Effect of repeated loading on the size of cracks in saturated reinforced concrete beams

Conclusions

• 1. The width of cracks in reinforced-concrete beams subjected to the action of loads applied only once (≤0.5 P_ult) is in satisfactory agreement with the width calculated by applying the norm SNiP II-I, 14–69 in the case of retention in a dry medium as well as in the case of high-head saturation.

• 2. Repeated static and vibratory loads cause the initial crack width to increase in beams retained in a dry medium in direct relation to the number of cycles and in inverse relation to the cycle characteristic and the degree of distribution of the reinforcement.

• 3. The same loads applied on beams subjected to high-head saturation cause the crack width to increase for small values of α and ρ and to decrease in an attenuated manner for high values of these characteristics.

• 4. The recommended relations permit determining the design value of the crack width by taking into consideration the prolonged action of repeated loads.

• 5. When deformed bars are used, the correction coefficients given in the norm SNiP II-I, 14–69 should be used for correcting the values of the crack widths.