Resudial Stresses In I-beams and Its Effect on Rods Buckling

Stability calculation of steel rods should consider residual stresses, as well as local imperfections (bends, buckling). Codes of EU, USA, PCR considering difference between welded and rolled I-beams on compression and compression with bending. Coefficient of longitudinal bending has values that consider the presence of different values of residual stresses for welded and rolled I-beams. Russian code for the design of steel structures (SP 16.13330) for conditionally centrally compressed rods does not distinguish between methods of I-beams production. To determine residual stresses, a wide range of Russian profiles with different thin-walled was studied. Residual stresses for small-sized profiles were carried out by partitioning, for large I-beams - by drilling blind holes. The actual values of residual stresses in flanges and walls are established; most suitable curves for their approximation are selected. The actual shape of I-beams was also measured with a laser scanner. According to the results of curvature measuring, the limit and average values of local flanges deflection are established. Considering experimental studies, FE-modeling of rods with residual stresses was performed for both rolled and welded I-beams. In addition to code eccentricities, local shape imperfections were modeled. It is established that rolled I-beams show higher values of critical forces than welded ones by 8-16%. This is true for steels C355 and C390 with a lambda-factor of more than 4, and for C255 with lambda-factor more than 3. According to the study, a coefficient is proposed that increases the bearing capacity of rolled I-beams for medium and large flexibilities.