Papers by Keyword: Fracture Process Zone FPZ

Abstract: In fracture tests involving the Single-Edge-Notched beam loaded in Three or Four-Point-Bending as well as in other specimen shapes, the specimen weight contributes to the overall loading of the system. Unless special methods are put into practice, the contribution of the specimen weight is not compensated, leading to misevaluations of fracture parameters obtained in the experiments. In this work a method taking into account the exact contribution of the specimen self-weight is proposed to evaluate the Resistance-curve of mortar. Cohesive crack modeling accounting for the structure self-weight is used to generate the necessary load-displacement response to perform the validation of the proposed method.

Abstract: Compared with the extensive research on properties of the fracture process zone (FPZ) under quasi-static loading conditions, much less information is available on its dynamic characterization, especially for high-strength concrete (HSC). This paper presents the very recent results of an experimental program aimed at disclosing the loading rate effect on the size and velocity of the (FPZ) in HSC. Eighteen three-point bending specimens were conducted under a wide range of loading rates from from 10-4 mm/s to 103 mm/s using either a servo-hydraulic machine or a self-designed drop-weight impact device. Four strain gauges mounted along the ligament of the specimen were used to measure the FPZ size. Surprisingly, the FPZ size remains almost constant (around 20 mm) when the loading rate varies seven orders of magnitude.

Abstract: Steel reinforced high strength and high performance concrete (SRHSHPC) specimens were experimented to study the mechanical behaviors between steel and concrete interface. In experiment, interfacial bond softening process was observed, which can be explained in terms of damage along the interface, leading to progressive reduction of shear transfer capability between steel and high strength and high performance concrete (HSHPC). In this paper, bond softening process along the interface is considered in the analysis of crack-induced debonding. Interfacial bond-slip mechanism between steel and HSHPC is studied in detail based on fracture mechanics. With the help of acoustic emissions technology, the crack propagation in the interlayer was observed, thus the interfacial crack propagation and fracture model is set up. Under the assumption that the interlayer is weak concrete compared with concrete matrix, the stress field as well as displacement field around the crack tip is deduced. The characteristics of interfacial fracture process are discussed and a model for interfacial fracture process zone is built up. With this model, the size of fracture process zone can be derived. At last, the influence of the fracture process zone on interfacial fracture toughness is determined using critical fracture toughness. All these may contribute to improvement of theory for SRHSHPC composite structure.

Abstract: In this paper, some numerical tests on the fracture process zone (FPZ) in concrete tension specimen were carried out with Material Failure Process Analysis code (MFPA2D) to investigate the behavior of the FPZ and the effect of the meso-scale heterogeneity of concrete on fracture process. The numerical results provide a clear indicator of the FPZ of concrete. The numerical results show that the FPZ accompanied by AE events gradually develops ahead of the notch tip with the increase of the loading in the concrete tension specimen. Moreover, many of the AE events bring about very small energy at the beginning of loading stage. Zones of higher energy events demonstrate a localization zone around the notch tip. The zones of AE events progresses forward gradually, and much densely distributed AE events can be observed in the FPZ. Moreover, the numerical simulations about AE events agreed well with those of the microcracks obtained by laboratory findings.