Strength Ratio Research Articles

Seismic Strength Evaluation of Corroded Reactor Containment Building

The purpose of this study is to investigate the effects of the corrosion phenomenon on the seismic strength of a reactor containment building (RCB) in nuclear power plants (NPPs). A corrosion degradation model is proposed based on the rationale of NPP structures and applied to the reinforcements near the base mat of RCB. Three corrosion levels associated with the service life of the structure up to 60 years are considered in this study. Seven different cases are considered depending on the location of corrosion. A series of pushover analyses are performed to evaluate the seismic responses of the corroded RCB, considering all cases with different levels of damage due to corrosion. The results are obtained in terms of global responses, in which capacity curves, base shear at different limit states, demand–capacity ratios, and reserve strength ratios (RSR) are quantified. The findings of this study demonstrate that corrosion can cause a reduction in structural capacity in terms of base shear of up to 19.5% during its service life of 60 years and that is dependent on how the corrosion is propagated within RCB. The results also illustrate that corrosion in the elements in the tension zone increases the sensitivity of the responses subjected to seismic loads.

Clinical and magnetic resonance imaging outcome after proximal hamstring tendon repair at mean 3 years follow-up

PurposeThe purpose of this study was to assess clinical and radiological outcome in patients after proximal hamstring tendon repair. We hypothesized that there is a significant correlation among subjective clinical outcome and interlimb asymmetries in muscle strength, fatty infiltration, and hamstring volume.MethodsThis retrospective monocentric case series included patients with surgical repair after proximal hamstring tendon rupture. Clinical outcome was assessed utilizing: Healthy Days Core Module (CDC HRQOL-4), numeric pain rating scale (NRS), modified Harris Hip Score (mHHS), Tegner Activity Scale (TAS), return to pre-injury activity level (RTPA), and patient satisfaction score. Postoperative hamstring strength was measured using a handheld dynamometer and radiological outcome was determined by postoperative magnetic resonance imaging (MRI).ResultsTwenty-seven patients with a mean age of 51.2 (± 12.6) years were available for follow-up at a mean of 41.11 (± 18.4) months. Patients state a mean of 10.6 (± 11.5) days in the unhealthy days (UHD) index and 88.9% show “good health” in the simple summary score (SSS). Mean subjective outcome scores were as follows: NRS 1.1 (± 2.4), mHHS 90.3 (± 14.8) and TAS 5.7 (± 2.2). A total of 59.3% RTPA and 88.9% state to be somewhat or very satisfied with their surgery. Mean interlimb strength ratio was 0.88 (± 0.21). MRI demonstrated a fully restored muscle–tendon unit, significantly greater fatty infiltration in the injured hamstrings (p = 0.009, d = 0.558), and a mean interlimb hamstring volume ratio of 0.94 (± 0.11). With respect to the 10% benchmark, patients had no significant asymmetries in muscle strength (p = 0.677, d = 0.084) or hamstring volume (p = 0.102, d = − 0.34). Correlation analysis revealed moderate correlation among asymmetries in strength and volume (p = 0.073, r = 0.373). In patients with the operated side inferior to the healthy side (n = 15), there was strong correlation among asymmetries in strength and volume (p = 0.002, r = 0.725). Statistically significant correlation was found between interlimb muscle volume atrophy and increase in fatty infiltration (p = 0.015, r = 0.481).ConclusionProximal hamstring repair results in good clinical outcome with satisfactory recovery of hamstring strength and volume. Interlimb asymmetries, in terms of muscle strength, fatty infiltration, and hamstring volume do not correlate with clinical outcome.Study TypeRetrospective cohort study; Level of evidence, 3.

Degradation of Interfacial Bond for FRPs Near-Surface Mounted to Concrete Under Fatigue: An Analytical Approach

In this study, an analytical model was developed for the local bond degradation behavior between a near-surface mounted (NSM) fiber-reinforced polymer (FRP) and concrete under fatigue loading. A trilinear local bond stress–slip relationship was adopted to characterize the fundamental bond behavior at the FRP-epoxy-concrete interface at different stages of elastic, softening and debonding. A series of post-fatigue direct pull-out tests (DPTs) of NSM FRP-bonded concrete blocks was conducted to provide the local bond degradation laws for the analytical model. The bond region was discretized into finite elements to include the effect of bond degradation to different extents, and a closed-form solution was derived by virtue of appropriate boundary conditions in each fatigue cycle. The model is capable of predicting the FRP strain distribution, local bond stress distribution and relative slip development at a targeted number of fatigue cycles. The reliability of the analytical model was confirmed by experimental data, and its sensitivity to various parameters such as local bond strength, the residual bond strength ratio and Young’s modulus of FRP reinforcement was also assessed in this study.

