Cyclic bond behaviour of plain bars. Part II: Analytical investigation

The development of monotonic and cyclic non-linear analysis models for reinforced concrete (RC) structures has become a key issue both in order to define seismic design "displacement-based" procedures for new constructions and for the seismic evaluation of older ones. These models have to properly account for interaction mechanisms between reinforcing bars and surrounding concrete. The existing literature regarding the bond performances of deformed reinforcing bars offers many experimental data and constitutive relationships, monotonic and hysteretic, taking into account the main parameters that influence bond capacities. With respect to plainbars, whose study is very important in seismic analysis of existing RC structures, it is noted that bond–slip relationships are substantially absent, particularly in cyclic field. Low bond capacities and cyclic degradation phenomena, however, have a great influence on different deformation sources, especially on fixed end rotation, which makes a significant contribution to the total deformation capacity of the element. In this paper, basing on experimental results from monotonic and cyclic pull-out tests reported in the companion paper, an analytical investigation of bond–slip hysteretic behaviour for plain reinforcing bars is presented and discussed