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]

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]

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]

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]

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]

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]

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]

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]

• 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]

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]

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]

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]

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]

This paper presents a novel concept for significantly enhancing the strength and durability of ancient closed-box tombs. These tombs hold significant philosophical values, and their architecture serves as a valuable data source, providing insights into the cultural stage of the society in which it was constructed. Throughout medieval and modern times, clay bricks remained a prevalent material for tomb construction due to their affordability and design flexibility. However, these structures currently face neglect and weakening, requiring imperative intervention of protection to prevent them from potential deterioration or extinction. The key objective of this research is to explore the potential use of graphene oxide (GO), a novel nanomaterial, as a treatment method to enhance the durability of mud brick tombs in Aswan, Egypt. Samples of mud bricks were examined and characterized using various techniques, including SEM-EDX, TEM, PLM, XRF, XRD, and mechanical properties analysis. The results indicated that GO nanomaterials significantly improve the mechanical properties of mud brick tombs, allowing them to resist more compressive loading and ultimately resulting in more durable and long-lasting structures. By using these innovative materials, effective restoration and preservation of these ancient structures for future generations could be viable. This research has the potential to revolutionize the preservation of closed-box tombs, ensuring these historical landmarks stand longer the test of time. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study focused on evaluating the strain generated within short concrete columns reinforced with glass-fiber-reinforced polymer (GFRP) bars and spirals under concentric compressive axial loads. This research was motivated by the lack of sufficient data in the literature regarding strain in such columns. Five full-scale RC columns were cast and tested, comprising four strengthened with GFRP reinforcement and one reference column reinforced with steel bars and spirals. This study thoroughly examined the influence of various test parameters, such as the reinforcement type, longitudinal reinforcement ratio, and spacing of spiral reinforcement, on the strain in concrete, GFRP bars, and spirals. The experimental results showed that GFRP–RC columns exhibited similar strain behavior to steel–RC columns up to 85% of their peak loads. The study also highlighted that the bearing capacity of the columns increased by up to 25% with optimized reinforcement ratios and spiral spacing, while the failure mode transitioned from a ductile to a more brittle nature as the reinforcement ratio increased. Additionally, it is preferable to limit the compressive strain in GFRP bars to less than 20% of their ultimate tensile strain and the strain in GFRP spirals to less than 12% of their ultimate strain to ensure the safe and reliable use of these materials in RC columns. This research also considers the prediction of the axial load capacities using established design standards permitting the use of FRP bars in compressive members, namely ACI 440.11-22, CSA-S806-12, and JSCE-97, and underscores their limitations in accurately predicting GFRP–RC columns' failure capacities. This study proposes an equation to enhance the prediction accuracy for GFRP–RC columns, considering the contributions of concrete, spiral confinement, and the axial stiffness of longitudinal GFRP bars. This equation addresses the shortcomings of existing design standards and provides a more accurate assessment of the axial load capacities for GFRP–RC columns. The proposed equation outperformed numerous other equations suggested by various researchers when employed to estimate the strength of 42 columns gathered from the literature. [ABSTRACT FROM AUTHOR]

Bamboo, as a green building material, plays a vital role in construction. Bamboo has good properties and appearance, making it highly attractive for building structures and designs. Since the compressive capacity of bamboo is considerably lower than its tensile capacity, with the ratio typically ranging between 300% to 900%, this limits its application dimensions in construction. Therefore, filling the original bamboo structural members with specific materials or applying different connection methods can not only maintain the appearance of the bamboo structure but also improve its compressive capacity and overall durability, thus expanding the application range of bamboo structural members and enhancing the performance of the architectural design process. Two hollow bamboo specimens were among the eight BFC specimens tested for this paper. Key components such as transverse stiffeners, steel bars, filler materials, and bamboo nodes were examined for their influence on the specimens' ductility, peak strain, ultimate bearing capacity, and failure mechanisms. The test results showed that the ratio of the ultimate bearing capacity of BFC specimens to hollow bamboo samples could reach up to 538%, while the peak strain differences were minimal. A non-linear finite element model was developed and its accuracy confirmed based on the test results. This work proposes a new approach to determine the final axial compressive capacity of BFC columns by creating an elastic model of transversely isotropic cylinders. As a result, the primary goal of this study is to establish a foundation for more scientific building design techniques and procedures by examining the axial compression mechanics of structural bamboo filled with cement and concrete (BFC) and how it influences building design. [ABSTRACT FROM AUTHOR]