A Finite Element Method orthotropic multi-yield elastic-inelastic model of a wood-adhesive-steel composite

Composite elements made of wood reinforced by adhesively inter-layered steel lamina can be employed as structural elements in building engineering, thanks to their favorable ratios of strength and stiffness to mass and their ductility. The mechanical response of such composite, under loading, can be predicted by employing a Finite Element Method with a proper model of each material. In this work, the Finite Element Method model is formulated within the theories of Continuum Mechanics and irreversible thermodynamics of deformation, finite strains hypothesis, and kinematics of large displacements. For the wood material constituent an orthotropic elastic–plastic-damage constitutive law is adopted, to address the effects of irreversible strains, formulated by a multi-surface yield, both for plasticity and damage, where each yield surface operates disjointedly each other, at the level of stress–strain component. The validity of the proposed model and its computational technique is revealed by analyzing the stress–strain path until the failure of a composite element. Thus, the numerical results are compared with the experimental data obtained in a tension test of that composite element. The proposed model adequately represents the mechanical behavior of the composite.

The Influence of the Root Diameter of Cunninghamia lanceolata (Chinese Fir) on the Strength and Deformation Behavior of Sand

This study used triaxial tests to examine the impact of the root diameter of Cunninghamia lanceolata (Chinese fir) on the mechanical behavior of sand, including stress–strain development, strength, volumetric strain, and failure envelope. It also revealed the reinforcement mechanisms of roots with different diameters based on root–soil interactions. The results showed the following: (1) The addition of roots significantly enhanced sand strength and reduced volumetric deformation. The average peak strength increased by 31.8%, while the average peak volumetric strain decreased by 34.3%. (2) Roots provided additional cohesion and increased the friction angle of the sand, causing the failure envelope to shift upward and deflect. (3) Smaller-diameter roots improved the mechanical properties of sand more significantly, leading to higher peak strength, shear strength parameters, and smaller volumetric deformation. As the root diameter increased from 1 mm to 5 mm, the peak strength ratio decreased from 1.78 to 1.13, and the peak volumetric strain increased from 0.48 to 0.79. (4) Smaller-diameter roots, which form denser networks, allowing more roots to resist loads, and have a higher elastic modulus providing greater tensile stress, also possess higher tensile strength and critical sliding tensile stress, making them less likely to fail, thereby making the mechanical reinforcement of sand more significant.

Study of the motion and interaction of micro-swimmers with different scales in Poiseuille flow

We conducted numerical simulations using the immersed boundary–lattice Boltzmann method to investigate the motion and interaction of microswimmers of different scales in Poiseuille flow. The squirmers self-propelling via generating surface waves were used as the model for microswimmers. The movement of two squirmers with different scale ratios (0.6–1.5), swimming Reynolds numbers (0.1–2.0), swimming strength (1–7), and blockage ratios (0.125–0.25) in Poiseuille flow was studied. Five classical motion patterns were identified: periodic tumbling, steady motion, periodic oscillation, damped oscillation, and chaotic motion modes. Initially, we examined the interaction between a pair of squirmers of the same scale and elucidated the causes of their different motion pattern transitions using the pressure distribution, direction angle, and swimming velocity of the squirmers. We investigated the variation of transport velocity with blockage ratio and swimming strength. A pair of squirmers with small ratios tended to migrate in a stable motion pattern, while those with large ratios showed a high tendency to change their motion patterns. Pushers with an increasing swimming Reynolds number were adsorbed to the wall and migrated stably along the wall.

