Reinforcement Shape Research Articles

Effect of reinforcement shape on physical properties and representative volume element of particles-reinforced composites: Statistical and numerical approaches

We are considering the effect of the particle shape on the effective elastic properties and representative volume element of two-phase composites. In this work, microstructures with ellipsoidal and spherical particles are considered. Three dimensional particles are randomly generated for different volume fractions without any contact between neighbouring spheres according to Poisson process. The used analysis is based on numerical homogenization approaches by finite element method and morphological characterization of microstructures by random fields. The effects of various parameters such as particles volume fraction, contrast in phase properties and particles shape were identified. The statistical methods are introduced and then coupled with numerical simulations. The notion of statistically representative volume, named the deterministic representative volume element (RVE), is used. The variation of this RVE as a function of particles volume fraction for heterogeneous materials is presented. These variations suggest us to identify the morphological distribution of particles which is more anisotropic and which needs a large RVE size.

Prediction and experimental validation of electrical percolation by applying a modified micromechanics model considering multiple heterogeneous inclusions

Classical micromechanics modeling cannot capture the effect of percolation threshold at a low volume fraction of conductive fillers, even though multiple heterogeneities are considered in the modeling to investigate the effect of reinforcement dispersion, electrical tunneling behavior, and conductive networks. In this study, an analytical homogenization approach for composites containing multiple heterogeneities with conductive coated layers was developed in order to predict the percolation threshold effect, the tunneling effect using hard/soft core concept, and the effective electrical conductivity of polymer matrix composites (PMCs) containing randomly oriented ellipsoidal inclusions coated by conductive layers. The electrical conductivities of polymerized cyclic butylene terephthalate (pCBT)-based composites containing nanofillers such as carbon blacks (CBs), graphene nanoplatelets (GNPs), and carbon nanotubes (CNTs) were prepared by the recently developed composite manufacturing processing using solvent-free powder mixing and in-situ polymerization for inducing uniform dispersion of nanofillers of various shapes and dimensions within a polymer matrix. When comparing the experimentally measured electrical conductivities of those composites with the predicted values obtained from the developed micromechanics models, it is confirmed that the developed approach successfully captures the percolation threshold and the tunneling effect of reinforcements on the effective electrical conductivities of composites containing various shapes of reinforcements.

Reinforcement shapes clines in female mate discrimination in Drosophila subquinaria.

Reinforcement of species boundaries may alter mate recognition in a way that also affects patterns of mate preference among conspecific populations. In the fly Drosophila subquinaria, females sympatric with the closely related species D. recens reject mating with heterospecific males as well as with conspecific males from allopatric populations. Here, we assess geographic variation in behavioral isolation within and among populations of D. subquinaria and use cline theory to understand patterns of selection on reinforced discrimination and its consequences for sexual isolation within species. We find that selection has fixed rejection of D. recens males in sympatry, while significant genetic variation in this behavior occurs within allopatric populations. In conspecific matings sexual isolation is also asymmetric and stronger in populations that are sympatric with D. recens. The clines in behavioral discrimination within and between species are similar in shape and are maintained by strong selection in the face of gene flow, and we show that some of their genetic basis may be either shared or linked. Thus, while reinforcement can drive extremely strong phenotypic divergence, the long-term consequences for incipient speciation depend on gene flow, genetic linkage of discrimination traits, and the cost of these behaviors in allopatry.

Shear behavior of post-tensioned FRP-reinforced concrete slabs under static and fatigue loading

A reinforcement system for short span concrete slab bridges combining post-tensioned carbon FRP (CFRP) tendons with non-prestressed glass FRP (GFRP) reinforcement can limit the stresses in the GFRP bars to significantly improve fatigue performance. Despite this, the failure mode may be governed by shear and conventional stirrups are, in general, not practical for the construction of slab bridges; therefore the use of innovative shear reinforcement methods is required. Twenty-five FRP-post-tensioned slabs with various types of FRP shear reinforcement were tested under static or fatigue loading. The main variables included the size, shape and type of FRP shear reinforcement used. Fatigue shear strengths at one million cycles were typically in the range of 50–60% of the ultimate static load capacity. Double-headed shear bars were found to be an excellent solution for the shear reinforcement of shallow concrete members which were easy to install and provided high load capacities and good fatigue performance. The fatigue shear strengths of members with anchored shear reinforcement were conservatively predicted using the simplified modified compression field theory, accounting for the change in concrete tensile strength under fatigue loading.

