Effect of Loading Frequency on Flexural Fatigue Behaviour of Concrete

Abstract

Frequency of loading plays a signicant role in influencing the fatigue response of concrete. It is widely accepted in the literature that concrete fatigue life increases with increase in loading frequency. This behaviour is counter-intuitive, as the specimen is expected to fail in less number of cycles when subjected to higher loading frequency. This paper aims at understanding the fracture and failure mechanisms responsible for this counter intuitive behaviour through an experimental investigation. The flexural fatigue experiments are performed on concrete beam specimens subjected to three different loading frequencies: 0.5 Hz, 2 Hz and 4 Hz with the aid of acoustic emission technique. The mechanical and acoustic emission results reveal that the increased fatigue life for specimens subjected to higher loading frequencies is attributed to the widely distributed and randomly oriented micro cracks that can blunt the effect of high stresses by increasing the energy required to cause failure. The concrete specimens subjected to lower loading frequencies tend to exhibit brittle behaviour and consequently fail at lower number of fatigue load cycles. 1

Effect of the Cyclic Crack Opening-Closure during Epoxy-Curing Period of a CFRP Strengthening System Bonded on Concrete Substrate

“…This frequency was also applied during the second phase of fatigue of ES2 (see the fatigue test program of beam ES2 below). This higher value of frequency was adopted as it was previously used by several authors to study the behavior of RC beams strengthened with CFRP [25][26][27][28]. Considering that all cycled specimens were subjected to the same frequency of 4 Hz (except during first phase of fatigue test of ES2), it was assumed that comparison of specimen behavior between each other makes sense.…”

Fatigue behavior of prefatigued reinforced concrete beams rehabilitated with near surface mounted carbon fiber reinforced polymer reinforcement

“…Reinforced concrete (RC) bridges are subjected to increased cyclic stresses that lead to gradual degradation in stiffness. A large number of cycles might cause a sudden collapse even at stress levels that are within the elastic stage . Fatigue stress‐life prediction models (S‐N curves) of nonstrengthened and strengthened RC beams are based on specimens tested under constant amplitude cyclic loads without considering the effect of loading history and the accumulated fatigue damage.…”