Modified Steel Bar Model Incorporating Bond-Slip for Seismic Assessment of Concrete Structures

Abstract

This paper presents a simplified model for describing the response of a longitudinal bar embedded in concrete taking into account the bond‐slip phenomenon. The model is developed by assuming a linear bond‐slip field along the bar anchorage length and provides a simplified stress‐strain relationship to assign to the longitudinal reinforcement. The analytical approach adopted makes the proposed model very convenient from a computational standpoint because, unlike many other refined models, it does not require a multi‐level iterative process. Moreover, the assumptions made are particularly appropriate for modeling bond‐slip of smooth bars generally used in older reinforced concrete buildings. The implementation strategy of the proposed bond‐slip model in a general‐purpose nonlinear structural analysis software and comparisons with experimental results are discussed in a companion paper

Influence of Low-Cycle Fatigue and Corrosion Phenomena on the Ductile Behaviour of Steel Reinforcing Bars

“…Many works in the current literature [24,25,26], in fact, evidenced the inadequacy to consider full bond models for the representation of the hysteretic behaviour of r.c. components once that yielding is overpassed, due to significant relative slips between steel and concrete, that cannot consequently be neglected.…”

“…The hardening slip model, based on the formulation by Braga et al [25] and implemented to include hardening phenomena of steel reinforcements [27], was consequently developed and adopted for numerical simulations.…”

“…Mean values of the mechanical properties (yielding strength R e , tensile strength R m , elongation to maximum load A gt ) of the corresponding steel grades, coming from the experimental mechanical tensile tests presented in [25], were adopted, while the hardening branch slope was defined according to Eqn. (8), in which ε p represents the strain corresponding to the end of the yielding plateau (≅ 2.0%):…”

“…The hardening slip model was implemented in OpenSees using the trilinear hysteretic material [23], with the three characteristic points of the loading envelope opportunely determined in relation to the energy equivalence principle (figure 7), as well as already presented in [25]. The following assumptions were made for the elaboration of the hardening slip model to use for steel reinforcing bars (figure 8):…”

Significance of Earthquake Incidence on Response of Plan-Irregular Infilled R/C Buildings

“…Previous studies have pointed out the influence of the infills-induced shear failure of the columns, resulting in increased strength and stiffness at low hazard levels, and triggering shear-dominated story mechanisms [15], [16], while the response of the bare frames is characterized by increased flexibility due to bond slip effects [17], [18]. These additional mechanisms and components result in increased plan irregularity both in terms of stiffness and strength.…”