Comparison of Shear Strength Equation for Flat Plates with GFRP Plate

In this study, shear test performed to investigate the shear behavior of flat plate that reinforced by embedded GFRP(glass fiber reinforced polymer) plate with openings. Shape of the GFRP shear reinforcement is a plate with several openings to ensure perfect integration with concrete. The test parameters include the distance between the column face and the first line of GFRP plate and number of GFRP plate vertical strip. The result of test showed that when number of GFRP plate vertical strip was increased, shear strength improved. The shear strength for flat plate reinforced GFRP plate in various codes including ACI 318, BS 8110, EUROCODE 2, and KCI were compared to provide more rational approach for reinforced concrete flat plates with GFRP plate.

Multi-wire submerged arc welding: a study of secondary process parameters

The goal of this thesis is to investigate the effect of secondary process parameters on the geometry of the weld bead in multi-wire submerged arc welding. Bead-on-plate welding experiments will be conducted using 3, 4 and 5 wires. The parameters being varied will be the wire stick out, the angles of the torches and the spacing in between. Primary process parameters like voltage, current and welding speed will be kept constant. Penetration, bead width and height, percentage dilution, HAZ, weld penetration shape factor and weld reinforcement shape factor will be measured and evaluated. Fewer experiments will be needed because of the use of a design of experiments approach, namely a fractional factorial design. This will allow to determine the significance of each single parameter and their mutual interaction with respect to weld bead shape.

프론트 사이드 멤버의 경사 충돌 성능

Front impacted SUV vehicle shows that the front parts of side members are collapsed by the bending due to the transverse load exerted at the end of side members. Side member models were impacted with various angles in order to study the crash performance according to the impact angle. Even for the small impact angle of <TEX>$10^{\circ}$</TEX>, crash performance seriously deteriorated and the deformations for impact angle <TEX>$15^{\circ}$</TEX> were similar to those from the front body impact analysis. In addition, the angled front impact analysis for the straight member with hat section was carried out and the effects of inner reinforcement shape on crash performance was investigated.

A Simplified Method for Analysis of Geosynthetic Reinforcement Used in Pile Supported Embankments

The inclusion of geosynthetic reinforcement in the piled embankment can help transfer loads to the piles and reduce total and differential settlements. In order to select the appropriate reinforcement material, the reasonable calculation of the deflection and tension is very important. Current design methods usually do not represent the true three-dimensional (3D) nature of the displacements, strains, and stresses of the geosynthetics, and the resulting error may be large and cannot be neglected in some cases. In this study, two- and three-dimensional finite element analyses were conducted to identify the behavior of geosynthetic reinforcement and investigate the accuracy of the assumptions made in the current design methods. Based on the numerical results, a new 3D deflected shape of the geosynthetic reinforcement was suggested, and then the corresponding governing equation was derived and solved based on the membrane theory. To investigate the validity of the proposed method, the predicted maximum deflection, deflection shape, and the developed tensile force of the geosynthetics have been compared with the experimental data collected from the literatures and finite element analysis results.

