Numerical analysis of plain and fiber reinforced concrete structures during cyclic loading: Influence of frictional sliding and crack roughness

Abstract

Concrete is a quasi-brittle material, characterized by a non-negligible, finite-sized fracture process zone (FPZ) in which various toughening mechanisms play a significant role on crack development and propagation. Concrete is often reinforced with fibers to improve the serviceability and longevity of concrete structures by controlling the maximal crack widths and providing residual carrying capacity to initiated cracks. In quasi-brittle materials such as concrete, toughening mechanisms such as crack deflection due to the presence of large heterogeneities, contact shielding, i.e., wedging and crack closure induced by debris and rough crack faces, crack bridging by tough aggregates, unbroken ligaments and fibers (in fiber-reinforced concretes), are mostly governing damage evolution under monotonic and especially under cyclic loadings [1]. All these items contribute to a complex non-linear response in terms of load-displacement curves observed in experimental investigations. Many investigations have been performed on plain concrete, but not so many for high-performance fiber-reinforced concrete [2] which is the main subject of investigation within the DFG Priority Program 2020. In order to better understand the influence of these toughening mechanisms on the formation of hysteresis during cyclic loading-unloading of plain and steel fiber-reinforced high-performance concrete, we model these mechanisms and their evolving influence on damage development using a discrete crack approach, and take into account the imperfect closure of cracks and friction between crack faces that come in contact during loading/unloading of the specimen. Within the scope of this contribution, we present the formulation of the model and illustrate its performance through selected numerical experiments under monotonic and cyclic loading of plain and fiber-reinforced high-performance concrete specimens. Model predictions are compared with laboratory measurements.

Multi‐level approach for modelling the post‐cracking response of steel fibre reinforced concrete under monotonic and cyclic loading

“…In this contribution, an improvement of a previously proposed crack model [2,8] for plain and fiber reinforced concrete was presented. It was shown, that consideration of a crack closure/reopening mechanism utilizing two multi-surface plasticity models enables a reasonable agreement of the numerical and experimental loading/unloading behavior in three-point cyclic beam bending test both for plain concrete as well as fiber-reinforced concrete beams.…”

“…Zero-thickness interface elements are inserted along the faces shared between every two solid elements, in regions where cracking is expected (see Fig. 1) [2,8,9]. The solid material is assigned a linear elastic behavior, while the interface elements are equipped with non-linear traction-separation laws to characterize the fracture behavior of high-performance plain and fiber reinforced concrete (HPC and HPFRC).…”

“…Numerous attempts have also been made to develop theoretical models that describe the behavior of plain and fiber-reinforced concrete under cyclic loading (e.g., [5][6][7]), but a final consensus is yet to be reached. This contribution presents an extension of a material model for plain and fiber reinforced concrete, previously proposed by the authors [2,8], which accounts for the formation of hysteresis loops during loading/unloading cycles due to internal frictional mechanisms.…”