on its mechanical integrity, so it is necessary to understand how ageing degrades the mechanical response of the high-density pressboard. In this study, spacers made of high-density pressboard and pieces of copper conductor were immersed in uninhibited paraffinic oil and aged at 150 °C for different periods of time, trying to realistically represent the process suffered by a power transformer during its whole lifespan. The evolution caused by the thermal ageing over some chemical parameters (acidity and moisture content) and dielectric properties (AC breakdown voltage, dielectric dissipation factor, resistivity and degree of polymerisation) of the oil and the pressboard was studied experimentally. Compressive mechanical tests were performed on samples of the aged high-density pressboard, and the compressive stiffness during the ageing process was related with other chemical and dielectric parameters. [ABSTRACT FROM AUTHOR]

A ship equipment pedestal is a structure that connects power equipment to a hull. It must have a high load-bearing capacity and the ability to withstand large impact loads. In this paper, a novel structure with a positive-negative Poisson's ratio is proposed. The deformation mechanism and mode of this structure under quasistatic compression loading are analysed via numerical simulation. Based on this new structure, a multicellular pedestal is designed, and its bearing capacity and impact resistance are analysed. The structural parameters of the pedestal are optimized. An experiment is conducted to evaluate the impact resistance of the pedestal model, which confirms that the proposed multicellular pedestal exhibits excellent impact resistance. [ABSTRACT FROM AUTHOR]

The mechanical properties of deep rock masses are significantly influenced by temperature and other factors. The effect of temperature on the strength of deep rock masses will pose a serious challenge to deep resource exploitation and engineering construction. In this paper, the thermal-mechanical coupling calculation model is established by particle flow code (PFC2D) to study the uniaxial compression response of rock masses with microcracks after temperature load. The strength of failure, microcracks, and strain was analyzed. The results show that: (i) When the soft rock thickness ratio Hs/H < 0.5, the displacement caused by the applied temperature is concentrated at the structural plane, and the contact force is concentrated at the end of the initial microcrack. When Hs/H ≥ 0.5, the displacement caused by the applied temperature is concentrated on both sides of the initial microcrack, and the contact force is concentrated in the hard rock area. (ii) The number of microcracks decreases with the increase of soft rock thickness under different working conditions. When the soft rock thickness ratio Hs/H < 0.5, the relationship curve between the number of microcracks and the vertical strain shows two stages of change. When Hs/H ≥ 0.5, the relationship curve between the number of cracks and the vertical strain changes shows three stages of change. (iii) When the soft rock thickness ratio Hs/H < 0.5, the failure strength decreases with the increase of soft rock thickness ratio at T = 100°C and 200°C. When T = 300°C and 400°C, the failure strength decreased first and then increased. When Hs/H ≥ 0.5, the failure strength increases with the increase of soft rock thickness at T = 200°C, 300°C, and 400°C. At T = 100°C, the failure strength decreases with the increase of soft rock thickness. [ABSTRACT FROM AUTHOR]

This paper presents the problem of natural vibration of a two-stage hydraulic cylinder subjected to Euler compression load. The considered hydraulic cylinder is freely supported at both of its ends. The linear vibration problem of the telescopic hydraulic cylinder is based on the kinetic stability criterion using Hamilton’s principle and the Bernoulli-Euler theory. The stiffness of the guide and sealing elements between successive stages of the hydraulic cylinder were considered in this paper. These stiffnesses were modelled using translational and rotational springs. The effects of cylinder wall thickness, piston rod diameter, and thickness of guiding and sealing elements on the natural vibration of the system were analysed. Results are presented in the form of characteristic curves on the plane load – natural frequency with different parameters characterizing the considered hydraulic cylinder. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Featured Application: This study presents a new pullback load calculation model from the perspective of pipe–borehole wall contact. Pipeline pullback load is a crucial basis for drill rig selection and pipeline strength design. This paper presents a new pullback load calculation model from the perspective of pipe–borehole wall contact. The pipe–borehole wall contact analysis includes the distribution of contact pressure and the relationship between the external load and compressive displacement. The friction force between the pipe and the borehole wall was calculated based on the pipe–borehole wall contact analysis and adhesion theory without depending on the empirical friction coefficient. The effects of the eccentricity were also considered when calculating the fluid drag force. Through case studies, we verified the applicability of the model and discussed the possible reasons for the errors between the theoretical and field-measured results. This study can provide a helpful tool for analyzing the pipe–borehole wall contact and pullback loads for horizontal directional drilling. [ABSTRACT FROM AUTHOR]

