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

344

6

Fig. 7. Geometry of the investigated points for the high precision digital levelling measurements (a), Dywidag bars tested during the load test (b)

During the load configurations 2 and 3 the maximum vertical displacements in correspondence of the special joint were equal to 12-13 mm (Fig. 8) and the residual vertical displacements evaluated on the final reading without any loads were less than one millimeter.

b

a

Fig. 8. Vertical displacements on the right-end side (a) and on the left-hand side (b) of the viaduct deck

In Fig. 9.a the relative displacements between the upper and lower part of the special joint on both side of the deck have been plotted for all the load configurations. The graph emphasized a very good symmetry between the displacements recorded on the right and left side of the joint at span No.7. The maximum displacement recorded between the upper and lower part of the joint was equal to 1 mm, whereas the residual displacement evaluated on the unloaded final configuration was equal to - 0,06 mm, the upper and lower part of the joint were closer after the end of the test. However, it is significant to note that the bearings were detached therefore without any load applied. In Fig. 9.b, the axial stress trend for all the load configurations has been plotted. The largest increase was measured for the side Dywidag bars (1A and 10A) on load configurations 2 and 3 and was between 49÷53 MPa (39÷43 kN). The internal bar (6A) was characterized by a lower axial stress value, which was equal to 38 MPa. On the final unloaded configuration an axial stress variation of 5% was measured. All the axial load and stress increments measured during the static load test evaluated with the dynamic approach have been summarized in the following Table 2.

Table 2. Axial load and stress increment evaluated with the dynamic approach.

bar No. 1A bar No. 6A

bar No. 10A

Axial load increase kN (Axial stress increase MPa)

43 (53)

31 (38)

39 (49)

a

b

Fig. 9. Relative displacement between upper and lower paìrt of the special joint on span No. 7 (a), Axial stress trend along the Dywidag bars instrumented with strain gauges on the special joint of span No. 7 (b)