Yoshihito Yamamoto

Nagoya University | Meidai · Department of Civil Engineering

The perfobond (PBL) shear connector reinforced with transverse rebar effectively contributes to sufficient ductility, bearing capacity, and anti-fatigue behavior to hybrid structures. The construction practice involves the placement of the transverse rebar at the bottom position within the concrete dowel, whereas past studies employed transverse re...

The bond between concrete and steel is one of the most critical properties of reinforced concrete and affects the overall structural performance. The current research realistically evaluates the macroscopic bond behavior, quantitatively highlights the detailed internal fracture process, and clarifies the internal fracture mechanism. The numerical a...

A R T I C L E I N F O Keywords: RC slender beam Size effect on shear strength Beam and arch actions Diagonal crack width Crack space A B S T R A C T This study aims to clarify the mechanism of the size effect on the shear behavior for reinforced concrete (RC) slender beams. Three Dimensional Rigid-Body-Spring-Method (3D RBSM), a basic analytical to...

Numerical analyses focused on the detailed fracture process of concrete in a reinforced PBL shear connector with the transverse rebar subjected to a simple push-out test employing coupled RBSM and solid FEM model were performed to reveal the internal failure mechanism, quantitatively. The numerical model effectively captured the shear capacity and...

In this study, the reduction mechanism of the compressive properties of concrete with mechanically induced crack of different widths and angles was evaluated using a discrete mechanical model. Analytical investigations were conducted along with experiments to visualize the change in the stress transfer in a cross-section due to the presence of a pr...

The purpose of this study was, on the one side, to evaluate the deterioration mechanism of the shear performance caused by rebar cut-off setting for RC beams, and on the other, to clarify the reinforcing mechanism of stirrups to shear against rebar cut-off setting. The shear performances of the beam specimens with and without cut-off point in longi...

The purpose of this paper is to clarify the mechanism of shear strength reduction for reinforced concrete deep beams with varying stirrup ratios, due to the beam size increase. Three Dimensional Rigid-Body-Spring-Method was the applied numerical tool. By using the simulation results of reinforced concrete deep beams with the effective depth smaller...

In this study, DEF expansion crack propagation process under different restraint condition was numerically investigated by mesoscale discrete model, which describes concrete material with coarse aggregate phase and mortar phase using 3D-Rigid Body Spring Model. The purpose of this study is to clarify the impacts of origination of expansion and aggr...

An analytical investigation focusing on the concrete damage progress of the PBL shear connector under the influence of various lateral pressures, employing a coupled RBSM and solid FEM model was carried out. The analytical model succeeded in simulating the test shear capacities and the failure modes adequately. The internal failure process was also...

The use of new precast jointing and anchoring methods have increased and the meso-scale simulations are effective for performance evaluation and detailed fracture process. The Voronoi diagram is essential to reproduce the fracture characteristics of concrete in RBSM, however, it is difficult to express geometrical details of deformed rebars by Voro...

The bond degradation subjected to corrosion-induced crack was investigated numerically using 3D Rigid Body Spring Model (RBSM) in which rebar was modeled by solid elements without modeling explicitly the details of rebar ribs. The proposed numerical model considers both corrosion expansion and shear stress transfer behavior through the interface el...

Shear failure after flexural yielding is a typical failure mode for a reinforced concrete (RC) member subject to cyclic load, and it is caused by the phenomenon that the initial shear strength is decreased with the increasing plastic ductility until the shear capacity degrades to be lower than the flexural strength. In this study, the flexure-shear...

This study proposed an analytical method based on the Three Dimensional Rigid Body Spring Model (3D-RBSM) to realistically simulate bond behavior of deformed rebar in concrete. In this method, concrete was modeled by rigid particles using a voronoi mesh with random geometry and rebar was modeled by beam element connected to concrete through a link...

The attempts to use PBL have increased sufficiently in concrete-steel composite structures, provides merits for construction convenience and adequate mechanical performance. There are less numerical studies, primarily focusing on the detailed internal failure mechanism. Understanding the failure mechanism is important for establishing rational desi...