In this paper, joint precast piles with a cross-section of 400 × 400 mm and a pin-joined connection were considered, and their interaction with the soil of Western Kazakhstan has been analyzed. The following methods were used: assessment of the bearing capacity using the static compression load test (SCLT by ASTM) method, interpretation of the field test data, and the dynamic loading test (DLT) method for driving precast concrete joint piles, including Pile Driving Analyzer (PDA by ASTM) and Control and Provisioning of Wireless Access Points (CAPWAP) methods. According to the results, the composite piles tested by the PDA (by ASTM) method differ by 15 percent compared to the static load method, while the difference between the dynamic DLT (by ASTM) method and the static load (by ASTM) method was only 7 percent. So, according to the results, the alternative dynamic method DLT (by ASTM) is very effective and more accurate compared to other existing methods. [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]

This paper presents an experimental study of the seismic behavior of concrete columns reinforced with glass fiber-reinforced polymer (GFRP) bars. Seven full-scale square columns were tested under sustained compressive axial loading combined with monotonic or cyclic lateral loading. The test program included two types of reinforcement (GFRP and steel bars) and different axial load levels (0, 20, and 33% of the axial capacity). The experiments showed that GFRP reinforcement could be used in concrete columns subjected to lateral loads, provided that ties are capable of properly confining the concrete core up to failure, thereby contributing to improving their deformation and energy dissipation capacity. Tests also confirmed the influence of the axial load level on the loadbearing capacity, deformation, and energy dissipation capacity of GFRP-reinforced concrete columns. [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]

In this paper, an analytical solution for exploring the buckling characteristics of functionally graded (FG) plate is presented based on a quasi-3D shear deformation theory. It is considered that the plate is subjected to different types of in-plane compressive load. The FG plate is placed on three-parameter foundation WinklerPasternak-Kerr. The overall material properties of FG plate are assumed to be varied across the thickness and are estimated through the Voigt micromechanical model. The governing equations are obtained on the base of the quasi-3D deformation theory that contain undetermined integral forms and involves only four unknowns to derive. Equations of motion are derived from the principal of virtual work and the analytical solution is used to determine the critical buckling loads. By the discussion of numerical examples and the comparison with those of the reports in the literature, the convergence and the reliability of the present approach are validated. Finally, the parametric investigations of the in-plane buckling are carried out, including the influence of boundary conditions, elastic foundation, plate geometric parameters and power law index. The results reveal that the critical buckling loads are strongly influenced by several parameters such as boundary conditions, elastic foundation parameters and geometric shape of the plate. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Petroleum Research & Studies is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) 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.)

Reinforced concrete interfaces, either cracks within monolithic elements or joints between concretes cast at different times may become critical under cyclic actions, due to stiffness and interface resistance degradation. Among the numerous parameters affecting the behavior of interfaces, this paper focuses on the effect of externally applied compressive stress. In conjunction with this parameter, the diameter of the reinforcing bars crossing the interface, their embedment length, and the anchorage of the interface reinforcement, by bond or using epoxy resin, are investigated. Roughened concrete interfaces crossed by reinforcing bars were subjected to cyclic shear slips, with or without compressive stress normal to the interface. The presented experimental results prove the beneficial effect of the external compressive stress on the ultimate shear resistance of interfaces, accompanied by the reduction of the effect of small embedment length of the interface reinforcement, due to its reduced contribution: the externally imposed compression leads to smaller crack openings at the interface, in most cases smaller than 0.40 mm, and to reduction of the reinforcement clamping effect. The shear resistance is activated at reduced shear slip values (0.20 mm–0.40 mm compared to 0.20–0.80 mm for interfaces under zero external compression), while the interface resistance degradation is also reduced (e.g., during the second load cycle, to 15% on average, compared to 30% for interfaces under zero external compression). Finally, an equation previously proposed by the authors is applied for the prediction of the shear resistance of interfaces under normal force, leading to satisfying accuracy. [ABSTRACT FROM AUTHOR]

