Production of steel I beam by prestressing method and also investigation of bending behavior and residual stress

The main objectives of the study are to produce internal prestressed steel I-beam (strut) by welding joining, to determinate bending behaviours of the beams and also to investigate permanent/residual stresses generated after prestressing and welding process.Hot rolled steel (Fe42grade) plates and T-profiles were used to produce prestressed I-beams. While steel plates were under various axial tensile stresses (50, 100,150, 200 and 272 MPa) or without stress, they were joined to the T-profile by inert gas welding and then removed the tensile stress on the steel plates. Steel I beams with or without prestressed conditions, in dimension of 50x55x500 mm, were fabricated by this method.Flexural capacities of the manufactured I-beams were determined by means of three point bending test. Maximum bending load and yield strength were observed for beam prestressed with 200 MPa. Thereby, it was determined that the bending load and the yield strength of I beam could be increased about 16% and 14% respectively.Test results indicated that permanent tensile stress at upper flange of the beam in the longitudinal direction and permanent compressive stress in the transverse direction are increased with increasing the prestress up to 200 MPa. At lower flange of the beam, in the longitudinal direction, the higher permanent tensile stress affected by welding and prestressing process was observed. Permanent tensile stresses were determined at the transverse direction and mid-point of this flange. Nevertheless, toward the side of the lower flange, this tensile stress reversed to compressive stress. At the web of I-beams, tensile permanent stresses and compressive stresses were determined for with and without prestressed beams respectively. At the welding seam, joining the lower flange to the beam web, shear stress was observed particularly for the prestressed steel I-beams.