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Deflection behavior of a prestressed concrete beam reinforced with carbon fibers at elevated temperatures

Mohammed FARUQI, Mohammed Sheroz KHAN

《结构与土木工程前沿(英文)》 2019年 第13卷 第1期   页码 81-91 doi: 10.1007/s11709-018-0468-4

摘要: Fiber reinforced polymer(FRP) have unique advantages like high strength to weight ratio, excellent corrosion resistance, improving deformability and cost effectiveness. These advantages have gained wide acceptance in civil engineering applications. FRP tendons for prestressing applications are emerging as one of the most promising technologies in the civil engineering industry. However, the behavior of such members under the influence of elevated temperatures is still unknown. The knowledge and application of this could lead to a cost effective and practical considerations in fire safety design. Therefore, this study examines the deflection behavior of the carbon fiber reinforced polymer(CFRP) prestressed concrete beam at elevated temperatures. In this article, an analytical model is developed which integrates the temperature dependent changes of effective modulus of FRP in predicting the deflection behavior of CFRP prestressed concrete beams within the range of practical temperatures. This model is compared with a finite element mode (FEM) of a simply supported concrete beam prestressed with CFRP subjected to practical elevated temperatures. In addition, comparison is also made with an indirect reference to the real behavior of the material. The results of the model correlated reasonably with the finite element model and the real behavior. Finally, a practical application is provided.

关键词: FRP     CFRP     concrete     elevated temperatures     deflections     prestress    

Experimental study on shear behavior of reinforced concrete beams with web horizontal reinforcement

Dong XU,Yu ZHAO,Chao LIU

《结构与土木工程前沿(英文)》 2014年 第8卷 第4期   页码 325-336 doi: 10.1007/s11709-014-0080-1

摘要: In determining the shear capacity of reinforced concrete beams, current codes do not provide any calculation method to evaluate the influence of web horizontal reinforcement, although they exist as structural reinforcements (or skin reinforcement). The present paper comprises results of 11 reinforced concrete beams in an effort to investigate the influence of web horizontal reinforcement on the shear behavior of reinforced concrete beams. The primary design variables are the shear-span-depth ratio, different reinforcement ratio of stirrups and web horizontal reinforcement. Influence of web horizontal reinforcement on crack patterns and failure mode was studied. It was found that web horizontal reinforcement can increase the shear capacity of the beams and restrain growth of inclined cracks effectively. Test results are very valuable, as very few references of shear tests can be found focusing on the effect of web horizontal reinforcement on the shear capacity of the beams.

关键词: reinforced concrete beam     shear strength     web horizontal reinforcement     experiments    

Effect of eccentricity in reinforced concrete beam-column-slab connection under cyclic loading

Rooh ULLAH, Amjad NASEER, Muhammad FAHIM, Mohammad ASHRAF, Eid BADSHAH

《结构与土木工程前沿(英文)》 2021年 第15卷 第2期   页码 390-398 doi: 10.1007/s11709-021-0690-3

摘要: Beam–column connections are one of the most critical elements of reinforced concrete structures, especially in seismically active regions, and have been extensively evaluated experimentally and numerically. However, very limited experimental studies about eccentric reinforced concrete connections including the effect of connected slabs are available. This study presents the experimental results of two half-scale eccentric beam-column-slab connections subjected to quasi-static cyclic loading. The horizontal eccentricity ( ) is maintained at 12.5% and 25% of column width ( ) for specimens 1 and 2, respectively. The damage pattern, performance levels, displacement ductility ( ), energy dissipation, and connection strength and stiffness are compared for both specimens, and the effect of eccentricity is evaluated. It is concluded that the eccentricity has no significant effect on the lateral load carrying capacity; however, the overall strength degradation increases with the increase in eccentricity. Similarly, the elastic stiffness of specimen 2 decreased by 14% as the eccentricity increased from 12.5% to 25%; however, the eccentricity had no significant effect on the overall stiffness degradation. decreased by 43%, and the energy dissipation capacity decreased by 40% in specimen 2 with higher eccentricity. The story drifts corresponding to the performance levels of the life safety (LS) and collapse prevention (CP) were found to be 28% lesser in specimen 2 than in specimen 1.

