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Hybrid flexural components: Testing pre-stressed steel and GFRP bars together as reinforcement for flexural

Mohammed FARUQI, Oved I. MATA, Francisco AGUINIGA

《结构与土木工程前沿（英文）》 2018年 第12卷 第3期   页码 352-360 doi: 10.1007/s11709-017-0453-3

摘要：

Concrete members historically have used either pre-stressed steel or steel bars. In recent years there has been an increased interest in the use of fiber reinforced polymer (FRP) materials. However, the flexure behavior of a hybrid system reinforced by the combination of pre-stressed steel and glass fiber reinforced (GFRP) is still relatively unknown. The purpose of this work is to study this. Two slabs of 100 and 150-millimeter thickness, with a span of 2.1 m reinforced with both pre-stressing steel and GFRP were constructed and tested to failure using ACI 318-11 and ACI 440.1R-15. The concrete had strength of 31 MPa and the slabs were respectively reinforced with 5#4 bars and 3#5 bars. Each slab had 37.41 mm2 prestressing wire with a failure stress of 1722.5 MPa. The experimental flexural strength and deflection of slabs were compared with their respective sizes theoretical slabs. The theoretical slabs were either reinforced with pre-stressed steel or GFRP rebars, or a hybrid system. It was found that the hybrid system produces better results.

关键词： Partial pre-stressing     composite structures     GFRP bars    

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Predetermination of potential plastic hinges on reinforced concrete frames using GFRP reinforcement

Dominik KUERES; Dritan TOPUZI; Maria Anna POLAK

《结构与土木工程前沿（英文）》 2022年 第16卷 第5期   页码 624-637 doi: 10.1007/s11709-022-0832-2

摘要： In the past, glass fiber-reinforced polymer (GFRP)-reinforcement has been successfully applied in reinforced concrete (RC) structures where corrosion resistance, electromagnetic neutrality, or cuttability were required. Previous investigations suggest that the application of GFRP in RC structures could be advantageous in areas with seismic activity due to their high deformability and strength. However, especially the low modulus of elasticity of GFRP limited its wide application as GFRP-reinforced members usually exhibit considerably larger deformations under service loads than comparable steel-reinforced elements. To overcome the aforementioned issues, the combination of steel and GFRP reinforcement in hybrid RC sections has been investigated in the past. Based on this idea, this paper presents a novel concept for the predetermination of potential plastic hinges in RC frames using GFRP reinforcement. To analyze the efficiency of the concept, nonlinear finite element simulations were performed. The results underscore the high efficiency of hybrid steel-GFRP RC sections for predetermining potential plastic hinges on RC frames. The results also indicate that the overall seismic behavior of RC structures could be improved by means of GFRP as both the column base shear force during the seismic activity as well as the plastic deformations after the earthquake were considerably less pronounced than in the steel-reinforced reference structure.

关键词： glass fiber-reinforced polymer     GFRP     hybrid section     plastic hinge     seismic design     reinforced concrete    

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Prediction of cutting force in turning of UD-GFRP using mathematical model and simulated annealing

Meenu GUPTA, Surinder Kumar GILL

《机械工程前沿（英文）》 2012年 第7卷 第4期   页码 417-426 doi: 10.1007/s11465-012-0343-2

摘要：

Glass fiber reinforced plastics (GFRPs) composite is considered to be an alternative to heavy exortic materials. According to the need for accurate machining of composites has increased enormously. During machining, the obtaining cutting force is an important aspect. The present investigation deals with the study and development of a cutting force prediction model for the machining of unidirectional glass fiber reinforced plastics (UD-GFRP) composite using regression modeling and optimization by simulated annealing. The process parameters considered include cutting speed, feed rate and depth of cut. The predicted values radial cutting force model is compared with the experimental values. The results of prediction are quite close with the experimental values. The influences of different parameters in machining of UD-GFRP composite have been analyzed.

