Development and validation of an analytical bond model for cyclic excitations

Correct evaluation of bond-slip effects is a crucial point when investigating progressive damage and energy dissipation capabilities of RC framed structures, in particular in the beam-to-column joint region. Despite investigation of bond phenomena has attracted strong international interest since long, the possibility of developing new models, more accurate than those currently available in literature, able to deal with monotonic and cyclic loading as well, without renouncing to ease of implementation remains undoubtedly a very hot issue. In this work a new model is defined by adding the effects of different bond resistance contributes, namely mechanical bond, cyclic friction and virgin friction, defined by means of continuous functions, which allow to fit with reasonable precision experimental bond-slip paths, even along reloading branches. New damage rules able to account for generalized excitation are introduced to update the main law parameters at each load reversal. The proposed model is fitted against the well known pull-out cyclic tests provided by Eli-gehausen, relative to short–anchorage pull-out oligo-cyclic tests in good confinement conditions. Experimental cyclic tests reported by several authors are subsequently adopted for further validation of the proposed analytical model.