关键词: corner connection     eccentricity     strength degradation     stiffness degradation     energy dissipation     performance levels    

Shear behavior of ultra-high-performance concrete beams prestressed with external carbon fiber-reinforced

《结构与土木工程前沿(英文)》 2021年 第15卷 第6期   页码 1426-1440 doi: 10.1007/s11709-021-0783-z

摘要: The ultra-high-performance concrete (UHPC) and fiber-reinforced polymer (FRP) are well-accepted high-performance materials in the field of civil engineering. The combination of these advanced materials could contribute to improvement of structural performance and corrosion resistance. Unfortunately, only limited studies are available for shear behavior of UHPC beams reinforced with FRP bars, and few suggestions exist for prediction methods for shear capacity. This paper presents an experimental investigation on the shear behavior of UHPC beams reinforced with glass FRP (GFRP) and prestressed with external carbon FRP (CFRP) tendons. The failure mode of all specimens with various shear span to depth ratios from 1.7 to 4.5 was diagonal tension failure. The shear span to depth ratio had a significant influence on the shear capacity, and the effective prestressing stress affected the crack propagation. The experimental results were then applied to evaluate the equations given in different codes/recommendations for FRP-reinforced concrete structures or UHPC structures. The comparison results indicate that NF P 18-710 and JSCE CES82 could appropriately estimate shear capacity of the slender specimens with a shear span to depth ratio of 4.5. Further, a new shear design equation was proposed to take into account the effect of the shear span to depth ratio and the steel fiber content on shear capacity.

关键词: beam     external prestressing     ultra-high-performance concrete     fiber-reinforced polymers     shear behavior     design equation    

Investigation of the parameters affecting the behavior of RC beams strengthened with FRP

Kadir SENGUN; Guray ARSLAN

《结构与土木工程前沿(英文)》 2022年 第16卷 第6期   页码 729-743 doi: 10.1007/s11709-022-0854-9

摘要: Three-point bending tests were carried out on nineteen Reinforced Concrete (RC) beams strengthened with FRP in the form of completely wrapping. The strip width to spacing ratios, FRP type, shear span to effective depth ratios, the number of FRP layers in shear, and the effect of stirrups spacing were the parameters investigated in the experimental study. The FRP contribution to strength on beams having the same strip width to spacing ratios could be affected by the shear span to effective depth ratios and stirrups spacing. The FRP contributions to strength were less on beams with stirrups in comparison to the tested beams without stirrups. Strengthening RC beams using FRP could change the failure modes of the beams compared to the reference beam. In addition to the experimental study, a number of equations used to predict the FRP contribution to the shear strength of the strengthened RC beams were assessed by using a limited number of beams available in the literature. The effective FRP strain is predicted by using test results, and this prediction is used to calculate the FRP contribution to shear strength in ACI 440.2R (2017) equation. Based on the statistical values of the data, the proposed equation has the lowest coefficient of variation (COV) value than the other equations.

关键词: carbon     glass     strengthening     shear strength     reinforced concrete beam     fiber reinforced polymer    

Analysis of stiffness and flexural strength of a reinforced concrete beam using an invented reinforcement

Nazim Abdul NARIMAN, Martin HUSEK, Ilham Ibrahim MOHAMMAD, Kaywan Othman AHMED, Diyako DILSHAD, Ibrahim KHIDR

《结构与土木工程前沿(英文)》 2021年 第15卷 第2期   页码 378-389 doi: 10.1007/s11709-021-0706-z

摘要: In this study, we conducted experimental tests on two specimens of reinforced concrete beams using a three-point bending test to optimize the flexure and stiffness designs. The first specimen is a reinforced concrete beam with an ordinary reinforcement, and the second specimen has an invented reinforcement system that consists of an ordinary reinforcement in addition to three additional bracings using steel bars and steel plates. The results of the flexure test were collected and analyzed, and the flexural strength, the rate of damage during bending, and the stiffness were determined. Finite element modeling was applied for both specimens using the LS-DYNA program, and the simulation results of the flexure test for the same outputs were determined. The results of the experimental tests showed that the flexural strength of the invented reinforcement system was significantly enhanced by 15.5% compared to the ordinary system. Moreover, the flexural cracks decreased to a significant extent, manifesting extremely small and narrow cracks in the flexure spread along the bottom face of the concrete. In addition, the maximum deflection for the invented reinforced concrete beam decreased to 1/3 compared to that of an ordinary reinforced concrete beam. The results were verified through numerical simulations, which demonstrated excellent similarities between the flexural failure and the stiffness of the beam. The invented reinforcement system exhibited a high capability in boosting the flexure design and stiffness.

