Prototyping and Validation of MEMS Accelerometers for Structural Health Monitoring—The Case Study of the Pietratagliata Cable-Stayed Bridge

Chiara Bedon,Salvatore Noè,Matteo Izzi,Enrico Bergamo

doi:10.3390/jsan7030030

Abstract

In recent years, thanks to the simple and yet efficient design, Micro Electro-Mechanical Systems (MEMS) accelerometers have proven to offer a suitable solution for Structural Health Monitoring (SHM) in civil engineering applications. Such devices are typically characterised by high portability and durability, as well as limited cost, hence resulting in ideal tools for applications in buildings and infrastructure. In this paper, original self-made MEMS sensor prototypes are presented and validated on the basis of preliminary laboratory tests (shaking table experiments and noise level measurements). Based on the well promising preliminary outcomes, their possible application for the dynamic identification of existing, full-scale structural assemblies is then discussed, giving evidence of their potential via comparative calculations towards past literature results, inclusive of both on-site, Experimental Modal Analysis (EMA) and Finite Element Analytical estimations (FEA). The full-scale experimental validation of MEMS accelerometers, in particular, is performed using, as a case study, the cable-stayed bridge in Pietratagliata (Italy). Dynamic results summarised in the paper demonstrate the high capability of MEMS accelerometers, with evidence of rather stable and reliable predictions, and suggest their feasibility and potential for SHM purposes.

Highlights

Nowadays, buildings and infrastructure are designed to sustain ordinary or extreme dynamic loads, whose magnitude is determined from probabilistic approaches (i.e., EN 1991 [1])
In recent years, thanks to the simple and yet efficient design, Micro Electro-Mechanical Systems (MEMS) accelerometers have proven to offer a suitable solution for Structural Health Monitoring (SHM) in civil engineering applications
Several research efforts have been devoted in the last decade to the development of reliable and cost-effective monitoring devices equipped with Micro Electro-Mechanical Systems (MEMS)

Summary

Measuring Devices

The typical measuring device considered in this study is composed of a printed circuit (PC) board with two RJ45 connectors for in-and-out connections (see Figure 1a). To ensure the consistence of the measurements when recording, a check square wave with 1 Hz frequency is sent from the personal computer and is recorded by each device. The theoretical root-mean-square (rms) noise is evaluated by filtering the noise density with a first-order low-pass 20 Hz filter leading to: rms = 45 √μg. In this context, the result of Equation (2) is a theoretical value; the actual electro-mechanical noise might be even higher, being influenced by the final layout of the PC board, the production techniques, the frequency of the power supply, and the temperature

Shaking Table Testing

Noise Level Assessment

The Case-Study Bridge

Summary of Past EMA and FEA Predictions

Findings

Test Methods and Setup