PSI - Issue 64

Nicoletta Bianchini et al. / Procedia Structural Integrity 64 (2024) 352–359 Bianchini N., Sabra Z, Green K.. Wrigth, R. Structural Integrity Procedia 00 (2024) 000 – 000

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Table 3 summarises the limit analysis results for each numerical model considering 11.5 tons single axle loading distribution as specified by CS454 “Assessment of highway bridges and structures”. The arch mechanism remains constant for all M1, M2, M3, characterized by two hinges at the intrados at the beginning of the curvature of the arches where the trust line touches the internal surface of the arch. On the other hand, M4, with two rings, presents a more complex mechanism with hinges forming at the interface between the two rings and sliding at the crown of the arch, as expected.

Table 2. List of the material properties per each numerical model, typical values given by CS 454 Figure 4.2.7b. *Reference model.

Compressive strength [N/mm 2 ]

Angle of dispersion of live loads [deg.]

Friction [deg.]

Unit weight [kN/m 3 ]

Surface fill

Masonry

Backfill

Masonry

Backfill

Masonry

Backfill

Surface fill

34.4 (0.6 rad) 34.4 (0.6 rad)

M1*, M2, M4

30

26.6

21.57

15.69

22.56

4.5

5

30

26.6

M3

11.76

10.19

22.56

4.5

5

From Table 3, it is possible to conclude that the flooded conditions lead to the lowest adequacy factor equal to 1.908, roughly 39% less than the M1 model, while the defects modelled in M2 affects the capacity by approximately 14%. On the other hand, the two rings in model M4 led to a difference of approximately 22% less than the M1 model. M3 results have the lowest capacity due to the reduction in the unit weight of masonry and backfill, leading to rapid instabilities even though the collapse mechanism was not affected.

Table 3. Limit analysis results in terms of adequacy factor and arch mechanisms

Identifier

Description

Adequacy Factor

Mechanism

M1 M2 M3

Reference model Including defects Flooded condition

3.15 2.70 1.91

M4

Two rings

2.47

4. Conclusions This paper focuses on the analysis of flooding conditions in literature by analysing a typical masonry arch bridge with features commonly found in the Surrey region. The bridge has been investigated by means of non-destructive and minor destructive in-situ intrusive tests This phase is the diagnosis, which is as important as the assessment of the