Infrastructure systems are tied closely to the function of human society in many aspects. Effective approaches to maintaining infrastructure are critical for public safety. The assessment of structural conditions, diagnosis of structural damage, and infrastructure safety protection may be achieved by monitoring and analyzing structural responses. Many approaches have been pursued to monitor different types of structural responses; displacement monitoring is one of the commonly used approaches. Various types of sensors have been developed to monitor structural displacement with a range of cost, ease-of-use, and effectiveness. Radar systems provide a family of high-accuracy displacement measurements. Specifically, continuous-wave (CW) radar is a promising technology for structural applications. CW radar transmits the microwave to the target continuously and captures the signal reflected. By analyzing the difference between the transmitted and reflected microwaves, the radar can measure the relative displacement between the target and the radar. Some specific types of CW radars have been developed to monitor structural displacement and have demonstrated promising performance. Radar-based structural monitoring applications are presented and specific types of CW radars developed for structural monitoring are introduced. The operating mechanism for conducting displacement measurement with CW radars is presented. The hardware designs of the CW radars and the signal processing from radar signals to final displacement information are described. The structural displacement monitoring using the CW radar is quantified in both laboratory and field validation experiments. Challenges associated with applying the CW radar to monitoring structural displacement are summarized, and future work to improve the performance of CW radar is suggested.

Chapter Contents:

• 10.1 Introduction
• 10.2 Background
• 10.2.1 Structural health monitoring
• 10.2.2 Existing displacement sensing technologies
• 10.2.3 Radar techniques
• 10.2.3.1 Ground penetrating radar
• 10.2.3.2 Remote sensing radar
• 10.2.3.3 Distance measurement radar
• 10.3 Continuous radar sensor hardware
• 10.3.1 CW radar system
• 10.3.1.1 Antenna
• 10.3.1.2 RF board
• 10.3.1.3 Baseband board
• 10.3.1.4 Wireless communication device
• 10.3.1.5 Power system
• 10.3.2 AC-coupled radar
• 10.3.2.1 AC coupling design
• 10.3.3 DC-coupled radar
• 10.3.4 Active transponder
• 10.4 Continuous radar sensor software
• 10.4.1 Signal-processing algorithms
• 10.4.1.1 Automated DC tuning process
• 10.4.1.2 Automated displacement-processing algorithm
• 10.5 Continuous radar sensor measurement characterization
• 10.5.1 Dynamic displacement experiments
• 10.5.2 Static deflection experiments
• 10.5.3 Moving load experiment
• 10.5.4 Oblique angle tests
• 10.6 Continuous radar full-scale structural experiments validation
• 10.6.1 Sweetwater Park Bridge experiment
• 10.6.1.1 Sweetwater Park Bridge
• 10.6.1.2 Instrumentation
• 10.6.1.3 Description of load conditions
• 10.6.1.4 Measurement results
• 10.6.2 Vehicle load experiment
• 10.7 Conclusions
• References

Inspec keywords: sensors; CW radar; radar signal processing; structural engineering; condition monitoring; displacement measurement

Other keywords: radar-based structural monitoring applications; structural applications; radar signals; high-accuracy displacement measurements; continuous-wave radar; wave radar sensor; monitoring analyzing structural responses; CW radar; structural displacement monitoring; structural damage; radar systems; structural conditions; specific types; monitoring structural displacement

Subjects: Signal processing and detection; Spatial variables measurement; Inspection and quality control; Radar equipment, systems and applications