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Smart Structures and Systems Volume 29, Number 2, February 2022 , pages 267-278 DOI: https://doi.org/10.12989/sss.2022.29.2.267 |
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Bending characteristics of Prestressed High Strength Concrete (PHC) spun pile measured using distributed optical fibre strain sensor |
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Hisham Mohamad, Bun Pin Tee, Mun Fai Chong, Siew Cheng Lee and Krisada Chaiyasarn
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| Abstract | ||
| Pre-stressed concrete circular spun piles are widely used in various infrastructure projects around the world and offer an economical deep foundation system with consistent and superior quality compared to cast in-situ and other concrete piles. Conventional methods for measuring the lateral response of piles have been limited to conventional instrumentation, such as electrical based gauges and pressure transducers. The problem with existing technology is that the sensors are not able to assist in recording the lateral stiffness changes of the pile which varies along the length depending on the distribution of the flexural moments and appearance of tensile cracks. This paper describes a full-scale bending test of a 1-m diameter spun pile of 30 m long and instrumented using advanced fibre optic distributed sensor, known as Brillouin Optical Time Domain Analysis (BOTDA). Optical fibre sensors were embedded inside the concrete during the manufacturing stage and attached on the concrete surface in order to measure the pile's full-length flexural behaviour under the prescribed serviceability and ultimate limit state. The relationship between moments-deflections and bending moments-curvatures are examined with respect to the lateral forces. Tensile cracks were measured and compared with the peak strains observed from BOTDA data which corroborated very well. By analysing the moment-curvature response of the pile, the structure can be represented by two bending stiffness parameters, namely the pre-yield (EI) and post-yield (EIcr), where the cracks reduce the stiffness property by 89%. The pile deflection profile can be attained from optical fibre data through closed-form solutions, which generally matched with the displacements recorded by Linear Voltage Displacement Transducers (LVDTs). | ||
| Key Words | ||
| BOTDA; bending stiffness; moment-curvature; prestressed high strength concrete; spun pile; tensile cracks | ||
| Address | ||
| (1) Hisham Mohamad: Civil & Environmental Engineering Department, Universiti Teknologi PETRONAS, 32610 Seri Iskandar, Perak, Malaysia; (2) Bun Pin Tee, Siew Cheng Lee: Smart Sensing Technology Sdn. Bhd., 40150 Shah Alam, Selangor, Malaysia; (3) Bun Pin Tee: School of Civil Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia; (4) Mun Fai Chong: Dynamic Pile Testing Sdn. Bhd., 40150 Shah Alam, Selangor, Malaysia; (5) Krisada Chaiyasarn: Thammasat School of Engineering, Thammasat University Rangsit, Klong Luang Pathumthani, Thailand. | ||