Abstract:With the past five years' study by the authors, an advanced distributed strain sensing technique has been developed for the health monitoring of infrastructures. A series of research work including theoretical and experimental modal analyses were conducted based on the dynamic measurements of strain distribution. This paper systematically reviews the work. With a brief introduction of the basic features of the developed dynamic distributed strain sensing techniques in the first place, the strain-response-based modal analysis theory is further presented. Modal testing techniques are then discussed to obtain the macro-strain Frequency Response Function (FRF) and identify the modal parameters, including resonant frequencies, damping ratio, and Modal Macro-Strain Vector (MMSV). In time and frequency domains, the macro-strain FRF is close to a displacement FRF rather than a velocity or acceleration one, so the relation between macro-strain FRF and frequency can provide a more sensitive indicator at low modes, especially, when the resonant frequencies are small. The identified resonant frequency and damping ratio from dynamic strain measurements have the same precision as those from the conventional transducers such as accelerometers and strain gauges. The curves of MMSV versus mode shape share the same mapping relation with the time-series and frequency responses of the measured macro-strain versus displacement responses, which means that MMSV essentially is a direct modal strain measurement. Based on the above findings, the advantages of modal strain over modal displacement in the engineering applications of low-frequency measurements, dynamic model reconstruction and structural damage identification are discussed as well.