Shear Stiffness Research Articles

Sex Differences in Aging-related Myocardial Stiffening Quantitatively Measured with MR Elastography.

Purpose To investigate the feasibility of using quantitative MR elastography (MRE) to characterize the influence of aging and sex on left ventricular (LV) shear stiffness. Materials and Methods In this prospective study, LV myocardial shear stiffness was measured in 109 healthy volunteers (age range: 18-84 years; mean age, 40 years ± 18 [SD]; 57 women, 52 men) enrolled between November 2018 and September 2019, using a 5-minute MRE acquisition added to a clinical MRI protocol. Linear regression models were used to estimate the association of cardiac MRI and MRE characteristics with age and sex; models were also fit to assess potential age-sex interaction. Results Myocardial shear stiffness significantly increased with age in female (age slope = 0.03 kPa/year ± 0.01, P = .009) but not male (age slope = 0.008 kPa/year ± 0.009, P = .38) volunteers. LV ejection fraction (LVEF) increased significantly with age in female volunteers (0.23% ± 0.08 per year, P = .005). LV end-systolic volume (LVESV) decreased with age in female volunteers (-0.20 mL/m2 ± 0.07, P = .003). MRI parameters, including T1, strain, and LV mass, did not demonstrate this interaction (P > .05). Myocardial shear stiffness was not significantly correlated with LVEF, LV stroke volume, body mass index, or any MRI strain metrics (P > .05) but showed significant correlations with LV end-diastolic volume/body surface area (BSA) (slope = -3 kPa/mL/m2 ± 1, P = .004, r2 = 0.08) and LVESV/BSA (-1.6 kPa/mL/m2 ± 0.5, P = .003, r2 = 0.08). Conclusion This study demonstrates that female, but not male, individuals experience disproportionate LV stiffening with natural aging, and these changes can be noninvasively measured with MRE. Keywords: Cardiac, Elastography, Biological Effects, Experimental Investigations, Sexual Dimorphisms, MR Elastography, Myocardial Shear Stiffness, Quantitative Stiffness Imaging, Aging Heart, Myocardial Biomechanics, Cardiac MRE Supplemental material is available for this article. Published under a CC BY 4.0 license.

The mechanical performance of reinforced bituminous interfaces with paving fabric under freeze-thaw conditioning

The application of paving fabric at the interface of bituminous layers as a rehabilitation strategy has proved its effectiveness in extending the pavement service life by delaying the manifestation of reflective cracking on the surface. However, this enhanced performance relies on the adhesion bond supplied at the interface, which in the case of debonding, the structural benefits provided by the interlayer can be compromised. Gaining authentic knowledge about the bonding condition at a reinforced interface exposed to different conditioning impacts helps to improve the reliability of the input data, which has not been adequately considered in the mechanistic-based design methods proposed for reinforced bituminous structures. This research was dedicated to understanding the mechanical behavior of double-layer bituminous layers composed of two different hot mixtures and reinforced with paving fabric when subjected to freeze-thaw cycling. To attain this objective, the initial step involved determining the optimal dosage of bitumen for use as a tack coat at the interface of the paving fabric, which was established as 0.0014 m3/m2 through asphalt retention tests. Subsequently, the results from the shear test, conducted using the slant shear device, were utilized to establish three comparative criteria at the interface, aimed at elucidating distinctions when compared to unreinforced cases. These criteria include the energy absorbed by the interface during shearing, shear stiffness, and the coefficient of interface bonding (CIB). This study revealed that by increasing the number of freeze-thaw cycling, the reinforced interface keeps the shear stiffness and the CIB values unchanged. However, in terms of energy absorption capabilities, the unreinforced interfaces showed better performance. This study showed that using the CIB value to quantify the bonding strength at the interface and energy dissipation and initial shear stiffness to quantify the evolution of interface bonding over number of F-T cycles are all proper representatives to include into mechanistic-empirical design methods for reinforced structures in order to present realistic models.