As basic structural components of the ship hull, stiffened plates suffer both thrust and shear loads while ships sail in rough sea environments. In order to guide the scaled model design effectively, the similarity law is investigated in this paper. The parameters that determine the nonlinear behaviour of the stiffened plate under compression and shear loading are defined and the nonlinear similarity method is improved. This method is applied to design a scaled model under combined bending and torsional moment, and the collapse test is conducted to research the collapse characteristics. The collapse behaviour of actual ship structures under combined loads predicted by the model test is compared with that obtained by the nonlinear finite element analysis. The good agreement represents the capability of the newly improved nonlinear similarity law. The present research provides a proper way to investigate the collapse characteristics of actual ship structures through a model test. [ABSTRACT FROM AUTHOR]

Peeling wheat yields higher-quality flour. During processing in a flaking machine, wheat kernels undergo continuous compression within the machine's chamber. As this compression persists, damage to the kernels intensifies and accumulates, eventually leading to kernel breakage. To study the damage characteristics of wheat kernels during peeling, this study established a continuous damage model based on Hertzian contact theory and continuous damage theory. The model's accuracy was validated through experiments, culminating in the calculation of critical parameters for wheat peeling. This study focused on different wheat varieties (Ningmai 22 and Jichun 1) and kernel sizes (the thicknesses of the small, medium, and large kernels were standardized as follows: Ningmai 22—2.67 ± 0.07 mm, 2.81 ± 0.07 mm, and 2.95 ± 0.07 mm; Jichun 1—2.98 ± 0.11 mm, 3.20 ± 0.11 mm, and 3.42 ± 0.11 mm). Continuous compression tests were conducted using a mass spectrometer, and critical damage parameters were analyzed and calculated by integrating the theoretical model with experimental data. The test results showed that the average maximum crushing force (Fc) for small, medium, and large-sized kernels of Ningmai 22 was 96.71 ± 2.27 N, 110.17 ± 2.68 N, and 128.41 ± 2.85 N, respectively. The average maximum crushing deformation (αc) was 0.65 ± 0.08 mm, 0.68 ± 0.13 mm, and 0.77 ± 0.17 mm, respectively. The average elastic–plastic critical pressure (Fs) was 50.21 N, 60.13 N, and 59.08 N, respectively, and the average critical values of elastic–plastic deformation (αs) were 0.37 mm, 0.38 mm, and 0.39 mm, respectively. For Jichun 1, the average maximum crushing force (Fc) for small-, medium-, and large-sized kernels was 113.34 ± 3.15 N, 125.28 ± 3.64 N, and 136.15 ± 3.29 N, respectively. The average maximum crushing deformation (αc) was 0.75 ± 0.11 mm, 0.83 ± 0.15 mm, and 0.88 ± 0.18 mm, respectively. The average elastic–plastic critical pressure (Fs) was 58.11 N, 64.17 N, and 85.05 N, respectively, and the average critical values of elastic–plastic deformation (αs) were 0.45 mm, 0.47 mm, and 0.52 mm, respectively. The test results indicated that during mechanical compression, if the deformation is less than αs, the continued application of the compression load will not result in kernel crushing. However, if the deformation exceeds αs, continued compression will lead to kernel crushing, with the required number of compressions decreasing as the deformation increases. If the deformation surpasses αc, a single compression load is sufficient to cause kernel crushing. Since smaller wheat kernels are more susceptible to breakage during processing, the peeling pressure (F) within the chamber should be controlled to remain below the average elastic–plastic critical pressure (Fs) of small-sized wheat kernels. Additionally, the kernel deformation (α) induced by the flow rate and loading in the chamber should be kept below the average elastic–plastic critical deformation (αs) of small-sized wheat kernels. This paper provides a theoretical foundation for the structural design and optimization of processing parameters for wheat peeling machines. [ABSTRACT FROM AUTHOR]

