Shear Performance of Fiber-Reinforced Cementitious Composites Beam-Column Joint Using Various Fibers

Increasing demands of reinforcement in the joint panel are now requiring more effective system to reduce the complicated fabrication by widely used precast system. The joint panel is responsible to keep the load transfer through beam and column as a crucial part in a structural frame that ensures the main feature of the whole structure during earthquake. Since precast system might reduce the joint panel monolithic integrity and stiffness, an innovation by adding fiber into the grouting system will give a breakthrough. The loading test of precast concrete beam-column joints using FRCC (Fiber-Reinforced Cementitious Composites) in joint panel was conducted to evaluate the influences of fiber towards shear performance. The experimental factor is fiber types with same volume fraction in mortar matrix of joint panel. Two specimens with Aramid-fiber and PP-fiber by two percent of volume fraction are designed to fail by shear failure in joint panel by reversed cyclic testing method. The comparison amongst those experiment results by various parameters for the shear performance of FRCC beam-column joints using various fibers are discussed. Preceding specimens was using no fiber, PVA fiber, and steel fiber has been carried out. Through the current experimental results and the comparison with previous experiment results, it can be recognized that by using fibers in joint panel was observed qualitatively could prevent crack widening with equitable and smaller crack width, improved the shear capacity by widening the hysteretic area, increased maximum load in positive loading and negative loading, and decreased the deformation rate. Elastic modulus properties of fiber are observed to give the most impact towards shear performance

Simulation of Scattering of Bending Characteristics of FRCC based on Bridging Law Considering Fiber Distribution

It is well known that tensile and bending characteristics of fiber-reinforcedcementitious composite (FRCC) are influenced by fiber orientation and distribution. In this study, a visualization simulation is conducted using sodium silicate solution (known as water glass) to observe the flow patterns of the fibers in the beam specimen. The results of the visualization simulation are discussed mainly for the distribution of the position of each single fiber. In this study, based on the visualization results, Poisson distribution for expressing the position of fibers is adopted to calculate the bridging law (tensile stress – crack width relationship), inwhich the pullout properties of the single fiber are considered. The influence of fiber orientation is also considered in the calculation using the elliptic function characterized by the principal orientation angle and the orientation intensity. The scattering of maximum tensile stress (bridging strength) can be confirmed by Monte Carlo simulation (MCS), in which the fiber distribution following Poisson distribution is considered. The calculated bridging law is modeled by trilinear model, and section analysis is conducted to compare with the bending test results using polyvinyl alcohol (PVA) fiber. The possibility to evaluate the variation of bendingstrength can be found out by considering fiber distribution

Evaluation of Shear and Tensile Bridging Characteristics of PVA Fibers Based on Bridging Law

Strain-Hardening Cementitious Composites (SHCC), in which short fibers are mixed in mortar, show improved tensile performance and ductility of the cementitious material because fibers bridging the crack transfer tensile forces after first cracking. It is considered that the stress field at the shear crack surface in the structural element under the shear force is a biaxial stress field in which tensile and shear stresses exist concurrently. In fiber-reinforced cementitious composites, both tensile and shear stresses are transmitted via fibers that bridge shear cracks. It is necessary that the effect of fibers bridging a shear crack under tensile and shear stresses is investigated. In this study, uniaxial tension tests were carried out for specimens which have a square cross-section and an inclined notch. The biaxial stress field can be expressed by the inclined crack surface produced by the tensile loading. From the test results, it was confirmed that the tensile stress decreased with increasing notch angle in the tension tests. A calculation method for the bridging law with an inclined crack was introduced and the calculation results were compared with the test results. Though the maximum tensile stress in the tests was smaller than that in the calculation results, the curves after the maximum stress show good agreements with the calculations. The maximum stress reached in the tests tends to decrease with increasing crack angle (notch angle) as in the calculation results

