A Review of Indirect Bridge Monitoring Using Passing Vehicles

Table 1

Indirect bridge monitoring summary (SHM levels: 1 = detect existence of damage, 2 = detect damage location, and 3 = detect damage severity).

Method		SHM level	Advantages	Drawbacks
Modal parameter based methods	Natural frequency	1	Simple.; Demonstrated in many experimental works. Acceptable vehicle speed.	Not always sensitive to damage.; Low frequency resolution when vehicle speed is high.
	Damping	1	Sensitive to damage.	Complexity.
	Mode shape	1 and 2	Local information.; Sensitive to damage.	Low vehicle speed. Sensitive to noise.; No experimental confirmation.
Nonmodal parameter based methods	Crowd sourcing	1	Field experiments: ongoing in service conditions.	Only feasible using same vehicle for all measurements.; Damage sensitivity unconfirmed experimentally.
	Wavelet	1, 2, and 3	Algorithms widely available.	Low vehicle speed.; Relies on local anomalies in the signal.; Results can be compromised by edge effects.
	TSD	1	Very high accuracy of measurements.; High vehicle speed.	Expensive equipment.; No experimental confirmation.
	Other	1, 2, and 3	Novel numerical algorithms for damage detection	Limited experimental confirmation.