Spherical shaped EAF slag fine aggregate is a promising alternative of natural sand in concrete as it imparts improved mechanical, durability and thermal properties. These features indicate the possibility of obtaining concrete of improved fire resistance by using spherical shaped EAF slag fine aggregate which have not yet been studied. The basic i...

In loop rebar joints, the bond stress of straight parts and bearing pressure of curved parts can be utilized effectively, the joint length can be shortened compared with the conventional lap joint. From such an advantage, adoption of cast in situ loop rebar joints is increasing. The performance evaluation of loop joints has been studied under vario...

The research manuscript deals with the brief introduction to the development and the validation of the new coupled numerical formulation, comprised of the Rigid Body Spring Model (RBSM) and the solid Finite Element Method (FEM) evaluating the bond behavior and failure mechanism of the actively confined and unconfined RC specimens loaded under pull-...

For wider utilization of spherical shaped EAF slag in pavement concrete, a thorough investigation on the thermal properties of slag concrete is required since the traditional design approach for deformation behavior due to thermal stress might not be applied directly if the thermal properties of EAF slag concrete are different from normal concrete....

In order to enhancement accuracy of shear design of reinforced concrete (RC) beams, detail understanding of the shear resistance mechanism is required. This study evaluated the shear resistance mechanism of RC beams based on arch and beam actions by using three dimensional Rigid-Body-Spring-Method (3-D RBSM). Firstly, RC deep and slender beams with...

Electric Arc Furnace oxidizing slag (EAF slag) is a steel manufacturing byproduct. Recently, due to the adoption of new production method, spherical shaped EAF slag has been produced and applicability of this material in concrete requires to be investigated. EAF slag possesses the characteristic property of high density. Moreover, lesser water is r...

Recently, due to the adoption of new production method, spherical shaped EAF slag has been produced and applicability of this material in concrete requires to be investigated. EAF slag possesses the characteristic property of high density. Moreover, lesser water is required when spherical shaped EAF slag is used in concrete. Considering these featu...

In this paper, both experimental and numerical studies were carried out to evaluate the concrete cracking behavior and the corrosion products movement during rebar corrosion process. The electric corrosion tests with an applied current density of 900μA/cm2 were conducted, in which the development of surface and internal cracks and the distribution...

In loop rebar joints, since the bond stress of straight portions and bearing pressure of curved portions can be utilized, the joint length can be shortened as compared with the conventional lap joint. From such an advantage, adoption of loop rebar joints is increasing. Performance evaluation of loop joints has been studied under various specificati...

This paper evaluated the effect of high strength rebar of SD685 on the cracking and deformation behavior. Four specimens with alternative combination of either SD345 or SD685 rebar along with either 30MPa or 70MPa concrete strength were experimentally tested and result were compared with the equations in JSCE design standards about crack width, cra...

This study aims to investigate the performance of spherical shaped EAF slag fine aggregate concrete. Two experimental series having W/C ratio of 0.4 and 0.6 were examined in this study to compare the effect of EAF slag fine aggregate. In each series, 4 types of concrete were produced for the slag replacement ratio of 0.0, 0.3, 0.5 and 1.0 and teste...

A coupled model is presented to simulate the failure localization of concrete and local buckling behavior of steel tube. The coupled model combines the three-dimensional Rigid Body Spring Model and the MITC shell FEM element to model concrete and steel tube, respectively, in a steel-tube confined concrete member. Simulation of published test experi...

The aim of this study is to experimentally investigate the effect of drying on a shear wall, and to clarify the mechanism of the changes in the structural performance due to drying. Two sufficiently hydrated wall specimens are prepared. Then, one is loaded without drying, while the other is tested after sufficient drying until the shrinkage of conc...

A newly developed coupled numerical model is presented to investigate the compressive localization and softening behavior of concrete under steel tube confinement. The coupled model combines the use of Rigid Body Spring Model (RBSM) and nonlinear shell finite element method (FEM) to simulate concrete and steel in steel-tube confined concrete member...

