# Dynamic Structural Response of a Corrugated Blast Wall Under Hydrogen Blast Loads
## 2 Blast Load Characteristics of Hydrogen and Hydrocarbons: A Review

Table 2: _Cont._peak overpressures and very long durations were observed. These blast load characteristics were because experiments in Region I were conducted in long tunnel-type closed ducts, and any unburned gas that did not escape into the atmosphere sufficiently combusted. Region II is characterized by high peak overpressures and relatively long durations. The experiments in Region II were conducted in quasi-confined explosion chambers, and there was more unburned gas than in the experiments in closed ducts because the exhaust was carried out through narrow pipes. Moreover, durations were shorter than in Region I because chamber and measurement conditions were symmetric, unlike the experiments in Region I. Lastly, Region III exhibits load characteristics that are either consistent with the equation proposed by [PERSON] et al. [58] or with much weaker overpressures and shorter durations. Load characteristics consistent with the equation tended to be observed when vent openings existed in explosion chambers. This supports the recommendation that the equation should be used for predicting blast load characteristics in partially confined spaces. In contrast, for explosion experiments conducted under extremely low confinement conditions or for small-scale phenomena, blast loads were characterized by peak overpressures and durations less than 0.1 MPa and 0.1 s, respectively. Figure 1: Time-overpressure curves based on experimental data for (**a**) hydrocarbon and (**b**) hydrogen explosions. Figure 2: Experimental correlations between peak overpressure and positive phase duration for (**a**) hydrocarbon and (**b**) hydrogen explosions [58]. Figure 2b presents the correlation between peak overpressure and duration for hydrogen blast loads and is also divided into three regions by applying the same methodology as for hydrocarbons. Blast load characteristics of hydrogen explosion experiments conducted in quasi-confined chambers or relatively large-scale tunnels are mostly located in Region I, while those of experiments conducted in pipes or chambers with vent openings are predominantly located in Region II. Lastly, load characteristics of experiments conducted under low confinement conditions or for small-scale phenomena are primarily located in Region III. Because gas explosions are highly nonlinear, and the confinement level is not the only factor that determines blast load characteristics, load characteristics of some explosion scenarios might not be consistent with the aforementioned analysis. Nonetheless, it has been empirically confirmed that for both hydrocarbon and hydrogen explosions, as the confinement level increases, more severe blast loads are observed, and blast load characteristics could be classified and analyzed according to explosion conditions. Figure 3 shows the correlations between peak overpressure and rising time-to-duration ratio for hydrocarbon and hydrogen explosions. The closer the x-axis value is to 0 or 1, the closer the blast load shape is to a right triangle, whereas the closer the x-axis value is to 0.5,  
Figure 4: Nondimensionalized time-nondimensionalized overpressure curves based on experimental data for (**a**) hydrocarbon and (**b**) hydrogen explosions. Figure 3: Experimental correlations between peak overpressure and rising time-to-duration ratio for (**a**) hydrocarbon and (**b**) hydrogen explosions. the closer the blast load shape is to an isosceles triangle. For hydrocarbon explosions, an inverse proportional trend between peak overpressure and rising time-to-duration ratio is observed. This indicates that as the peak overpressure of a blast increases, strain rates of a structure exposed to the blast load are also likely to increase because the rise time is shorter. For general steel grades, as the strain rate increases, fracture strain decreases, which could be disadvantageous from the perspective of the accidental limit state. In the case of hydrogen explosions, on the other hand, the correlation is less consistent with a simple inverse proportionality.