This paper reports and discusses the results of a series of monotonic compression drained and undrained triaxial tests performed on three compacted, slightly weathered silty sand tephras. In total, 18 drained and 18 undrained tests were performed on compacted specimens (at Dc ≈ 90 and 100%) isotropically consolidated at confining pressures of 50–200 kPa. It was observed that particle size distribution, weathering state, and mineralogy of the tephra deposits had significant effects on the stress–strain responses, friction angles, stress–dilatancy relations, and critical state characteristics. For instance, the coarser tephra (namely white–grey Kaharoa, that was less affected by weathering processes) showed a primarily dilative response. The effects of chemical composition, namely weathering degree and mineralogy, on geotechnical properties such as friction angle were investigated with an attempt to interlink the two characteristics for heterogeneous tephras. The measured friction angles (ϕ = 32.7°–42.8°), combined with the results of weathering degrees and mineralogical investigations, indicated that silty sand tephras, if properly compacted, are suitable fills for use in typical geotechnical applications. [ABSTRACT FROM AUTHOR]

Marine unbonded flexible pipes serve as the most essential equipment in offshore oil and gas exploration and exploitation. Axial compressive loads during installation or in service in the complex marine environment usually lead to buckling failure. A flexible pipe is a composite structure with multiple functional layers, of which the tensile armor layer plays a key role with regard to the response of the pipe subjected to axial loads. In this paper, a simplified three-dimensional finite element model is developed, focusing on the tensile layer and replacing the carcass layer, pressure sheath layer, and pressure armor layer by a cylindrical rigid body to reduce computational expense. By using this model, the buckling failure modes of the tensile armor layer (in particular the birdcaging phenomenon) are analyzed. Several key parameters that affect the stability of the flexible pipe under axial compression and torsion are emphasized, and their effects on its axial and torsional stiffness are compared and discussed. The results show that both the lay angle of the steel wires and the interlayer friction coefficient have a significant influence on the axial and torsional stiffness of the pipe, whereas the damaged length of the outer sheath has virtually no effect. [ABSTRACT FROM AUTHOR]

The utilization of lightweight aggregate concrete (LWC) plays a major role in reducing the self-weight of CFST (concrete-filled steel tube) columns, which is reflected in the behavior of the structural system. This paper aims to investigate the characteristics of lightweight concrete-filled steel tubular (LWCFST) columns under an axial compressive load, using a total of (48) LWCFST column models. The simulated models were divided into four groups with different concrete compressive strength, length-to-diameter ratios (L/D), and diameter-to-thickness ratios (D/t). Four concrete compressive values were examined (30, 40, 50, and 60) MPa, three length-to-diameter ratios short (L/D = 3), medium (L/D = 6), and long (L/D = 9), and four diameter-to-thickness ratios (36, 31, 26, and 21). The method of nonlinear finite element analysis (NLFEA) was used to fulfill the objective of this study where results were presented as graphical plots between the compressive loading versus the axial and lateral strains along with the failure modes. In addition, the results were compared with the AISC360-16 and EC4 codes predictions to examine their applicability on the LWCFST columns where the AISC was overpredicted in most cases with higher percentages under lower (L/D) values, whereas the EC2 was underestimated in most cases with high percentages up to 28%, which become closer to the NLFEA predictions at higher (L/D) values. It has been revealed that the utilization of steel tubes significantly improves the LWCFST column's mechanical performance, ductility, compressive strength, and toughness. Moreover, the structural behavior of the LWCFST columns and their associated failure modes was found to be highly affected by the geometrical properties of the CFST column (i.e., L/D ratio and D/t ratio) where specimens with small tube thickness show bad behavior. Finally, the utilization of high-strength concrete has a favorable performance compared to the utilization of thick steel tubes. [ABSTRACT FROM AUTHOR]

This paper presents the design and analysis of PRSEUS structures with no openings, small openings, and mid-sized openings. For the typical panel structure of the small-opening PRSEUS (Pultruded Rod Stitched Efficient Unitized Structure), five reinforcement schemes are developed using different types, such as mouth frames and convex platforms. Simulation analyses of tensile and compressive load are conducted. Compared to the non-opening PRSEUS panel, the small-opening PRSEUS panel's maximum von Mises stress increases by 4.57 times under uniaxial tensile load, and the maximum von Mises stress increases by 2.55 times under uniaxial compressive load. The reinforcement efficiency of the small-opening PRSEUS panel in all five schemes exceeded 30%, Scheme E exhibits the highest load-bearing efficiency under both tensile and compressive load conditions, at 673.63 MPa/kg and 503.38 MPa/kg, respectively. For the typical PRSEUS panel structure with a mid-sized opening, three reinforcement schemes are proposed based on different methods, such as grid and cross-shaped reinforcement. These address the impact of mid-sized openings on the bearing capacity of the PRSEUS pane by analyzing the bearing efficiency of the three schemes. Compared to the non-opening PRSEUS panel, the maximum von Mises stress increases by 15.22 times under a uniaxial tensile load and by 32.45 times under a uniaxial compressive load. The reinforcement efficiency of the mid-sized-opening PRSEUS panel in these three schemes is greater than 50%, with Scheme III providing the highest bearing efficiency under a tensile load at 20.74 MPa/kg and 50.66 MPa/kg under a compressive load. [ABSTRACT FROM AUTHOR]

