On the Numerical Modelling of Bond for the Failure Analysis of Reinforced Concrete

Abstract

The structural performance of reinforced concrete relies heavily on the bond between reinforcement and concrete. In nonlinear finite element analyses, bond is either modelled by merged, also called perfect bond, or coincident with slip, also called bond-slip, approaches. Here, the performance of these two approaches for the modelling of failure of reinforced concrete was investigated using a damage-plasticity constitutive model in LS-DYNA. Firstly, the influence of element size on the response of tension-stiffening analyses with the two modelling approaches was investigated. Then, the results of the two approaches were compared for plain and fibre reinforced tension stiffening and a drop weight impact test. It was shown that only the coincident with slip approach provided mesh insensitive results. However, both approaches were capable of reproducing the overall response of the experiments in the form of load and displacements satisfactorily for the meshes used.

On the dynamic response of reinforced concrete beams subjected to drop weight impact

“…The reinforcement was modelled with 5 mm beam elements assuming perfect bond between reinforcement and concrete, which has been shown to provide acceptable results [13]. The same nodes were used for concrete and reinforcement elements for both FE models.…”

“…The capacity of a structure to withstand the effect of impulse loading mainly depends on its ability to absorb the external energy applied by the load. Using a single degree of freedom model and assuming plastic impact, the external energy acting on the beam can be approximately determined as We = mw/(mw + mb)ꞏEk,0, where mw is the mass of the drop weight, mb is the effective mass of the beam, Ek,0 = mwꞏv0 2 /2 is the kinetic energy of the drop weight at impact, and v0 is the impact velocity [13]. Hence, the external energy applied to the beam will decrease with an increased beam mass.…”

“…Similarly, using tetrahedral elements can predict tension-shear damage and mixed-mode fracture in solids subjected to dynamic loading [64]. Merging the material model CDPM2 with tetrahedral elements has satisfactorily reproduced impact loading with respect to the bond between steel bars and concrete, merged and coincident with slip [13]. Compared to hexahedral elements, tetrahedral elements in LS-DYNA with CDPM2 seem to capture better diagonal shear cracks due to impact loading [65].…”

“…Compared to hexahedral elements, tetrahedral elements in LS-DYNA with CDPM2 seem to capture better diagonal shear cracks due to impact loading [65]. However, these studies neglect the strain rate effects both for the concrete and the steel bars [13,65].…”

A refined diffuse cohesive approach for the failure analysis in quasibrittle materials—part II: Application to plain and reinforced concrete structures

“…Cohesive zone models (CZMs) are among the most used fracture models for concrete, including asphalt, recycled, and fiber‐reinforced concrete. The adopted approach allows the embedded cohesive interfaces to permeate the whole discretized body as a part of the material characterization and ultimately leads to the prediction of complex crack paths or patterns in both plain and RC without requiring additional crack initiation criteria which are external to the constitutive model of the material, neither adaptive remeshing operations at the tip of advancing cracks, differently from many existing cohesive approaches applied to mixed‐mode fracture in concrete (see, for instance,). an embedded truss model (ETM), equipped with a bond‐slip relation, able to simulate the interaction between concrete and steel bars in RC structures, similarly to other existing approaches (see, for instance, and references therein). Such a model is conceived to allow the reinforcing bars to be crossed by the neighboring propagating cracks, so that no artificial crack arrest is experienced during the associated numerical simulations.…”