Using crack width for shear, stiffness, and stirrup strain history predictions for reinforced concrete beams

Shear failures in reinforced concrete structures occur with little or no warning. Reinforced concrete members with shear cracks should be evaluated to ensure safety. Existing evaluation methods have large variability, require time-consuming modeling or expert opinion. This study uses machine learning to investigate correlations of crack width with shear loading, stiffness, and stirrup strain histories. Experimental literature enables the assembly of a database of rectangular reinforced concrete slender beams with crack width measurements for beams with shear reinforcement amounts smaller and larger than the minimum required by ACI 318-19. Measured data include crack widths from 122 beams, load–displacement relationship from 100 beams, and stirrup strains from 46 beams. Gaussian Process Regression is used to correlate crack width and geometric, material and design properties to shear loading, stiffness, and stirrup strain histories. Ten-fold cross validation training shows mean absolute percent errors of 18, 33 and 77% for shear, stiffness, and stirrup strain history predictions. The proposed algorithms can be used to accelerate the evaluation of in-service structures and can be updated upon availability of additional data.

Shear failure analysis of UHPC-NC composites interface with U-shaped studs

Given the extensive utilization of composite structures of ultra-high performance concrete (UHPC) and normal concrete (NC) in engineering applications, there has been a growing emphasis on studying the shear failure and mechanical properties analysis of the UHPC-NC interface. U-shaped studs assume a crucial role in reinforcing the UHPC-NC interface. A three-dimensional finite element model was constructed with different parameters to investigate the shear failure and mechanical properties of UHPC-NC incorporating U-shaped studs. The failure mode and the influences of diameter, internal span, stud number and concrete compressive strength on the shear characteristics of the UHPC-NC interface were analyzed. The numerical analysis indicates the final failure mode of the UHPC-NC interface with U-shaped stubs is the fracture of the U-shaped stud. The diameter and internal span of studs influence the interface shear capacity, while interface shear capacity is not sensitive to the compressive strength of UHPC and NC. Moreover, a calculation formula for the shear capacity of the UHPC-NC interface with U-shaped studs was proposed, considering the influence of stud diameter and internal span. An exponential function is recommended for predicting the interface shear slip and the stiffness corresponding to 0.55 times the shear capacity is adopted as the elastic shear stiffness. The interface shear slip model and the expression for elastic shear stiffness were established, providing a reference for approximate calculation without experimental data.

Push-Out Analysis on the Shear Performance of a New Type of Bellow-Sleeved Stud

For continuous steel–concrete composite girder bridges based on the post-combined method, the conventional rectangular group studs contribute to the isolation of the steel girder and the concrete slab before prestressing, leading to the majority of prestress forces being introduced to the concrete slab. However, rectangular-group stud holes cause the prestress forces to be unevenly distributed. In this study, a new type of bellow-sleeved stud (BSS) was developed to mitigate the weakening effects of rectangular group stud holes on the slab. A steel corrugated sleeve with a diameter of 60 mm was employed to cover the stud, which served as an internal formwork to prevent the concrete from bonding with the root of the stud. After prestressing was complete, the steel sleeve was filled with ultra-high-performance concrete (UHPC) to create a reliable combination between the concrete slab and the steel girder. To investigate the shear performance of this new type of connection, eight push-out test specimens were designed, and finite-element models were built. This study drew a comparison between the BSS and the ordinary headed stud (OHS). The research findings suggested that the BSS is subjected to less bending–shear coupling and offers a 4.5% increase in shear strength and a 31.9% increase in shear stiffness compared with the OHS. The study also analyzed the structural parameters influencing the shear performance of the BSS. It is found that the steel sleeve of the BSS has a negative effect on shear performance, but this can be mitigated by infusing high-strength material into the sleeve. Furthermore, the study examined the effect of construction quality on shear performance and suggested that sleeve deviation and grout leakage considerably reduced the shear performance of the BSS. Accordingly, strict control over the construction quality of the BSS is necessary.