지지부재로 이형철근을 설치하는 띠형 강보강재의 인발성능 평가

본 연구에서는 지지부재가 설치된 띠형 강보강재에 대한 실내인발시험을 수행하였다. 주문진 표준사를 사용하여 상대밀도 80%인 모형지반을 조성하였고, 지지부재의 개수를 0~2개로 구분하여 실내인발시험을 수행하였다. 상재압은 <TEX>$50kN/m^2{\sim}200kN/m^2$</TEX>까지 4단계로 구분하여 적용하였고, 1mm/min 속도로 강보강재를 인발하였다. 표면이 매끄러운 띠형 강보강재의 인발저항력은 보강재 표면과 지반 사이에서 마찰저항만 발현되기 때문에 인발 초기에 급격히 증가하다가 지속적으로 감소하는 경향을 나타낸다. 반면, 지지부재를 설치한 강보강재의 인발저항력은 마찰저항뿐만 아니라 수동저항도 함께 발현되므로 계속적으로 증가하는 것으로 나타났다. 보강재의 형태에 관계없이 최대인발저항은 상재압이 증가함에 따라 선형적으로 증가하는 것으로 나타났다. 지지부재를 1개 설치한 경우에 비해 지지부재를 2개 설치했을 때의 최대수동저항은 작게 나타났다. 이는 지지부재의 설치 간격 및 위치에 따라 지지부재에서 발현되는 수동저항의 크기가 다르기 때문에 나타나는 현상으로 판단되며, 지지부재 설치 위치 및 간격에 따른 추가 인발시험을 통해 확인할 필요가 있다. Laboratory pullout tests were conducted to evaluate pullout performance of steel strip reinforcements with deformed steel bars as transverse members. The steel strip reinforcement has an installation hole to assemble a deformed steel bar. Jumunjin standard sand is used to form a relative density of ground model to 80%. Frictional resistance of steel strip reinforcement without transverse member increases sharply at the initial displacement and quickly decreases with displacement. Maximum frictional resistance increases linearly as normal pressure increasing, and soil-reinforcement interaction friction angle(<TEX>${\rho}_{peak}$</TEX>) of a steel strip reinforcement is estimated to <TEX>$14.64^{\circ}$</TEX>. Passive resistance increases with displacement and converge into maximum passive resistance in most cases. Maximum passive resistance increases linearly as normal pressure increasing irrespective of shape of the steel reinforcement. Pullout force of steel strip reinforcements with installation holes or transverse members largely increases about 4 to 7 times compared to frictional resistance force of steel strip reinforcements when embedment length(<TEX>$L_e$</TEX>) of steel strip reinforcements is 500 mm. In the case of using 2 transverse members, interference effect is observed due to the spacing of 2 transverse members and location of assembly holes and transverse members.

AN APPROACH OF COMPOSITE MATERIALS IN INDUSTRIAL MACHINERY: ADVANTAGES, DISADVANTAGES AND APPLICATIONS

Carbon fiber Composites forecasts indicate several years of supply that will exceed the anticipated de mand. Carbon fiber producers have used world leading technology to produce the m ost uniform and highest quality fiber. Carbon-fiber composites weight about one-fifth as much as steel, but can be similar or b etter in terms of stiffness and strength, depending on fiber grade and orientation. These composites do not rust or corrode like steel or aluminum. The aim of this paper is to present th e current scenario of carbon fiber composites in industries and go towards the a pproach of carbon fiber composites in future direct ion with its advantages, disadvantages and applications in industrial machin ery. Various type of composites based on reinforcem ent shape also presented in this paper. This paper also shows the Properties, C haracteristics, Challenges, Opportunities and Futur e Trends of Composites towards industrial environment.

Experimental Investigations of Fracture Process Using DIC in Plain and Reinforced Concrete Beams under Bending

ABSTRACTThe fracture behaviour of concrete and reinforced concrete beams under quasi‐static three‐point bending was comprehensively investigated with experiments at laboratory scale. The eight various concrete mixes were tested. The influence of the shape, volume and size of aggregate particles and reinforcement on concrete fracture under bending was studied. Displacements on the surface of concrete beams were measured by means of the digital image correlation (DIC) technique. Attention was paid to the formation of a localized zone and its characteristics. In order to avoid the effect of the search patch size and the cut‐off value at displacement and strain profiles, a consistent method was proposed to determine uniformly and accurately the width of a localized zone. Measured surface displacements from DIC were fitted by the error function ERF, whereas surface strains calculated from displacements were fitted by the usual normal distribution (Gauss) function. The width of a localized zone preceding a macro‐crack grew strongly with increasing maximum aggregate size and slightly with diminishing aggregate volume. It did not depend on the aggregate roughness and reinforcement presence.

Study on Test Scheme of Shield Tunnel Prestressed Segment Joint

Mechanical property of the segment joint for fabricated shield tunnel lining is the key factor for segment lining design and research. Based on the test prototype of shield tunnel segment lining with about 6m diameter, the test scheme of prestressed segment joint has been studied. On account for the influencing factors of prestressing force, prestressed reinforcement shape, joint shape and bending moment, the test structure and test conditions were designed. And the test content and methods were brought out, the test procedure and notes were discussed.

