Workshop on Structural Safety and Infrastructure Management Lloyd’s Register, London, 24th May 2017
Drive-by monitoring bridge damage detection using Velocity Instantaneous Curvature D. Martínez*, E.J. OBrien and A. Malekjafarian UCD School of Civil Engineering *
[email protected]
Drive-by monitoring Direct monitoring advantages: • Continuous readings • Satisfactory solution for bridges at high risk.
Direct monitoring issues • Power supply • Sensor installation • Cost (esp. for small bridges)
Indirect monitoring (drive-by monitoring) • Sensors installed in the vehicle • Traffic Speed Deflectometer (TSD) • Laser Doppler Vibrometers (LDV) • LDV measuring relative velocity
A sample section header
Damage Indicators • Difference Ratio (DR) and Moving Average Difference (MAD). 𝑑𝑎𝑚𝑎𝑔𝑒𝑑
• DR x =
• MAD x =
Curvature damage detection • • • •
M(x) EI
κ(x) = If EI Curvature Curvature calculation: differentiate the deflection of the bridge (v) twice. Instantaneous Curvature (IC) calculated from the vehicle measurements.
• IC x, t =
• • • • • • • •
ℎ𝑒𝑎𝑙𝑡ℎ𝑦
𝑉𝐼𝐶𝑎𝑣𝑒𝑟𝑎𝑔𝑒 (x)−𝑉𝐼𝐶𝑎𝑣𝑒𝑟𝑎𝑔𝑒 (x) 1 N
× 100 %
ℎ𝑒𝑎𝑙𝑡ℎ𝑦 min 𝑉𝐼𝐶𝑎𝑣𝑒𝑟𝑎𝑔𝑒 1 (N−1)/2 (N−1)/2 𝑑𝑎𝑚𝑎𝑔𝑒𝑑 ℎ𝑒𝑎𝑙𝑡ℎ𝑦 𝑉𝐼𝐶 (x) − 𝑉𝐼𝐶 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 (x) j=−(N−1)/2 N j=−(N−1)/2 ℎ𝑒𝑎𝑙𝑡ℎ𝑦 min 𝑉𝐼𝐶𝑎𝑣𝑒𝑟𝑎𝑔𝑒
× 100 (%)
• Accurate damage location in MAD. • No false positive risk using MAD.
v x−∆x,t −2v x,t +v x+∆x,t ∆x2
Deflection contour plot Y axis Bridge position X axis TSD vehicle position Collected moving measurements represented by a line. Minimum of three sensors needed for IC calculation. High sensitivity of IC, but not enough deflection measurement accuracy. TSD relative velocities (q) used for calculation. Velocity Instantaneous Curvature (VIC) q x−∆x,t −2q x,t +q x+∆x,t ∆x2
• VIC x, t = • 6 LDV obtaining 4 VIC values • VIC𝑎𝑣𝑒𝑟𝑎𝑔𝑒 x =
VIC123 x +VIC234 x +VIC345 x +VIC456 x 4
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