The effect of combined use of plybamboo sheathings and self-tapping screws in enhancing wood-frame shear wall performance

ABSTRACT Plybamboo panels are renewable and eco-friendly structural panels with high strength, good dimensional stability, and affordability, making them highly suitable for wood-frame construction. This study presents an experimental investigation of the wood-frame shear wall constructed with plybamboo-sheathing panels with self-tapping screws (STSs) subjected to monotonic and cyclic loadings. Performance parameters including shear strength, elastic shear modulus, ductility ratio, stiffness degradation, and energy dissipation were evaluated. Results indicate that the combined use of plybamboo sheathings and STSs can substantially reduce failures due to the tearing of sheathing, fastener head pull-through, and fastener withdrawal. The plybamboo-sheathed wood-frame shear walls with STSs had over 1.8 times shear strength and 1.4 times ultimate displacement than those of comparable wood-frame shear walls with nails, respectively, maintaining over 80% of their maximum lateral load capacity at a drift level over 4%. Moreover, the influence of aspect ratio and screw spacing on the elastic shear modulus, shear strength, and stiffness degradation of the plybamboo-sheathed wood-frame shear walls with STSs are consistent with those for common wood-frame shear walls.

Study of Panel Zone Behavior in Interior Beam–Column Joints with Reduced Beam Section (RBS)

Based on the post-earthquake investigation of the Beiling and Hanshen earthquakes, many welded rigid beam–column joints were found to exhibit brittle failure. The failure modes of the joint region and the overall steel frame structure under the action of the earthquake need to be studied. The seismic performance of different types of weakened beam-end interior joints was investigated. The finite element method was verified by high-strength steel beam–column joint tests conducted by our research team. Finite element modeling of weakened steel beam flanges and weakened steel beam web joints was carried out based on the validated finite element modeling method. The joints were studied and analyzed using seismic parameters such as joint stress clouds, equivalent story shear–inter-story displacement ratio curves, panel zone bending moment–shear ratio curves, ductility, stiffness, and energy dissipation. The results of this study showed that honeycomb open hole-type joints exhibit a better deformation and energy dissipation capacity compared to open circular web hole-type joints. However, their load carrying capacity is reduced, which is mainly due to the larger area of the web openings. Additionally, double reduced beam section (DRBS) joints exhibit superior seismic performance and plastic hinge outward movement characteristics compared to single reduced beam section (RBS) joints. It was also found that the deformation and energy dissipation of DRBS joints and steel beam honeycomb hole-type joints are mainly borne by the beams, with the panel zone’s participation in energy dissipation accounting for a smaller proportion of the energy.

Experimental studies on the mechanical behaviors of cold-formed thin-walled steel-foam concrete composite walls

This paper presents experimental studies to investigate the compressive and shear behaviors of cold-formed thin-walled steel-foam concrete composite walls. Three compressive walls and three shear walls were tested. The failure mode and load-displacement curve of the specimen were obtained from the compressive experiment. The compressive wall infilled with foam concrete mainly experienced distortion buckling of the end stud and local crushing failure of the concrete. The stud openings had a limited effect on the compressive bearing capacity of the composite wall. The failure mode and load-deformation curve were obtained in shear tests. The ductility index, shear stiffness, yield load, peak load, energy dissipation, and stiffness degradation were analyzed. The shear composite wall filled with foam concrete mainly occurred concrete crushing failure, local or distortional buckling failure of the end stud, and cracking failure of the calcium silicate board. The shear stiffness, shear capacity, ductility, and energy dissipation of the composite wall could be significantly improved after filling with foam concrete.

