PSI - Issue 64

Marco di Prisco et al. / Procedia Structural Integrity 64 (2024) 2133–2140 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

2137

5

Figure 5. Numbering of bridge beams used in structural verifications

The structural checks performed on the external beam (number T01 in Figure 5) are collected in Table 2 with reference to both the first (M01) and second (M02) model. The CFRP retrofitting system already applied on the beam was accounted in bending (CNR-DT 200 R1/2013), while it was neglected in favour of safety in shear. It is worth noting that MODEL 02 more accurately reproduces the vertical displacements measured during the loading test (Figure 9), hence this model was selected to define the bearing capacity of the bridge. The investigations developed by Politecnico di Milano on the external beam underline the presence of carbonation up to a depth of 40 mm. Hence, the verifications of all the beams were developed considering different amounts of resisting rebars (Figure 6): in the first case (case A) the prestressing strand area is fully accounted, no reduction in the resisting section due to corrosion is assumed; in the second case (case B) the lower layer of the strands and the strands on one face of the beam are neglected; finally, in the third case (case C) a configuration in which the minimum number of strands able to guarantee the satisfaction of the bending verification, considering the loading of a 44t truck (with an eccentricity of 80 cm with respect to the centre of the roadway) is accounted for. This load condition simulates the more reliable configuration of a truck transit on the bridge. The structural analysis, developed on the II category bridge, underlined that the bridge is compliant with the Standard in force at the time of construction (Circolare n. 384, 14 febbraio 1962), but it is not verified if the loading condition considered for a II category bridge by the D.M. 2008 Standard is imposed. However, the structure results adequate for the passing of a 44t truck according to the transitability admitted by the current Standards.

Table 2. Structural checks of T01 beam according to the loads expected by different code Circolare n. 384 14/02/62 NTC 2008

Truck 44 t e =1.30 m

Truck 44 t e =0.80 m

X Rd

M.01

M.02

M.01

M.02

M.01

M.02

M.01

M.02

kNm

1271

807.94

807.94

1189.30

1045.95

938.57

854.96

814.52

745.54

M + Case A M + Case B M + Case C

γ = M Rd /M Ed

-

1.57

1.57

1.07

1.22

1.35

1.49

1.56

1.70

kNm

918.3

807.94

807.94

1189.30

1045.95

938.57

854.96

814.52

745.54

γ = M Rd /M Ed

-

1.14

1.14

0.77

0.88

0.98

1.07

1.13

1.23

kNm

865.8

807.94

807.94

1189.30

1045.95

938.57

854.96

814.52

745.54

γ = M Rd /M Ed

-

1.07

1.07

0.73

0.83

0.92

1.01

1.06

1.16

kNm

-281.5

-212.34

-212.34

-367.19

-509.22

-247.04

-355.81

-170.53

-255.30

M -

γ = M Rd /M Ed

-

1.33

1.33

0.77

0.55

1.14

0.79

1.65

1.10

kN

387.33

199.81

199.81

340.48

342.78

209.53

212.60

180.43

181.37

V Left

γ = V Rd /V Ed

-

1.94

1.94

1.14

1.13

1.85

1.82

2.15

2.14

kN

387.33

199.81

199.81

244.93

248.43

199.29

201.56

175.22

175.78

V Right

γ = V Rd /V Ed

-

1.94

1.94

1.58

1.56

1.94

1.92

2.21

2.20