Experimental Study on Shear Behavior in Negative Moment Regions of Segmental Externally Prestressed Concrete Continuous Beams

摘要

External prestressing technology has achieved wide application in bridges. Although previous tests have made great progress in shear behavior of externally prestressed concrete beams, the research mainly focused on simply supported beams. To study the effects of joints and large negative moments on the shear behavior of segmental externally prestressed concrete continuous beams, a series of cantilever beam specimens were designed to simulate the negative moment regions in continuous beams. Then, the crack developing behavior, failure mode behavior, and mechanical behavior of specimens with different shear span to effective depth ratios, joint types, joint locations, and ratios of internal to external tendons were investigated in this experimental study. The test results show that failure cracks of segmental specimens are web shear cracks, whose locations and inclination angles are independent of joints. Eventually, both sides of the specimens move relatively along failure cracks and the specimens fail suddenly. The results also reveal that the deflections of segmental specimens after cracking develop very quickly, and the stress increments of prestressing tendons reach 20-24% of the tensile strength, which are larger than those of monolithic specimens. In addition, the shear strength provided by the concrete effects in regions near the interior supports of continuous beams is lower than that in regions near the supports of simply supported beams, and the contributions of the stirrup and prestressing tendon to the shear strength are 14-21 and 8-18%, respectively, in which the contribution of stirrup is greater than that of simply supported beams.