Optimal surface clothing with elastic nets

The clothing problem aims at identifying the shape of a planar fabric for covering a target surface in the three-dimensional space. It poses significant challenges in various applications, ranging from fashion industry to digital manufacturing. Here, we propose a novel inverse design approach to the elastic clothing problem that is formulated as a constrained optimization problem. We assume that the textile behaves as an orthotropic, nonlinear elastic surface with fibers distributed along its warp and weft threads, and we enforce mechanical equilibrium as a variational problem. The target surface is frictionless, except at its boundary where the textile is pinned, imposing a unilateral obstacle condition for the reactive forces at the target surface. The constrained optimization problem also accounts for an elongation condition of the warp and weft fibers, possibly with bounded shearing angle. We numerically solve the resulting constrained optimization problem by means of a gradient descent algorithm. The numerical results are first validated against known clothing solutions for Chebyshev nets, taking the limit of inextensible fibers. We later unravel the interplay between thread and shear stiffness for driving the optimal cloth shape covering the hemisphere and the hemicatenoid. We show how the metric of these target surfaces strongly affects the resulting distribution of the reaction forces. When considering the limit of covering the full sphere, we show how clothing with elastic nets allows to avoid the onset of singularities in the corresponding Chebyshev net, by developing corners at the cloth boundary.

Experimental and theoretical evaluation of inclined screws in glued laminated bamboo and timber-concrete composite beams

In the timber-concrete composite beam, the timber beam in tension tends to fail in a brittle manner, which results in insufficient utilization of material strength in the compression zone and significant deformation problems. To improve the mechanical performance of the weak sections in the composite beam, a novel type of glued laminated bamboo and timber (GLBT)-concrete composite beam is proposed in which the bamboo layers are placed in the tension and compression zones of the beam. In this paper, thirty-six shear experiments were conducted to investigate the shear behavior of inclined screws in GLBT-concrete composite beams. The test results showed that the failure modes of diagonally positioned screws in GLBT-concrete composite beams involved pull-out failure of the screw and cone expulsion failure of the concrete. The pure tensile-shear loaded screws experienced the pull-out failure and single-hinge bending failure. For bamboo thicknesses of 30, 60, and 300 mm, the shear capacity of diagonally positioned screws increased by 27.9 %, 34.7 %, and 40.7 %, respectively, compared to the screws in pure wood members. Besides, the shear stiffness was improved by 40.4 %, 78.1 %, and 88.7 %, respectively. It was found that as bamboo thickness increased, the shear capacity and stiffness of diagonally positioned screws gradually improved, although the rate of increase gradually diminished. Among the four types of embedding methods, the ±45° diagonal screw connectors exhibited the highest shear stiffness, while the 135° unidirectional inclined screws (pure compressive-shear screws) had the lowest shear capacity and stiffness. This paper presented a theoretical model for estimating the shear capacity of inclined screw connectors in GLBT-concrete composite beams, which considered the various stress distributions of the screw connectors embedded in bamboo and timber layers.

Mitigation of Soil Erosion and Enhancement of Slope Stability through the Utilization of Lignin Biopolymer.

Human activities have had a profound impact on the environment, particularly in relation to surface erosion and landslides. These processes, which are natural phenomena, have been exacerbated by human actions, leading to detrimental consequences for ecosystems, communities, and the overall health of the planet. The use of lignin (LIG) as a biopolymer soil additive material is regarded as an eco-friendly solution against soil erosion and slope failure which holds immense promise. However, significant research gaps currently hinder a comprehensive understanding of its mechanisms and effectiveness. Experimental studies offer a robust platform to address these gaps by providing controlled conditions for assessing soil stability, exploring mechanisms, and evaluating adaptability. Bridging these research gaps will contribute to the development of innovative and sustainable strategies for mitigating soil erosion and preventing slope failure, thereby promoting environmental resilience and resource conservation. This study aimed to investigate the effect of the LIG biopolymer on mitigation of soil erosion, slope failure and the enhancement of soil strength by conducting laboratory tests (UU triaxial, unconfined compressive strength (UCS), and soaking) as well as flume experiments under uniform rainfall events. The alterations in the engineering characteristics and erosion resistance of silty soil mixed with a LIG additive at concentrations of 1% and 3.0% by weight have been examined. The results show that the LIG-treated samples demonstrated an enhanced resistance to surface erosion and an enhanced prevention of slope failure, as well as improved shear stress, cohesion, stiffness, and resistance to water infiltration.

