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Smart Structures and Systems   Volume 15, Number 3, March 2015, pages 769-785
DOI: https://doi.org/10.12989/sss.2015.15.3.769
 
Performance monitoring of timber structures in underground construction using wireless SmartPlank
Xiaomin Xu, Kenichi Soga, Sarfraz Nawaz, Neil Moss, Keith Bowers and Mohammed Gajia

 
Abstract     [Buy Article]
    Although timber structures have been extensively used in underground temporary supporting system, their actual performance is poorly understood, resulting in potentially conservative and over-engineered design. In this paper, a novel wireless sensor technology, SmartPlank, is introduced to monitor the field performance of timber structures during underground construction. It consists of a wooden beam equipped with a streamlined wireless sensor node, two thin foil strain gauges and two temperature sensors, which enables to measure the strain and temperature at two sides of the beam, and to transmit this information in real-time over an IPv6 (6LowPan) multi-hop wireless mesh network and Internet. Four SmartPlanks were deployed at the London Underground\'s Tottenham Court Road (TCR) station redevelopment site during the Stair 14 excavation, together with seven relay nodes and a gateway. The monitoring started from August 2013, and will last for one and a half years until the Central Line possession in 2015. This paper reports both the short-term and long-term performances of the monitored timber structures. The grouting effect on the short-term performance of timber structures is highlighted; the grout injection process creates a large downward pressure on the top surface of the SmartPlank. The short and long term earth pressures applied to the monitored structures are estimated from the measured strains, and the estimated values are compared to the design loads.
 
Key Words
    wireless sensor network; timber structure; underground construction; grouting; earth pressure
 
Address
Xiaomin Xu, Kenichi Soga and Sarfraz Nawaz: Department of Engineering, University of Cambridge, Cambridge, UK
Neil Moss,Keith Bowers and Mohammed Gajia: Transport for London, London, UK
 

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