Numerical modeling of the tension stiffening in reinforced concrete members via discontinuum models

Abstract

This study presents a numerical investigation on the fracture mechanism of tension stiffening phenomenon in reinforced concrete members. A novel approach using the discrete element method (DEM) is proposed, where three-dimensional randomly generated distinct polyhedral blocks are used, replicating concrete and one-dimensional truss elements are utilized, representing steel reinforcements. Thus, an explicit representation of reinforced concrete members is achieved, and the mechanical behavior of the system is solved by integrating the equations of motion for each block using the central difference algorithm. The inter-block interactions are taken into consideration at each contact point with springs and cohesive frictional elements. Once the applied modeling strategy is validated, based on previously published experimental findings, a sensitivity analysis is performed for bond stiffness, cohesion strength, and the number of truss elements. Hence, valuable inferences are made regarding discontinuum analysis of reinforced concrete members, including concrete-steel interaction and their macro behavior. Results demonstrate that the proposed phenomenological modeling strategy successfully captures the concrete-steel interaction and provides an accurate estimation of the macro behavior.

In-plane structural performance of dry-joint stone masonry Walls: A spatial and non-spatial stochastic discontinuum analysis

“…In DEM, the discrete nature of DJ-SMWs can be explicitly represented by a structured discontinuum, where each block can interact with its surrounding through contact points. However, it should be noted that within DEM formulation, any polygonal or polyhedral bodies can be utilized, which may represent the irregular geometrical configuration of the masonry construction in the structural or any constituent material level, as discussed in previous studies [25][26][27][28][29]. Additionally, DEM offers several distinctive features compared to FEM-based continuous and discontinuous approaches, such as automatic contact detection (i.e., recognizing new contact points during the analysis) and simulating the complete detachment of blocks, prescribed as rigid or deformable.…”

Tensile Fracture Mechanism of Masonry Wallettes Parallel to Bed Joints: A Stochastic Discontinuum Analysis

“…The random generation of the polyhedral blocks is performed using an open-source software package NEPER. The interested readers can access the mathematical background and applications of this software in related sources [9][10][11][12][13]. The elastic response of the contact is controlled by the orthogonal springs both in the normal and shear directions, based on the assigned contact stiffness k n and k s , respectively; whereas the post-peak behavior is governed by the nonlinear parameters, namely tensile strength ( f T ) defined in the normal direction and cohesion (c) as well as the friction angle (φ) in the shear direction (see Figure 2).…”

“…The elastic response of the contact is controlled by the orthogonal springs both in the normal and shear directions, based on the assigned contact stiffness k n and k s , respectively; whereas the post-peak behavior is governed by the nonlinear parameters, namely tensile strength ( f T ) defined in the normal direction and cohesion (c) as well as the friction angle (φ) in the shear direction (see Figure 2). In the present study, semi-rigid blocks are used considering relatively high stiffness at the finite-difference zones (i.e., 10 times macro elastic stiffness) to lump the linear and nonlinear displacements at the joints as performed in relevant studies [3,6,13]. Therefore, deformations develop at the joints (i.e., along the boundaries of adjacent polyhedral blocks) instead of within the block domain and block deformations have negligible influence on the macro stress-displacement behavior of the system.…”

“…where t indicates the average thickness of the fracture zone, whereas E and G denote the macro elastic and shear modulus of masonry, respectively. Contact stiffness values have an inverse relationship with the thickness of the fracture zone (or the number of blocks), which means that the contact stiffness increases with a higher number of blocks, as discussed in the literature [13]. In the nonlinear regime, computed contact stresses are updated based on the defined failure criteria.…”

Fracture Behaviour of Real Coarse Aggregate Distributed Concrete under Uniaxial Compressive Load Based on Cohesive Zone Model

“…Based on the macroscopic experimental phenomena of concrete, several concrete crack models have been proposed to simulate the fracture behaviour of concrete. Among them, the discrete element method (DEM), the discrete crack model and smeared crack model are mainly used at present [ 1 , 2 , 3 , 4 , 5 ]. DEM was proposed by Cundall [ 6 ].…”