The compressive behavior of thin-walled CFST is numerically evaluated taking into account higher D/t ratios, cross-sectional shape, and type of loading application. The evaluation was performed using a newly-developed coupled numerical model which combines the use of 3D Rigid Body Spring Model and nonlinear shell FEM to simulate the behavior of con...

A newly developed coupled numerical model which combines the use of RBSM and nonlinear shell FEM is introduced. The model was used to investigate the effect of steel tube confinement in the localization and softening behavior of concrete. Analysis of steel-tube confined concrete columns showed that by increasing the level of confinement (expressed...

After the Great Hanshin earthquake in 1995, a large number of existing concrete structures were retrofitted by steel jacketing method in order to adjust in the increased design loads. In addition, the assessment of safety against excessive load and restorability performance is becoming increasingly important in Japan. In order to assess the above p...

In order to investigate the influence of crack through section, which is often generated under cyclic loading, on the shear behavior and strength of RC beam, an experimental method was attempted to introduce a 0.5 mm and 1.0 mm-wide pre-crack, respectively, in beam cross section. The two pre-cracked beams were tested and the shear behaviors were co...

In this paper, the transformation of solid phase and expansion cracking behaviors due to sulfate attack were evaluated by using RBSM-Truss Network Model. This analysis was constructed by combining a hydration model, a diffusion-reaction model, and a crack propagation model in order to evaluate the influence of feedback system of ion transfer throug...

Usage of high strength steel has enormously increased in construction of RC structures. For RC beams, we are well aware about the ductility and shear strength phenomenon regarding high strength steel, however, knowledge related to crack width and deformation is still lacking. In this research we conducted experiments on 4 beams considering combinat...

This study aims is to use EAF slag fine aggregate in pavement concrete. For this 4 different types of concrete were casted by using EAF slag fine aggregate with a volume ratio of 0.0, 0.3, 0.5 and 1.0 for a w/c, s/a, slump and air content of 0.4, 40%, 5cm and 5% respectively. From the results it is found that increment of slag ratio increases the m...

Electric Arc Furnace oxidizing slag (EAF slag) is an industrial by product. Around 3 million tons of EAF slag is produced annually in Japan. One of the characteristic property of EAF slag is high density and there is possibility of high applicability of EAF Slag to pavement concrete where low slump and high strength, and normal concrete is required...

The ability of Rigid Body Spring Model (RBSM) in simulating the behavior of confined concrete is demonstrated. First, the validation of the model in tri-axial test experiments is presented. The applicability of the model to simulate the behavior of concrete under passive confinement is then evaluated. Two types of passive confinement are presented:...

In this study, the analytical investigation using the analytical system coupled with hydration model, diffusion-reaction model and crack propagation model were conducted in order to validate the size effect of sulfate attack. This analytical system can reconstruct hydration process, transformation of liquid-solid phase and manifestation and propaga...

This study proposed a method to simulate crack propagation due to rebar corrosion based on Rigid-Body-Spring Method (RBSM) in which rebar is modeled by beam element in order to reduce computational cost for the analysis of structural level. The effects of local corrosion around the rebar as well as penetration of corrosion products into cracks were...

Three types of interface models for concrete-steel interaction in concrete-filled steel tube (CFST) were quantitatively and qualitatively investigated using published test results. The study is part of the development of a coupled rigid body spring model (RBSM) and shell finite element method (FEM) aimed at modeling CFST and similar concrete-steel...

Shear resistant mechanism was evaluated by using the detailed stress distribution obtained from analysis of RC beam failed in shear. First, the validity of the local stress distributions of concrete and stirrups obtained from 3-D RBSM was confirmed by comparing the test results of RC beams failed in shear. Next, the applicability of decoupling shea...

This paper presents an electro-mechanical model for evaluating the corrosion-induced damage in reinforced concrete under accelerated conditions. The model consists of structural analysis of concrete and the rebar using the Rigid Body Spring Method and corrosion current analysis with the truss networks model. The electric corrosion process is couple...

Air permeability alongside with water permeability are recognized as two basic parameters of concrete surface quality especially for structures which are exposed to harsh environment conditions. Indeed, most of the concrete defects like corrosion and cracks are due to migration of chloride and other deteriorating factors through the water and air p...

