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Abstract Carbon fibre-reinforced polymer (CFRP) plates can efficiently repair or enhance the mechanical properties of the square hollow section. However, the loading end of such a CFRP-strengthened member is prone to local bearing failure under compressive load. Given this limitation, an innovative CFRP-plate-strengthened square hollow section composite member (CFRP-SHSCM) was raised, and the thick-walled section was welded on both ends of the thin-walled steel column. The mechanical properties of CFRP-SHSCMs were investigated through parameter finite element (FE) analysis, focusing on the influence of the amount of CFRP layers (n c ), the slenderness ratio (λ), the initial geometric imperfections (v 0 ), the CFRP layouts (2S and 4S) and the length of the exposed steel column (L e ). The load–displacement curves, the bearing force, and typical failure modes were also acquired. Results indicated that with increasing n c and v 0 , and decreasing λ, the conventional CFRP-SHSCMs were prone to local bearing failure with poor ductility, leading to the insufficient use of the CFRP plate, in contrast, the improved CFRP-SHSCMs primarily underwent overall buckling failure and exhibited better bearing force and ductility. Finally, the modified Perry-Robertson formula was put forward to predict the ultimate load of the CFRP-SHSCMs. The coefficients of variation between the FE simulation and the theoretical results were 0.00436 and 0.0292, respectively.

Various mechanical parts come into high-load rolling and sliding contact at the contact surface. Even with technological advancements, mechanical failures still occur. Rolling-sliding mechanical contact issues are the primary cause of over 90 % of surface and subsurface metallic failures and they are only becoming worse. Using discretised continuum 2D finite element methods (FEM), this research investigates the parametric contact effect of a steel twin disc system subjected to rolling-sliding contact at varied surface friction and comprehensive load condition. The equivalent von Mises stress distribution, contact pressure distribution and shift position of maximum subsurface stress on the contour region are all influenced by changes in compressive load and coefficient of friction, according to a numerical surface-to-surface contact simulation performed with Abaqus at mean Hertzian pressure. The maximal equivalent stress, for a given load, reaches a peak in the subsurface and moves farther away from the surface when the coefficient of friction decreases and comes close to the contact surface when the coefficient of friction increases. Consistency is shown by the analytical and numerical results.

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.

An experimental investigation is carried out to evaluate the ultimate compressive capacity of welded stiffened aluminum panels in alloy 5083-H116 subjected to uniaxial compressive load along the short edge. A tensile test is carried out to find out the real material properties. Five full-scale stiffened panel specimens, one of them is intact and locked cracks are produced in the other four panels. A global survey of the initial geometric imperfections is performed before conducting the compressive test. Through-thickness locked cracks are located either in the center or quarter of the plate between the two attached stiffeners. The panels are tested, and their progressive collapse behavior is reported. The panels failed by two different deformation modes: stiffener tripping and local buckling of the plate. The load-shortening and load-lateral displacement relations are presented, and concluding remarks are stated regarding the effect of locked crack’s location, orientation and initial imperfection on the compressive capacity of welded aluminum panels.

The determination of the engineering properties of the cashew nut is essential as the basis for the design and development of appropriate and optimum post-harvest handling and processing machinery. The present study examined the physical, mechanical and colour properties of cashew nuts (n = 100) at a moisture content of 7.63% (wet basis) derived from Central Java, Indonesia. The main characteristics included the length, width, thickness, mass, volume, and density. The derivative properties consisted of the geometric diameter, arithmetic diameter, surface area, frontal surface area, transverse area, shape index, sphericity, bulk density, and porosity. The mechanical properties included the static friction, static and dynamic angle of repose, and compressive load (in four orientations). It was identified that the cashew nut from Central Java was dominant with a small-medium size with an average mass of 5.42 ± 0.99 g. This cashew nut was thicker, but shorter in length than the cashew nuts from India, Nigeria, and Ivory Coast. The results of the stepwise regression analysis determined that the volume had the most substantial relationship with the mass (R2 = 0.949), the bulk density had the highest correlation with the mass (R2 = 0.968), and the porosity showed a high correlation with the true density and mass (R2 = 0.997). The highest friction, static angle of repose, and-dynamic angle of repose occurred on the surface plywood, and the lowest was on the stainless-steel surface. In the context of designing appropriate cashew nut cracking equipment, it was recommended to provide the impact parallel to the longitudinal axis orientation due to the minimum compressive load (reduce the power requirement). Furthermore, the cashew nut colour properties of the L*, a*, b* coordinates were 35.988, 0.427, 1.718, respectively.

