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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]

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]

AbstractTo dampen the loading sequences in the constructions, using the shear walls is recommended. Shear walls, which withstand the lateral forces (i.e., parallel to the plane of the wall) of wind and seismic activity, prevent buildings from collapsing while columns and load-bearing walls support the structure’s compression load all the way to the foundation. Besides, some new techniques are innovated for strengthening the structure like outrigger system. The steel shear walls are mostly used in the steel structures due to their high strength, ductility, and low weight. Recently, implementing Corrugated Steel Shear Walls (CSSWs) has gained more attention because they can absorb much amount of energy compared to flat steel shear walls. There are two important parameters in the CSSWs that play crucial roles in controlling their strength; corrugation geometry and orientation. Therefore, the current research paper aims to study numerically the effects of four corrugation geometries (trapezoidal, square, zigzag, and curved) with two orientations on the cyclic behavior of the CSSWs. Finite Element Analysis (FEA) is used to simulate the seismic loading conditions and finally, this procedure is validated through the comparison of the modeled flat shear wall with the experimentally published results. The difference between the peak loads of hysteresis curves obtained numerically and experimentally is about 8.5%. The stated FEA procedure in this paper can be regenerated by other researchers. The results confirmed the applicability of the CSSWs compared to the flat shear walls. Also, the vertical corrugation infill patterns result in higher strength in comparison to the horizontal ones. For instance, in the zigzag and square corrugation shapes, the plastic energy dissipation of the vertically oriented specimens (13.84 and 14.01 KJ, respectively) is higher around 7% and 29%, respectively than the horizontally oriented ones (12.9 and 10.84 KJ, respectively). Besides, the trapezoidal and curved corrugation geometries show the highest cumulated energy and plastic energy dissipation. [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]

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]

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]

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]

This paper presents experimental and numerical investigations on the behavior of eccentrically loaded lightweight aggregate concrete encased steel (LWACES) columns after exposing to elevated temperatures. Sixteen concrete encased steel (CES) columns were considered in the study, 12 of which were exposed to elevated temperature then eccentrically loaded up to failure at different eccentricity ratios. The effect of temperature on the load–displacement relationships, failure load, and failure modes of the concrete encased steel (CES) columns was monitored and evaluated. Experimental results have shown that as the temperature increases, the load bearing capacity of the CES columns decreased. It has also been showed that, at high temperature, the normal‐weight concrete encased steel (NWCES) columns experienced larger degradation of the load bearing capacity compared to that of LWACES columns. Also, this study presents a numerical simulation of the behavior of LWACES columns at elevated temperatures with eccentric compressive load. The numerical model was implemented in conducting parametric study to understand the effect of temperature distribution, concrete cover, eccentricity ratio, and high temperature levels on the behavior of the thermally exposed (CES) columns. Numerical results have revealed that, at temperature value of 500°C, the ultimate capacity of LWACES with eccentricity ratios of 0.75, and 1 has decreased by 17%, and 23%, respectively, compared to that of the column with eccentricity ratio of 0.5. [ABSTRACT FROM AUTHOR]

A cylindrical structure used in a space launch vehicle should endure the compressive load and it must satisfy the requirement of compressive strength. For the light-weight of the structure and improving the performance of launch vehicle, a cylindrical structure reinforced by composite lattice can be used. Therefore, a compressive strength prediction technique of the cylindrical composite lattice structure is required. In this paper, the failure criterion was proposed using the compression test of a composite lattice subelement and a simple finite element analysis for the subelement. The failure criterion was introduced using the effect of the out-of-plane and in-plane bending deformation of the rib constituting the grid of structure on the compressive strength. The subelement specimen was prepared from two different structures and the compression test was performed using several fixture jigs which can generate various deformation of the specimen. The test results and finite element model were used to examine the effect of out-of-plane and in-plane bending deformation of the rib on the compressive strength and the failure criterion which can predict the compressive strength was derived using the relationships between each parameter. The compressive failure load of the cylindrical composite lattice structure was predicted by using the proposed method and the validity and accuracy of this method were verified through a comparison of the predicted results with the test results. It was possible to predict the compressive strength within a 5% error of the experimental result. [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]

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]

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]

