Department of Civil Engineering, Fuzhou University, Fuzhou 350108, China.
Hebei Province Key Laboratory of Evolution and Control of Mechanical Behavior in Traffic Engineering Structure, Shijiazhuang Tiedao University, Shijiazhuang 050043, China.
Sensors (Basel). 2018 Nov 23;18(12):4106. doi: 10.3390/s18124106.
Prestress loss evaluation in prestressed strands is essential for prestressed structures. However, the sensors installed outside the duct can only measure the total prestress loss. The sensors attached on strands inside the duct also have several problems, such as inadequate durability in an aggressive environment and vulnerability to damage during tensioning. This paper proposes a new installation method for long-gauge fiber Bragg grating (LFBG) sensors to prevent accidental damage. Then the itemized prestress losses were determined in each stage of the pre-tensioning and post-tensioning according to the LFBG measurements. We verified the applicability of the LFBG sensors for prestress monitoring and the accuracy of the proposed prestress loss calculation method during pre-tensioning and post-tensioning. In the pre-tensioning case, the calculated prestress losses had less deviation from the true losses than those obtained from foil-strain gauges, and the durability of the LFBG sensors was better than foil-strain gauges, whereas in post-tensioning case, the calculated prestress losses were close to those derived from theoretical predictions. Finally, we monitored prestress variation in the strand for 90 days. The itemized prestress losses at each stages of post-tensioning were obtained by the proposed calculation method to show the prospect of the LFBG sensors in practical evaluation.
预应力损失评估在预应力结构中至关重要。然而，安装在管道外的传感器只能测量总预应力损失。安装在管道内的传感器也存在一些问题，例如在恶劣环境中的耐久性不足以及在张拉过程中容易损坏。本文提出了一种新的长栅光纤布拉格光栅（LFBG）传感器安装方法，以防止意外损坏。然后，根据 LFBG 的测量结果，确定了预张拉和后张拉各个阶段的分项预应力损失。我们验证了 LFBG 传感器在预应力监测中的适用性以及所提出的预应力损失计算方法在预张拉和后张拉过程中的准确性。在预张拉情况下，计算得到的预应力损失与真实损失的偏差小于箔式应变计的测量结果，并且 LFBG 传感器的耐久性优于箔式应变计；在后张拉情况下，计算得到的预应力损失接近理论预测值。最后，我们对钢绞线的预应力变化进行了 90 天的监测。通过所提出的计算方法得到了后张拉各个阶段的分项预应力损失，展示了 LFBG 传感器在实际评估中的应用前景。