关键词： UD-GFRP     ANOVA     radial cutting force     PCD tool     Taguchi method     regression analysis     simulated annealing     multi objective techniques    

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Performance of a novel bent-up bars system not interacting with concrete

Aydin SHISHEGARAN, Mohammad Reza GHASEMI, Hesam VARAEE

《结构与土木工程前沿（英文）》 2019年 第13卷 第6期   页码 1301-1315 doi: 10.1007/s11709-019-0552-4

摘要： Increasing the bending and shear capacities of reinforced concrete members is an interesting issue in structural engineering. In recent years, many studies have been carried out to improve capacities of reinforced concrete members such as using post and pre-tensioning, Fiber Reinforced Polymer and other techniques. This paper proposes a novel and significant technique to increase the flexural capacity of simply supported reinforced concrete beams. The proposed method uses a new reinforcement bar system having bent-up bars, covered with rubber tubes. This technique will avoid interaction of bent-up bars with concrete. They are located in the zone where compressive and tensile forces act against one another. The compressive force in the upper point of the bent-up bars is exerted to the end point of these bars located under neutral axis. Moreover, the tensile stress is decreased in reinforcements located under the neutral axis. This will cause the Reinforced Concrete (RC) beam to endure extra loading before reaching yield stress. These factors may well be considered as reasons to increase bending capacity in the new system. The laboratory work together with finite element method analysis were carried out in this investigation. Furthermore, bending capacity, ductility, strength, and cracking zone were assessed for the new proposed system and compared with the conventional model. Both the FEM simulation and the experimental test results revealed that the proposed system has significant impact in increasing the load bearing capacity and the stiffness of the RC beams. In the present study, an equation is formulated to calculate bending capacity of a new reinforcement bar system beam.

关键词： bending capacity     rubber tube     stress transfer     bent-up bars     ductility     cracking    

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Experimental study on GFRP pipes under axial compression

QIAN Peng, FENG Peng, YE Lieping

《结构与土木工程前沿（英文）》 2008年 第2卷 第1期   页码 73-78 doi: 10.1007/s11709-008-0013-y

摘要： Fiber reinforced polymer (FRP) is suitable for structures in corrosive environment and long-span light-weight structures due to its high-strength, light-weight, and anti-corrosive qualities. The behavior of pultruded glass fiber reinforced polymer (GFRP) pipes, which are the members of long-span lattice structures, under axial compression was investigated by tests. Short GFRP pipes were first tested to determine the basic mechanical properties. Then the stability of long GFRP pipes was studied by axially compressive tests in four groups with different slenderness ratios, twelve specimens totally. Based on the results of the tests and literature, the formula of the buckling load of composite pipes under axially compressive load was presented based on Perry formula. It can well predict the buckling failure load GFRP pipe under axial compression.

关键词： anti-corrosive     compression     different slenderness     corrosive environment     long-span light-weight    

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The effect of carbon nanotubes and polypropylene fibers on bond of reinforcing bars in strain resilient

Souzana P. TASTANI,Maria S. KONSTA-GDOUTOS,Stavroula J. PANTAZOPOULOU,Victor BALOPOULOS

《结构与土木工程前沿（英文）》 2016年 第10卷 第2期   页码 214-223 doi: 10.1007/s11709-016-0332-3

摘要： Stress transfer between reinforcing bars and concrete is engaged through rib translation relative to concrete, and comprises longitudinal bond stresses and radial pressure. The radial pressure is equilibrated by hoop tension undertaken by the concrete cover. Owing to concrete’s poor tensile properties in terms of strength and deformability, the equilibrium is instantly released upon radial cracking of the cover along the anchorage with commensurate abrupt loss of the bond strength. Any improvement of the matrix tensile properties is expected to favorably affect bond in terms of strength, resilience to pullout slip, residual resistance and controlled slippage.The aim of this paper is to investigate the local bond of steel bars developed in adverse tensile stress conditions in the concrete cover. In the tests, the matrix comprises a novel, strain resilient cementitious composite (SRCC) reinforced with polypropylene fibers (PP) with the synergistic action of carbon nano-tubes (CNT). Local bond is developed over a short anchorage length occurring in the constant moment region of a four-point bending short beam. Parameters of investigation were the material structure (comprising a basic control mix, reinforced with CNTs and/or PP fibers) and the age of testing. Accompanying tests used to characterize the cementitious material were also conducted. The test results illustrate that all the benefits gained due to the synergy between PP fibers and CNTs in the matrix, namely the maintenance of the multi-cracking effect with time, the increased strength and deformability as well as the highly increased material toughness, were imparted in the recorded bond response. The local bond response curves thus obtained were marked by a resilient appearance exhibiting sustained strength up to large levels of controlled bar-slip; the elasto-plastic bond response envelope was a result of the confining synergistic effect of CNTs and the PP fibers, and it occurred even without bar yielding.

