PSI - Issue 82

Addisu Bonger et al. / Procedia Structural Integrity 82 (2026) 30–36 Addisu et al. / Structural Integrity Procedia 00 (2026) 000–000

33

4

Table 2. Material properties.

Concrete

Stemming

Young's modulus

GPa MPa MPa

34.2

0.08

Compressive strength

31

1

Tensile strength

2.6

0.1

Kg/m 3

Density

2300 10 -7 0.02

1800

10 -1

Permeability

(˗) (˗) (˗)

Porosity

0.4 2.0

Tension softening factor ( c parameter)

1.0

2.3. Simulation model Finite element model was discretized using hexahedral finite elements (1.4 cm mesh size) as shown in Fig. 2. The properties of nitromethane were defined by the time of initiation of deflagration t start and t peak when pressure reaches its maximum p peak and by the density ρ as shown in Table 1. Material properties were assigned to each element representing concrete and stemming as lined up in Table 2. The tension softening model for plain concrete is taken into account by c parameter (Maekawa et al., 2003) that is determined from fracture energy of concrete and the reference length of the finite element. Steel rebars, stud dowels and steel girders were defined by Young's modulus E = 210 GPa and yield strength f yt = 400 MPa. The upper steel plate (flange) of the girder is perfectly bonded to the concrete slab. 3. Simulation results Simulation results are evaluated based on crack propagation, gas pressure effects, and stress in the stud dowels and The final crack patterns immediately after the application of EDIC in the experimentally and computationally obtained are compared in Fig. 3a and Fig. 3b. Conical cup-shaped fractures connecting the cartridges and the heads of the stud dowels are formed. The development of principal strain trajectory nearly coincides with those of cup shaped fractures in the experiment (indicated by pink lines in Fig. 3(a)). In fact, the concrete located above the stud dowel heads can be removed as a single unit at construction site. The remaining concrete sections can then be easily removed manually. Following the nitromethane explosion, high pore pressure rapidly builds around the cartridge (Fig. 3c), with gas inflation initially confined. Cracking soon initiates, enabling gas to migrate through the cracked fracture planes. Driven by the pressure gradient, gas moves outward, inducing 3D ring-tension stresses that may further promote cracking. As gas permeates both concrete pores and cracks, it reaches crack fronts, increasing local pressure and aiding propagation. Once surface cracks form, the gas escapes into the atmosphere, assumed to be at ambient pressure in simulations. Gas primarily travels through micro-pores and cracks, as it cannot penetrate solid elements such as steel rebars and stud dowels. Consequently, the build-up of gas pressure may lead to deformation of the reinforcing bars and displacement of the surrounding concrete, promoting concrete crushing and crack propagation, as illustrated in Fig. 3d. A deformation of 6 mm in z-direction was recorded in the top reinforcing bar located at the center of the specimen, as illustrated in the graph in Fig. 3d. To assess the feasibility of reusing the steel girder and stud dowels, strain was evaluated at locations with maximum deformation from the simulation. As shown in Fig. 3e, the strain remained below the yield threshold, indicating no yielding occurred. This was further confirmed by experimental results (Wada et al., 2021), supporting the potential for reuse. girder, and are validated experimentally. 3.1. Simulation results for specimen A