FEM has become popular and, has significant importance for performance verification to understand load carrying capacity and failure mode, the stress and strain behavior, strain localization behavior and the cracking behavior of concrete structures. Moreover, the requirement moves toward evaluation of the structure behavior by using local informati...

It is known that when rebars in concrete structures are corroded, the structural performance can probably be changed due to losses of cross-sectional area of reinforcement as well as losses of bond strength. A number of researches have widely investigated on shear behavior of RC members with bond deterioration. However, it has yet to be made clear...

A number of RC bridge piers with termination point of main rebar (called as rebar termination) suffered flexural shear failure at termination point of main rebar rather than at footing-column joint, under effect of great earthquakes such as 1995 Kobe earthquake. In our previous work, the shear failure after yielding at footing-column joint of a RC...

This paper described new insights on the influence of interfacial transition zone on drying shrinkage strain and compressive strength of concrete through numerical simulation. Using Rigid Body Spring network Model, analysis of drying shrinkage and compression test of drying concrete are performed considering long and short term model of ITZ. As a r...

When a RC member is subjected to cyclic loading, shear failure often occurs after flexural yielding because of shear strength degradation. The effect of through crack on shear strength degradation was numerically evaluated by assuming that through cracks, caused by residual deformation of tension rebar after yielding, probably lead to shear strengt...

This study aims to investigate the effects of corrosion distribution, specifically non-uniform and localized corrosion, on cracks propagation in concrete. Different corrosion distributions along rebar length were simulated using a sodium chloride pond with various sizes set on the concrete cover, and a direct current was applied to accelerate the c...

The purpose of this study was to investigate the mechanism of shear strength degradation of RC member under cyclic loading. First, the shear failure after flexural yield of tension reinforcing bars of a RC column designed as bridge pier under cyclic loading was simulated by the method of three dimensional Rigid-Body-Spring-Model (3-D RBSM) and the...

This study aims to clarify the decisive geometric parameters relating corrosion penetration to surface crack width. The corrosion-induced crack propagation was simulated using the Rigid Body Spring Method considering varying geometric parameters of concrete sections, and regression analysis of the simulation results was performed. It was found that...

In this paper, numerical simulations of reinforced mortar beams subjected to projectile impact are conducted by using the proposed 3-D Rigid-Body-Spring Model (RBSM) in order to investigate mechanisms of crack propagation and scabbing mode of concrete members under high-velocity impact. The RBSM is one of the discrete-type numerical methods, which...

In this study, three dimensional numerical analysis systems, which can consider the change in physico- chemical property and expansive strain due to external sulfate attack, was constructed in order to evaluate the process of expansion cracking behavior. This analysis was coupled with cement hydration model, sulfate attack analysis and Rigid Body S...

When a reinforced concrete (RC) member is subjected to cyclic loading, the shear failure after flexural yielding of tension reinforcing bars (called as shear failure after flexural yielding in this study) is often observed at a small deformation, although it ordinarily suffers flexural failure and shows good deformation ability under monotonic load...

The mutual effect between electric corrosion of reinforcing bars and concrete cracks development caused by corrosion is investigated experimentally and analytically. In the experiment, a salt-water pool was set on the concrete cover of each specimen containing single round rebar for the implementation of electric corrosion. Then the radius losses a...

Concrete cracks propagation due to non-uniform corrosion was examined experimentally and analytically. In the experiments, the single-rebar slab specimens with different cover thicknesses were corroded using an electric corrosion method and the internal crack pattern was investigated. In the analysis, the corrosion expansion model incorporated into...

The behaviors of corrosion-induced concrete cover spalling were investigated experimentally and analytically, with a specific emphasis on the local corrosion along the rebar. In the experiments, the single rebar embedded in a slab specimen was corroded non-uniformly in the length direction by an electric corrosion method. The cracking behavior incl...

The tensile behavior of plain round reinforcing bars corroded with various radius losses along their length is investigated experimentally and analytically. In the experiments, various corrosion topographies are simulated through accelerated electric corrosion tests using bare rebar specimens and different cathode arrangements. The tensile performa...