Lattice structures have emerged as promising materials for aerospace structure applications due to their high strength-to-weight ratios, customizable properties, and efficient use of materials. These properties make them attractive for use in anti-ice systems, where lightweight and heat exchange are essential. This paper presents an extensive experimental investigation into mechanical compression properties of lattice trusses fabricated from AlSi10Mg powder alloy, a material commonly used in casted aerospace parts. The truss structures were manufactured using the additive manufacturing selective laser melting technique and were subjected to uniaxial compressive loading to assess their performance. The results demonstrate that AlSi10Mg lattice trusses exhibit remarkable compressive strength with strong correlations depending upon both topology and cells' parameters setup. The findings described highlight the potential of AlSi10Mg alloy as a promising material for custom truss fabrication, offering customizable cost-effective and lightweight solutions for the aerospace market. This study also emphasizes the role of additive manufacturing in producing complex structures with pointwise-tailored mechanical properties. [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]

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]

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.)

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]

Configuration-controllable metamaterials are a kind of metamaterials whose bandgaps can be effectively adjusted through configuration control, but the configuration changes also produce initial stress. In this paper, the distribution of the initial stress of the configuration-controllable metamaterial under axial displacement and the influence of initial stress on the band gap characteristics of the structure were analyzed using numerical and experimental methods. The results show that initial stress has a significant influence on the bandgap characteristics, and the position and width of the bandgap change with the magnitude of the initial stress. The bandgap distribution of the structure after considering the initial stress is more consistent with the reported experimental results. The influence of initial stress on bandgap cannot be ignored. When the compressive loading displacement is 10 mm, the frequency range of the first bandgap is 262 Hz–310 Hz and that of the second bandgap is 394 Hz–405 Hz. And the frequency range of the first and second bandgaps will be converted into 254 Hz–291 Hz and 391 Hz–400 Hz when considering initial stress. The initial stress generated by compression deformation reduces the frequency of the structural bandgap. The beginning and ending frequencies of the first bandgap will move toward low frequencies, and the first bandgap will close when the compression displacement reaches 30 mm. The initial stress generated by tensile deformation increases the frequency of the structural bandgap. The beginning and ending frequencies of the first bandgap move toward high frequencies, and the bandgap will close when the tensile displacement is 30 mm. [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]

A method for the determination of mechanical properties under compressive load is presented in this study. The short-span compression test is standardized for paper-based materials and was adapted for veneer in this study. Rotary cut veneer and solid wood of European beech (Fagus sylvatica L.) was tested parallel and transversal to fiber direction. The veneer thickness was varied between 1 and 3 mm. The mechanical properties Young's modulus, Poisson's ratio, yield point and compressive strength were measured. The results show that the correct determination of Poisson's ratio depends on the veneer thickness as well as on the fiber direction. For veneer with a thickness of at least 3 mm, it is suitable in fiber direction, but not transversal to the fiber direction. The comparison of the mechanical properties between veneer and solid wood confirms that the lathe checks mainly influence the veneer properties transversal to the fiber direction. [ABSTRACT FROM AUTHOR]

Interlocking Inter-Module Connections (IMCs) in Modular Steel Buildings (MSBs) have garnered significant interest from researchers. Despite this, the optimisation of plate thicknesses in such structures has yet to be extensively explored in the existing literature. Therefore, this paper focuses on optimising the thickness of interlocking IMCs in MSBs by leveraging established experimental and numerical simulation methodologies. The study developed various numerical models for IMCs with plate thicknesses of 4 mm, 6 mm, 10 mm, and 12 mm, all subjected to compression loading conditions. The novelty of this study lies in its comprehensive parametric analysis, which evaluates the slip prediction model. A random forest regression model, trained using the 'TreeBagger' function, was also implemented to predict slip values based on applied force. Sensitivity analysis and comparisons with alternative methods underscored the reliability and applicability of the findings. The results indicate that a plate thickness of 11.03 mm is optimal for interlocking IMCs in MSBs, achieving up to 8.08% in material cost reductions while increasing deformation resistance by up to 50.75%. The 'TreeBagger' random forest regression significantly enhanced slip prediction accuracy by up to 7% at higher force levels. [ABSTRACT FROM AUTHOR]