The paper investigates the effect of high temperature exposure on the performance of concrete confined through textile/fabric‐reinforced composites. Small‐scale cylindrical specimens (150 × 300 mm) were confined using two types of carbon fibers (dry and epoxy‐resin coated). For the sake of comparison, two confining layers were applied to all specimens. After curing, cylinders were exposed to four ranges of increasing temperatures—being 20°C (ambient), 80°C, 100°C, and 250°C and, after cooling down, were tested under compressive cyclic loading. The experimental results show that thermal stress significantly influences the confinement effectiveness of textile‐reinforced composites. Exposure to high temperatures reduces the ultimate confined strength and significantly influences the overall axial stress–strain behavior. [ABSTRACT FROM AUTHOR]

Highlights This paper focuses on the mechanical response and viscoelastic properties of double‐blade composite stiffened structure (DCSS) under low‐velocity impact (LVI). Firstly, the impact resistance and viscoelastic behavior of the DCSS are revealed by LVI testing at four different locations using the same initial velocity. Next, the damage morphologies at the impact locations are observed with ultrasonic A‐ and C‐scan equipment and optical microscopy. At last, the DCSS containing impact damage is implemented for axial compression and the strain values of the DCSS surface are obtained using a strain testing system to reveal its residual properties and buckling behavior. The results show that there are significant differences in the impact damage modes at the four different locations. The maximum impact resistance is observed at location D, while location A has the opposite. The DCSS has a certain viscoelastic behavior at LVI and conforms to an exponential decay model. Moreover, position B presents interface debonding damage due to stiffness discontinuities at the flange and skin bonding and severely weakens the load carrying performance of the DCSS. The impact resistance of different positions is analyzed by LVI experimental results. Viscoelastic properties exist at different impact locations and obey the exponential decay model. Impact damage alters the buckling load and residual strength of the DCSS. The damage mechanism of the triangular zone is revealed by damage morphology. [ABSTRACT FROM AUTHOR]

The aim of this paper is to propose a new approach permitting the investigation of the 3D pore variation of kaolin K13 in relation with mechanical loading. A mechanical loading consisting of one-dimensional compression and oedometric loading is applied to a sample of centimeter scale. A postmortem protocol using scanning electron microscopy (SEM) coupled with Focused Ion Beam (FIB) was carried out to observe and then obtain a large number of slices of an extracted sub-volume from the small sample. Image analysis using a new processing method enabled the reconstruction of the observed and extracted sub-volume in the form of a rebuilt sub-volume. The segmentation of pores and particles was carried out using an approach based on machine learning and the pore space properties can be quantified. Pore morphology was identified based on two parameters namely the flatness and the elongation. Spatial orientation can also be locally determined. The proposed treatment enabled the distribution of pore size (termed Im_PSD) to be deduced and these were then compared with the results of Mercury intrusion porosimetry technique. [ABSTRACT FROM AUTHOR]

Thermal–mechanical damage is an important problem threatening the safety of deep rock engineering. In this paper, the effects of coupling damage on the deformation and failure characteristics of rock mass were studied via cyclic loading damage, thermal damage and uniaxial compression acoustic emission (AE) tests, and the microscopic fracture process of the damaged rock mass was numerically simulated. Results showed that during heat treatment, the colour of the sample changed significantly, the mass, the P-wave velocity and the number of mineral species decreased. The peak strength and elastic modulus reach their maximum values at 600 °C and 300 °C, respectively, exhibiting a trend of initial increase and subsequent decrease. The rapid growth period of AE activity increased noticeably with increasing temperature, and the effect of energy accumulation became more significant at higher peak strengths. The failure mode was influenced primarily by the cyclic loading amplitude. In addition, an increase in the stress or temperature after crack initiation leads to a sharp increase in the damage within the rock. Temperature had a more significant effect on the generation of damage than stress. Stress-induced microcracks were concentrated in the weakly bonded particles, whilst temperature-induced microcracks were concentrated in the strongly bonded particles. Highlights: Temperature had a significant effect on the mineral composition of rock mass. The rapid growth period of AE activity was prolonged with the temperature increase. The failure mode of rock mass was mainly influenced by cyclic loading amplitude. Temperature-induced microcracks were concentrated in strongly bonded particles. [ABSTRACT FROM AUTHOR]

