PSI - Issue 5

C.A. Prato et al. / Procedia Structural Integrity 5 (2017) 332–339 C.A. Prato/ Structural Integrity Procedia 00 (2017) 000 – 000

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 Traffic load tests under passage of the code-prescribed vehicle.

2.1. Damping tests

Two series of tests were performed by exciting the bridge at center-span section and at quarter-span to generate response in both symmetric and anti-symmetric modes; typical test records are given in Figures 3 and 4. The spectra plotted in Figures 3(b) and 4(b) correspond to different zones of the time signals that were sampled with Hanning windows with suitable separations to calculate the damping of each mode as a function of the logarithmic decrement of spectral amplitudes.

(a)

-0.2 0.2 Acceleration [m/s 2 ] Acceleration [ /s 2 ] -0.1 0 0.1

0 2 4

6 8 10 12 14 16 18 20

Time [sec]

0.025

(b)

Window 1 Window 2 Window 3 Window 4

0.02

0 Acceleration [m/s 2 ] Accelerati [ /s 2 ] 0 0.005 Acceleration [m/s 2 ] 0.01 0.015 -0.2 0.2 Acceleration [m/s 2 ] -0.1 0 0.1

2

4

6

8

10

12

Frequency [Hz]

Fig. 3. (a) Typical record at mid-span section; (b) Fourier amplitude spectrum of records at mid-span section.

(a)

0 2 4

6 8 10 12 14 16 18 20

Time [sec]

(b)

0.012

Window 1 Window 2 Window 3 Window 4

0.01

0.004 Acceleration [m/s 2 ]

0.002 Acceleration [m/s 2 ] 0.006 0.008

0

0

2

4

6

8

10

12

Frequency [Hz]

Fig. 4. (a) Typical record at quarter-span section; (b) Fourier amplitude spectrum of records at quarter-span section.