关键词: three-point flexure test     softening stage     flexural crack     flexural strain    

Non linear modeling of three-dimensional reinforced and fiber concrete structures

Fatiha IGUETOULENE, Youcef BOUAFIA, Mohand Said KACHI

《结构与土木工程前沿(英文)》 2018年 第12卷 第4期   页码 439-453 doi: 10.1007/s11709-017-0433-7

摘要: Under the effect of the ascending loading, the behavior of reinforced concrete structures is rather non linear. Research in industry and science aims to extend forward the use of non-linear calculation of fiber concrete for structural parts such as columns, veils and pious, as the fiber concrete is more ductile behavior then the classical concrete behavior. The formulation of the element has been established for modeling the nonlinear behavior of elastic structures in three dimensions, based on the displacement method. For the behavior of concrete and fiber concrete compressive and tensile strength (stress-strain) the uniaxial formulation is used. For steel bi-linear relationship is used. The approach is based on the discretization of the cross section trapezoidal tables. Forming the stiffness matrix of the section, the integral of the surface is calculated as the sum of the integrals on each of the cutting trapezoids. To integrate on the trapeze we have adopted the type of Simpson integration scheme.

关键词: numerical modeling     column and beam     nonlinear analysis     fibers     pious     reinforcement     3D formulation     response load-deflection    

Applying the spectral stochastic finite element method in multiple-random field RC structures

Abbas YAZDANI

《结构与土木工程前沿(英文)》 2022年 第16卷 第4期   页码 434-447 doi: 10.1007/s11709-022-0820-6

摘要: This paper uses the spectral stochastic finite element method (SSFEM) for analyzing reinforced concrete (RC) beam/slab problems. In doing so, it presents a new framework to study how the correlation length of a random field (RF) with uncertain parameters will affect modeling uncertainties and reliability evaluations. It considers: 1) different correlation lengths for uncertainty parameters, and 2) dead and live loads as well as the elasticity moduli of concrete and steel as a multi-dimensional RF in concrete structures. To show the SSFEM’s efficiency in the study of concrete structures and to evaluate the sensitivity of the correlation length effects in evaluating the reliability, two examples of RC beams and slabs have been investigated. According to the results, the RF correlation length is effective in modeling uncertainties and evaluating reliabilities; the longer the correlation length, the greater the dispersion range of the structure response and the higher the failure probability.

关键词: uncertainty     spectral stochastic finite element method     correlation length     reliability assessment     reinforced concrete beam/slab    

Numerical modelling of reinforced concrete flexural members strengthened using textile reinforced mortars

《结构与土木工程前沿(英文)》 2023年 第17卷 第4期   页码 649-668 doi: 10.1007/s11709-023-0919-4

摘要: Externally bonded (EB) and near-surface mounted (NSM) bonding are two widely adopted and researched strengthening methods for reinforced-concrete structures. EB composite substrates are easy to reach and repair using appropriate surface treatments, whereas NSM techniques can be easily applied to the soffit and concrete member sides. The EB bonded fiber-reinforced polymer (FRP) technique has a significant drawback: combustibility, which calls for external protective agents, and textile reinforced mortar (TRM), a class of EB composites that is non-combustible and provides a similar functionality to any EB FRP-strengthened substrate. This study employs a finite element analysis technique to investigate the failing failure of carbon textile reinforced mortar (CTRM)-strengthened reinforced concrete beams. The principal objective of this numerical study was to develop a finite element model and validate a set of experimental data in existing literature. A set of seven beams was modelled and calibrated to obtain concrete damage plasticity (CDP) parameters. The predicted results, which were in the form of load versus deflection, load versus rebar strain, tensile damage, and compressive damage patterns, were in good agreement with the experimental data. Moreover, a parametric study was conducted to verify the applicability of the numerical model and study various influencing factors such as the concrete strength, internal reinforcement, textile roving spacing, and externally-applied load span. The ultimate load and deflection of the predicted finite element results had a coefficient of variation (COV) of 6.02% and 5.7%, respectively. A strain-based numerical comparison with known methods was then conducted to investigate the debonding mechanism. The developed finite element model can be applied and tailored further to explore similar TRM-strengthened beams undergoing debonding, and the preventive measures can be sought to avoid premature debonding.