In this paper, stability analysis of thin-walled functionally graded (FG) sandwich box beams under combined bending and axial forces was carried out. Based on higher order theory that includes sectional distortion and warping, a nonlinear displacement field of closed cross-section is adopted. The energy principle is applied in the context of elastic behavior of materials. Simple power-law is used to adjust the material properties in the thickness direction of each wall of FGM box beam. Ritz's method is adopted to obtain the nonlinear coupled equilibrium equations, and then the critical loads are obtained by means of the corresponding tangent stiffness matrix. A Finite Element simulation performed with the code ABAQUS software is used to verify the efficiency and accuracy of the present approach in lateral torsional buckling predictions. The effects of the power-law index and skin–core-skin thickness ratios on the critical loads of FG sandwich box beams are presented through several case studies. Moreover, the numerical solutions show that the previous effects play a significant role in the stability analysis of FG sandwich box beams. [ABSTRACT FROM AUTHOR]

The nonlinear buckling and postbuckling of functionally graded carbon nanotube reinforcement composite (FG-CNTRC) plates resting on the nonlinear effect of elastic foundation under combined load including external pressure and axial compression loads with uniformly distributed temperature rises are fully investigated in this paper. The FG-CNTRC plates are reinforced by FG-CNTRC stiffeners and the plate-foundation interaction is modeled using a nonlinear model. The higher-order shear deformation plate theory with the geometrical nonlinearities of von Kármán is applied to establish the basic formulations. Additionally, by using the anisotropic higher-order shear deformation beam theory, a new smeared stiffener technique is successfully developed for FG-CNTRC stiffeners. Galerkin's method is used to achieve the equilibrium equation system in the nonlinear algebraic forms, and the critical load and postbuckling load–deflection curve expression are explicitly determined. The numerical investigations discuss the influences of FG-CNTRC stiffeners, hardening/softening nonlinear elastic foundation, uniformly distributed temperature rises, geometrical and material features on nonlinear stability of stiffened FG-CNTRC plates. [ABSTRACT FROM AUTHOR]

This paper presents a mesoscale damage model for composite materials and its validation at the coupon level by predicting scaling effects in un-notched carbon-fiber reinforced polymer (CFRP) laminates. The proposed material model presents a revised longitudinal damage law that accounts for the effect of complex 3D stress states in the prediction of onset and broadening of longitudinal compressive failure mechanisms. To predict transverse failure mechanisms of unidirectional CFRPs, this model was then combined with a 3D frictional smeared crack model. The complete mesoscale damage model was implemented in ABAQUS®/Explicit. Intralaminar damage onset and propagation were predicted using solid elements, and in-situ properties were included using different material cards according to the position and effective thickness of the plies. Delamination was captured using cohesive elements. To validate the implemented damage model, the analysis of size effects in quasi-isotropic un-notched coupons under tensile and compressive loading was compared with the test data available in the literature. Two types of scaling were addressed: sublaminate-level scaling, obtained by the repetition of the sublaminate stacking sequence, and ply-level scaling, realized by changing the effective thickness of each ply block. Validation was successfully completed as the obtained results were in agreement with the experimental findings, having an acceptable deviation from the mean experimental values. [ABSTRACT FROM AUTHOR]

Polypropylene fiber reinforcement is an effective method to enhance the durability of concrete structures. With the increasing public interest in the widespread use of polypropylene fiber reinforced concrete (PFRC), the necessity of evaluating the mechanism of polypropylene fiber (PF) on the permeability of concrete has become prominent. This paper describes the influence of PF on the concrete permeability exposed to freeze-thaw cycles under compressive and tensile stress. The permeability of PFRC under compressive and tensile loads is accurately measured by a specialized permeability setup. The permeability of PFRC under compressive and tensile loads, the volume change of PFRC under compressive load, and the relationship between compressive stress levels at minimum permeability and minimum volume points of PFRC are discussed. The results indicate that the addition of PF adversely affects the permeability of concrete without freeze-thaw damage and cracks. However, it decreases the permeability of concrete specimens exposed to freeze-thaw cycles and cracking. Under compressive load, the permeability of PFRC initially decreases slowly and follows by a significant increase as the compressive stress level increases. This phenomenon correlates with the volume change of the specimen. The compressive stress level of the minimum permeability point and compressive stress level of the minimum volume point of PFRC exhibit a linear correlation, with a fitted proportional function parameter γ ≈ 0.98872. Under tensile load, the permeability of PFRC increases gradually with radial deformation and follows by a significant increase. The strain-permeability curves of PFRC under loading are studied and consist of two stages. In stage I, the permeability of PFRC gradually decreases with the increase of strain under compressive load, while the permeability increases with the increase of strain under tensile load. In stage II, under compressive load, the permeability of PFRC increases with the increase of freeze-thaw cycles, whereas under tensile load, the permeability gradually decreases with the increase of freeze-thaw cycles. The reduction of PF on the permeability of PFRC under tensile load is greater than that under compressive load. In future research, the relationship between strain and permeability of PFRC can be integrated with its constitutive relationship between stress and strain to provide a reference for the application of PF in the waterproofing of concrete structures. [ABSTRACT FROM AUTHOR]