Graphene platelets (GPLs) exhibit outstanding mechanical and physical properties and therefore are employed as a reinforcement in advanced polymer composite structures. The purpose of this paper is to analyze the biaxial buckling of functionally graded graphene-reinforced sandwich plates with a soft orthotropic core. A new high-order three-layer theory is developed for the accurate modeling and analysis of the sandwich structure. The sandwich plate is divided into three layers including two face sheets and a core and a different third-order kinematic assumption is dedicated to each layer. The transverse flexibility of each layer as well as the displacements continuity at the interfaces are considered. Additionally, the continuity conditions and the conditions of zero transverse stresses in the whole structure are satisfied. The plate is subjected to a biaxial compressive loading and the governing equations are derived using the principle of minimum potential energy. Analytical solutions are presented for simply supported boundary conditions to obtain the critical buckling load. The influences of plate geometry and GPL properties on buckling load are investigated. The results obtained in specific cases are compared with the published results and the validity of the present results is confirmed. It can be drawn that the use of GPL increases the buckling load of graphene-reinforced sandwich plates. [ABSTRACT FROM AUTHOR]

Uneven settlement of the strata induced by ground fissure activity trigger great damage to a shield tunnel crossing a ground fissure zone. It is of great significance for the safe maintenance of tunnels to accurately predict the mechanical response of the tunnel structure under the dislocation of a ground fissure. In this paper, an analytical solution of mechanical behaviors of a shield tunnel crossing an active ground fissure zone is proposed. The shield tunnel-strata interaction in a ground fissure site is simplified as a Timoshenko beam placed on a Vlasov foundation. The governing differential equation and the closed-form solution for an equivalent shield tunnel subjected to additional load induced by the dislocation of ground fissure are derived. The proposed solution is adopted to analyze the mechanical behaviors of a shield tunnel, including tunnel displacement, rotation, bending moment, and shear force. The results of a model test and a numerical model are provided to verify the rationality of the proposed analytical solutions. Finally, a parameter sensitivity analysis about the additional load forms, the compression and shear modulus of the foundation, and the shear stiffness coefficients of the tunnel are conducted. The result shows that the form and value of the additional load has a large impact on the deformation and a slight impact on the internal forces of the tunnel. The foundation compression modulus determines the constraint effect of the strata, and the deformation and internal force response of a tunnel decrease with the increasing foundation shear modulus. In addition, the increase of shear coefficient enhances the shear stiffness of a tunnel, but largely increases the internal force as well. [ABSTRACT FROM AUTHOR]

Columns in traditional timber structures are commonly seen resting on stone bases and are very important in resisting lateral loads. This paper numerically modeled the lateral resistance of the columns combined with experimental investigation. Different numerical models were developed, based on which sensitivity analyses were performed. A practical numerical modelling strategy was further proposed and verified. The analysis results indicated that instead of material properties and contact area, the columns' lateral performance was much more sensitive to the variation of surface curvature at bottom surface. Without consideration of the surface curvature, the modeling error in the initial stiffness and peak load of a column was more than 607% and 8%, respectively. By best matching the load–displacement curves of tested column specimens, the optimal surface curvature was identified as 1/20306.5 mm−1. Then, a practical finite numerical model, characterized by the optimal curvature at the bottom surface, was proposed. This modelling method was validated by use of existing test results of traditional timber columns with different diameters and vertical compression loads. The modelling load–displacement curves agreed well with experimental curves both in terms of the initial lateral stiffness and peak load. Detailed simulation results based on the practical modelling strategy were presented and discussed. [ABSTRACT FROM AUTHOR]

