The effect of changing loads on the deflection of RC beams reinforced with ribbed bars

The paper presents a way of taking account of the effect of changing loads on the deflection of RC beams reinforced with ribbed bars. The proposed solutions were verified experimentally, based on the results of tests performed by the author. The beams were subjected to multiple repeatable loads. The deflection increment dependent on the value of the basic parameters characterising the changing loads (cycle maximum load M_max, stress ratio R, number of load cycles N_i). The increment of the deflection of RC beams reinforced with ribbed bars subjected to changing loads increases with increases in the number of load cycles N_i (logN_i, to be more accurate), and is greater for higher values of ratio k and lower values of ratio R (k = M_max/M_n; R = M_min/M_max; M_min – minimal moment of cycle; M_max – maximal moment of cycle; M_n – failure moment under short-term loads). The relations for the number of load cycles N_i are similar.