Effect of one-part geopolymer filler on the performance of cold bitumen emulsion mixtures

ABSTRACT This study aims to assess the performance of cold bitumen emulsion mixtures modified with a one-part geopolymer based on blast furnace slag and an alkaline activator. This material is generally prepared in a liquid solution, from an aluminosilicate source and an alkaline compound, and is dedicated to the precast sector. In this study, it was obtained by mechanosynthesis, a solvent-free process consisting of high-energy ball milling. The powder was incorporated as a filler in the formulation of 0/10 asphalt mixes. Other cold mixtures with limestone and blast furnace slag filler were manufactured to evaluate the influence of the additive nature on the cohesive strength at different curing times, compressive strength, water sensitivity, rutting resistance and resilient modulus. The potential chemical reactivity between each filler and each emulsion was monitored by in situ Fourier transform infrared spectroscopy. The results pointed out that the cohesive strength of the mixes containing one-part geopolymer is two to three times higher than that of the other formulations after 24 h curing. High compressive strength of the one-part geopolymer-based mixes is noticed; however, their compressive strength ratio is slightly lower, in comparison with the other mixes. The rutting percentage of the one-part geopolymer-based mixes reaches 4% at 30,000 cycles and their resilient modulus above 6,000 MPa at 15 °C. These results are attributed to the geopolymerisation reaction occurring between the filler and the emulsion, traduced by a shift in infrared spectroscopy. Therefore, the addition of one-part geopolymer filler, produced according to a non-solvent process, is a promising solution to enhance the implementation and durability of cold mixtures.

Multiple-quantum magic-angle spinning NMR spectra in the static limit: The I = 3/2 case.

A simplified theoretical description of multiple-quantum excitation and mixing for nuclear magnetic resonance of half-integer quadrupolar nuclei is presented. The approach recasts the multiple-quantum nutation behavior in terms of reduced excitation and mixing curves through a scaling of the first-order offset frequency by the quadrupolar coupling constant. The two-dimensional correlation of the static first-order anisotropic line shape to the second-order anisotropic magic-angle-spinning (MAS) line shape is utilized to transform the three-dimensional integral over the three Euler angles into a single integral over the dimensionless first-order offset parameter. These transformations lead to a highly efficient algorithm for simulating the multiple-quantum (MQ)-MAS spectrum for arbitrary excitation and mixing radio frequency (RF) field strengths, pulse durations, and MAS rates within the static limit approximation, which is defined in terms of the rotation period, pulse duration, RF field strength, and quadrupolar coupling parameters. This algorithm enables a more accurate determination of the relative site populations and quadrupolar coupling parameters in a least-squares analysis of MQ-MAS spectra. Furthermore, this article examines practical considerations for eliminating experimental artifacts and employing affine transformations to improve least-squares analyses of MQ-MAS spectra. The optimum ratio of RF field strength to the quadrupolar coupling constant and the corresponding pulse durations that maximize sensitivity within experimental constraints are also examined.

Reactionary powder concrete based on alkali-activated cement

The development of reactive powder concretes based on alkali-activated cements for the construction and protection of critical infrastructure is of woldwide importance for improving the safety of their exploitation. The factors influencing the kinetics of strength gain and drying shrinkage of reactive powder concretes using sodium silicate pentahydrate as an alkaline activator were determined.It was shown that increasing the ratio of alkali-activated cement to sand from 1:3 to 1:1 and using the activator in the liquid state increased the concrete strength gain: the compressive strength was 52.3 MPa, 85.0 MPa, 100.6 MPa, and 124.7 MPa at the ages of 1, 3, 28, and 90 days of hardening, respectively. The ratio of compressive strength to flexural strength was 5.3...5.9 at an age of 28 days, indicating a high fracture toughness of the obtained material. An increase in the content of alkali-activated cement in concrete determined a decrease in the influence of sand granulometry on concrete strength,due to its “floating” placement in the cement matrix.The introduction of a fine calcite additive ensured to reduce the shrinkage of concrete by 1.3...1.5 times at an age of 90 days due to the densification of the microstructure and the intensification of crystallisation processes. The implementation of these measures resulted in a high strength alkali-activated cement reactive powder concrete of strength classC80/95, high fracture toughness and reduced drying shrinkage.

Is Strength the Main Risk Factor of Overuse Shoulder Injuries? A Cohort Study of 296 Amateur Overhead Athletes.