On the elasto-plastic buckling of Integrally Stiffened Panels (ISP) joined by Friction Stir Welding (FSW): Numerical simulation and optimization algorithms

Integrally Stiffened Panels (ISP) structures are composed of a base plate and one (or several) longitudinal stiffness sections of simple or complex shape. When compared to conventional reinforced structures, they present an integral profile, as the stiffened panel is obtained as a whole by means of an extrusion process. The choice of a ISP profile can lead to a more robust and defects-free solution, simultaneously maintaining the possibility to adopt complex reinforcement shapes. In the present work, three algorithms are studied and compared in the cross-section optimization of Integrally Stiffened Panels for aeronautical applications: (i) the classical Levenberg–Marquardt, (ii) the Simulated Annealing methodology, and a recently proposed approach involving (iii) a differential/nature-based algorithm called Hybrid Differential Evolution Particle Swarm Optimization (HDEPSO). Numerical simulation models are introduced for several shapes of ISP. Additionally, the presence of a Friction Stir Weld (FSW) zone is also taken into account, from the joining between distinct ISP's. This can allow us to infer about the influence of the heat affected zoned (HAZ) in the overall stability of the structure, under compressive buckling loads within the elasto-plastic regimen. Results show that the use of the proposed optimization algorithm represents a viable option, giving an added insight in terms of the buckling resistance and mechanical design in nonlinear material and geometric scenarios.

Experimental and numerical investigations of welding distortion induced by CO2 gas arc welding in thin-plate bead-on joints

Thin plates are widely used in aerospace, naval, and automobile industries to reduce the weight of component. Welding distortion occurring in thin plate joint or structure is inevitable and often results in loss of dimensional control, structural integrity and manufacturing costs increase due to additional straightening work. In the present study, a computational approach based on finite element method with considering both materials nonlinearity and geometrical nonlinearity was developed to investigate welding distortion and residual stress in low carbon steel thin-plate bead-on joints induced by arc welding process. Besides temperature-dependent thermal physical and mechanical properties and moving heat source model, the weld reinforcement shape was also considered in the finite element model. Meanwhile, experiments were carried out to verify the numerical results. In the experiments, an arc welding robot was used to perform the bead-on welding. The comparison between simulation results and measurements suggests that the developed finite element model can capture the features of welding distortion and residual stress distribution in thin plate welded joints. Moreover, the influences of heat input on buckling propensity were examined numerically. In addition, the mechanisms of out-of-plane deformation formation in the thin-plate bead-on joints were discussed.

매립형 GFRP 판으로 보강된 콘크리트 보의 전단강도식 평가

본 논문에서는 새로운 형상의 GFRP 판으로 전단 보강된 철근콘크리트 보의 전단강도 산정식을 제안하기 위하여 기존의 설계규준에 포함된 전단강도식을 수정하여 적용이 가능한지 연구한다. GFRP 판은 개구부가 있는 plate의 형태로서 콘크리트와의 일체화 거동을 위하여 콘크리트에 매립하여 시공한다. 총 6개의 시험체에 대한 전단실험을 수행하고, 전단경간비는 2.4로 설정한다. 실험 변수는 전단보강량 및 전단보강재의 형상으로 선정한다. GFRP 판의 형상에는 기본격자형 및 평행사변형 두 가지가 있다. GFRP 판으로 보강된 콘크리트 보의 전단강도식은 CSA A23.3-04 기준식과 ACI 318-11 기준식의 수정식을 통해 제안되었다. 결과적으로 실험에 의한 전단강도와 제안식에 의한 전단강도를 비교한 결과, ACI 318-11 수정식보다 CSA A23.3-04 수정식이 전단강도를 더 잘 예측하는 것으로 나타났다. In this paper, we will study the possibility of the design standard applied by modifying the shear strength equation so that we can propose the shear strength equation of reinforced concrete beams strengthened with the new type of GFRP plate. The new GFRP shear reinforcement is manufactured into a plate shape with several openings to ensure perfect integration with concrete. The test was performed on 6 specimens with shear span-to-depth ratio of 2.4. Test variables are the amount of the shear reinforcement and the shape of shear reinforcement. The two types of GFRP plate with different shapes are a rectangle and a parallelogram. A shear strength equation for concrete beams with the proposed GFRP plate was suggested through modifying the existing shear strength equation for concrete beams in CSA A23.3-04 and ACI 318-11. Comparing the test results with the estimations based on the proposed equation, CSA A23.3-04 modified equation predicted the shear strength better than ACI 318-11 modified equation.

Reward and punishment: investigating cortico-bulbar excitability to disclose the value of goods.

A continuing challenge for neuroscientists is to develop new conceptual tools and methodologies for understanding, predicting, and modeling the influences of rewarding/punishing outcomes on human behavior and decision-making. Reinforcement shapes behaviors from the most primitive (fight/flight, ingest/regurgitate, approach/avoid) to complex (buy/sell). Understanding the neural processes underlying reinforcement is critical for understanding economic and social decision-making. Moreover, comprehension of de-ranged processing and responses to reinforcing stimuli is crucial across a range of psychology fields and society as a whole, including psychiatric and neurological illness, eating disorders, criminality, and sociopathy (Vicario and Crescentini, 2012).

