Bond under Repeated Loading

Abstract

Characteristic results of more than 100 cyclic pull-out tests are presented including various load histories (simulating realistic load spectra) like random loading or variable amplitude loading with increasing or decreasing tendencies in addition to the constant amplitude loading with different amplitudes. Slip measurements are compared to acoustic emission measurements. Repeated loading produces a progressive deterioration of bond caused by the propagation of micro-cracks and progress of micro-crushing in concrete. Deterioration of bond may be observed by measuring slip or acoustic emission events. It is quantitatively shown that the actual slip is significantly influenced by the load history: maximum and minimum levels of repeated load, type of amplitude (constant or variable), frequency, sequency of amplitudes and number of load cycles, respectively.