Tolerances for TBM thrust load based on crack opening performance of fiber-reinforced precast tunnel segments

2021 ◽  
Vol 111 ◽  
pp. 103847
Author(s):  
Pablo Augusto Krahl ◽  
Ingrid Irreño Palomo ◽  
Saulo José de Castro Almeida ◽  
Gustavo Henrique Siqueira ◽  
Newton de Oliveira Pinto Júnior ◽  
...  
Keyword(s):  
Crack Opening ◽  
Fiber Reinforced ◽  
Thrust Load

scholarly journals Modeling of Bridging Law for Bundled Aramid Fiber-Reinforced Cementitious Composite and its Adaptability in Crack Width Evaluation

Materials ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 179
Author(s):  
Daiki Sunaga ◽  
Takumi Koba ◽  
Toshiyuki Kanakubo
Keyword(s):  
Fiber Orientation ◽  
Crack Width ◽  
Volume Fraction ◽  
Characteristic Point ◽  
Crack Opening ◽  
Aramid Fiber ◽  
Cementitious Composite ◽  
Fiber Reinforced ◽  
Cross Sectional ◽  
Bridging Law

Tensile performance of fiber-reinforced cementitious composite (FRCC) after first cracking is characterized by fiber-bridging stress–crack width relationships called bridging law. The bridging law can be calculated by an integral calculus of forces carried by individual fibers, considering the fiber orientation. The objective of this study was to propose a simplified model of bridging law for bundled aramid fiber, considering fiber orientation for the practical use. By using the pullout characteristic of bundled aramid fiber obtained in the previous study, the bridging laws were calculated for various cases of fiber orientation. The calculated results were expressed by a bilinear model, and each characteristic point is expressed by the function of fiber-orientation intensity. After that, uniaxial tension tests of steel reinforced aramid-FRCC prism specimens were conducted to obtain the crack-opening behavior and confirm the adaptability of the modeled bridging laws in crack-width evaluation. The experimental parameters are cross-sectional dimensions of specimens and volume fraction of fiber. The test results are compared with the theoretical curves calculated by using the modeled bridging law and show good agreements in each parameter.

Micro-fiber reinforced cement composites. II. Flexural response and fracture studies

1995 ◽  
Vol 22 (4) ◽  
pp. 668-682
Author(s):  
N. Banthia ◽  
J. Sheng
Keyword(s):  
Crack Opening ◽  
Fiber Reinforcement ◽  
High Volume ◽  
Flexural Behavior ◽  
Cement Composites ◽  
Fiber Reinforced ◽  
Host Matrix ◽  
Flexural Response ◽  
Reinforced Cement ◽  
Resistance Curves

In Part I of this paper, stress–strain curves for micro-fiber reinforced cement-based composites containing high volume fractions of carbon, steel, and polypropylene fibers were obtained. Considerable strengthening, toughening, and stiffening of the host matrix due to micro-fiber reinforcement under both static and impact conditions were reported. In this paper, composites are characterized under an applied flexural load. Both notched and unnotched specimens were tested in four-point flexure; significant improvements in the flexural behavior due to fiber reinforcement were noted. Notched specimens were tested to study the growth of cracks in these composites and to develop a valid fracture criterion. With this objective, crack growth resistance curves and crack opening resistance curves in terms of the stress intensity factor were constructed. The paper recognizes the potential of these composites in various applications and stresses the need for further research. Key words: Portland cement-based materials, fiber reinforcement, fracture toughness, R-curves.

scholarly journals Meso-Scale Formulation of a Cracked-Hinge Model for Hybrid Fiber-Reinforced Cement Composites

Fibers ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 56
Author(s):  
Enzo Martinelli ◽  
Marco Pepe ◽  
Fernando Fraternali
Keyword(s):  
Crack Opening ◽  
Computational Cost ◽  
Cement Matrix ◽  
Homogeneous Material ◽  
Cement Composites ◽  
Fiber Reinforced ◽  
Reinforcing Fibers ◽  
Reinforced Cement ◽  
Displacement Based ◽  
Hinge Model

This study presents a non-linear cracked-hinge model for the post-cracking response of fiber-reinforced cementitious composites loaded in bending. The proposed displacement-based model follows a meso-mechanical approach, which makes it possible to consider explicitly the random distribution and orientation of the reinforcing fibers. Moreover, the model allows for considering two different fiber typologies whereas the cement matrix is modelled as a homogeneous material. The proposed mechanical model combines a fracture-based, stress-crack opening relationship for the cementitious matrix with generalized laws aimed to capture the crack-bridging effect played by the reinforcing fibers. These laws are derived by considering both the fiber-to-matrix bond mechanism and fiber anchoring action possibly due to hooked ends. The paper includes a numerical implementation of the proposed theory, which is validated against experimental results dealing with fiber-reinforced cement composites reinforced with different short fibers. The excellent theory vs. experiment matching demonstrates the high technical potential of the presented model, obtained at a reasonable computational cost.

scholarly journals Microscale Cohesive-Friction-Based Finite Element Model for the Crack Opening Mechanism of Hooked-End Steel Fiber-Reinforced Concrete

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 669
Author(s):  
Yassir M. Abbas
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Steel Fiber ◽  
Crack Opening ◽  
Fiber Reinforced Concrete ◽  
Embedment Depth ◽  
Fe Model ◽  
Fiber Reinforced ◽  
Steel Fiber Reinforced Concrete ◽  
Fiber Matrix