Numerous finite element methods have been widely used to predict the response of normal/high strength concrete columns confined with Fiber Reinforced Polymer (FRP) under different loading conditions. In this regard, simulating the response of FRP-confined reactive powder concrete (RPC) columns has been less emphasized. The present study aimed to propose a finite element model based on fiber finite element methodology in order to predict the behavior of FRP confined RPC columns under axial compressive load with different eccentricities. The columns were modeled with a nonlinear beam-column element with two nodes with distributed plasticity. In addition, the proposed finite element model in the present study indicated its simplicity, low computational efforts, and flexibility by adopting a perfect bond between RPC and FRP. Further, the obtained results from the finite element analysis were compared to those from available tested specimens. Based on the comparisons, the proposed model can provide highly satisfactory predictions. Finally, the proposed model can be useful for efficient applications in practical engineering projects.

This study investigates the load transfer mechanism that includes the effect of helix bending deflection on end-bearing capacity, distribution of ground pressure under the helix and soil deformation around the screw pile. The helix to shaft diameter ratio of 2.5 and 2.8 with a strong helix and a weak helix were used. The model ground was prepared with fine sand at 80% of relative density. To investigate the load transfer mechanism, the experimental tests were modelled in a 3D finite element code. A good agreement between the experimental and numerical approaches was found. The numerical analyses showed that large influence zone exists under screw pile with strong helix, which resulted in higher mobilized soil shear strength that contributed to higher end-bearing capacity. In the case of strong helix, uniform pattern of pressure distribution was observed under the central shaft and the helix. Similar pattern of pressure distribution under the central shaft was observed in weak helix case but the pattern of pressure distribution under the helix changed from uniform to triangular to trapezoidal at various stages during the load test. The normalized end-bearing capacity decreased linearly with the increase in normalized helix bending deflection in both approaches, i.e. experimental and numerical.

This experimental investigation reveals the projected benefits of concrete-filled double-skin tubular columns. These columns are made up of an outside steel tube, an interior UPVC pipe, and a sandwich of concrete among these tubes. The effect of the dimension ratio of the outer-to-inner tube, the thickness ratio of the outer tube, and the internal tube material (steel/UPVC) on the ultimate compressive strength of double-skin tubular columns samples filled with concrete are investigated. Finally, the experimental findings were compared to previously published design approaches in AISC (2010), GB50936 (2014), and EC4 (2004). The analysis revealed that GB50936 (2014) produces the best outcomes, followed by AISC (2010) and EC4 (2004). In addition, the samples were tested in elevated temperatures to study their post-fire axial capacity. It was discovered that the type of infilled concrete and interior tube material has no major impact on the performance of samples at elevated temperatures.

This work reports the investigations of the electric potential impacts on the mechanical buckling of the piezoelectric nanocomposite doubly curved shallow shells reinforced by functionally gradient graphene platelets (FGGPLs). A four-variable shear deformation shell theory is utilized to describe the components of displacement. The present nanocomposite shells are presumed to be rested on an elastic foundation and subject to electric potential and in-plane compressive loads. These shells are composed of several bonded layers. Each layer is composed of piezoelectric materials strengthened by uniformly distributed GPLs. The Halpin–Tsai model is employed to calculate the Young’s modulus of each layer, whereas Poisson’s ratio, mass density, and piezoelectric coefficients are evaluated based on the mixture rule. The graphene components are graded from one layer to another according to four different piecewise laws. The stability differential equations are deduced based on the principle of virtual work. To test the validity of this work, the current mechanical buckling load is analogized with that available in the literature. Several parametric investigations have been performed to demonstrate the effects of the shell geometry elastic foundation stiffness, GPL volume fraction, and external electric voltage on the mechanical buckling load of the GPLs/piezoelectric nanocomposite doubly curved shallow shells. It is found that the buckling load of GPLs/piezoelectric nanocomposite doubly curved shallow shells without elastic foundations is reduced by increasing the external electric voltage. Moreover, by increasing the elastic foundation stiffness, the shell strength is enhanced, leading to an increase in the critical buckling load.

