不同环境下后张梁内预应力筋应力时变规律

Time variation of stress of prestressed reinforcement in post-tensioned beams under different environments

为了研究不同环境下后张梁内预应力筋应力时变规律,设计4根预应力混凝土试验梁,分别置于室外遮蔽环境、自来水干湿循环、氯盐溶液干湿循环、氯盐溶液干湿循环并箍筋通电四种环境,采用振弦式锚索测力计测量预应力筋应力。试验结果表明:环境温度与预应力筋应力变化呈正相关。与室外遮蔽环境的试验梁相比,自来水干湿循环下预应力筋应力增大约3%,与潮湿环境导致的混凝土湿胀相关。与自来水干湿循环相比,氯盐溶液干湿循环后预应力筋应力增大约2.5%,与氯盐引起的盐胀相关。箍筋锈蚀后预应力筋应力提升约4%,箍筋锈蚀导致的锈胀力会在试件纵向引起变形。此外,分析了箍筋锈蚀对预应力筋应力变化值的影响规律,建立箍筋锈蚀率与预应力筋应力变化值之间的关系,计算结果与试验结果较为吻合。

To study the stress variation in the prestressed tendons of prestressed concrete beams under different environments,four post-tensioned beams were cast and exposured in different environments:outdoor shielded environment,wet-dry cycles with tap water or salty solution,and a wet-dry cycles by salty solution coupled with galvanization.The strain gauges were applied to test stress on the prestressed tendons.The test results show that the ambient temperature is positively correlated with the stress variation of prestressed tendons.Compared with the test beam in the outdoor shielded environment,the stress of the prestressed reinforcement increases by 3%under the dry and wet cycle of tap water because of the expansion of concrete.Applying the salty solution for wetting cycles causes the further 2.5%increase in the stress of prestressed tendon,which is related to the volume expension induced by salty crystallizatio.Stirrups corrosion causes 4%growth in the stress of the prestressed tendon because the corrosion induced expansion force increases the longtidinal length of the specimen.In addition,the influence of stirrup corrosion on stress variation of prestressed tendons was analyzed,and the relationship between stirrup corrosion and stress variation of prestressed tendons was established,which was in good agreement with the test results.