매립형 유공 GFRP 판으로 보강된 RC보의 전단거동에 관한 실험적 연구

이 연구의 목적은 매립형 유공 GFRP(glass fiber reinforced polymer) 판으로 보강된 철근콘크리트 보의 전단 거동에 관하여 실험적으로 연구하였다. 보강재의 형상, 보강면적, 보강재 두께 및 폭의 영향을 변수로 선정하였다. 전단경간비가 2.8인 일반보 총 9개의 시험체에 대한 전단실험을 수행하였다. GFRP 판이 철근 스터럽으로 보강한 경우보다 단위보강면적당 전단강도가 3.6배 향상되었다. 보강면적에 따른 전단성능을 평가한 결과 전단보강면적이 증가함에 따라 전단강도도 증가하였다. 보강재의 형상에 따라 전단성능의 영향을 평가한 결과 평행사변형 GFRP 판이 기본격자형 GFRP판보다 전단강도가 우수한 것으로 나타났다. 일정한 보강면적에서 보강재의 폭 및 두께를 변수로 두었을 때 폭이 증가할수록 전단성능이 향상되는 것을 확인할 수 있었다. 결과적으로, GFRP 판으로 전단 보강된 철근콘크리트 보의 ACI 318M-08 기준식에 의한 최대전단강도와 실험에 의한 최대전단강도를 비교하였다. 또한, ACI 318M-08, CSA-04, EC2-02기준식의 최대전단보강면적과 시험체의 최대전단보강면적을 비교하였다.

Cold Bending Properties of Under-Matched Butt Joints for High Strength Steel

In this paper, cold bending properties of Q620-CF steel butt joints were analyzed based on the finite element method. Finite element analysis (FEA) results indicate that the flush under-matched butt joints have lower bending properties than the flush equal-matched butt joints, but under-matched butt joints with definite reinforcement shape can get greater bending force and better cold bending angles than the flush equal-matched butt joints. It shows that shape design of the reinforcement can improve the bending load-carrying capacity of under-matched joints. The reliability of the FEA has been verified by the experiment.

Experiment on the Bonding Performance of BFRP Bars Reinforced Concrete

Through the pull-out test methods, the concrete strength、reinforcement diameter Basalt Fiber Reinforced Plastics Bars、the anchorage length、 stirrup rate and other factors on the bonding properties of the BFRP reinforced concrete is analyzed. The BFRP bars and reinforcing steel bars bonding properties is compared. BFRP reinforced concrete bond failure mode has two types .As the concrete strength increases, the bond strength of the BFRP reinforced concrete increased. With the increase BFRP bars diameter and shear lag relationship, the cohesive force of the BFRP reinforced concrete decrease accordingly. And the failure modes of the shape of the BFRP reinforcement concrete in BFRP bonding properties with a big impact for the specimens’ configuration stirrups on the ductility. When BFRP bars loading under the same load level, the end of the slip is greater than the free end slip.

Bond behaviour of flat stainless steel rebars in concrete

In recent years there has been an increasing interest in applying stainless steel (SS) reinforcement in concrete structures to avoid corrosion derived durability problems. Concrete-steel bond behaviour and applicability of existing standards have not yet been extensively studied with respect to SS. Moreover, an interest in applying flat rebars as reinforcement elements has emerged. The idea is based on the optimization of the rebar surface in contact with the concrete as well as on the reinforcement optimization for shallow slabs. To advance in the evaluation of the bond between concrete and flat SS strips and to compare with the behaviour of standard carbon steel (CS) round reinforcement 72 bond tests have been conducted. The test program consists of pull-out tests to centrally reinforced concrete specimens. Traditional concrete and self compacting concrete are used for embedding. For a better analysis and understanding of the failure aspect of the specimens, fluorescent epoxy injection has been conducted. Results are compared to the CEB-FIP 1990 bond model. The authors conclude that, the use of SS instead of CS is not considerably influencing the bond capacity of the reinforcement when ribbed samples are used while parameters as reinforcement shape or rib pattern are more deterministic. An adaptation of the CEB-FIP 1990 bond model is proposed for flat reinforcements tested in this work.