The paper presents the study of L-type corner joint between three wooden elements connected with a 3D printed connector obtained by applying fused filament fabrication (FFF) method as additive manufacturing and black polylactic acid (PLA) filament as material. The solid wood elements are made of beech (Fagus Sylvatica L.) and their jointing simulates the connection between leg and two stretchers (rail) of a chair. The corner joints with 3D printed connectors were subjected to mechanical testing under tensile and compression loads and the results were compared with those of the classical mortise-tenon jointed assembly of the same components, considered as the reference one. The results have shown that the assembly with the 3D printed connector was more resistant to tensile load than the reference, but couldn't reach the performance of the classical mortise-tenon joint when it was subjected to compression load. The analysis of the defects occurred in the connectors after mechanical testing revealed a good interlayer adhesion, but fractures in the structure of the PLA material, specific to hard and breakable materials. Instead, the wooden elements were less affected in this case compared with the classical joints, where large fractures of wooden components occurred, both for the leg and stretcher elements. The conclusion is that the 3D printed connector protects the wooden components from breaking in case of applying tensile and compression loads, being the first affected by the stresses occurred in the joint. [ABSTRACT FROM AUTHOR]

Distributed nonstructural elements (NSEs), such as piping systems, are restrained against seismic actions using proprietary or, at times, custom-designed braces. The strengths of these elements are provided in the component brochures published by the manufacturers, with no information on their deformation capacities. Previous research on the seismic performance of NSEs provide several formulations to calculate possible reductions in design force by relying on ductility capacity of their seismic restraints. However, designers require a realistic estimate of the ductility capacity of the seismic restraints to use these formulations. This paper discusses the results of a test program on the behavior of brace assemblies under monotonic tensile and compression loading. The results are used to identify the potential failure modes of the tested brace assemblies and to quantify their ductility capacity. Further, design examples are presented to highlight the need for the use of capacity design principles in the design of brace assemblies and their anchors. [ABSTRACT FROM AUTHOR]

In sharp contrast to prefabricated cracks, the damage to rock masses resulting from external disturbances such as excavation disturbances and tectonic movement varies substantially as to the incidence, density, and magnitude of defects. The growth ratio of the energy dissipation density proportion D(Rω (α)) of the damaged rock under impact loading is closely related to the static damage factor D(α) and is theoretically explored based on the Weibull distribution in this paper. Sandstones with varied damage levels after distinct static precompression, as described by CT imaging, are used to evaluate the impact load of different driving pressures. In addition, a high-speed camera and geometric fractal are used to exhibit the ejection and fragmentation characteristics of the pulverized sandstones after impact loading. The experimental outcomes confirm the theoretical study where the function of D(Rω (α)) involving D(α) obeys the Weibull distribution, and the D(Rω (α)) slowly rises with the expansion of the damage factor. With the increase of either the damage level or driving pressure of the sandstone, the number of pulverized rocks, the fragmentation degree, and the D(Rω (α)) all increase. These results further advance rock dynamic theory and corroborate the energy evolution, ejection, and fragmentation characteristics of damaged sandstone under impact loading. These results can also serve as references for rock dynamic risk mitigation under dynamic catastrophes.. [ABSTRACT FROM AUTHOR]

This paper experimentally investigates the influence of saturation on dynamic behaviors of concrete under both tension and compression stress states. Two grades of concrete were saturated to 0%, 50%, and 100% by oven drying and water soaking procedures. Split Hopkinson pressure bar (SHPB) tests, reaching the highest strain rate of about 170 s−1 , were carried out for dynamic compression. Dynamic splitting tensile tests were carried out by an Instron high-speed test machine, achieving the highest strain rate of about 40 s−1. The test results show that concrete specimens with different saturation ratios are all strain rate-sensitive. Under tensile loading, the effect of free on viscosity is only found to affect concrete's behavior when the strain rate is not very high. The strain rate sensitivity increases with water content when the strain rate is lower than about 3 s−1. However, when the strain rate is greater than 3 s−1 , strain rate sensitivity of concretes with different saturations become similar. Under compressive loading, free water in pores reduces the rate effect because it increases the hydrostatic pressure inside the specimen and leads to hydraulic fracturing. The microcracks caused by the hydraulic fracturing effect in the specimen result in macroscopic strength degeneration. [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]

