PSI - Issue 72

Boris Folić et al. / Procedia Structural Integrity 72 (2025) 286 – 293

292

effect of friction is calculated, the force due to the effect of friction increases by 2.107 times. Activated force of passive resistance for RC diaphragm width 8m, see in Tab 2.

Table 2. Passive earth pressure on RC diaphragm Caisson. Soil condition; k p [1] γ [kN/m 3 ] H [m]

F p =k p ·γ·H

2 /2

B·F p [MN] 44.52 93.80 16.60

BS* [MN] 18.27 18.27 18.27

Σ H i [MN]

[kN/m]

Dry or moist Dry or moist

4.60 9.69 4.60

20 20 10

11 11

5564.08 11724.90 2075.26

62.79 112,07

34,87

Submerged, Saturated

9.5

*BS for right caisson

According to Fig. 7, the passive resistance of the soil is activated only behind the diaphragm of height H, while the shear force in base acts just below the depth D f . If there is an exclusively horizontal movement of the caisson at the base, due to shearing at the base, passive pressure is activated at the depth Df, but due to the movement of the supports, the integrity of the arches is threatened. As we are dealing with shallow fixed arches, this problem is further accentuated. The integrity of the bridge and immovability, i.e. controlled movement within the desired limits, is ensured exclusively through RC diaphragms at the depth H. The places of repair of the cracks on the small arch and the middle caisson can be seen in Fig. 11.

Fig. 11. (a) Below the deck view of the repaired middle caisson. (b) On the deck view of the repair on smaller arch.

Trojanović (1961) talks about the necessity of calculating rheology, and the influence of flow, on deflections. Four years before the flood, he states that external prestressing often does not give satisfactory behavior of the structure. But the Vallet II arch, in the hands of a skillful and dexterous designer, can be rational. Petrović (1994, 2004), states that "for months we calculated that bridge, the mobility, the rheology of the concrete, and as if to spite it, it has a stomach (think of a deck), you can see it in winter". The authors of the paper do not know whether this refers exclusively to the period after flood or before the accidental event, and it was not specified in the lectures. If it was not visible before the flood, then the flood caused the supports to move and rotate, in such a way that the road plate gets excessive deflection. The bridge has a small flaw, namely the road plate of the large arch does not have a longitudinal slope. It is usual to create an overhang in the middle (span), or to have a continuous slope towards one end. Here, it was logical to create an overhang in the middle by 20 cm (which is a slope of 2 ‰). It is possible that the "belly" would not appear then. The smaller arch has a constant longitudinal slope of the road towards the coast of 2 ‰.