Dynamic slip behavior and off-fault damage of tension-induced fractures constrained by different grain sizes in granite

The mineralogy and texture of granite have been found to have a pronounced effect on its mechanical behavior. However, the precise manner in which the texture of granite affects the shear behavior of fractures remains enigmatic. In this study, fine-grained granite (FG) and coarse-grained granite (CG) were used to create tensile fractures with surface roughness (i.e. joint roughness coefficient (JRC)) within the range of 5.48–8.34 and 12.68–16.5, respectively. The pre-fractured specimens were then subjected to direct shear tests under normal stresses of 1–30 MPa. The results reveal that shear strengths are smaller and stick-slip behaviors are more intense for FG fractures than for CG fractures, which is attributed to the different conditions of the shear surface constrained by the grain size. The smaller grain size in FG contributes to the smoother fracture surface and lower shear strength. The negative friction rate parameter a – b for both CG and FG fractures and the larger shear stiffness for FG than for CG fractures can account for the more intense stick-slip behaviors in FG fractures. The relative crack density for the post-shear CG fractures is greater than that of the FG fractures under the same normal stress, both of which decrease with the distance away from the shear surface following the power law. Moreover, the damage of CG fracture extends to a larger extent beneath the surface compared with the FG fracture. Our findings demonstrate that the grain size of the host rock exerts a significant influence on the fracture roughness, and thus should be incorporated into the assessment of fault slip behavior to better understand the role of mineralogy and texture in seismic activities.

Performance Assessment of Commercial Building for Symmetric and Asymmetric Plan Configurations in Different Seismic Zones of Bangladesh Using ETABS

Bangladesh is among the nations most vulnerable to earthquakes worldwide. Being a developing country, it has been a challenging issue to ensure commercial prosperity along with safety against seismic hazards. Structural engineers also face difficulties in accurately designing buildings with maximum economy and efficiency. ETABS, a leading global engineering software with BNBC 2020 guidelines plays a vital role in these cases. In this study, analysis of a B+G+6 storied building for Symmetric & Asymmetric Plan configuration has been performed using ETABS software. Both kinds of structures have experienced a range of loads for example- dead loads, live loads, partition loads, wind loads, and seismic loads, as well as load combinations that have been pursued following BNBC 2020 requirements. The objective of this work is to evaluate the seismic impact resulting from varying seismic coefficients for four seismic zones in Bangladesh, given identical symmetric and asymmetric plan arrangements. Four required metrics were evaluated between the structural performances of symmetric and asymmetric structures: storey drift, overturning moment, storey shear, and storey stiffness. The structural software provided the analytical results and parameter computations. The comparison's result demonstrates that the asymmetric structure exhibits greater storey rigidity and less storey drift over the longer axis.

Evaluating the shear stiffness of asymmetric angle-ply layers in diagonal cross-laminated timber

Evaluating the shear stiffness of asymmetric angle-ply layers in diagonal cross-laminated timber

Experimental and theoretical investigations on the static behavior of low aspect ratio shear stud connectors in ultra high performance concrete

In reinforcement project for early-built orthotropic steel bridge decks (OSDs) using ultra high performance concrete (UHPC), low aspect ratio shear stud connectors in UHPC are required. In present study, push-out tests of six static UHPC specimens with and without reinforcement bars were first conducted. The failure modes, load-slip curves and shear capacity of shear stud connectors embedded in UHPC with an aspect ratio of 1.84 were investigated. Subsequently, the experimental results of shear capacity and load-slip curves were compared with the theoretical calculation results. Finally, a new theoretical model of shear stiffness was proposed for low aspect ratio shear studs based on the energy equivalence theory. The experimental results indicated that the failure mode of all specimens was stud shank failure, while the UHPC slabs without reinforcement bars showed extensive cracks. The effect of reinforcement bars on the behavior of shear studs embedded in UHPC slabs can be negligible. The reinforcement bars mainly affected the internal force flow in the UHPC, thus limiting crack initiation and extension. The compressive strength of the UHPC and the weld collar had significant impact on the shear capacity of short studs in the UHPC. In calculating the load-slip curves of short shear stud connectors in UHPC, the theoretical results calculated using the fractional form equations were in better agreement with the experimental results. The proposed theoretical model neglecting the deformation of shear stud in elastic stage can accurately predict the shear stiffness of low aspect ratio shear stud connectors in UHPC.