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]

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]

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]

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]

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]

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]

This paper studied the compressive behavior of a composite sandwich panel with a lozenge‐shaped core reinforced with graphene nanoparticles (GNPs) under different conditions. The fabrication process involves the utilization of Kevlar fibers and epoxy resin to construct the sandwich panels, followed by introducing polyurethane (PU) foam through vacuum‐assisted resin transfer molding (VARTM). Flat‐wise compression testing is conducted to assess the mechanical properties and behavior of the sandwich panels. The study investigates the effect of various parameters, including core angle, core height, weight percentage (wt%) of GNPs, and PU foam, on the compressive strength of the structure. The experimental results are validated through finite element simulation using ABAQUS software, and a satisfactory agreement is observed between the simulated and experimental data. The research findings indicate that the inclusion of 3 wt% of GNPs in the structure leads to a notable 25% enhancement in the compressive strength of the sandwich panel. However, when the GNP content was further increased to 0.4 wt%, a contrasting trend was observed and the strength of the structure decreased by about 12%. Furthermore, an increase in the core angle is associated with a substantial 46% improvement in the sandwich panel's strength. Conversely, an increase in the core height is found to cause an 18% reduction in the sandwich panel's strength. Also, the addition of PU foam results in a significant increase of approximately 42% and 58% in the strength and energy absorption of the sandwich panel, respectively. This comprehensive parametric study offers valuable insights to engineers and designers seeking to construct sandwich panels with optimal strength against compressive loads. Highlights: Adding GNPs modifies the mechanical properties of the sandwich panel.Adding 0.4% of GNPs leads to the reduction of the structure's strength.Increasing the core angle increases the sandwich panel's strength.Increasing the core height decreases the sandwich panel's strength.PU foam significantly increases the sandwich panel's strength. [ABSTRACT FROM AUTHOR]

Fillers play a decisive role in the mechanical properties of polymer composites. In this paper, different particle sizes of nitroguanidine were obtained to regulate the internal filler structure of triple‐base propellants (TBP) to improve their mechanical response in different environments. A series of morphological and structural characterizations on nitroguanidine (NQ) particles were conducted using techniques. The results indicated that the obtained NQ particles maintained a high level of crystalline quality while preserving their molecular integrity. The mechanical properties of TBP were systematically evaluated under various loading conditions, including cryogenic tensile, compressive, and impact loads, as well as dynamic thermomechanical effects. Additionally, three‐point bending simulations were employed to elucidate the mechanical responses and damage mechanisms. Under axial tensile and compressive loads, reducing the particle size of NQ significantly enhanced the tensile and compressive strength. The maximum tensile strength and compressive strength can reach 344.62 MPa and 104.79 MPa. Moreover, the compressive failure mode transitioned from cracking to axial shrinkage. Conversely, when subjected to radial bending loads, TBP exhibited contrasting behavior, including a decrease in the glass transition temperature from 84.73°C to 76.93°C and a non‐monotonic trend in impact strength (initially increasing from 4.96 to 8.85 kJ/m2 and then decreasing to 2.27 kJ/m2). This study provides valuable insights into the mechanical performance of TBP, supporting the development of high‐energy, high‐strength TBP formulations. Highlights: SEM analysis confirms the pronounced orientation effect of rod‐like NQ.The orientation and particle size of NQ decide TBP's radial impact resistance.Submicron NQ enhances the compression resistance property of TBP.Submicron NQ brings about a shift in the microscopic damage morphology of TBP. [ABSTRACT FROM AUTHOR]