Unstiffened and stiffened cylindrically curved plates are often used in ship structures. For example, they can be found on a deck with a camber, a side shell at the fore and aft parts, and the circular bilge part of a ship structure. It is believed that such cylindrically curved plates can be fundamentally modelled using a portion of a circular cylinder. From estimations using cylindrically curved plate models, it is known that the curvature generally increases the buckling strength compared to a flat plate under axial compression. The existence of curvature is also expected to increase both the ultimate and buckling strengths. In the present study, a series of finite element analyses were conducted on stiffened curved plates with several varying parameters such as the curvature, panel slenderness ratio, and web height and type of stiffener applied. The results of numerical calculations on stiffened and unstiffened curved plates were examined to clarify the influences of such parameters on the characteristics of their buckling/plastic collapse behavior and strength under an axial compression.

Background and aims: Iranian lifting guidelines are used as a risk assessment tool to prevent back pain in various industries. It is believed that the tools and methods used for the assessment should be simple and yet accurate.Given that this guideline adopted the American Conference of Governmental Hygienists (ACGIH) threshold limit values (TLVs) for lifting as allowable load limits and the accuracy of the allowable weight values has not been investigated. The objective of this study was to investigate the effect of trunk angle and anthropometric dimensions on the accuracy of the allowable weight limits. Methods: In this study, 15 workers who had experience in manual handling were asked to perform lifting tasks in accordance with the Iranian guidelines. The subjects’ anthropometric and trunk inclination angles were recorded using a triaxial accelerometer (inclinometer) for each task, and the compressive forces were estimated using 3DSSPP and then compared with NIOSH’s recommended limits (3400N). Results:The results showed that among 25 tasks, the mean trunk angle of 13 tasks was between 90 and 130 degrees. Statistically, considering a standard deviation above the determined mean, the average compressive forces estimated for 9 tasks were greater than NIOSH recommendation (3400). Conclusion: In most tasks, vertical height and horizontal distance of external loads from the body leads to awkward postures that can be the main reasons for increased compressive force. Lack adaption some anthropometric measurements result in increased mechanical loads on the back. Therefore, it seems that the limit values for Iranian lifting guideline are not sufficiently accurate to assess the risk of back injuries and needs to be reviewed.

In bone tissue engineering, the design of in vitro models able to recreate both the chemical composition, the structural architecture, and the overall mechanical environment of the native tissue is still often neglected. In this study, we apply a bioreactor system where human bone-marrow hMSCs are seeded in human femoral head-derived decellularized bone scaffolds and subjected to dynamic culture, i.e., shear stress induced by continuous cell culture medium perfusion at 1.7 mL/min flow rate and compressive stress by 10% uniaxial load at 1 Hz for 1 h per day. In silico modeling revealed that continuous medium flow generates a mean shear stress of 8.5 mPa sensed by hMSCs seeded on 3D bone scaffolds. Experimentally, both dynamic conditions improved cell repopulation within the scaffold and boosted ECM production compared with static controls. Early response of hMSCs to mechanical stimuli comprises evident cell shape changes and stronger integrin-mediated adhesion to the matrix. Stress-induced Col6 and SPP1 gene expression suggests an early hMSC commitment towards osteogenic lineage independent of Runx2 signaling. This study provides a foundation for exploring the early effects of external mechanical stimuli on hMSC behavior in a biologically meaningful in vitro environment, opening new opportunities to study bone development, remodeling, and pathologies.

This study focuses on the effect generated by a compressive load, in the range 15%−60% of the ultimate load (Fu), in the chloride penetration rate of cement-based materials. The modifications produced in the microstructure influence the transport properties, and, thus, the validation of several interesting parameters, such as, the load value and the loading time, including both static and dynamic loading modes, was evaluated. This analysis was performed by impedance spectroscopy (IS), a non-destructive technique that allowed, after the appropriate modeling analysis, the assessment of the resistivity of the sample, a parameter that has been correlated to the diffusion coefficient in a previous investigation. The experimental arrangement was designed to allow the recording of the impedance spectra under the effect of a compressive load and, thus, the real-time monitoring of the chloride diffusivity was provided. An increase in the diffusion coefficient was verified for a load at 60%Fu whereas no variations were obtained for the load fixed at 30%. A relevant difference could be checked if the values were measured once the load was removed, showing the importance of the precise loading stage for the chloride diffusion study.