Stiffness Anisotropy and Micro-Mechanism of Calcareous Sand with Different Particle Breakage Ratios Subjected to Shearing Based on DEM Simulations

Stress-induced anisotropy in calcareous sand can cause an uneven displacement in island reef engineering. In this study, stiffness, as a quantitative indicator, is explored to reveal the stress-induced anisotropy in calcareous sand. Based on the discrete element method, the stiffness anisotropic characteristics of calcareous sand during shearing, as well as the impact of particle breakage, are investigated by numerical simulations. Both the macro and micro responses, i.e., the maximum shear modulus, contact normal, strong and weak contact normal force, and the direction of particle breakage, are explored for calcareous sand with different particle breakage ratios. The results show that calcareous sand exhibits notable anisotropy during shearing, with the maximum shear modulus in the vertical direction (deviatoric stress direction) being significantly greater than that in the horizontal direction. Moreover, the higher the particle breakage rate, the lower the stiffness and its anisotropy. The micro-mechanism results indicate that the primary particle breakage during the shearing process occurs in the vertical direction. That is, the particle breakage weakens the strong contact force in the vertical direction, leading to a redistribution of the strong contact forces from the vertical direction to other directions. This redistribution mainly manifests in a decrease in the anisotropy of contact normal and contact vector within the sample, as well as a decrease in the proportion of strong contact forces in the overall contacts. This, in turn, reduces the shear strength and stiffness of calcareous sand, particularly in the vertical direction, and results in a decrease in the maximum shear modulus and its anisotropy. The maximum reduction can be up to 50% of the original value. These insights can provide a certain theoretical support for the uneven displacement and long-term stability of calcareous sand for islands and reefs.

Experimental Study of Direct Shear Properties of Anisotropic Reservoir Shale

Understanding the shear mechanical properties of shale reservoirs is of great significance in the study of the formation stability around horizontal shale wells and the propagation and evolution of fractures for shale fracturing. However, the existing direct shear test results are limited due to small sample sizes and low shear rates. Based on previous experimental research results, the mechanical properties of anisotropic reservoir shale in direct shear tests with different experimental conditions were explored in this study. It was found that the shear mode, shear strain rate, and normal stress have a significant impact on the deformation and failure characteristics of shale. The peak shear displacement, peak shear strength, and shear stiffness of shale present an increasing trend of fluctuation, with an increase in the bedding angle. The peak shear strength of shale decreases with an increase in the shear strain rate, and this decrease trend descends with an increase in the shear strain rate. The shape of the shear fracture zone and the shear fracture mode of shale exhibit bedding effect characteristics. The fractal dimension of the shale shear fracture surface morphology shows a trend of fluctuation with the variation in the bedding angle. Further, the shear strain rate was found to play a dominant role in the fractal dimension of the shear fracture surface. The larger shear strain rate strengthens the bedding effect of the roughness for the shear fracture surface morphology. The results of this study provide a theoretical reference for determining the engineering geomechanics characteristics of shale reservoirs.