Shoulder pain is one of the most common musculoskeletal complaints in overhead athletes. This study investigated the prevalence of the main risk factors and sex differences related to the development of shoulder pain in a cohort of amateur overhead athletes. The external rotation/internal rotation (ER/IR) isometric strength ratio <0.75% is the most prevalent risk factor associated to overuse shoulder injuries in both sexes. Cohort study. Level 3. A total of 296 (147 male and 149 female) amateur overhead athletes from handball, volleyball, and water polo participated in this cross-sectional study. Isometric strength, rotational range of motion, and scapular control were analyzed bilaterally. The measurements and motions were randomized between sides. The ER/IR isometric strength ratio deficit among the disciplines was presented in 264 and 229 out of 296 athletes in the dominant and nondominant sides, respectively. Normalized isometric strength showed significant differences for dominant (P < 0.01; ε² = 0.47) and nondominant IR (P < 0.01; ε² = 0.60). No significant differences were observed between dominant (P = 0.44; ε² = 0.05) and nondominant ER (P = -0.24; ε² = 0.07). The prevalence of glenohumeral IR deficit (GIRD) (P = 0.81) and total arc of motion differences (TAMD) (P = 0.39) was low, with no difference between sexes. Male (16.3%) and female (12.1%) athletes had low rate of obvious scapular dyskinesis in their dominant shoulders. Muscle strength was the most prevalent risk factor. The ER/IR ratio imbalance was present in both sides, without sex differences. Risk factors such as scapular dyskinesis, GIRD, and TAMD were present in low percentages, without sex differences. It is advisable to implement shoulder exercises to strengthen ER muscles to decrease differences between internal and external rotators and prevent injuries in overhead athletes.

Analysis of the optimal heat treatment temperature for AlNiCo-based semi-hard magnetic materials based on temperature-dependent yield strength prediction model

To improve the starting characteristics of permanent magnet hysteresis motors, AlNiCo-based on semi-hard magnetic materials (ASMM) is proposed. The microstructural design is carried out by combining the advantages of soft magnetic composites (SMCs) and AlNiCo8 while choosing BaTiO3 with the negative thermal expansion property to eliminate the voids. The material composition as well as the range of heat treatment temperatures are determined by the phase transition kinetics. The temperature-dependent yield strength prediction model considering stress-equivalent magnetic fields is then developed. The model establishes the quantitative relationship between yield strength, ambient temperature, magnetostriction coefficient, elastic modulus, and Poisson's ratio. The comparisons between the model and experiments are made. It can be obtained that the yield strain is related to the microstructure and morphology, and the optimum heat treatment temperature is 680°C under the condition of ensuring the highest yield strength. This method can be used to optimize the parameters of the material preparation process and provide a reference for the optimized design of high-speed and ultra-high-speed motors.

EXPERIMENTAL STUDY ON FLEXURAL BEHAVIOR OF RED MERANTI (SHOREA SPP.) GLULAM BEAM OF VARIOUS NUMBER OF LAMINAE

This research aims to study flexural behavior of Red Meranti (Shorea spp.) glulam beam of various number of laminae by carrying out testing beams made from four, six, and eight laminae. Four points bending test method according to ASTM 198-22 was applied. The research results show that glulam composed of a smaller number of laminas reaches a smaller flexural rigidity. The empirical equations for flexural strength ratio and modulus of rupture ratio, and the trend of flexural rigidity between glulam and solid proposed in this study can be used in designing the flexural members of timber buildings, timber bridges, and in calculating the deflection of timber beams.

Optimizing Thermosetting Epoxy Asphalt with Styrene–Butadiene Rubber and Styrene–Butadiene–Styrene Modifiers for Enhanced Durability in Bridge Expansion Joints