This study offers an in-depth structural analysis of the threading mechanism in a motorized leg-lengthening nail, a key device used in bone-lengthening surgeries. The primary aim is to assess the structural integrity and performance of the nail during the lengthening process. The paper starts with a comprehensive overview of the nail's design, historical background, and functionality, emphasizing the critical components of the lengthening mechanism. The methodology section details the structural analysis approach, incorporating both finite element analysis (FEA) and manual calculations. FEA simulations are employed to analyze the nail's behavior under compressive loads, considering realistic conditions such as the 95th percentile of human body weight. The analysis focuses on stress concentrations, deflections, and overall structural stability to pinpoint the potential weaknesses. Due to budget limitations that prevented the creation of physical prototypes, manual calculations were utilized to validate the FEA results. The findings identify stress concentrations, especially in the areas where male and female threads engage, leading to the design of recommendations to enhance strength and reliability. Experimental results corroborate the accuracy of the FEA simulations. The study concludes with suggestions for improving thread design, emphasizing safety, durability, and functionality. These recommendations aim to guide the future iterations of the motorized leg-lengthening nail, thereby promoting the development of safer and more effective devices for bone-lengthening surgeries. This structural analysis significantly contributes to understanding the mechanical behavior of the motorized leg-lengthening nail, playing a crucial role in advancing medical devices for bone-lengthening procedures. [ABSTRACT FROM AUTHOR]

The commonly used aluminum–copper alloys in industry are mainly rolled plates and extruded or drawn bars. The aluminum–copper alloys' anisotropy generated in the manufacturing process is unfavorable for subsequent applications. Its underlying mechanism shall be interpreted from a microscopic perspective. This paper conducted the loading simulation on Al–4%Cu alloy crystals at the microscopic scale with molecular dynamics technology. Uniaxial tension and compression loading were carried out along three orientations: X-< 1 ¯ 12 >, Y-< 1 1 ¯ 1 >, and Z-<110>. It analyzes the micro-mechanisms that affect the performance changes of aluminum–copper alloys through the combination of stress–strain curves and different organizational analysis approaches. As shown by the results, the elastic modulus and yield strength are the highest under tension along the < 1 1 ¯ 1 > direction. Such is the case for the reasons below: The close-packed plane of atoms ensures large atomic binding forces. In addition, the Stair-rod dislocation forms a Lomer–Cottrell dislocation lock, which has a strengthening effect on the material. The elastic modulus and yield strength are the smallest under tension along the <110> direction, and the periodic arrangement of HCP atom stacking faults serves as the main deformation mechanism. This is because the atomic arrangement on the <110> plane is relatively loose, which tends to cause atomic misalignment. When compressed in different directions, the plastic deformation mechanism is mainly dominated by dislocations and stacking faults. When compressed along the <110> direction, it has a relatively high dislocation density and the maximum yield strength. That should be attributed to the facts below. As the atomic arrangement of the <110> plane itself was not dense originally, compression loading would cause an increasingly tighter arrangement. In such a case, the stress could only be released through dislocations. This research aims to provide a reference for optimizing the processing technology and preparation methods of aluminum–copper alloy materials. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) will cause internal short-circuits and even induce thermal runaway when they are subjected to compression and impact loadings. It is of great significance to explore the influencing factors of battery failure under different mechanical abuses for the crashworthiness design of the cells. In this paper, taking cylindrical LIBs as the research object, the force-electrical-thermal responses of the cells under different compression/impact conditions were studied by using a self-made plane compression and local indentation experimental system. The experimental results were compared with the corresponding finite element (FE) ones, and there was in good agreement with each other. Based on the explicit nonlinear FE method, the effects of loading velocity, indenter shape, and indenter diameter on the failure behaviors and mechanical responses of LIBs were also discussed. It is shown that localized indentation is more likely to induce the failure of the cells compared with plane compression. The peak force significantly decreases with the decrease of the indenter diameter, and the failure displacement also decreases correspondingly. It is noted that the failure displacement increases with the increase of the impact velocity, however, the failure displacement will decrease gradually when the impact velocity is more than 15 m/s. These results will provide some guidance for the multi-objective optimal design and safety assessment of LIBs. [ABSTRACT FROM AUTHOR]