Evaluation of fiber orientation of ECC considering fluid mechanics

科学研究費助成事業 研究成果報告書：挑戦的萌芽研究 2012-2014課題番号:2465631

Experimental study on bond behavior between CFRP plates and concrete under combination of fracture mode

Diagonal tension cracks in reinforced concrete members adversely affect the performance of flexural members strengthened by externally boned fiber-reinforced polymer (FRP) materials. The interface between the CFRP plate and concrete is influenced by both shear bond and peeling for such conditions. The objective of this study is to understand bond behavior in CFRP plate and concrete systems under the combination of fracture mode (peeling and shear) by special double-face shear bond test specimen. The specimens were designed for different initial angles at the middle of the specimen to ensure that the interface acts for both shear and peeling conditions. From the test results, the bond behavior under the combination of fracture mode can be observed using special specimens. It is confirmed that the tensile load decreases as the peeling angle increases. The relationship between peeling angle and tensile load is determined to evaluate the bond strength under the combination of fracture mode. Based on the test results, a new calculation method under the combination of fracture mode is proposed. The proposed method makes good prediction of the bond strength between CFRP plate and concrete for shear-peeling fracture conditions

Impact of Corrosion on the Bond Strength between Concrete and Rebar: A Systematic Review

Corrosion of the reinforcement affects more than the cross-sectional area of the rebar. The volume of steel also increases due to expansive corrosion products, leading to the cracking, delamination, and spalling of concrete. As a result, the bond capacity between concrete and rebar is affected. Researchers have extensively examined the impact of corrosion on the bond strength between concrete and rebar to propose empirical, theoretical, or numerical predictive models. Therefore, research programs on this topic have increased rapidly in recent years. This article presents a systematic literature review to explore experimental methods, outcomes, and trends on this topic. The Web of Science search collected 84 relevant research articles through a rigorous selection. Key factors that affect bond strength degradation, including concrete cover, concrete strength, and stirrups, have been documented. However, a general model is still unavailable due to discrepancies caused by differences in testing methods to evaluate the effect of corrosion on bond strength. Furthermore, researchers attempted to clarify the degradation mechanism of bond strength affected by corrosion. As a result, new alternatives have been proposed to build a practical model to assess the bond strength deterioration of corroded structures

Influence of Matrix Strength on Bridging Performance of Fiber-Reinforced Cementitious Composite with Bundled Aramid Fiber

The bundled aramid fiber has good bond properties in the cementitious matrix, and is expected to have high bridging performance in the fiber-reinforced cementitious composite (FRCC). To investigate the influence of matrix strength on the bridging performance of FRCC with the bundled aramid fiber, the uniaxial tension test of FRCC, the pullout test for an individual fiber, and the calculation of bridging law are conducted with the main parameters of matrix strength and fiber volume fraction. From the test results, the maximum tensile load of FRCC and the maximum pullout load of an individual fiber increase as the matrix strength also increases. The calculation result of the bridging law considering the effect of matrix strength expresses the bridging performance of the bundled aramid fiber well. The calculation result also shows that the bridging strength has a linear relationship up to a compressive strength of around 50 MPa

Influence of Matrix Strength on Bridging Performance of Fiber-Reinforced Cementitious Composite with Bundled Aramid Fiber

The bundled aramid fiber has good bond properties in the cementitious matrix, and is expected to have high bridging performance in the fiber-reinforced cementitious composite (FRCC). To investigate the influence of matrix strength on the bridging performance of FRCC with the bundled aramid fiber, the uniaxial tension test of FRCC, the pullout test for an individual fiber, and the calculation of bridging law are conducted with the main parameters of matrix strength and fiber volume fraction. From the test results, the maximum tensile load of FRCC and the maximum pullout load of an individual fiber increase as the matrix strength also increases. The calculation result of the bridging law considering the effect of matrix strength expresses the bridging performance of the bundled aramid fiber well. The calculation result also shows that the bridging strength has a linear relationship up to a compressive strength of around 50 MPa