This paper is focused on the mechanical performance of the Dou-Gong bracket at the corner under vertical load. A full-scaled specimen was tested under the static compressive load. The load-displacement curves, load distribution law and displacement of components were discussed. A finite element model was established and validated with test results. The deformation and stress of the whole Dou-Gong bracket and main components were analyzed, and the influence of the wood properties and friction coefficients was studied. The results show that there are four stages in the load-displacement curve and the plastic stiffness is 76.36% lower than that in the elastic stage. The components in the oblique 45° direction mainly transfer the force, while the load distribution ratios in the width and oblique 45° directions of the lower layer is closer to 1. The displacements of the components in oblique 45° direction in the No. 2 and No. 3 layers are smaller than those of the components in width direction. With the increase of the compressive strength, the elastic moduli in the radial direction and the friction coefficients, the stiffness in the plastic stage increases and the maximum displacement decreases. However, the compressive strength and the elastic moduli in the longitudinal direction have little effect on the load-displacement curves. [ABSTRACT FROM AUTHOR]

This paper presents a numerical approach for investigating fatigue delamination propagation in composite stiffened panels loaded in compression in the post-buckling field. These components are widely utilized in aerospace structures due to their lightweight and high-strength properties. However, fatigue-induced damage, particularly delamination at the skin–stringer interface, poses a significant challenge. The proposed numerical approach, called the "Min–Max Load Approach", allows for the calculation of the local stress ratio in a single finite element analysis. It represents the ratio between the minimum and maximum values of the stress along the delamination front, enabling accurate evaluation of the crack growth rate. The methodology is applied here in conjunction with the cohesive zone model technique to evaluate the post-buckling fatigue behavior of a composite single-stringer specimen with an initial delamination. Comparisons with experimental data validate the predictive capabilities of the proposed approach. [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]

The new-type stainless steel–concrete–carbon steel double-skin tubular (SCCDST) members, characterized by their exceptional corrosion resistance and mechanical bearing capacity, have promising applications in ocean engineering, particularly in deep-water engineering. The external hydraulic pressure and interfacial action of various materials intensify the complexity of composite performance of SCCDST members. This paper describes an analytical investigation on the concentric compressive performance of SCCDST members under external hydraulic pressure. The full-range mechanism, including load–displacement response, bearing capacity contribution, and contact pressures, was investigated through the finite element (FE) model that was validated by the failure mode, bearing capacity, and response of axial load versus strain. Subsequently, influences of key geometric–physical parameters were analyzed, e.g., diameter-to-thickness ratios (Do/to, Di/ti), material strengths (fyo, fyi, and fc), hollow ratios (χ), and water depths (H). Typical results indicate that: the initial active confinement action derived from the hydraulic pressure can enhance the interfacial contact pressure and axial compression capacity of SCCDST members due to the tri-axial compression state; the enhancement of confinement effect is mainly from the interfacial interaction between outer stainless steel tube and concrete infill; influence of water depth on bearing capacity cannot be ignored, e.g., the bearing capacity of an SCCDST member with larger hollow ratio (χ = 0.849) is not enhanced under a higher hydraulic pressure (H = 900 m) because of the cross-sectional buckling failure risk. Finally, a modified method considering the effect of water depth was proposed and verified for SCCDST members under hydraulic pressure. [ABSTRACT FROM AUTHOR]