关键词： carbon nanotubes     strain resilient cementitious composite     polypropylene fibers     tensile bending     bond    

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Ductility improvement of GFRP-RC beams using precast confined concrete block in compression zone

《结构与土木工程前沿（英文）》 doi: 10.1007/s11709-023-0968-8

摘要： Fiber-reinforced polymers (FRPs) have received considerable research attention because of their high strength, corrosion resistance, and low weight. However, owing to the lack of ductility in this material and the quasi-brittle behavior of concrete, FRP-reinforced concrete (FRP-RC) beams, even with flexural failure, do not fail in a ductile manner. Because the limited deformation capacity of FRP-RC beams depends on the ductility of their compression zones, the present study proposes using a precast confined concrete block (PCCB) in the compression zone to improve the ductility of the beams. A control beam and four beams with different PCCBs were cast and tested under four-point bending conditions. The control beam failed due to shear, and the PCCBs exhibited different confinements and perforations. The goal was to find an appropriate PCCB for use in the compression zone of the beams, which not only improved the ductility but also changed the failure mode of the beams from shear to flexural. Among the employed blocks, a ductile PCCB with low equivalent compressive strength increased the ductility ratio of the beam to twice that of the control beam. The beam failed in pure flexure with considerable deformation capacity and without significant stiffness reduction.

关键词： ductility     four-point bending test     glass fiber-reinforced polymer     precast confined concrete block    

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Structural performance assessment of GFRP elastic gridshells by machine learning interpretability methods

Soheila KOOKALANI; Bin CHENG; Jose Luis Chavez TORRES

《结构与土木工程前沿（英文）》 2022年 第16卷 第10期   页码 1249-1266 doi: 10.1007/s11709-022-0858-5

摘要： The prediction of structural performance plays a significant role in damage assessment of glass fiber reinforcement polymer (GFRP) elastic gridshell structures. Machine learning (ML) approaches are implemented in this study, to predict maximum stress and displacement of GFRP elastic gridshell structures. Several ML algorithms, including linear regression (LR), ridge regression (RR), support vector regression (SVR), K-nearest neighbors (KNN), decision tree (DT), random forest (RF), adaptive boosting (AdaBoost), extreme gradient boosting (XGBoost), category boosting (CatBoost), and light gradient boosting machine (LightGBM), are implemented in this study. Output features of structural performance considered in this study are the maximum stress as f1(x) and the maximum displacement to self-weight ratio as f2(x). A comparative study is conducted and the Catboost model presents the highest prediction accuracy. Finally, interpretable ML approaches, including shapely additive explanations (SHAP), partial dependence plot (PDP), and accumulated local effects (ALE), are applied to explain the predictions. SHAP is employed to describe the importance of each variable to structural performance both locally and globally. The results of sensitivity analysis (SA), feature importance of the CatBoost model and SHAP approach indicate the same parameters as the most significant variables for f1(x) and f2(x).