Femoral fractures are frequent in adolescents and children, and most fractures occur within the centre of the bone, typically referred to as the femur shaft. Plate and screws are ideal fixation methods for femoral fractures close to the articular surfaces. When using plates and screws, estimating the load on the plates and screws before starting treatment is important. The primary focus of this paper is the examination of fixation plates utilized in the treatment of femur bone fractures. The study employs the finite element method to conduct this analysis. Initial modelling of the femur bone is executed through the utilization of CATIA V5 software. Subsequently, the investigation transitions to the ANSYS R14.5 environment, where more in-depth analysis is carried out. The modelling of the fracture fixation plates is done on commercially available CAD software CATIA V5. The stress distribution of different biomaterials in the bone plate system is calculated when the system is subjected to compressive loads with varying healing times. Here we have used stainless steel (SS316-L), titanium alloy (Ti6Al4V) and magnesium alloy (AZ31). More focus was given to the magnesium alloy. Here a fracture gap of 1mm gap was taken for analysis. A comprehensive compressive force amounting to 750 N was applied to the bone-plate assembly during the simulation. This force magnitude corresponds to the approximate weight of an average human body. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is a key technology for the individualized and resource-efficient production of structural components. Recent developments in manufacturing technologies enable improved quality of additively manufactured components and therefore they become more and more important in lightweight constructions. An example is the substitution of solid material by porous lattice structures. Those embedded lattice structures lead to highly weight-efficient structures. Most recent investigations focus on numerical and experimental studies to describe the mechanical behavior of lattice structures. In this paper, a method to determine analytical expressions for the axial stiffness properties of lattice structures is presented. The displacement method and direct stiffness method are used to derive symbolic parameter-dependent formulas for the axial stiffnesses and effective Young's moduli for f2cc,z, and bcc unit cells. Furthermore, an empirical approach based on Finite Element simulations is presented to describe the stiffness reduction for non-embedded or rather free lattice structures. The results are further validated by physical experiments. Stereolithography is used for specimen production. f2cc,z, and bcc lattice structures are embedded in thin-walled rectangular aluminum tubes and tested under compression load. Furthermore, lattices without a surrounding tube are tested. The analytical and empirical solutions are in good agreement with the experimental and numerical results. [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 benefits of using glued laminated bamboo (GLB) as a structural material are numerous, such as its low weight, high specific strength, and low carbon footprint. However, as a viscoelastic material, GLB materials exhibit creep, which is a significant characteristic that needs to be considered. To ensure the safety and serviceability of structures that utilize GLB, it is essential to accurately estimate the long-term performance of GLB composites under external forces. This paper reports on an experimental investigation into the creep characteristics of GLB under tensile and compressive loads. The experiments were conducted at various load levels for a period of 500 h under a controlled environmental condition. The Burgers model and the five-parameter model were used to characterize creep behavior and predict the long-term deformation by extrapolating beyond the experimental period. The long-term deformation of the GLB may be overestimated by the Burgers model due to its constant creep rate for the viscous component. In contrast, the five-parameter model introduces a modification factor that results in a nonlinear viscous component, allowing a more accurate fit and a reasonable deformation estimate. Highlights • Creep characteristics of GLB were studied under tensile and compressive loads. • Burgers and five-parameter models were used to describe the creep behavior. • Extrapolation of Burgers model overestimates the creep deformation of GLB. • Five-parameter model provides reasonable deformation estimate for GLB. [ABSTRACT FROM AUTHOR]

M. G. Zertsalov [1] carried out a brief review of methods used for calculating the bearing capacity of bored piles in rocky soils along the lateral surface under compressive loading. In this paper, the author sets out to review methods for calculating the bearing capacity of a pile based on the resistance of the rocky soil beneath the pile bottom end. [ABSTRACT FROM AUTHOR]

This paper describes both an experimental study and a numerical investigation on the compressive behavior of new types of solid as well as hollow composite columns, which consist of Unplasticized Polyvinyl Chloride (UPVC) tubes filled with expansive concrete. 32 specimens were categorized into four groups and cast with expansive concrete. Half of the specimens were confined additionally with two layers of GFRP wraps. Furthermore, two specimens were cast with ordinary concrete to be compared with those expansive counterparts. All the composite columns were tested under the monotonic compressive loading. The effects of GFRP confinement, aspect ratio of composite columns (L / D), and hollowness of concrete core on compressive behavior were investigated. It was demonstrated that adding expansive agents improved the load-carrying capacity and ductility of columns by enhancing the tri-axial state of stress in the concrete core. Moreover, an increase in aspect ratio decreased both peak load and its corresponding axial strain. Approximately 40% increase was observed in the values of peak load for specimens confined with GFRP wraps. Generally, concrete core removal in the hollow specimens resulted in slightly higher average compressive stress. Finally, a finite element (FE) simulation was performed using ABAQUS software, and the numerical results were validated with experimental tests of the present study. [ABSTRACT FROM AUTHOR]

