NONLINEAR JOINT ELEMENT FOR THE ANALYSIS OF REINFORCEMENT BARS USING FINITE ELEMENTS

Reinforcement bars are commonly found in engineering works such as soil nailing, tunnel excavation with the NATM process and in the conventional and pre-stressed reinforced concrete structures.Three approaches are found in the literature for the finite element analysis of such inclusions: the discrete, the smeared and the embedded methods.Each method has its own advantages, however none of them can account for the behavior of the interface between the reinforcement bar and the reinforced medium.The contact simulation is crucial in many cases since the critical failure zone could be the interface itself.This kind of simulation was achieved with the semi-embedded method, proposed by the authors, which combines the advantages of the discrete and embedded methods.In this case reinforcements are composed by real bar elements linked to solid elements by means of joint elements.Each joint element comprises a set of real nodes which are connected to the bar elements and another set of virtual nodes that are linked to particular positions within a trespassed solid element.Joint elements can adopt a nonlinear constitutive model in order to simulate the behavior of an interface failure zone.This paper describes a new and simpler formulation for the semi-embedded method that renders the implementation straightforward.A pull-out test application example is performed showing excellent accuracy.