The high- and low-temperature performance of asphalt-based seamless expansion joints seriously affects road performance. The purpose of this paper is to explore the application of thermosetting epoxy asphalt-based materials in bridge expansion joints. The composite modification of asphalt was performed using Styrene–Butadiene rubber (SBR) and Styrene–Butadiene–Styrene (SBS) copolymer. The study then investigates the impact of five different dosages of SBR/SBS-modified asphalt on the performance of epoxy asphalt. The results of the cone penetration test, tensile test, and stress relaxation test of SBR/SBS-modified epoxy asphalt (SSEA) and BJ200 (a commercial Seamless expansion joint material) were comparatively analyzed. The Marshall test, rutting test, three-point bending test, and freeze–thaw split test were used to evaluate the road performance of SSEA mixtures. The test results show that with the increase in asphalt content, the shear resistance and tensile strength of SSEA decrease, and the low-temperature relaxation ability and elongation at break increase. The content of SBR/SBS-modified asphalt has a positive effect on the low-temperature performance of SSEA mixtures, and the residual stability in water and freeze–thaw splitting strength ratio (TSR) are higher than that of BJ200. Based on the requirement of balancing high and low-temperature performance, SSEA-3 has the best overall performance, and the dosage of SBR and SBS modifier is 12% and 2.5%, respectively. The ratio of epoxy resin, SBR/SBS-modified asphalt, and the curing agent is 1:4:1.6, and its use is recommended in areas with slight temperature differences.

The Use of Conversion Factor and Strength Ratio in the Estimating of Basaltic Rocks Strength and Investigation of Their Changes with the Concrete Curing Time

The Use of Conversion Factor and Strength Ratio in the Estimating of Basaltic Rocks Strength and Investigation of Their Changes with the Concrete Curing Time

The effect of MWCNT concentration on the electrical resistance change characteristic of glass/fiber epoxy composites under low cycle fatigue loading

Abstract In this study, the effect of multi-walled carbon nanotube concentration on the electrical resistance change characteristics of multi-walled carbon nanotube filled glass/epoxy composites under low-cycle fatigue loading was experimentally investigated. For this purpose, multi-walled carbon nanotube concentrations of 0.2, 0.3, and 0.4 wt.% within composites were utilized to ensure electrical conductivity. The rectangular specimens for fatigue tests were manufactured by vacuum bagging method. The fatigue tests were conducted in a load-controlled manner with an ultimate strength ratio of 0.6 and at a stress ratio of 0.1. The results showed that the alteration in electrical resistance within the composites experiences a sharp and exponential rise when the concentrations of multi-walled carbon nanotube reach 0.2 and 0.3 wt.%, whereas the rate of this increase in electrical resistance is more gradual at 0.4 wt.%. multi-walled carbon nanotube concentration. The electrical resistance change curves of multi-walled carbon nanotube filled composites at various fatigue life levels were determined for statistical analysis using the Weibull distribution method. Finally, the average stiffness loss and the average residual fatigue life were determined at the electrical resistance changes corresponding to 95, 80, and 50 % Weibull reliabilities at various fatigue life levels and various multi-walled carbon nanotube concentrations.

Cyclic and monotonic undrained response of unsaturated filtered copper tailings

This article studies the undrained behavior of filtered copper tailings in unsaturated conditions under monotonic and cyclic loading at controlled matric suction. Two dry densities with the same water content were used. The material behavior was studied in terms of the increase of saturation, the evolution of suction, and volumetric strain during the transition from unsaturated to saturated conditions. The results show that, during the shearing, suction decreases and the degree of saturation increases, regardless of the type of load applied (cyclic or monotonic). This effect is related to the volume reduction of the air phase during the transition to a fully saturated condition. In terms of undrained shear strength, the evolution of the material is studied in terms of the phase transformation line (PTL), comparing its location in saturated and unsaturated cases. Regarding the cyclic strength ratio (CSR), the unsaturated condition shows a higher value than the saturated case by about 26% and 58% for the high and low densities, respectively. However, when the volumetric strain is higher than 3% or the double amplitude axial strain exceeds 2%, a cyclic strain localization takes place, leading to an extension failure over the sample.

Investigating the Compressive Strength of Clay Brick Masonry: A Case Study of Nangarhar, Afghanistan

In Afghanistan, masonry structures using burnt clay bricks have long been used for public and private buildings. However, still, there is no standard for masonry structural design based on local material properties. This study investigated the compressive strength of clay brick masonry prisms in Nangarhar, Afghanistan, through experimental testing and finite element modeling (FEM). Three brick classes, with compressive strengths between 8 and 14 MPa, were used to construct prism specimens. The research aimed to propose specific values for masonry compressive strength using local materials and examine the effects of brick strength (fb), mortar strength (fj), joint thickness (tj), and slenderness ratio (h/t) on masonry compressive strength (fm). Test results showed fm values of 17.2 MPa for first-class, 10.0 MPa for second-class, and 7.6 MPa for third-class brick masonry, indicating the influence of the brick’s quality. Key findings showed that an increase in fb causes an equal increase in fm, a 5% increase in fj leads to a 1% increase in fm, a 5 mm increase in tj gives an 8% fm increase, and a 5.5% increase in h/t results in a 1% decrease in fm. The research provides valuable information for evaluating the compressive strength of masonry structures based on the quality of local materials, which can be used to revise Chapter 7 of the Afghanistan Building Code, 2012.