One of the important directions for green development in the world today is to expand the application methods of recycled concrete, improve the utilization rate of waste aggregates, and slow down the consumption of natural resources. The column structure with a large length and slenderness ratio is the most widely used compression unit in practical engineering, which conforms to the principle of sustainable development. In this paper, we study the mechanical properties and failure modes of long columns fabricated from steel tubes filled with recycled large aggregate self-compacting concrete (RLASCC-ST-LC) under compression load. Moreover, we examine the influence of steel tube thickness, recycled large-aggregate particle size, the strength of self-compacting concrete, and the length-to-diameter ratio on the performance of the members through finite element modelling. The results indicated that RLASCC-ST-LCs exhibited different degrees of buckling damage, and the damage processes were basically the same as that of steel tube concrete. When the thickness of steel pipe increased from 4 mm to 5 mm, the ultimate bearing capacity of the component increased by 12.1%; when the strength of self-compacting concrete increased from 30 MPa to 40 MPa and 50 MPa, the ultimate loads of the component increased by 6.96% and 12.4%, respectively. However, the increase in the aspect ratio weakened the bearing capacity of the component, and the ultimate bearing capacities reduced by 4.78% and 10.51% when the aspect ratios were 8, 10, and 12. Finally, based on the existing design codes, the theoretical calculation formulas are proposed for the ultimate bearing capacities of RLASCC-ST-LCs. These findings have significant implications for the widespread application of RLASCC-ST-LCs. [ABSTRACT FROM AUTHOR]

Fused Filament Fabrication (FFF) is one of the frequently used material extrusion (MEX) additive manufacturing processes due to its ability to manufacture functional components with complex geometry, but their properties depend on the process parameters. This paper focuses on studying the effects of process parameters, namely infill density (25%, 50%, 75%, and 100%), on the mechanical and thermal response of the samples made of poly(lactic acid) (PLA) reinforced with short glass fibers (GF) produced using FFF process. To perform a comprehensive analysis, tensile, flexural, compression, differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA) tests were used. The paper also aims to manufacture by FFF process of composite structures of the fuselage section type, as structural elements of an unmanned aerial vehicle (UAV), and their testing to compression loads. The results showed that the tensile, flexural and compression strength of the additive manufactured (AMed) samples increased with the increase of infill density and therefore, the samples with 100% infill density provides the highest mechanical characteristics. The AMed samples with 50% and 75% infill density exhibited a higher toughness than samples with 100% infill. DSC analyses revealed that the glass transition (Tg), and melting (Tm) temperature increases slightly as the infill density increases. Thermogravimetric analyses (TGA) show that PLA-GF filament loses its thermal stability at a temperature of about 311 °C and the increase in fill density leads to a slight increase in thermal stability and the complete degradation temperature of the AMed material. The compression tests of the fuselage sections manufactured by FFF made of PLA-GF composite showed that their stiffening with stringers oriented at an angle of ±45° ensures a higher compression strength than the stiffening with longitudinal stringers. [ABSTRACT FROM AUTHOR]

Mechanical behaviors at fatigue crack tips of cracked specimens under negative loading ratios are studied in detail by the finite element method in this paper. Three factors induced by specimen type and loading type on fatigue crack field are discussed, including constraint, compressive loading effect (CL effect) and crack contact closure. For mode I crack under negative loading ratios, the effects of the CL effect and crack contact closure on plastic strain accumulations are dominant, with the constraint effect being minor. The constraint effect has effects on the monotonous plastic zone, while the CL effect and contact closure both have effects on the reversed plastic zone (RPZ) and residual tensile plastic zone (RTPZ). That is, the higher the constraint, the smaller the size of the monotonous plastic zone; the greater the CL effect, or the smaller the contact degree, the larger the size of RPZ and RTPZ. For mode II crack, there is only CL effect on the crack tip field without the effect of constraint and contact closure, so plastic strain accumulation at the mode II crack tip is much greater than that at the mode I crack tip when they are under the same loading level. [ABSTRACT FROM AUTHOR]

This paper presents a proposed static test and numerical study on the mechanical properties of steel-shell–concrete-structure-immersed tunnel nodes, which is used to investigate the seismic performance and damage mechanism of steel-shell–concrete-structure-immersed tunnel nodes. The test is based on the immersed tube tunnel project in the deep China channel, and the nodes representing the outermost and innermost vertical walls of the immersed tube tunnel, i.e., L-shaped and T-shaped node specimens, were designed and fabricated at a scale of 1:5, and the specimens were mainly subjected to the combined effect of vertical axial compression and lateral displacement loads. The test results show that the L-shaped node will exhibit brittle damage characteristics with high lateral load carrying capacity and energy dissipation capacity during the ultimate load phase, while the T-shaped node exhibits bending damage with better ductility, so the outermost vertical wall should be locally reinforced to ensure the necessary ductility of the structure in the actual project. In addition, by comparing the numerical calculation and experimental results, it is found that there is good agreement in terms of load–displacement curves and crack distribution, which shows that the modeling method proposed in this paper can accurately simulate the mechanical properties of immersed tunnel nodes and can guide the section design of immersed tunnels with steel shell–concrete structures. [ABSTRACT FROM AUTHOR]