关键词: fiber reinforced polymer     textile reinforced mortar     finite element analysis     concrete damage plasticity     calibration and validation     parametric study    

Experimental investigation on concrete overlaid with textile reinforced mortar: Influences of mix, temperature

《结构与土木工程前沿(英文)》 2023年 第17卷 第2期   页码 271-283 doi: 10.1007/s11709-022-0896-z

摘要: Textile reinforced mortar is widely used as an overlay for the repair, rehabilitation, and retrofitting of concrete structures. Recently, textile reinforced concrete has been identified as a suitable lining material for improving the durability of existing concrete structures. In this study, we developed a textile-reinforced mortar mix using river sand and evaluated the different characteristics of the textile-reinforced mortar under various exposure conditions. Studies were carried out in two phases. In the first phase, the pullout strength, temperature resistance, water absorption, and compressive and bending strength values of three different textile-reinforced mortar mixes with a single type of textile reinforcement were investigated. In the second phase, the chemical resistance of the mix that showed the best performance in the abovementioned tests was examined for use as an overlay for a concrete substrate. Investigations were performed on three different thicknesses of the textile reinforced mortar overlaid on concrete specimens that were subjected to acidic and alkaline environments. The flexural responses and degradations of the textile reinforced mortar overlaid specimens were examined by performing bending tests. The experimental findings indicated the feasibility of using textile reinforced mortar as an overlay for durable concrete construction practices.

关键词: textile reinforced mortar     bending tests     acid and alkaline environment     concrete overlay    

Axial compression tests and numerical simulation of steel reinforced recycled concrete short columnsconfined by carbon fiber reinforced plastics strips

Hui MA; Fangda LIU; Yanan WU; Xin A; Yanli ZHAO

《结构与土木工程前沿(英文)》 2022年 第16卷 第7期   页码 817-842 doi: 10.1007/s11709-022-0844-y

摘要: To research the axial compression behavior of steel reinforced recycled concrete (SRRC) short columns confined by carbon fiber reinforced plastics (CFRP) strips, nine scaled specimens of SRRC short columns were fabricated and tested under axial compression loading. Subsequently, the failure process and failure modes were observed, and load-displacement curves as well as the strain of various materials were analyzed. The effects on the substitution percentage of recycled coarse aggregate (RCA), width of CFRP strips, spacing of CFRP strips and strength of recycled aggregate concrete (RAC) on the axial compression properties of columns were also analyzed in the experimental investigation. Furthermore, the finite element model of columns which can consider the adverse influence of RCA and the constraint effect of CFRP strips was founded by ABAQUS software and the nonlinear parameter analysis of columns was also implemented in this study. The results show that the first to reach the yield state was the profile steel in the columns, then the longitudinal rebars and stirrups yielded successively, and finally RAC was crushed as well as the CFRP strips was also broken. The replacement rate of RCA has little effect on the columns, and with the substitution rate of RCA from 0 to 100%, the bearing capacity of columns decreased by only 4.8%. Increasing the CFRP strips width or decreasing the CFRP strips spacing could enhance the axial bearing capacity of columns, the maximum increase was 10.5% or 11.4%, and the ductility of columns was significantly enhanced. Obviously, CFRP strips are conducive to enhance the axial bearing capacity and deformation capacity of columns. On this basis, considering the restraint effect of CFRP strips and the adverse effects of RCA, the revised formulas for calculating the axial bearing capacity of SRRC short columns confined by CFRP strips were proposed.

