Investigation of Low-Cost Accelerometer Performance for Vibration Analysis of Bridges Kirk Grimmelsman Abstract The use of low-cost MEMS accelerometers for dynamic testing and vibration analysis of civil infrastructure has been steadily increasing since these devices first became commercially available. MEMS accelerometers are available with a variety of different input ranges, sensitivities, and with analog or digital outputs. These accelerometers have become ubiquitous in smartphones, and are also used in the majority of the wireless vibration monitoring systems. MEMS accelerometers with analog output capabilities are of particular interest for long-term SHM applications of civil infrastructure systems since they can be easily integrated with the data acquisition systems employed for the many other types of sensors that are often used for these applications. A low-cost MEMS accelerometer with nominal performance characteristics compatible for most bridge monitoring applications was previously evaluated by the authors to assess its performance and capabilities. The primary focus of the prior study was comparing the frequency characteristics of the MEMS accelerometer against a laboratory-grade accelerometer for specific harmonic excitations provided by a laboratory shaker. The present study is a continuation of the prior evaluation. In this study, several of the low-cost, analog output MEMS accelerometers were installed on a cantilever beam that was subject to free vibrations. The dynamic properties of the beam obtained from the MEMS accelerometer measurements are compared and evaluated against those obtained from more conventional instrumentgrade accelerometers also attached to the same structure. The objective of the analysis was to evaluate the performance of the MEMS accelerometers in identifying the dynamic characteristics of the system, including natural frequencies, mode shapes, and damping ratios. Vibration measurements from an in-service highway bridge using both the low-cost MEMS accelerometers and a commercially available MEMS accelerometer were also compared and evaluated. This paper describes the testing program and the data analysis approach and compares the dynamic characterization results from the low-cost MEMS accelerometer and the more expensive instrument-grade accelerometers. Keywords MEMS accelerometers · Cantilever beam · Highway bridge · Vibration testing 1 Introduction and Scope A large variety of accelerometers with different sensing technologies, signal conditioning requirements, performance characteristics, and costs are available today from numerous sensor vendors. This can present a challenge in selecting the appropriate accelerometer types in the design of Structural Health Monitoring (SHM) systems for highway bridges. The vibration characteristics are generally known for many short- to medium-span length, multi-beam highway bridges. This class of bridge structure is the most numerous type of bridge in the US highway bridge inventory. Generally speaking, the global structural vibration modes of interest are located in the DC to 50 Hz frequency band and measured vibration amplitudes under operational traffic loads typically less than ±1 g, and rarely ever exceed ±2 g’s for this class of structure. There are many types of accelerometers that are capable of meeting or exceeding these general performance characteristics. Micro Electro-Mechanical System (MEMS) accelerometers are increasingly being selected for SHM and vibration testing applications for bridges since they are typically very small and inexpensive, their power requirements are minimal, they can meet the nominal performance requirements for measuring bridge vibrations, and they are available with analog or digital outputs which simplifies integration with various data acquisition design. The primary performance characteristics to K. Grimmelsman ( ) Intelligent Infrastructure Systems, Philadelphia, PA, USA e-mail: kgrimmelsman@iisengineering.com © The Society for Experimental Mechanics, Inc. 2022 K. Grimmelsman (ed.), Dynamics of Civil Structures, Volume 2, Conference Proceedings of the Society for Experimental Mechanics Series, https://doi.org/10.1007/978-3-030-77143-0_13 129
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