DOI: 10.36347/sjet.2018.v06i04.001

Pages: 95-110

Cambering is used to offset the downward deflections in steel beams due to gravity loads by producing an initial upward camber and a curved shape. Two methods can be used to perform cambering; (1) cold cambering and (2) heat cambering. Research has shown that significant residual stresses develop in the cross-section when cambering that may influence the structural performance upon further loading. An extensive research project was performed to evaluate the influence of both cold and heat cambering on such residual stresses. Experimentally, cold cambering was achieved by creating significant plastic deformations in steel beams using a hydraulic actuator. Heat cambering was achieved by applying Vee heats to the web and strip heats to the flange at intervals along the length of the steel beams. This caused yielding in the heated regions at high temperatures due to restraint from the unheated material. In both cases, residual stresses were measured after the completion of the tests. Finite element models were developed for both cold-cambered and heat-cambered beams to further investigate the development and patterns of residual stresses. Heating cycles were simulated in the finite element models using time-temperature curves generated using a heat transfer analysis performed with the finite difference method. Experimental and analytical residual stress results compared favorably well to each other. Results indicated that cold-cambering does not cause a major concern with respect to residual stresses. The results indicate that residual stresses in heat-cambered are significant, reaching or exceeding the yield stress. The residual stress results are much higher than assumed in AISC equations used to predict the moment capacity of steel beams. However, the results indicate that high stresses are localized near the heated area and thus, the stresses only have a small influence on the load-displacement behavior of steel beams under further loading.