关键词: steel reinforced recycled concrete     CFRP strips     short columns     axial compression behavior     recycled aggregate concrete    

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    

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    

Slender reinforced concrete shear walls with high-strength concrete boundary elements

《结构与土木工程前沿(英文)》 2023年 第17卷 第1期   页码 138-151 doi: 10.1007/s11709-022-0897-y

摘要: Reinforced concrete structural walls are commonly used for resisting lateral forces in buildings. Owing to the advancements in the field of concrete materials over the past few decades, concrete mixes of high compressive strength, commonly referred to as high-strength concrete (HSC), have been developed. In this study, the effects of strategic placement of HSC on the performance of slender walls were examined. The finite-element model of a conventional normal-strength concrete (NSC) prototype wall was validated using test data available in extant studies. HSC was incorporated in the boundary elements of the wall to compare its performance with that of the conventional wall at different axial loads. Potential reductions in the reinforcement area and size of the boundary elements were investigated. The HSC wall exhibited improved strength and stiffness, and thereby, allowed reduction in the longitudinal reinforcement area and size of the boundary elements for the same strength of the conventional wall. Cold joints resulting from dissimilar concrete pours in the web and boundary elements of the HSC wall were modeled and their impact on behavior of the wall was examined.

关键词: slender walls     high-strength concrete     rectangular and barbell-shaped walls     cold joints    

Punching of reinforced concrete slab without shear reinforcement: Standard models and new proposal

Luisa PANI, Flavio STOCHINO

《结构与土木工程前沿(英文)》 2020年 第14卷 第5期   页码 1196-1214 doi: 10.1007/s11709-020-0662-z

摘要: Reinforced concrete (RC) slabs are characterized by reduced construction time, versatility, and easier space partitioning. Their structural behavior is not straightforward and, specifically, punching shear strength is a current research topic. In this study an experimental database of 113 RC slabs without shear reinforcement under punching loads was compiled using data available in the literature. A sensitivity analysis of the parameters involved in the punching shear strength assessment was conducted, which highlighted the importance of the flexural reinforcement that are not typically considered for punching shear strength. After a discussion of the current international standards, a new proposed model for punching shear strength and rotation of RC slabs without shear reinforcement was discussed. It was based on a simplified load-rotation curve and new failure criteria that takes into account the flexural reinforcement effects. This experimental database was used to validate the approaches of the current international standards as well as the new proposed model. The latter proved to be a potentially useful design tool.

关键词: punching shear strength     reinforced concrete     slabs     reinforcement ratio    

标题 作者 时间 类型 操作

Deflection behavior of a prestressed concrete beam reinforced with carbon fibers at elevated temperatures

Mohammed FARUQI, Mohammed Sheroz KHAN

期刊论文

Experimental study on shear behavior of reinforced concrete beams with web horizontal reinforcement

Dong XU,Yu ZHAO,Chao LIU

期刊论文

Effect of eccentricity in reinforced concrete beam-column-slab connection under cyclic loading

Rooh ULLAH, Amjad NASEER, Muhammad FAHIM, Mohammad ASHRAF, Eid BADSHAH

期刊论文

Shear behavior of ultra-high-performance concrete beams prestressed with external carbon fiber-reinforced

期刊论文

Investigation of the parameters affecting the behavior of RC beams strengthened with FRP

Kadir SENGUN; Guray ARSLAN

期刊论文

Analysis of stiffness and flexural strength of a reinforced concrete beam using an invented reinforcement

Nazim Abdul NARIMAN, Martin HUSEK, Ilham Ibrahim MOHAMMAD, Kaywan Othman AHMED, Diyako DILSHAD, Ibrahim KHIDR

期刊论文

Non linear modeling of three-dimensional reinforced and fiber concrete structures

Fatiha IGUETOULENE, Youcef BOUAFIA, Mohand Said KACHI

期刊论文

Applying the spectral stochastic finite element method in multiple-random field RC structures

Abbas YAZDANI

期刊论文

Numerical modelling of reinforced concrete flexural members strengthened using textile reinforced mortars

期刊论文

Experimental investigation on concrete overlaid with textile reinforced mortar: Influences of mix, temperature

期刊论文

Axial compression tests and numerical simulation of steel reinforced recycled concrete short columnsconfined by carbon fiber reinforced plastics strips

Hui MA; Fangda LIU; Yanan WU; Xin A; Yanli ZHAO

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

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

Dominik KUERES; Dritan TOPUZI; Maria Anna POLAK

期刊论文

Slender reinforced concrete shear walls with high-strength concrete boundary elements

期刊论文

Punching of reinforced concrete slab without shear reinforcement: Standard models and new proposal

Luisa PANI, Flavio STOCHINO

期刊论文