Investigation on laminated steel slit shear walls with low yield steel

To improve the energy dissipation capacity of steel slit shear walls made of thin plates and mitigate the adverse effects from the large out-of-plane deformation and potential local buckling failure, a novel laminated steel slit (LSS) shear wall assembled from two single-layer steel slit (SSS) shear walls is proposed in this study. First, the theoretical analysis method for predicting the shear strength and stiffness of the LSS shear walls is proposed. To validate the theoretical method as well as investigate the hysteretic performance of the LSS shear walls, two specimens made from different materials, common carbon steel and low yield steel, are designed and tested experimentally under quasi-static cyclic loading. Refined finite element models are developed to simulate the hysteretic behaviors of the LSS shear walls, which show good agreement with the test results. Further, the performance differences between the LSS shear walls and SSS shear walls are analyzed using the validated numerical simulation approach. The strength and stiffness of the LSS shear walls are greater than the summation of the individual SSS shear walls, attributed to the interaction between the different layers in the LSS shear walls. The energy dissipation efficiency of the LSS shear walls is improved and the stiffness degradation is effectively delayed, thanks to the incorporation of the low yield steel material. Finally, to evaluate the effects of the contributing factors on the seismic performance of the LSS shear walls, a series of parametric analyses are performed. Parametric analysis results show that the use of the low yield steel helps to improve the ductility and energy dissipation capacity of the LSS shear walls and delay the stiffness degradation. A large link width ratio, small link length ratio and large link thickness ratio can all contribute to a large strength, stiffness and absolute energy dissipation of the LSS shear walls, but the former two at the same time deteriorate the stiffness degradation.

The role of the extracellular matrix in the reduction of lateral force transmission in muscle bundles: A finite element analysis

Background and objectiveAging is associated with a reduction in muscle performance, but muscle weakness is characterized by a much greater loss of force loss compared to mass loss. The aim of this work is to assess the contribution of the extracellular matrix (ECM) to the lateral transmission of force in humans and the loss of transmitted force due to age-related modifications. MethodsFinite element models of muscle bundles are developed for young and elderly human subjects, by considering a few fibers connected through an ECM layer. Bundles of young and elderly subjects are assumed to differ in terms of ECM thickness, as observed experimentally. A three-element-based Hill model is adopted to describe the active behavior of muscle fibers, while the ECM is modeled assuming an isotropic hyperelastic neo-Hookean constitutive formulation. Numerical analyses are carried out by mimicking, at the scale of a bundle, two experimental protocols from the literature. ResultsWhen comparing numerical results obtained for bundles of young and elderly subjects, a greater reduction in the total transmitted force is observed in the latter. The loss of transmitted force is 22 % for the elderly subjects, while it is limited to 7.5 % for the young subjects. The result for the elderly subjects is in line with literature studies on animal models, showing a reduction in the range of 20–34 %. This can be explained by an alteration in the mechanism of lateral force transmission due to the lower shear stiffness of the ECM in elderly subjects, related to its higher thickness. ConclusionsComputational modeling allows to evaluate at the bundle level how the age-related increase of the ECM amount between fibers affects the lateral transmission of force. The results suggest that the observed increase in ECM thickness in aging alone can explain the reduction of the total transmitted force, due to the impaired lateral transmission of force of each fiber.

Enhance the performance of steel-wood composite screw connections with fast-curing adhesive

In composite floors composed of the H-steel and the wood panel, screw connection is one of the design keys. In this paper, the method of using fast-curing epoxy resin to anchor the screw tip was proposed, and six sets of pull-out tests and five sets of push-out tests of epoxy-wood-combined anchored screws were conducted to analyze the influence of the effective meshing length and the epoxy meshing ratio on the connection performance, respectively. Firstly, compared with ordinary screws, the pull-out stiffness and strength of epoxy-anchored screws were increased by 79.8 % and 153.9 %, respectively. Secondly, compared with the ordinary screw connection, the initial shear stiffness and capacity of the steel-wood composite connection were increased by 60.0 % and 22.8 % when the epoxy meshing ratio was 0.25, respectively. Thirdly, the modified effective meshing length of epoxy-anchored screws was proposed. Finally, based on the calculation formula for screws with two plastic hinges in Eurocode 5, the two parameters of pull-out resistance and yield moment for the screw were modified, thus improving the calculation accuracy of shear capacity for combine-anchored screw connections by about 21.0 %.