PSI - Issue 60

Dhanesh N. et al. / Procedia Structural Integrity 60 (2024) 456–470 Dhanesh et al. / StructuralIntegrity Procedia 00 (2019) 000 – 000

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Fig. 9. Critical position of vehicles from the dent location.

3.4.4. Boundary Conditions The model is curtailed at the bridge crossing, hence the lateral displacements (U 1 and U 2 ) at this face are restrained. As the depth of the model is sufficient to capture the global behavior, all three displacements (U 1 , U 2, and U 3 ) at the bottom surface are restrained. On the other side faces, symmetry boundary conditions are applied. 4. Generation of Base State for Integrity Assessment 4.1. Replication of Dent Permanent plastic strain is induced in the pipeline due to local denting. To simulate this, an artificial indenter of the shape of the dented profile is generated in the form of a deformation profile based on the Caliper data, and the same is applied to the respective section of the pipeline. Finite element analysis with geometric as well as material nonlinearity was carried out. After the entire indentation is applied, the deformation indenter is withdrawn. By this procedure, the dented profile in the pipeline model can be generated with residual strain and locked-in stresses. To account for the elastic rebound, the indentation is amplified so that the desired dent profile is achieved. Fig.10 shows the comparison of the measured dented profile (spline interpolated) and the residual dent in the FE model.

Fig. 10. Comparison of the dented profile (measured) and the residual dent (FE model).

4.2. Assessment of Dented Pipeline under Gravity Loads

At this stage stresses in the dented pipeline under gravity load are generated. This is achieved by carrying out Step-3 to Step 8 given in Section 3 sequentially. The geostatic state of vertical stress obtained from Step-3 is shown in Fig. 11.