Experiments on Large Structures - Dynamic Behavior of Concrete and Seismic Engineering - page 217

were calibrated from responses measured during low-speed crossings (quasi-static
tests). These tests allow the measurement of the static deformation of the bridge and
an equivalent to the line of influence to be measured at a selected point.

The dynamic amplification factor can be determined, as indicated in Figure 6.13,
and an average calculated for each series of vehicles crossing, by working out the
relationship between both response parameters. The same procedure is applied for
strain measures. As is often the case with bridges, the positions of the two
displacement transducers on the bridge were limited by the depth of the river and its
currents. To overcome this problem, accelerations were integrated to give a rough
estimate of the displacements to assess values of the dynamic amplification factor in
different locations.

Time, s

Figure 6.13. Assessment of the dynamic amplification factor (DAF)

Displacement * Displacement ** Strain

Vehicle

Min. Max. Min. Max Min. Max.

10-tire lorry
Lorry and trailer
2 lorries in line
2 lorries side by side
All tests

1.19
1.08
1.09
1.10
1.12

1.20
1.09
1.10
1.10
1.12

1.10
1.03
1.05
1.06
1.07

1.11
1.04
1.06
1.07
1.07

1.06
1.01
1.03
1.04
1.03

1.07
1.02
1.03
1.05
1.04

*Measured displacements ( LVDT ) **Average of the integrated accelerations

Table 6.2. Average values of the DAF