大跨度PC桥梁有效预应力衰变行为监测与评估模型研究

Study on Monitoring and Evaluating Model of Decaying Behavior of Effective Prestress for Long-span PC Bridges

在桥梁正常使用阶段,为了对预应力钢束的预应力量值衰减程度及分布性态实现有效监测,同时对其当前的服役状态实现客观评估,将研发的"预应力钢索张力测试仪"应用于束筋预应力有效值的监测。这一技术综合考虑模拟边界修正条件并结合二级差测定法的误差修正,实现了对有效预应力可靠的定周期监测。基于现行规范中较为成熟的预应力损失理论,建立了有效预应力的衰变评估模型。以典型钢束应力测值为接口参数,实现了两类名义预应力损失参数的识别,从而可同步获知结构有效预应力纵向沿程的实际分布状况。大比例模型梁实桥应用结果表明:模型梁纵向沿程的预应力空间分布波动幅值小于既定的目标误差限值。评估结果能够反映结构中有效预应力衰减状况的一般规律,为完善大跨度PC桥梁结构劣化状况检测与评估技术体系奠定了基础。

For the sake of monitoring the decaying degree and distributing condition of prestress value of prestressing tendon effectively and assess the condition of prestressing reservation practically in service stage,an invented instrument named stretching force tester was applied to monitor the effective prestress of strand.The precision of this technology was guaranteed by means of amending analogous boundary condition and minimizing test errors through the tool of double-stage differences and reliable monitoring on effective prestress periodically was realized.Based on comparatively sophisticated prestress loss method in current specification,an evaluation model on attenuation of effective prestress was built up.By means of obtained stress datum on typical strand,recognition on two types of nominal coefficient for prestress loss was realized,and the distribution patterns for effective prestress along longitudinal direction could be obtained simultaneously.The experimental results of a large-scale beam model show that the fluctuation amplitude of prestress along longitudinal direction is less than specified relative error threshold.