Abstract
Reliable structural health monitoring (SHM) including nondestructiveevaluation (NDE) is essential for safe operation of infrastructure systems. Effectivemonitoring of the rock components of civil infrastructures such as tunnels and cavernsremains challenging. The feasibility of employing smart optical fibre sensor (OFS) andpiezoelectric impedance sensor made up of lead zirconate titanate (PZT) forcomprehensive health monitoring of rocks, covering load history monitoring/retrieval aswell as damage assessment is presented in this paper. The rock specimens are subjected tocyclic loading and their conditions are continuously monitored using OFS and PZTsensors. OFS based multiplexed fibre Bragg grating (FBG) sensors are surface bonded onthe rock specimens. Their strain sensing performance is compared with the conventionalelectric strain gauges (ESGs). In addition, PZT patches are also bonded on the specimensto study the damage pattern during different loading cycles. Unlike the FBGs or ESGs,PZT patches are used as bi-functional sensors and actuators, enabling them to be efficientdetectors of incipient damages using the principle of electromechanical impedance. Theexperimental study demonstrated superior performance of these smart FBG and PZTimpedance sensors. This work is expected to be useful for SHM based NDE application ofrock structures such as caverns and tunnels.
Highlights
Owing to the scarcity of land, Singapore is looking towards underground space to meet the ever increasing residential, commercial and transportation demands
This paper demonstrates the feasibility of employing piezoceramics such as lead zirconate titanate (PZT) patches for structural health monitoring (SHM) of rocks by means of a detailed experimental study as described
An SHM scheme was established by using different types of sensors on rock specimens
Summary
Owing to the scarcity of land, Singapore is looking towards underground space (i.e., tunnels and caverns) to meet the ever increasing residential, commercial and transportation demands. Civil engineering structures especially underground constructions deteriorate with time as a result of aging of materials, excessive use, overloading, climatic conditions, inadequate maintenance and deficiencies in inspection methods. All these factors contribute to the obsolescence of constructed systems. Smart sensing technologies are relatively new, careful laboratory evaluation is essential before they could be employed in real-life monitoring of rock structures such as caverns and tunnels Another purpose served by laboratory tests is to calibrate PZT sensors against damage for the rocks (granite) encountered in Singapore. The combination of PZT and FBG for successful SHM is presented
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