A kind of helical optical fiber sensing strain testing device and method of prestressed FRP tendon

Abstract

A helical optical fiber sensing strain test device for prestressed FRP tendons, including helically embedded helical sensing optical fibers wound around prestressed FRP tendons, after the coordinated deformation of the beam-column structure and prestressed FRP tendons, the photosensitive signal is converted The processing system captures the changes in the photosensitive parameters of the helical sensing fiber, amplifies and converts the spectral signal through the ring-down of the helical cavity, and outputs and records the corresponding axial strain value of the prestressed FRP tendon by the terminal of the computer data processing system. The invention also provides a corresponding test method, which can effectively eliminate the bending radial effect for the longitudinal strain test of the prestressed FRP tendon embedded in the beam and column structure under the typical composite stress state such as compression bending or tension bending. For the interference of longitudinal strain target test results, continuous strain monitoring of prestressed FRP tendons is carried out with higher precision, which provides basic data for real-time grasp of the effective prestressing status of prestressed FRP tendons and accurate assessment of structural prestress loss.

Description

technical field [0001] The invention belongs to the technical field of mechanical measurement of bridge engineering experiments, is suitable for strain testing of prestressed FRP tendons, and in particular relates to a spiral optical fiber sensing strain testing device and method for prestressed FRP tendons. Background technique [0002] At present, concrete structures using prestressed FRP tendons are more and more widely used in civil engineering and construction engineering. Identification is a key link related to the overall structural safety and objective evaluation of performance, especially in the practice of health monitoring and operation and maintenance of long-span bridge engineering. However, the most mature and widely used steel string strain gauges in the monitoring of traditional reinforced concrete and prestressed concrete structures rely on a large number of welded connections in the layout method, which is helpless for typical inorganic non-metallic materia...

AI Technical Summary

Problems solved by technology

However, the most mature and widely used steel string strain gauges in the monitoring of traditional reinforced concrete and prestressed concrete structures rely on a large number of welded connections in the layout method, which is helpless for typical inorganic non-metallic materials such as fiber reinforced fabric prestressed FRP bars , only another type of surface-attached strain testing technology can be selected for strain testing of prestressed FRP tendons

[0003] From this, a series of "bottleneck" problems that restrict the test accuracy of surface-attached strain testing technology are derived, which are mainly reflected in the following three aspects: (1) Attached strain elements (strain gauges, strain gauges) are arranged on prestressed FRP bars On the surface, after the concrete is vibrated, it will cause mechanical damage to the strain element, which will seriously affect the survival rate of the test element; For beam and column members, even for the same measurement area, the strain test elements laid out on the upper and lower edges of the prestressed FRP tendons show a large difference in value in the traditional test method. The reason is that the radial effect (stress and deformation) has a significant effect on the axial strain, and for prestressed FRP tendons with larger diameters, the effect of this effect is more significant; (3), the traditional surface-attached strain test element is coiled back and forth on the surface of the FRP to be tested , there are multiple straight line segments and semi-circular arc segments. During the strain test, the strain change state of the straight line segment and the arc segment is significantly different, and in the follow-up long-term monitoring period, it is greatly affected by the working environment such as temperature and humidity. , will have a greater impact on the strain test accuracy

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