PSI - Issue 62

Alberto Gennari Santori et al. / Procedia Structural Integrity 62 (2024) 339–346 Gennari Santori A. et al. / Structural Integrity Procedia 00 (2019) 000–000

345

7

6. Axial stress evaluation of the joint bars during an exceptional vehicle transit

All the on-site measurements were carried out during the transit of an exceptional vehicle characterized by a load equal to 150 tons, 33 meters long and equipped with 15 axles. To avoid torsional stress and minimize all the dynamic effects, the vehicle moved along the entire deck at a constant speed of 5 km/h. The following parameters were evaluated during the test: Axial stress variation of the Dywidag bars on the spans 5, 7 and 9 special joints by installing strain gauges. The monitored bars have been on span 5 bars 1B and 10BA, on span 7 bars 2B, 10B and on span 9 bars 1A, 4A and 10A. Vertical displacement of the deck in correspondence of the special joints by using a robotic total station. For each single special joint, the measurement was carried out in the state of transit of the vehicle above it. The values of the axial load evaluated for different Dywidag bars located on different joints (span 5, 7 and 9) have been shown in the following Table 3. The continuous trend of the axial strain of the Dywidag bars is plotted on Fig. 10. The obtained result highlighted the similar mechanical behavior between the different special joints. In the case of the joint located on span No. 9 the bars on the side (1A and 10A) had a higher value of the axial load if compared with the central bar 4A. This peculiar aspect was highlighted also on the static load test performed on span No.7.

Table 3. Axial load on the Dywidag bars and maximum vertical displacements measured during the exceptional vehicle transit on the deck.

Position vehicle

Measurement Area

Maximum vertical displacement

Residual vertical displacement

Bar (No.)

On span No.5

On span No.7 On span No.9

mm

mm

stress (MPa)

stress (MPa)

stress (MPa)

3

20

<1

not monitoring

1

105

9

1

5

24

<1

10

109

9

1

1

10

112

13

7

22

<1

10

8

104

11

1

0

9

107

9

23

<1

4

1

7

78

10

1

9

105

The maximum vertical displacements recorded on the joints located on spans 3, 5, 7 and 9 are shown in the following Table 3. The vertical displacements are similar for all the special joints instrumented and after the special vehicle transit residual vertical displacements equal to 1mm have been recorded.

Fig. 10. Strain trend on different Dywidag bars during the exceptional vehicle transit on the deck.

7. Conclusions

During the safety assessment of infrastructures, the aspects to be analyzed are different: mechanical characterization of materials, state of conservation of the structural elements and its evolution over time, evaluation of mass and stiffness involved and definition of the real constraints scheme. The case study described in this paper is an example