关键词： machine learning     gridshell structure     regression     sensitivity analysis     interpretability methods    

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Ordinary Portland Cement (OPC) and Portland Pozzolane Cement (PPC) mixes and different diameter of TMT bars

A D POFALE, S P WANJARI

《结构与土木工程前沿（英文）》 2013年 第7卷 第1期   页码 39-45 doi: 10.1007/s11709-013-0193-y

摘要： Since last two decades, the Portland Pozzolane Cement (PPC) is extensively used in structural concrete. But, till to date, a few literature is available on bond strength of concrete using PPC mixes. There are many literatures available on bond strength of concrete mixes using Ordinary Portland Cement (OPC). Hence, a comparative study was conducted on bond strength between OPC and PPC mixes. In the present investigation, total 24 samples consisting of M20, M35 and M50 grades of concrete and 16 and 25 mm diameter of TMT bar were tested for 7 and 28 days. The pullout bond test was conducted on each specimen as per IS: 2770-1967/1997 [1] and the results were observed at 0.25 mm slip at loaded end called as critical bond stress and at maximum bond load called as maximum bond stress. It was observed that the critical bond strength of PPC mixes is 10% higher than OPC mixes. Whereas, marginal improvement was noticed in maximum bond strength of PPC mixes. Hence, based on these findings, it could be concluded that development length for PPC mixes could be reduced by 10% as compared with same grade of OPC mixes.

关键词： bond strength     Portland Pozzolane Cement (PPC) concrete     Ordinary Portland Cement (OPC) concrete     bond between concrete and steel     pullout test     development length    

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Induction motors variable speed drives diagnosis through rotor resistance monitoring

K. YAHIA, S. ZOUZOU, F. BENCHABANE

《能源前沿（英文）》 2012年 第6卷 第4期   页码 420-426 doi: 10.1007/s11708-012-0192-z

摘要： Induction motor driven by vector control method makes high performance control of torque and speed possible. The decoupling of flux and electromagnetic torque obtained by field orientation depends on the precision and the accuracy of the estimated states. Rotor asymmetries lead to perturbations of air gap flux patterns in induction machines. These perturbations in flux components affect the electromagnetic torque, as well as stator currents and voltages. This paper first investigates the control of the induction motor using an extended Kalman filter (EKF) for a direct field-oriented control. It then studies the broken rotor bars (BRBs) fault by the monitoring the rotor resistance. The hypothesis on which the detection is based is that the apparent rotor resistance of the motor will increase when a rotor bar breaks. The rotor resistance is estimated and compared with its nominal value to detect BRBs fault. The EKF estimates the rotor flux, speed and rotor resistance on line by using only measurements of the stator voltages and currents. Simulation results show the effectiveness of the proposed method in the cases of load torque perturbation and speed reversion.

关键词： induction motor     vector control     broken rotor bars (BRBs) diagnostic     extended Kalman filter (EKF)    

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Prediction of cutting forces in machining of unidirectional glass fiber reinforced plastics composite

Surinder Kumar GILL, Meenu GUPTA, P. S. SATSANGI

《机械工程前沿（英文）》 2013年 第8卷 第2期   页码 187-200 doi: 10.1007/s11465-013-0262-x

摘要：

Machining of plastic materials has become increasingly important in any engineering industry subsequently the prediction of cutting forces. Forces quality has greater influence on components, which are coming in contact with each other. So it becomes necessary to measure and study machined forces and its behavior. In this research work, experimental investigations are conducted to determine the effects of cutting conditions and tool geometry on the cutting forces in the turning of the unidirectional glass fiber reinforced plastics (UD-GFRP) composites. In this experimental study, carbide tool (K10) having different tool nose radius and tool rake angle is used. Experiments are conducted based on the established Taguchi’s technique L18 orthogonal array on a lathe machine. It is found that the depth of cut is the cutting parameter, which has greater influence on cutting forces. The effect of the tool nose radius and tool rake angles on the cutting forces are also considerably significant. Based on statistical analysis, multiple regression model for cutting forces is derived with satisfactory coefficient (R2). This model proved to be highly preferment for predicting cutting forces.