The entire mechanical properties of steel fiber-reinforced concrete (SFRC) are significantly dependent on the fiber–matrix interactions. In the current study, a finite element (FE) model was developed to simulate the pullout response of hooked-end SFRC employing cohesive–frictional interactions. Plain stress elements were adapted in the model to exemplify the fiber process constituents, taking into consideration the material nonlinearity of the hooked-end fiber. Additionally, a surface-to-surface contact model was used to simulate the fiber’s behavior in the pullout mechanism. The model was calibrated against experimental observations, and a modification factor model was proposed to account for the 3D phenomenalistic behavior of the pullout behavior. Realistic predictions were obtained by using this factor to predict the entire pullout-slip curves and independent results for the peak pullout load. The numerical results indicated that the increased fiber diameter would alter the mode of crack opening from fiber–matrix damage to that combined with matrix spalling, which can neutralize the sensitivity of the entire pullout response of hooked-end steel fiber to embedment depth. Additionally, the fiber–matrix bond was enhanced by increasing the fiber’s surface area, sensibly leading to a higher pullout peak load and toughness. The developed FE model was also proficient in predicting microstructural stress distribution and deformations during the crack opening of SFRC. This model could be extended to fully model a loaded SFRC composite material by the inclusion of various randomly oriented dosages of fibers in the concrete block.

scholarly journals Effect of Thickness on Fatigue Crack Propagation in Injection Molded Short Carbon Fiber Reinforced Plastics

2018 ◽  
Vol 165 ◽  
pp. 07002 ◽  
Author(s):  
Kenichi Shimizu ◽  
Yuya Hasegawa ◽  
Keisuke Tanaka
Keyword(s):  
Carbon Fiber ◽  
Crack Propagation ◽  
Crack Opening Displacement ◽  
Crack Opening ◽  
Plate Thickness ◽  
Fiber Reinforced ◽  
Opening Displacement ◽  
Short Carbon Fiber ◽  
Carbon Fiber Reinforced ◽  
Short Carbon

The influence of plate thickness on the fatigue crack propagation behavior was studied by using center-notched specimens which were cut from injection-molded plates of short carbon-fiber reinforced polyphenylene sulfide (PPS) at two fiber angles relative to the molding flow direction (MFD), i. e. θ=0 deg. (MD), 90 deg. (TD). The short carbon-fiber reinforced plastics (SCFRP) plates have three-layer structure where the fiber orientation is parallel to MFD in the shell layer and is nearly perpendicular in the core layer. The fraction of the core layer increases with increase in the plate thickness. In the relation between the crack propagation rate, da/dN, and stress intensity factor, ΔK, da/dN increases with increase in thickness for MD specimen. Conversely, da/dN decreases for TD specimen. The crack opening displacement along the crack was measured by using the digital image correlation (DIC) method. The measured crack opening displacement become larger with increase in the plate thickness for MD specimens. Contrary, measured values become smaller with increase in the plate thickness for TD specimen. The crack-tip-opening radius, Δρ, was estimated from the parabolic approximation of the crack opening displacement distribution near the crack tip. The relationships between da/dN and Δρ for all specimens tend to merge into a unique relationship.

Fiber Reinforced Concrete Crack Opening Evaluation Using Digital Image Correlation Techniques

2020 ◽  
pp. 270-278
Author(s):  
Kaio Cézar da Silva Oliveira ◽  
Gabriela Silva Dias ◽  
Isadora Queiroz Freire de Carvalho ◽  
Wandersson Bruno Alcides de Morais Silva ◽  
Danilo José Pereira Freitas ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Crack Opening ◽  
Fiber Reinforced Concrete ◽  
Image Correlation ◽  
Fiber Reinforced ◽  
Concrete Crack ◽  
Correlation Techniques

scholarly journals A Wedge-DCB Test Methodology to Characterise High Rate Mode-I Interlaminar Fracture Properties of Fibre Composites

2018 ◽  
Vol 183 ◽  
pp. 02052 ◽  
Author(s):  
Sathiskumar A. Ponnusami ◽  
Hao Cui ◽  
Borja Erice ◽  
Mehtab V. Pathan ◽  
Nik Petrinic
Keyword(s):  
Crack Opening ◽  
High Rate ◽  
Experimental Methodology ◽  
Dynamic Mode ◽  
Mode I ◽  
Fiber Reinforced ◽  
Fracture Properties ◽  
Interlaminar Fracture ◽  
Cohesive Zone Modelling ◽  
High Level

A combined numerical-experimental methodology is presented to measure dynamic Mode-I fracture properties of fiber reinforced composites. A modified wedge-DCB test using a Split-Hopkinson Bar technique along with cohesive zone modelling is utilised for this purpose. Three different comparison metrics, namely, strain-displacement response, crack propagation history and crack opening history are employed in order to extract unique values for the cohesive fracture properties of the delaminating interface. More importantly, the complexity of dealing with the frictional effects between the wedge and the DCB specimen is effectively circumvented by utilising right acquisition techniques combined with an inverse numerical modelling procedure. The proposed methodology is applied to extract the high rate interlaminar fracture properties of carbon fiber reinforced epoxy composites and it is further shown that a high level of confidence in the calibrated data can be established by adopting the proposed methodology.

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