A family of locking-free Kriging-based Timoshenko beam elements with a new implementation of the discrete shear gap technique was recently developed (referred to as K-beam-DSG1 elements). Performance of the K-beam-DSG1 elements has been shown to be very satisfactory in the linear static analysis of beams for a wide variety of thicknesses. This paper presents further development of the K-beam-DSG1 elements to free vibration and bifurcation buckling analyses of prismatic and non-prismatic beams. Consistent Kriging-based mass matrices are used for free vibration analysis and similarly, consistent Krigingbased geometric stiffness matrices are used for buckling analysis. The results show that for most of the cases, the K-beam-DGS1 elements yield remarkably accurate natural frequencies and critical compressive loads using a reasonable number of elements to discretize the beam. For an axially functionally graded fixed-fixed supported beam, however, the elements fail to predict the critical load accurately. [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]

Buckling of the longitudinal rebar is one of the main forms of plastic hinge failure in reinforced concrete (RC) columns after an earthquake. This rebar buckling significantly impacts the seismic bearing capacity and energy dissipation capacity. To restrain the development of longitudinal rebar buckling behavior and delay the degradation of lateral strength in RC columns, this paper developed a new type of buckling restraint rebar (BRR) consisting of three components: longitudinal rebar, a restraint sleeve, and foam material. First, the BRR mechanical properties under compression and tension‐compression cyclic loading were obtained through quasi‐static loading tests. Then, the BRR compression and tension‐compression cyclic loading processes were numerically simulated based on ABAQUS finite element software. The simulated results were compared with the test results. Finally, a stress–strain constitutive model for this new BRR was proposed based on this study. Results showed that the restraint sleeve could significantly enhance the lateral stiffness and the bearing capacity of longitudinal reinforcement after yielding. The compressive performance of BRR was mainly affected by the length and wall thickness of the sleeve. The cyclic performance was mainly affected by the length of the sleeve and the clearance between the sleeve and the reinforcement. The BRR constitutive model proposed in this paper can accurately reflect the influence of restraint sleeves on the stiffness of longitudinal reinforcement after yielding. [ABSTRACT FROM AUTHOR]

This paper presents an improved design approach based on the direct strength method (DSM) in American Iron and Steel Institute (AISI) design specification S100 for cold-formed steel (CFS) built-up closed cross-section columns subjected to local, global, and local–global interaction buckling modes. Initially, the failure mode and load data corresponding to various design parameters such as intermediate fastener connection spacing, boundary conditions, material properties, slenderness, and cross sections from various researchers are collected, including the authors' test results. The design predictions using the current DSM design provisions are compared with the collected test results. The results show that the current DSM approach requires improvisation to adequately predict the axial compression load. The data are then analyzed to understand the behavioral features of the built-up closed cross-section column such as limit for interaction buckling, erosion of strength due to arrant interaction buckling, and increase in strength due to flange or web overlapping effect. The interpretation methods used to improve the current design approach are presented. The original DSM design procedure is improved by failure mode classification and modified slenderness to account for increase and erosion in strength. Finally, the safety (accuracy and reliability) of the design predictions from the improved DSM-based approach is assessed using the large amount of data collected. Since the introduction of the direct strength method to the North American Specification for the Design of Cold-Formed Steel Structural Members (AISI S100) in 2001, it has gained traction among design engineers due to its simplicity, advantages over other design methods, and specific design curves for individual buckling modes. To implement the DSM for CFS built-up members, several researchers have proposed different design approaches, and research is still happening. This study is also aimed toward the same objective but is specific to the local–global interaction in built-up members. It is demonstrated why the DSM prediction is unsafe for CFS built-up members with larger intermediate fastener connection spacing and excessively safe for CFS built-up members with closer intermediate fastener connection spacing. An intermediate fastener connection spacing limit that separates the local–global interaction buckling and element overlapping effect is determined. A design proposal for limiting the interaction buckling mode and considering the overlapping effect of elements in the DSM design method is suggested. More specifically, the proposed design method is in line with the current AISI approach so the designer need not confuse how to use this new design approach in practice. Therefore, for further ease of understanding, two design examples for built-up closed cross-section columns—(1) subjected to local–global interaction buckling; and (2) subjected to element overlapping effect—are included in this paper. It is also recommended that future research may focus on further classifying the AISI main specification sections, E2 and F2 (simple classifications based on the global failure modes), based on the interaction buckling modes in built-up cross-section members. [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]