关键词： unidirectional glass fiber reinforced plastics (UD-GFRP) composites     machining     cutting forces (tangential     feed and radial force)     ANOVA     regression modeling     carbide tool (K10)    

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Experimental and statistical investigation of a new concrete-composite beam with encased polymer tube wrapped by FRP

Abdelmadjid SI SALEM,Souad AIT TALEB,Kamal AIT TAHAR

《结构与土木工程前沿（英文）》 2015年 第9卷 第2期   页码 154-162 doi: 10.1007/s11709-015-0296-8

摘要： A new concrete-composite beam with high mechanical performances to weight ratio is developed in this study. The proposed design technique consists to embed a cylindrical polymer tube wrapped by a GFRP Jacket in the mechanically ineffective concrete tensile zone. An experimental investigation is carried out on composite beams under bending loads until failure to evaluate the flexural capacity and the corresponding failure mechanisms. Based on the experimental results, statistical and preliminary reliability analyses using the FORM method are performed to assess the safety margin of the new beam. The confrontation between test and simulation results shows a satisfactory agreement, and represents a promising revelation regarding the improvement in terms of strength and ductility of such design compared to conventional reinforced concrete beams with traditional one.

关键词： design     GFRP-Jacket     polymer tube     test     reliability analysis    

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Seismic behavior experimental study of frame joints with special-shaped column and dispersed steel bar beam

Shuchun LI, Bo DIAO, Youpo SU,

《结构与土木工程前沿（英文）》 2009年 第3卷 第4期   页码 378-383 doi: 10.1007/s11709-009-0064-8

摘要： To overcome the problem that steel bars are put too close at a flame joint with special-shaped beam and column, mechanical performance of three groups of six RC flame joints with special-shaped (L, T and+) column and dispersed-steel bars-beam on the top floor under cyclic loads were studied. Experimental comparison was conducted between special-shaped (L, T and+) column and normal beams. The cracking load, yielding load, ultimate bearing capacity, failure patterns, and hysteretic properties at joint core area were investigated. The seismic behaviors of the joints with different proportions of dispersed-steel-bar beams were analyzed. The results of experimental analysis indicate that the mechanical and seismic behaviors of frame joints with T-shaped and+-shaped column are nearly not changed when suitable proportion steel bars are dispersed to flange plane. Stiffness degeneration of flame joint with L-shaped column is rather serious due to concrete damage stiffness. Theoretical result indicates that distributing area of the dispersed steel-bar beams in the flange plate should be strictly controlled to avoid anchor destroy.

关键词： beam with dispersed steel bar     flame joints with special-shaped beam and column     seismic behavior     scale of dispersed steel bars    

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Investigation on modeling parameters of concrete beams reinforced with basalt FRP bars

Jordan CARTER, Aikaterini S. GENIKOMSOU

《结构与土木工程前沿（英文）》 2019年 第13卷 第6期   页码 1520-1530 doi: 10.1007/s11709-019-0580-0

摘要： Fiber-reinforced polymer (FRP) bars are widely used as internal reinforcement replacing the conventional steel bars to prevent from corrosion. Among the different types of FRP bars, basalt FRP (BFRP) bars have been used in different structural applications and, herein, three already tested concrete beams reinforced with BFRP bars are analyzed using three-dimensional (3-D) finite element analysis (FEA). The beams were tested in four-point bending. In the FEA the behavior of concrete is simulated using the “Concrete-Damaged Plasticity” model offered in ABAQUS software. The research presented here presents a calibrated model for nonlinear FEA of BFRP concrete beams to predict their response considering both the accuracy and the computational efficiency. The calibration process showed that the concrete model should be regularized using a mesh-dependent characteristic length and material-dependent post-yield fracture and crushing energies to provide accurate mesh-size independent results. FEA results were compared to the test results with regard to failure load and crack patterns. Both test the results and the numerical results were compared to the design predictions of ACI 440.1R-15 and CSA S806-12, where CSA S806-12 seems to overestimate the shear strength for two beams.

