Fiber inclusions lead to significant improvements of post-cracking behavior of mortar composites by bridging cracks and providing resistance to crack opening processes. Typically localized failure modes of plain concrete composites may turn quasi-ductile through the addition of steel fibers. In this case, the development of multiple crack patterns leads to strain-hardening processes characterized by large energy absorption prior to fracture localization. In this work fiber reinforced concrete is analyzed and modeled with two different approaches. On one hand, a continuum (smeared-crack) formulation based on non-linear microplane theory is presented. On the other hand, a constitutive theory is formulated to model the non-linear response of fiber reinforced mortar-mortar interfaces in the framework of discrete approach. Following recent proposal, see [1], the mixture theory [2] is considered in both models to describe mechanical behavior of fiber-concrete or fiber-mortar composites. Also the interaction between concrete/mortar and steel fibers in the form of fiber debonding and dowel effects are similarly treated in both the macroscopic and interface models. Both constitutive formulations are used to simulate failure behavior of FRC at the macro and mesoscopic level of observations. The last one is based on FE discretizations accounting for the three main concrete constituents: (i) aggregates, (ii) mortar and (iii) mortar-aggregate interfaces. Mechanical behavior of fiber reinforced mortar is modeled, alternatively, by means of continuum finite elements based on non-linear microplane constitutive theory for FRC, or by means of a combination between inelastic mortar-mortar interfaces where fibers are considered to be located, and elastic continuum elements in between interface s. Both microplane and interface models consider the quadratic hyperbola for shear and normal strengths coupling proposed in [3] as mortar/concrete maximum strength criterion. Their strain-softening laws are formulated in terms of the fracture energy release under mode I or II failure modes. After describing both constitutive models, this work focuses on numerical analysis of FRC failure behavior at different scales of observation. The main objective is to comparatively evaluate the capabilities of the proposed models and numerical tools to capture the transition from brittle to ductile behavior of fiber-reinforced concrete when different fiber contents and directions are considered. In case of the continuum model, the performance of the localization indicator is also evaluated as well as the sensitivity of FRC failure mode regarding fiber content and loading condition. Final objective is the comparison of critical localization directions predicted by the continuum model with critical fracture directions obtained with mesoscopic discretizations. REFERENCES [1] S., Pietruszczak and A., Winnicki, Constitutive Model for Concrete with Embedded Sets of Reinforcement , ASCE-J. Engrg. Mech., 129 (7), 725-738, (2003). [2] C., Truesdell and R., Toupin, The classical field theories , Handbuch der Physik, Springer Verlag, III/I, Berlin, (1960). [3] I., Carol, P.C., Prat and C.M., Lopez, A Normal/Shear Cracking Model. Interface Implementation for Discrete Analysis, ASCE J. Engrg. Mech., 123 (8), 765-773, (1997).
Multiscale Failure Analysis of Fiber Reinforced Concrete based on continuum and discrete models
Caggiano A;
2011-01-01
Abstract
Fiber inclusions lead to significant improvements of post-cracking behavior of mortar composites by bridging cracks and providing resistance to crack opening processes. Typically localized failure modes of plain concrete composites may turn quasi-ductile through the addition of steel fibers. In this case, the development of multiple crack patterns leads to strain-hardening processes characterized by large energy absorption prior to fracture localization. In this work fiber reinforced concrete is analyzed and modeled with two different approaches. On one hand, a continuum (smeared-crack) formulation based on non-linear microplane theory is presented. On the other hand, a constitutive theory is formulated to model the non-linear response of fiber reinforced mortar-mortar interfaces in the framework of discrete approach. Following recent proposal, see [1], the mixture theory [2] is considered in both models to describe mechanical behavior of fiber-concrete or fiber-mortar composites. Also the interaction between concrete/mortar and steel fibers in the form of fiber debonding and dowel effects are similarly treated in both the macroscopic and interface models. Both constitutive formulations are used to simulate failure behavior of FRC at the macro and mesoscopic level of observations. The last one is based on FE discretizations accounting for the three main concrete constituents: (i) aggregates, (ii) mortar and (iii) mortar-aggregate interfaces. Mechanical behavior of fiber reinforced mortar is modeled, alternatively, by means of continuum finite elements based on non-linear microplane constitutive theory for FRC, or by means of a combination between inelastic mortar-mortar interfaces where fibers are considered to be located, and elastic continuum elements in between interface s. Both microplane and interface models consider the quadratic hyperbola for shear and normal strengths coupling proposed in [3] as mortar/concrete maximum strength criterion. Their strain-softening laws are formulated in terms of the fracture energy release under mode I or II failure modes. After describing both constitutive models, this work focuses on numerical analysis of FRC failure behavior at different scales of observation. The main objective is to comparatively evaluate the capabilities of the proposed models and numerical tools to capture the transition from brittle to ductile behavior of fiber-reinforced concrete when different fiber contents and directions are considered. In case of the continuum model, the performance of the localization indicator is also evaluated as well as the sensitivity of FRC failure mode regarding fiber content and loading condition. Final objective is the comparison of critical localization directions predicted by the continuum model with critical fracture directions obtained with mesoscopic discretizations. REFERENCES [1] S., Pietruszczak and A., Winnicki, Constitutive Model for Concrete with Embedded Sets of Reinforcement , ASCE-J. Engrg. Mech., 129 (7), 725-738, (2003). [2] C., Truesdell and R., Toupin, The classical field theories , Handbuch der Physik, Springer Verlag, III/I, Berlin, (1960). [3] I., Carol, P.C., Prat and C.M., Lopez, A Normal/Shear Cracking Model. Interface Implementation for Discrete Analysis, ASCE J. Engrg. Mech., 123 (8), 765-773, (1997).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.