Yielding Behaviour of Steel Beams as a Result of the Shape of the Strands' Fixity Profile

Seven simply supported steel beams were built and tested to provide a better understanding of how prestressed strands affect the steel beams’ behavior during the yielding stage. Steel beams had identical clear span lengths (2.85 m) and gross-section areas (3268 mm2). The strengthened sample was constructed using two external strands. The steel beams were divided into two types based on whether the exterior strand’s eccentricity was present or not. One of the steel beams serves as a reference. The remaining six steel beams were strengthened by external strands, which were divided according to the eccentric positions of the strands with the jacking stress (fpj = 815 MPa). It was found that strand eccentricity increase increased the ultimate load and yielding of tested strengthened beams. Also, the percentage of yielding to ultimate load ratio (Py/Pu) increased with the strand eccentricity. Finally, compared to the reference beam, the yielding strain positions for all tested beams shifted from the bottom to the top region, and all strain in the top and bottom zones were enhanced compared to the reference due to the external prestress strand, which improved the bottom and top flanges and the resistance of the web under the applied load.