基于实测挠度的PC梁桥长期预应力损失研究

Study on the Long-Term Prestress Loss of PC Box-girder Bridge Based on the Actual Deflection

桥梁结构在长期使用过程中预应力损失估算偏低,是造成大跨径预应力混凝土变截面箱梁桥或连续刚构桥(简称PC梁桥)普遍开裂和过度下挠的一个重要原因。长期预应力损失与施工工艺、环境温度、荷载、混凝土收缩徐变、预应力筋松弛等因素有关。为了研究PC梁桥成桥后预应力损失发展规律,提出了一种基于桥梁实测挠度的预应力损失计算方法,考虑了混凝土裂缝导致截面刚度下降以及对挠度影响,给出了混凝土开裂后的梁体刚度折减公式,计算过程简单,实用性强,并以虎门大桥辅航道桥多年实测挠度数据验证所提出方法的可行性。研究成果可为同类桥梁的设计与施工提供参考。

The underestimate of the long-term prestress loss of the prestressed concrete(PC)box-girder bridge becomes one of the main reasons for cracking and excessive deflection of continuous rigid frame bridges. The long-term loss of prestress is related to construction technology,ambient temperature,load,concrete shrinkage and creep,prestress tendon relaxation,etc. In order to study the prestress loss of tendons in PC box-girder bridges,a calculation method of the prestress loss based on the measured deflection in midspan is proposed,in consideration of the cross-section stiffness decrease due to cracking as well as its deflection. Based on the measured deflection data in midspan of the auxiliary channel bridge of the Humen Bridge for many years,the calculating process is simple and practical,which can verify the correctness of the proposed method. The findings in this paper can provide additional input for the design and construction of the similar bridges.