In this study, the degradation process of shear strength of RC members after flexural yielding subjected to cyclic loading was evaluated numerically. First, the validity of the 3-D RBSM with the proposed constitutive model subjected to cyclic loading was demonstrated by simulating the shear failure test of RC member after flexural yielding subjecte...

This paper presents the numerical simulations of the reinforced concrete (RC) panels and the RC shear walls under monotonic and cyclic loading in order to validate the ability of the proposed model which is based on the Rigid-Body-Spring Model (RBSM) to predict the crack propagation behaviours. The authors have already developed constitutive models...

This paper presents a full scale experiment of rockfall protection net by using a full scale rockfall collision test facility. a rock model of 2.0ton in weight and collision energy parameter of 400kJ made by slope set at vacant quarry are used. A real size net, i.e. 15×30m is used as a as a product under test. The dynamic deformation process of net...

The use of a discrete-type numerical approach based on the three-dimensional Rigid-Body-Spring Model (RBSM) is proposed to simulate the crack propagation behavior of reinforced concrete (RC) shear walls subjected to monotonic and cyclic loadings, which are tested in the context of the international benchmark ConCrack (http://www.concrack.org/). In...

The explosive behavior of RC members due to thermal stress and vapor pressure under high temperature was investigated numerically using a developed method. RBSM-TRUSS Network model was adopted as an analytical method, in which 3-dimensional Rigid Body Spring Method (RBSM) based on dynamic equation of motion as structural analysis and truss network...

The purpose of this study is to clarify the effect of stirrups in deep beams by investigating the shear failure mechanism analytically by using the 3-D Rigid-Body-Spring Model analytical tool. The investigation of the analytical results of the internal stress state and 3-D deformations of deep beams were the key objectives of this study. Firstly, t...

Three-dimensional (3-D) effects in short deep beams without stirrups that failed in shear were investigated experimentally and analytically. Two deep beams with a shear span to depth ratio (a/d) of 0.5 and with different beam widths were tested. The effect of beam width on load-carrying capacity, failure mode, crack pattern and 3-D behavior was inv...

This study presents numerical simulations of the shear failure behavior of prestressed concrete (PC) beams under impact load. Concrete is modeled by three dimensional Rigid-Body-Spring Model (3D RBSM) with random mesh discretized Voronoi Diagram. Reinforcing material is modeled as a series of ordinary beam elements and linkage-springs. The constitu...

本研究は，帯鉄筋により補強された横拘束コンクリートの内部抵抗機構を解明することを目的として，著者らが提案している，コンクリートの準微視的な力学挙動をモデル化した3次元RBSMの適用性を検証するとともに，供試体形状・寸法，帯鉄筋形状，帯鉄筋比および帯鉄筋間隔を変化させた横拘束コンクリートの1軸圧縮破壊解析を行ったものである．既往の実験結果および提案式との比較により，提案手法は，1軸圧縮下における横拘束コンクリートの耐力および軟化・局所化挙動に加え，応力分布性状や帯鉄筋の変形性状などの詳細な力学応答までを妥当な精度で再現できることが分かった．さらに，実験では観察が困難な内部の3次元的な損傷進展過程および応力分布性状を可視化することにより，横拘束コンクリートの内部抵抗・破壊機構を解析的に評価した．

3次元剛体バネモデルによりコンクリートの圧縮破壊挙動を定量的に再現することを目的とし，同手法の構成モデルの検討と材料パラメータの同定を行った．その結果，垂直バネの引張側に引張軟化挙動を，圧縮側に逆S字形の非線形挙動を，せん断バネにモール・クーロン型の降伏基準と軟化をモデル化することにより，1軸圧縮下におけるコンクリートの軟化・局所化挙動および高拘束圧領域に至るまでの多軸効果による強度増加，体積変化挙動を妥当な精度で再現できることが分かった．

This research attempted to grasp flexural capacity of RC (Reinforced Concrete) beams connected with loop-shaped re-bar joints through experiments of one-way bending and alternating bending. As the experimental results, it became clear that the RC beams connected with the loop-shaped re-bar joints have enough abilities in both flexural capacity and...