Seven simply supported steel beams were tested to examine the effects, in terms of strengthening, of external prestressing of strands on the shear behaviour of steel beams. All beams had the same steel section and clear span length and strengthening was implemented using two external prestressing strands. The tested beams were divided into two groups based on the presence of the external prestressing strands: the first group thus consisted of just one steel beam, as a reference, while, the second group had six steel beams strengthened by external prestressing strands divided according to the eccentricity location of a prestressing strand with jacking stress fpj = 1120.061 MPa. During the tests, it was found that the shear load strain curves for the tested beams were slightly stiffer than for the reference beams and that the percentage of stiffening increased with any increase in the eccentricity of strand locations from the shear points; the maximum shear load increased by 0.521%, 29.565%, 38.26%), 61.739%, 24.347% and 86.956% with an increases in the eccentricity location from (0 to 165) mm compared to the reference beam. The maximum shear strain increased by 9.664%, 3.553%, 8.121%, 62.436%, 37.563% and 13.451% with an increase s in the eccentricity location from (0 to 165) mm respectively as compared with the reference beam.
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