PSI - Issue 27

Aditya Rio Prabowo et al. / Procedia Structural Integrity 27 (2020) 77–84 Prabowo et al / Structural Integrity Procedia 00 (2019) 000 – 000

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the arrangement of the pipe network, in which the maximum overpressure of the gas with 9.5% concentration is far higher than 8% and 11% in a parallel branch (O-A-B-D-E) in the pipe network (Fig. 4). Besides the gas state, material and structural performances under natural gas explosion accidents are assessed. Geopolymer concrete slab (Fig. 5) is taken as the test subject in which parallel cracks were observed on the surface that facing the explosion source. Results of the static test indicate that low flexural rigidity causes a more significant deflection.

(a) (b) Fig. 4. Explosion pressure accounting for pipeline arrangements: (a) parallel branch; and (b) transverse branch (Niu et al., 2019),

Fig. 5. Concrete specimen after tunnel explosion experiment (Meng et al., 2020).

4.2. Marine shipping facility The role of ship/marine vessel as transportation does not make the subject is an exception from explosion risk. Threats coming from terrorist attack, or TNT weapon during war state insist the structural performance against explosion load be investigated. Assessment of the scaled model of ship hull (Table 2) indicates that rubber sandwich coatings in Model II reduce peak pressure of explosion compared to the Model I, which is without the coating. Damage characteristic due to shockwave of the explosion is studied by experimental design, as presented in Fig. 6. It is found that the strain gauges 1- 3# are damaged right after the detonation within the time approximately t ≈ 10−5s. This phenomenon proves that the damage of the plate is caused by both detonation waves and shockwaves. The strains at the gauges 4-6# are slightly disturbed within this time period. A more detailed structural assessment subjected to explosion load is conducted by considering fracture analysis and constitutive modeling of steel behaviors. Laboratory experiments, i.e., compressive and tensile tests, are also performed to deal with the observation of the evolution of the material microstructure starting from deformation until fracture. Results of the main explosion experiment suggest that at a crack tip inside the damaged plate, in a plane normal to the thickness (Fig. 7a), observers are capable of distinguishing a macro-crack followed by a meso-crack (Figs. 7b-c). The crack can be represented by an elongated ellipse, followed by lines, which as an enlarging crack, it is observed as tortuous paths (see Fig. 7d). Table 2. Test results of coating effect on ship structure response against underwater explosion (Chen et al., 2009). Event no. Charge size (g) Charge stand-off (m) Test model Peak pressure (MPa) The first bubble pulse period (ms) Period of the firs structure mode (ms)

1 2 3 4 5 6 7

500 500 500 500 500 500 500

6 5 4 6 6 5 4

Model II Model II Model II Model I Model I Model I Model I

11.6 10.6 8.7 11.6 11.7

158.1 165.4 173.8 N/A 165.4 173.8 158

190.5 190.5 190.5 170.9 170.9 170.9 170.9

10 8.9