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

DFRCCにおける繊維の分散性評価と架橋強度のばらつきの検討

DFRCCの引張特性のばらつきの評価を目的として，マトリックス内の繊維分散を考慮した引張応力－ひび割れ幅関係（架橋則）の構築を試みた。ケイ酸ナトリウム水溶液（水ガラス）を用いた繊維の可視化実験で得られた繊維撮影画像を基に繊維の分散性をポアソン分布で評価し，架橋則へ導入した。モンテカルロ・シミュレーションによりポアソン分布に基づいた分散性を与え，架橋則における最大引張応力（架橋強度）のばらつきを確認した。さらに，それらの架橋則をトリリニアモデルに変換して断面解析を行い，PVA繊維を用いたDFRCCの4点曲げ載荷試験結果と比較した結果，繊維の分散性に起因する強度のばらつきを推定できる可能性を示した