Influence of Low-Cycle Loading on Rigidity and Crack Development of Partially Prestressed Concrete Elements.

Partially prestressed elements with cross-section as were loaded repeatedly by two symmetrically applied loads. The elements No. 1 to 10 were pretensioned, the elements No. 12 to 14 were posttensioned with epoxide-glued contact joints and the elements Nos 15 to 19 case monolithically and posttensioned. In the area between two loads (except the divided elements) there was no web reinforcement present. The prestressing reinforcement consisted of two cables with cross-section diameter 15, 5 mm. Together, the beams were loaded 120 to 150 times and the parameters measured were deflections, strains on the upper, and the lower edges of the cross-section as well as the crack widths. The strain were used for calculations of the upper and lower edge strains and curvatures. The curves of variation of the parameter k allow one to obtain an overall view concerning the values and rates of deformation and crack width stabilization during the process of the low cycle loading.