关键词： basalt Fiber-reinforced polymer bars     reinforced concrete beams     finite element analysis     damaged plasticity model     design codes    

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Combination form analysis and experimental study of mechanical properties on steel sheet glass fiber reinforced polymer composite bar

《结构与土木工程前沿（英文）》 2021年 第15卷 第4期   页码 834-850 doi: 10.1007/s11709-021-0743-7

摘要： The concept of steel sheet glass fiber reinforced polymer (GFRP) composite bar (SSGCB) was put forward. An optimization plan was proposed in the combined form of SSGCB. The composite principle, material selection, and SSGCB preparation technology have been described in detail. Three-dimensional finite element analysis was adopted to perform the combination form optimization of different steel core structures and different steel core contents based on the mechanical properties. Mechanical tests such as uniaxial tensile, shear, and compressive tests were carried out on SSGCB. Parametric analysis was conducted to investigate the influence of steel content on the mechanical properties of SSGCB. The results revealed that the elastic modulus of SSGCB had improvements and increased with the rise of steel content. Shear strength was also increased with the addition of steel content. Furthermore, the yield state of SSGCB was similar to the steel bar, both of which indicated a multi-stage yield phenomenon. The compressive strength of SSGCB was lower than that of GFRP bars and increased with the increase of the steel core content. Stress-strain curves of SSGCB demonstrated that the nonlinear-stage characteristics of SSGCB-8 were much more obvious than other bars.

关键词： steel sheet GFRP composite bar     combination form     numerical modeling     mechanical properties test     strength    

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标题 作者 时间 类型 操作

Hybrid flexural components: Testing pre-stressed steel and GFRP bars together as reinforcement for flexural

Mohammed FARUQI, Oved I. MATA, Francisco AGUINIGA

期刊论文

Predetermination of potential plastic hinges on reinforced concrete frames using GFRP reinforcement

Dominik KUERES; Dritan TOPUZI; Maria Anna POLAK

期刊论文

Prediction of cutting force in turning of UD-GFRP using mathematical model and simulated annealing

Meenu GUPTA, Surinder Kumar GILL

期刊论文

Performance of a novel bent-up bars system not interacting with concrete

Aydin SHISHEGARAN, Mohammad Reza GHASEMI, Hesam VARAEE

期刊论文

Experimental study on GFRP pipes under axial compression

QIAN Peng, FENG Peng, YE Lieping

期刊论文

The effect of carbon nanotubes and polypropylene fibers on bond of reinforcing bars in strain resilient

Souzana P. TASTANI,Maria S. KONSTA-GDOUTOS,Stavroula J. PANTAZOPOULOU,Victor BALOPOULOS

期刊论文

Ductility improvement of GFRP-RC beams using precast confined concrete block in compression zone

期刊论文

Structural performance assessment of GFRP elastic gridshells by machine learning interpretability methods

Soheila KOOKALANI; Bin CHENG; Jose Luis Chavez TORRES

期刊论文

Ordinary Portland Cement (OPC) and Portland Pozzolane Cement (PPC) mixes and different diameter of TMT bars

A D POFALE, S P WANJARI

期刊论文

Induction motors variable speed drives diagnosis through rotor resistance monitoring

K. YAHIA, S. ZOUZOU, F. BENCHABANE

期刊论文

Prediction of cutting forces in machining of unidirectional glass fiber reinforced plastics composite

Surinder Kumar GILL, Meenu GUPTA, P. S. SATSANGI

期刊论文

Experimental and statistical investigation of a new concrete-composite beam with encased polymer tube wrapped by FRP

Abdelmadjid SI SALEM,Souad AIT TALEB,Kamal AIT TAHAR

期刊论文

Seismic behavior experimental study of frame joints with special-shaped column and dispersed steel bar beam

Shuchun LI, Bo DIAO, Youpo SU,

期刊论文

Investigation on modeling parameters of concrete beams reinforced with basalt FRP bars

Jordan CARTER, Aikaterini S. GENIKOMSOU

期刊论文

Combination form analysis and experimental study of mechanical properties on steel sheet glass fiber reinforced polymer composite bar

期刊论文