Carbon nanofibers (CNFs) were directly synthesized on Portland cement particles by chemical vapor deposition. The so-produced cements contained between 2.51–2.71 wt% of CNFs; depending on the production batch. Several mortar mixes containing between 0 and 10 wt% of the modified cement were produced and the electrical properties at various ages and the load sensing capabilities determined. The percolation threshold related to the electrical conductivity was detected and corresponded to the amount of the present CNFs, 0.271, 0.189, 0.135 and 0.108 wt%. The observed threshold depended on the degree of hydration of the Portland cement. The studied mortars showed a strong piezoresistive response to the applied compressive load reaching a 17% change of the electrical resistivity at an applied load of 3.5 MPa and 90% at 26 MPa. This initial study showed that the studied material is potentially suitable for future development of novel fully integrated monitoring systems for concrete structures.

We have studied an application of the Voronoi tessellation method in the modeling of open-cell aluminium foam under uniaxial compressive loading. The Voronoi code was merged with computer-aided design (CAD) for converting the polyhedral model into an irregular open-cell cellular structure to create porous samples for compression testing simulations. Numerical simulations of the uniaxial compression uniformly over the upper surface of the sample in the z-axis direction at a constant 20 N load was realised. Samples with three different porosities (30%, 60% and 80%) were studied. A nonlinear elasto-plastic material model with perfect plasticity, without hardening, based on the von Mises yield criterion was applied below 10% strain. Corresponding stress–strain curves were observed and the influence of porosity on deformation mechanism was discussed. Samples with higher porosity exhibited significantly higher normal stress under the same load, and increased stress plateaus. An increase of porosity produced an increase of both compressive and tensile stresses and struts exhibited complex stress fields. Voronoi-based modeling was in accordance with experimental results in the literature in the case of the quasi-static condition and linear elastic region (below 1% strain). Further study is necessary to enable the simulation of real dynamic behaviour under all deformation regimes by using the Voronoi tessellation method.

Objective : To determine the failure mode of depressive osteochondral fracture under the maximum compressive load. Design : An experimental cadaveric study. A compressive load was applied through an indenter on a femoral condyle to create a depressive osteochondral fracture until the maximum load was reached. Background : Most depressive osteochondral fractures occur without a gross articular cartilage injury because a large amount of load is reabsorbed by the surrounding tissues, especially the subchondral bone under the cartilage. We asked what the mode of depressive osteochondral fracture is. It might function as a load adsorber from the articular cartilage. Methods : Three groups of depressive osteochondral fractures were studied. Croup 1 consisted of 12 pieces of middle third of normal median and lateral femoral condyles. Groups 2 and 3 consisted of 12 pieces of osteoporotic and osteosclerotic middle of both femoral condyles. Using a universal testing machine, a depressive osteochondral fracture was created by applying a uniaxial compressive load through an indenter until the load rose to the maximum level. At that point, the load applied was stopped in order to minimize the extent of subchondral trabeculae fracture. Maximum load was recorded. Pressure and stiffness were calculated. The pattern of depressive fracture was studied histologically. Results : The failure mode of depressive osteochondral fracture wan such that the bone under the articular cartilage had a subchondral plate fracture, an interlacing of bone trabeculae under the plate, and a few fractures of the bone trabeculae. The interlacing of subchondral bone trabeculae was most evident in the normal bone as compared with the osteoporotic and osteosclerotic bones. The osteosclerotic bone failed at the highest load, while the osteoporotic bone failed at the lowest. Conclusion : The subchondral plate fracture and the interlacing of subchondral bone trabeculae under the plate are the characteristics of the failure mode of depressive ostechondral fracture. This failure mode occurs before there is a discernible fracture of the subchondral bone trabeculae. The amount of load causing fracture depends on the quality of the bone. Relevance : The failure mode, especially the interlacing of subchondral bone trabeculae, night function as a load absorber from the articular cartilage. Therefore, the quality of subchondral bone is important for protection of the articular cartilage from compressive load injury.