Experimental test on an RC beam equipped with embedded barometric pressure sensors for strains measurement

The current trend in structural health monitoring (SHM) is to install increasingly large numbers of distributed, heterogeneous types of sensors, for a timely and exhaustive detection of any possible damage scenario evolving in the system. These sensors should be low-cost, easy to install, robust and durable. Among others, strain remains one of the most straightforward measurands for monitoring the state of a structural element and for assessing its health condition. However, for application to reinforced concrete structures, currently available strain sensing devices, such as electric strain gauges or fibre optic sensors, do not fully satisfy the aforementioned requirements, generally proving difficult to install, fragile and expensive. In this paper, an innovative monitoring technology, called Smart Steel System (S3), is proposed that measures strains in reinforced concrete members, by incorporating commercial barometric pressure MEMS sensors in appropriate sealed cavities embedded in the reinforcing steel bars. The results of an experimental campaign are reported, in which a reinforced concrete beam, instrumented with both S3 devices and conventional electrical strain gauges, is subjected to increasing loading and unloading cycles until collapse. The tests show the superior robustness of the S3 system during construction and loading as well as its good sensing accuracy, demonstrating its potential for a massive use in SHM applications.