This paper evaluates the various approaches to strength and stiffness analysis of fracture osteosynthesis using a headless Herbert screw. The problem has been extensively addressed using several scientific approaches, namely the analytical approach, stochastic approach, experimental approach, and (marginally) using the finite elements method. The problem is illustrated on the use of a prototype headless screw Ti: 4.0/1.4 × 30/7 (manufacturer: Medin, Czech Republic) and the surgical treatment of the fifth metatarsal fracture. Mathematical equations for the analytical calculation of the maximum stresses in the screw were established for tensile/compression loading. This problem is also interesting because of its static indetermination in tension and compression; for this reason, it was necessary to use the deformation condition, i.e., the relationship between screw extension and bone contraction. The stochastic (probabilistic) approach, i.e., application of the Monte Carlo method, takes advantage of the mathematical equations derived during the analytical solution by respecting of the natural variabilities and uncertainties. The analytical and stochastic approaches were validated by measurements on porcine bones and by the finite element method. The data measured experimentally were also processed and used for deriving an equation, appropriately approximating the data. The main part of the measurement was to determine the axial force generated during osteosynthesis with a headless screw. The obtained compressional force was used to determine the maximal stress in the screw and bone. Finally, the methods were compared. In this paper, comprehensive and original approaches based on the authors' experience with multiple methods are presented. Obtained results are necessary for headless screw designers during optimalization of the implants and are also useful for surgeons developing new surgical techniques. This biomechanical problem was solved in cooperation with the engineering industry and physicians to improve the quality of care for patients with trauma in orthopedics and surgery. [ABSTRACT FROM AUTHOR]

In Recognition of the 90th Birthday of Millard Beatty Professor Beatty has contributed a wide variety of research papers and book articles on topics in finite elasticity, continuum mechanics and classical mechanics, including some fundamental experimental work. Finally, Professor Beatty's passion for teaching is exhibited in a number of his didactic related articles on classical mechanics and is emphasized further in two volumes on the principles of engineering mechanics. In a series of fundamental papers, the first of which, Part 1, appeared in 1992 in this journal, Beatty, together with Michael Hayes, developed the constitutive theory of an isotropic Bell constrained material. While this three-part work concluded their joint research on Bell materials, later, in 2005, Beatty and Hayes got together again and arranged for the production, and served as co-editors of, the special volume: "Mechanics and Mathematics of Crystals - Selected Papers of J. L. Ericksen". Along the way, Beatty also developed a number of special mathematical results which dealt with: determinants having complex conjugate elements; general integrals arising in plane finite elasticity; and an integral identity applicable to continuum mechanics. [Extracted from the article]

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]

This paper focuses on the study of the strength of facade sandwich panels used in building construction. The paper describes the results of experimental and numerical research on the behavior of sandwich panels made of polyisocyanurate core (PIR) and their structural connections when exposed to tensile and compressive loads. In the initial phase of this study, laboratory tests were performed to determine the physical and mechanical characteristics of the material from which the sandwich panels are made. Laboratory tensile and compression tests were performed on small samples of sandwich facade panels. In order to verify the obtained results, they were compared with the numerical analysis performed in the ANSYS software. The numerical model was found to accurately predict the results of the laboratory tests, suggesting that the model can be used to predict the behavior of these panels under different loads in service. The study showed that the foam core sandwich panel exhibits excellent mechanical properties. The results indicate the suitability of foam-based composite structures in the construction industry for various applications, such as roof and wall structures. The findings of this study may help in the development of lightweight and durable construction materials for the industry. [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]