Distributed strain measurements in a CFA pile using high spatial resolution fibre optic sensors. (1st April 2018)

• Record Type: Journal Article
• Authors: Bersan, Silvia; Bergamo, Otello; Palmieri, Luca; Schenato, Luca; Simonini, Paolo
• Is Part Of: Engineering structures. Volume 160(2018)
• Page Start: 554
• Page End: 565
• Publication Date: 2018-04-01
• Subjects: Distributed strain sensing -- Fibre optic sensors -- Optical frequency domain reflectometer -- CFA piles -- Static load test -- Load-transfer curves; Structural engineering -- Periodicals; Structural analysis (Engineering) -- Periodicals; Construction, Technique de la -- Périodiques; Génie parasismique -- Périodiques; Pression du vent -- Périodiques; Earthquake engineering; Structural engineering; Wind-pressure; Periodicals; 624.105
• DOI: 10.1016/j.engstruct.2018.01.046
• Languages: English
• ISSNs: 0141-0296

Abstract

Highlights: Strain measurements with 10 mm spatial resolution were performed along a pile. High spatial resolution enabled identifying local variations of pile axial stiffness. Identification of local effects led to sound analysis of strain data. Load-transfer curves were derived combining 1-d FEM and least square optimization. Abstract: Static load tests on fully instrumented piles are a useful tool for optimizing the design of pile foundations. By measuring the change in strain along a test pile it is possible to estimate pile-soil interface properties and infer site-specific and technology-specific load-transfer curves to be adopted for design. This paper presents strain measurements obtained from a distributed sensor installed in a continuous flight auger (CFA) pile undergoing a static load test. Distributed sensing was performed using optical frequency domain reflectometry (OFDR), which provided a spatial resolution of 10 mm. The high spatial resolution allowed to highlight local defects, as those produced by undesired variations in the pile cross-section area that can lead to erroneous data analysis if not fully understood. The paper also presents an approach for the derivation of load-transfer curves from continuous strain data.