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Prediction of load transfer depth for cost-effective design of ground anchors using FBG sensors embedded tendon and numerical analysis

  • Received : 2015.07.07
  • Accepted : 2016.02.29
  • Published : 2016.06.25

Abstract

The load transfer depth of a ground anchor is the minimum length required to transfer the initial prestressing to the grout column through the bonded part. A thorough understanding of the mechanism of load transfer as well as accurate prediction of the load transfer depth are essential for designing an anchorage that has an adequate factor of safety and satisfies implicit economic criteria. In the current research, experimental and numerical studies were conducted to investigate the load transfer mechanism of ground anchors based on a series of laboratory and field load tests. Optical FBG sensors embedded in the central king cable of a seven-wire strand were successfully employed to monitor the changes in tensile force and its distribution along the tendons. Moreover, results from laboratory and in-situ pullout tests were compared with those from equivalent case studies simulated using the finite difference method in the FLAC 3D program. All the results obtained from the two proposed methods were remarkably consistent with respect to the load increments. They were similar not only in trend but also in magnitude and showed more consistency at higher pullout loading stages, especially the final loading stage. Furthermore, the estimated load transfer depth demonstrated a pronounced dependency on the surrounding ground condition, being shorter in hard ground conditions and longer in weaker ones. Finally, considering the safety factor and cost-effective design, the required bonded length of a ground anchor was formulated in terms of the load transfer depth.

Keywords

ground anchors;laboratory and field tests;FBG sensors;numerical analysis;load transfer depth

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Cited by

  1. A Review of Rock Bolt Monitoring Using Smart Sensors vol.17, pp.4, 2017, https://doi.org/10.3390/s17040776
  2. Study on the Optimal Groove Shape and Glue Material for Fiber Bragg Grating Measuring Bolts vol.18, pp.6, 2018, https://doi.org/10.3390/s18061799
  3. Assessing the Difference in Measuring Bolt Stress: A Comparison of Two Optical Fiber Sensing Techniques vol.2018, pp.1687-7268, 2018, https://doi.org/10.1155/2018/7582605

Acknowledgement

Supported by : Ministry of Land, Infrastructure and Transport of Korean