Full-scale axial load tests were performed on five screw injection piles founded in medium-dense to dense sand at a site in Delft, the Netherlands. Each pile was instrumented with distributed fiber-optic sensors along its full length, giving detailed insights into the shaft and base response under compression loading. The paper focuses on the pile base response and combines the test results with a newly compiled database of instrumented load tests on screw displacement piles in sand. Given the range of screw displacement piles on the market, the influence of different installation methods and pile geometries on the base resistance can be assessed through the database. In summary, the analysis showed that all screw displacement pile types tended to mobilize base capacities similar to bored or nondisplacement piles. Despite high variability in the database, no significant trend with pile geometry, such as length or diameter, was evident. [ABSTRACT FROM AUTHOR]

Titanium and titanium alloys have been widely applied in the manufacture of aircraft engines and aircraft skins, the mechanical properties of which have a crucial influence on the safety and lifespan of aircrafts. Based on nanotwinned titanium models with different twin boundary spacings, the impacts of different loadings and twin boundary spacings on the plastic deformation of titanium were studied in this paper. It was found that due to the different contained twin boundaries, the different types of nanotwinned titanium possessed different dislocation nucleation abilities on the twin boundaries, different types of dislocation–twin interactions occurred, and significant differences were observed in the mechanical properties and plastic deformation mechanisms. For the { 10 1 - 2 } twin, basal plane dislocations were likely to nucleate on the twin boundary. The plastic deformation mechanism of the material under tensile loading was dominated by partial dislocation slip on the basal plane and face-centered cubic phase transitions, and the yield strength of the titanium increased with decreasing twin boundary spacing. However, under compression loading, the plastic deformation mechanism of the material was dominated by a combination of partial dislocation slip on the basal plane and twin boundary migration. For the { 10 1 - 1 } twin under tensile loading, the plastic deformation mechanism of the material was dominated by partial dislocation slip on the basal plane and crack nucleation and propagation, while under compression loading, the plastic deformation mechanism of the material was dominated by partial dislocation slip on the basal plane and twin boundary migration. For the {1124} twin, the interaction of its twin boundary and dislocation could produce secondary twins. Under tensile loading, the plastic deformation mechanism of the material was dominated by dislocation–twin and twin–twin interactions, while under compression loading, the plastic deformation mechanism of the material was dominated by partial dislocation slip on the basal plane, and the product of the dislocation–twin interactions was basal dislocation. All these results are of guiding value for the optimal design of microstructures in titanium, which should be helpful for achieving strong and tough metallic materials for aircraft manufacturing. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of long, large-diameter bored piles' behavior under static and dynamic load tests for a megaproject located in El Alamein, on the northern shoreline of Egypt. Site investigations depict an abundance of limestone fragments and weak argillaceous limestone interlaid with gravelly, silty sands and silty, gravelly clay layers. These layers are classified as intermediate geomaterials, IGMs, and soil layers. The project consists of high-rise buildings founded on long bored piles of 1200 mm and 800 mm in diameter. Forty-four (44) static and dynamic compression load tests were performed in this study. During the pile testing, it was recognized that the pile load–settlement behavior is very conservative. Settlement did not exceed 1.6% of the pile diameter at twice the design load. This indicates that the available design manual does not provide reasonable parameters for IGM layers. The study was performed to investigate the efficiency of different approaches for determining the design load of bored piles in IGMs. These approaches are statistical, predictions from static pile load tests, numerical, and dynamic wave analysis via a case pile wave analysis program, CAPWAP, a method that calculates friction stresses along the pile shaft. The predicted ultimate capacities range from 5.5 to 10.0 times the pile design capacity. Settlement analysis indicates that the large-diameter pile behaves as a friction pile. The dynamic pile load test results were calibrated relative to the static pile load test. The dynamic load test could be used to validate the pile capacity. Settlement from the dynamic load test has been shown to be about 25% higher than that from the static load test. This can be attributed to the possible development of high pore water pressure in cohesive IGMs. The case study analysis and the parametric study indicate that AASHTO LRFD is conservative in estimating skin friction, tip, and load test resistance factors in IGMs. A new load–settlement response equation for 600 mm to 2000 mm diameter piles and new recommendations for resistance factors φ qp, φ qs, and φ load were proposed to be 0.65, 0.70, and 0.80, respectively. [ABSTRACT FROM AUTHOR]

