Crack Resistance of RC Columns Strengthened by Jacketing

The results of an experimental study on crack-resistance of large scale compressed-bent reinforced concrete columns strengthened under initial load are represented in this paper. Structural performance of unstrengthened reference samples and jacketed samples under initial load of 30%, 50%, 70% and 90% of the bearing capacity of the reference samples was investigated. During the tests of the columns cracks pattern along the length of the columns, cracks length and width development were observed and recorded. Crack width vs Load graphs were plotted for the analysis of cracks development. Crack width at each loading stage was recorded to determine the critical crack. The load N_w when the critical crack reached the width of w_max = 0.3 mm (according to Eurocode-2: Design of Concrete Structures) was considered as a loss of serviceability of the column. Analyzing the increase of columns serviceability after reinforced concrete jacketing the conclusion was made that higher load level during strengthening results in the lover strengthening effect. The maximum increase in serviceability of the columns considering the ultimate crack width was achieved when the sample was jacketed without any initial loading and the minimum - for the samples jacketed under the load of 90% of their bearing capacity.