This paper focuses on the finite element analysis simulation of the impact properties of composite sandwich structures made of carbon fiber-reinforced polymer lamina. In the existing studies, the composite sandwich structures with A-shaped cores have superior mechanical properties under quasi-static plane compression loads compared to W-shaped, Y-shaped, and X-shaped cores. However, there is limited research on the impact resistance of this structure. This paper studied the resistance of a composite A-shaped core structure to ballistic impact. Using ABAQUS/explicit finite element analysis software, ballistic impact tests for the composite A-shaped core structure were simulated based on the Hashin and Yeh failure criteria with a progressive damage model introduced in the user-defined subroutine VUMAT. First, the composite Y-shaped core sandwich structure was verified via experiments and simulations to determine the accuracy of the method, and then the composite A-shaped sandwich structure was subjected to a series of ballistic impact simulations. With varied impact velocity, the damage to the front and rear face sheet and cores via ballistic loads was simulated to illustrate the overall dynamic response process of the sandwich structure. Subsequently, a curve was fitted using a ballistic limit velocity equation, which was used as the criterion to evaluate the impact resistance of the composite A-shaped core structure. The results showed that, under the same relative density and the same number of component layers, the ballistic limit velocity of the composite A-shaped core sandwich structure was bigger than the composite Y-shaped core sandwich structure. The composite A-shaped core structure had 12.23% higher ballistic limit velocity than the composite Y-shaped core, indicating the impact resistance capabilities of the A-shaped core structure. In addition, the impact location's effect on the impact response was investigated. [ABSTRACT FROM AUTHOR]

Few works investigate the fatigue of short fiber reinforced thermoplastics under cyclic compression. Furthermore, the heat buildup approach to quickly predict the fatigue lifetime of these materials has not yet been investigated for compression–compression loadings. This paper first describes an experimental protocol to perform well‐controlled cyclic compression tests without anti‐buckling device that may induced bias. The uniaxiality of the global loading is checked during the test based on kinematic and thermoelastic coupling field measurements. Then, the paper compares the results from fatigue and heat buildup tests performed on polyetheretherketone reinforced with 30 wt% of short carbon fibers for several load ratios. It is shown that the fatigue lifetime is higher in compression than in tension and depends on the compression load ratio. The heat buildup approach appears to be relevant to quickly predict the fatigue lifetime of the material for the different loading ratios studied, including compression–compression. Highlights: Protocol to perform well‐controlled compression tests based on field measurements.Influence of load ratios on fatigue lifetime of PEEK CF30 under compression loadings.Quick prediction of fatigue lifetime from heat buildup measurements in compression. [ABSTRACT FROM AUTHOR]

The woven structure made of naturally curved (in-plane) ribbons has smooth geometry and fewer geometric imperfections, but there is no study of its buckling mechanical properties under vertical loads. The aim of this paper is to investigate buckling mechanical properties of spherical woven structures. Three spherical woven structures with different ribbon types and six new spherical woven structures with different ribbon widths and thicknesses were designed and the quasi-static vertical compression tests were carried out. The buckling load of spherical woven structures were studied by nonlinear finite element and ring buckling theory. Results indicate that the failure mode of the spherical weave structure under vertical loading can be divided into two stages, where a flat contact region forms between the spherical weave structure and the rigid plate and inward dimple of ribbons. Spherical weave structures using naturally curved (in-plane) ribbon weaving have better buckling stability than those woven with straight ribbon. Based on theoretical and finite element analysis, we propose a buckling load equation and buckling correction factor equation for the new spherical weave structure under vertical compression load. The formula is validated and has good agreement with the test results, which could help to design the stability of spherical weave structures with in-plane ribbons. [ABSTRACT FROM AUTHOR]

Soils are known to be inherently anisotropic, resulting in complex responses to loading. This paper aims to develop an elastoplastic solution for the undrained expansion of a cylindrical cavity in sands adopting a non‐associated and anisotropic model, SANISAND. The rigorous derivation of the stress‐strain state of the soil element is provided following a standardized solving procedure. The dilatancy and crushing of the soil are invoked in the three‐dimensional cavity expansion solution by adopting the critical state soil mechanics and limiting compression curve, respectively. By combining this with a governing equation that considers the undrained condition, the stress‐strain state of the surrounding soil around the cavity can be determined. A subroutine is then implemented into the ABAQUS FEM simulation to verify the solution. The solutions are also validated against those based on an isotropic model, and anisotropic sand is used to investigate the effects of the initial effective mean stress, at‐rest coefficient of earth pressure, and overconsolidation ratio on the stress distribution, stress path, and boundary surfaces. [ABSTRACT FROM AUTHOR]