Design of a two-seater seaplane wing spar structure with composite materials

A two-seater, mono-wing seaplane was initially developed for survey and rescue operations, with an empty weight of 470 kg and a maximum takeoff weight of 650 kg. Fiber-reinforced composite materials, consisting of fiber reinforcement and thermosetting polymer, were used in this airframe to reduce weight because the structural properties can be customized by adjusting the orientation of the fiber fabric layup and removing redundant material, which is impossible with metal. This paper presents a comprehensive overview of the design process for the aircraft's primary I-beam wing spar, employing composite material. Before conducting design calculations, it is critical to consider the variability of characteristics of composite materials caused by fabrication conditions such as temperature, humidity, and defects. As a result, it is imperative to conduct thorough testing of carbon fiber-reinforced composites following many different testing requirements. The coupon tests capture critical characteristics such as strength, stiffness, and Poisson's ratio across several orientations. The wing spar I-beam structure was subsequently developed with three primary considerations: stiffness (maximum deflection), strength, and stability (structural buckling). Following preliminary sizing of the I-beam wing spar, a simple initial layup was recommended, with primary loading in each component. The initial design was then subjected to a more detailed calculation using classical lamination theory, which took into account distributed load along the wing, spar taper, ply-drops along the span, and composite layup guidelines in order to reduce structural weight while ensuring the main spar's ability to withstand operational loads effectively. The calculating results show that the spar with an optimized composite design has a lighter weight than the original design by around 43%, while it can withstand the same loads with no analytical failure.

Crack evolution mechanism of stratified rock mass under different strength ratios and soft layer thickness: Insights from DEM modeling

Research on stratified rock masses, which are common geological formations, has primarily focused on their mechanical properties, while studies on crack evolution and microscopic damage mechanisms remain limited. This study addresses this gap by investigating the combined effects of strength ratios and soft layer thicknesses on the microcrack evolution mechanism of stratified rocks using the discrete element method (DEM). Through FISH language programming in the particle flow code (PFC), this study reveals the acoustic emission (AE) characteristics, crack initiation and propagation, damage degree, and final failure characteristics. The key findings are: (1) Higher strength ratios between the hard and soft components of stratified rocks make specimens more sensitive to increases in soft layer thickness. (2) Three types of AE events were identified: continuous active, intermittent active, and silent. (3) Cracks initiate at the interface between components and propagate along the interface into the rock matrix. The strength ratios determine the crack propagation path and the damage extent of the components. (4) The failure of stratified rocks is primarily controlled by the soft component. Crack connections typically form vertical and sub-vertical tensile failure planes in the hard component, and a shear failure surface with a “V”-shaped intersection in the soft component.

Evaluation of self-healing in reactive powder concrete with urea–formaldehyde/epoxy microcapsules

The use of microcapsules as preservative vessels for healing materials has led to a great revolution in the repair of materials. Microcapsules have been used in medicine, agriculture, metallurgy and mechanics. In civil engineering applications, microcapsules are usually used for the self-healing of concrete, asphalt and cementitious materials. Concrete and cement are widely used in civil engineering and are the predominant construction materials worldwide. The objective of this study was to design and produce urea–formaldehyde microcapsules for the recovery of reactive powder concrete (RPC). It was found that RPC specimens with and without microcapsules exhibited different behaviours. All of the RPC specimens containing microcapsules were found to have lower strengths than specimens without microcapsules. The smallest reductions in compressive strength were observed in specimens with a microcapsule content of 4–6% by weight of cement. The healing ratio of compressive strength increased with an increase in the weight percentage of microcapsules. Scanning electron microscopy and energy-dispersive spectroscopy were used to observe the process of crack healing, and the results showed that the cracks were filled with healing products.