This paper presents findings from an experiment examining a novel curve-shape sandwich composite made of fiber-reinforced polymer (FRP) facesheets and flexible cores under transverse compressive loading. The curve-shape sandwich composites aim to enhance strength and stiffness while minimizing material use, particularly as liner for rehabilitation of large buried infrastructure like pipes and culverts. The study involved fabricating and testing 24 circular liners with various facesheet–core combinations. Results include deflection measurements, load data, and tensile strain values at different points on the liners. The stiffness of each sandwich specimen was compared to theoretical predictions based on composite facesheet behavior. Notably, bulkermat cores demonstrated superior stiffness and strength compared to three-dimensional (3D) woven fabric cores, exhibiting higher composite action. In contrast, solid-wall liners exhibited greater deformations than sandwich liners. To predict these significant deformations, an iterative analytical model was developed, accounting for geometric nonlinearity. This model accurately predicted test data prior to any material nonlinearity, such as facesheet or core failure. Additionally, the model was used to perform a parametric analysis, exploring various liner characteristics, including diameter, FRP layers, core thickness, and liner shape. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) concrete printing is increasingly becoming popular because it provides a powerful platform for the fabrication of structural components in freeform architectural shapes. Although manufacturing technology and material property improvement are advancing rapidly, the development of methods to predict the structural capacity of printed elements is lagging. This paper presents an experimental and numerical investigation to predict the axial load capacity of a printed concrete wall module. The module geometry contains two parallel thin wall sections connected by an internal sine wave. The thin wall section reduces the concrete consumption, and the internal sine wave provides lateral stability during printing and in the hardened state. It is a popular pattern printed by many researchers and in some real constructions. Two wall module specimens with the prescribed geometry were 3D-printed and tested under compression. The maximum loads of 2,890 and 2,924 kN were obtained for the first and second wall specimens, respectively. Additionally, samples were taken from different locations of a printed prototype to identify printed material characteristics. These experimental characteristics were then introduced to a finite-element numerical model for predicting the structural performance of the printed wall module under compression load. The results showed that the experimental maximum load and stiffness have 1% and 5% differences with numerical outputs, respectively. Based on such a validated model, the failure modes are discussed, and an analytical method is proposed for predicting the axial capacity for the prescribed geometry. [ABSTRACT FROM AUTHOR]

• Mechanical and thermal properties of straw boards with high densities are studied. • Tensile strength prediction method of straw boards is proposed. • Correlation between thermal conductivity and density of straw boards is revealed. • Feasibility of using straw boards for load bearing and insulation is verified. • Wheat straw strand board is identified as transversely isotropic material. Straw is an environmentally friendly, cost-effective, and abundant raw material for building boards. To assess the feasibility of using straw boards in building envelops, such as being alternative sheathing panels in light-gauge steel-framed members, for instance, walls and floors, both the mechanical and thermal properties of straw boards with high densities were investigated. The straw boards involved in this study include five wheat straw strand boards (WSSB12, WSSB15, WSSB18, WSSB25, and WSSB30) and a paper straw board (PSB58) named with a combination of the respective board type and thickness. Among them, the WSSBs are a type of straw composite, while the PSB is an improved straw bale with sheathing paper, which is mainly for enhancing the board integrality. Moreover, the former is composed of smashed straw fibers and isocyanate resin and has higher densities, while the latter is without using any artificial binders. Mechanical properties, including compression, tension, and bending properties, were investigated by tests and a proposed prediction method of tensile strength. In the experimental studies of compression properties, the failure modes, characteristics of load-deformation curves, and the differences in material directivity were analyzed and discussed. The results show that the WSSBs were considered to be transverse isotropic material with brittle characteristics in the plane. Then, the experimental studies of bending properties were carried out, and the results show that the bending strength is less than the compressive strength for WSSBs, while the bending strength of PSB is greater than its compressive strength. And the bending elastic modulus and the compression elastic modulus are close for either the WSSBs or the PSB. Furthermore, finite element models of the bending test specimens using the user material subroutine UMAT were developed to predict the tensile strength f t , and the constraint checks were conducted. It is verified that the prediction results of f t are believable, and the prediction method proposed is feasible. For the thermal properties of straw boards, tests were performed using the temperature control box - heat flux meter method, and the thermal conductivity λ was mainly focused. It is found that a significant linear correlation exists between the density ρ and λ , and the proposed fitting formula can be used to predict the thermal conductivities of such materials. Finally, brief comparisons of the mechanical and thermal properties between the straw boards and the oriented strand boards (OSBs) were conducted, and the feasibility of applying straw boards in building envelops, such as alternative sheathing panels with load bearing and insulation demands was verified. This study contributes to popularizing the application of straw boards in engineering structures by a compromising consideration of mechanical and thermal properties, which plays a positive role in the development of green buildings. [ABSTRACT FROM AUTHOR]

Steel side-plate connections are reliable load path alternatives because they eliminate the fabrication challenges associated with continuity plates, especially for concrete-filled tubes (CFTs). In this paper, a new easy-to-fabricate moment connection for connecting I-beams to CFT columns using the monolithic side-plate technique is proposed. In this connection, the vertical side plates are entirely replaced by column webs to save steel material by eliminating the use of double steel plates in the connection panel zone and resolving the biaxial fabrication issues associated with the lack of welding access between the orthogonal side plates and the column. Four full-scale experimental tests consisting of two couples of relatively identical bolted and welded connections were conducted under a cyclic lateral displacement control loading protocol and a constant compressive axial load was applied to the column to evaluate the seismic performance of the connection. Furthermore, standard geometrical limitations, such as the column width and beam depth, were challenged. The results indicated that the new proposed connection exhibits sufficient stiffness and high level of ductility up to more than 4% of story drift without any strength degradation, implying that this new connection can be classified as a prequalified rigid moment connection to be used in special moment frames (SMFs) located in high seismic regions. In this paper, a monolithic side-plate connection is proposed and four full-scale specimens with oversized geometrical characteristics are experimentally investigated. The favorable results of this study show that this connection can be used as a prequalified rigid beam-to-column moment connection in intermediate and special steel moment frames consisting of box columns. The proposed easy-to-implement connection offers advantages such as decreased weight, fewer welding operations, and biaxial connection capability, which are not possible with conventional side plates. This connection is successfully implemented in an IMAX multicomplex building, with 151,676 m2 gross area and 82.32 m height. The proposed idea is applicable to any project with large box-shaped columns in high seismic regions and the achievements of this study can provide experimental support for the seismic design of these buildings. Critical factors in the connection performance are the column width and side-plate geometry, and considering other specific aspects of this connection, there is a lot of potential for further numerical and experimental investigations. Although not shown in this work, the proposed approach gives us the necessary flexibility to easily develop a biaxial moment connection, and further research is recommended in this case. [ABSTRACT FROM AUTHOR]

Purpose: The present paper aims at the multi-objective optimization of a reentrant hexagonal cell auxetic structure. In addition, a parametric analysis will be carried out to verify how each of the design factors impact each of the responses. Design/methodology/approach: The multi-objective optimization of five different responses of an auxetic model was considered: mass, critical buckling load under compression effort, natural frequency, Poisson's ratio and failure load. The response surface methodology was applied, and a new meta-heuristic of optimization called the multi-objective Lichtenberg algorithm was applied to find the optimized configuration of the model. It was possible to increase the failure load by 26.75% in compression performance optimization. Furthermore, in the optimization of modal performance, it was possible to increase the natural frequency by 37.43%. Finally, all 5 responses analyzed simultaneously were optimized. In this case, it was possible to increase the critical buckling load by 42.55%, the failure load by 28.70% and reduce the mass and Poisson's ratio by 15.97 and 11%, respectively. This paper addresses something new in the scientific world to date when evaluating in a multi-objective optimization problem, the compression and modal performance of an auxetic reentrant model. Findings: It was possible to find multi-objective optimized structures. It was possible to increase the critical buckling load by 42.82%, and the failure load in compression performance by 26.75%. Furthermore, in the optimization of modal performance, it was possible to increase the natural frequency by 37.43%, and decrease the mass by 15.97%. Finally, all 5 responses analyzed simultaneously were optimized. In this case, it was possible to increase the critical buckling load by 42.55%, increase the failure load by 28.70% and reduce the mass and Poisson's ratio by 15.97 and 11%, respectively. Originality/value: There is no work in the literature to date that performed the optimization of 5 responses simultaneously of a reentrant hexagonal cell auxetic structure. This paper also presents an unprecedented statistical analysis in the literature that verifies how the design factors impact each of the responses. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering Sciences & Information Technology is the property of Arab Journal of Sciences & Research Publishing (AJSRP) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)