# Dynamic Structural Response of a Corrugated Blast Wall Under Hydrogen Blast Loads
## 4 Results
At peak overpressures of 1.6 MPa or greater, fractures were observed regardless of duration. Moreover, a deflection exceeding the recommended deflection limits for blast walls provided by FABIG [69] was observed in the blast load scenario with a peak overpressure of 0.5 MPa. This excessive deflection shows the potential difficulty of sufficiently responding to hydrogen explosion accidents with a corrugated blast wall designed for hydrocarbon fuels. The P-I diagram and the resistance curve, briefly mentioned earlier, are representative tools typically employed for the structural response analysis of blast walls. While these tools have long been utilized as powerful tools in blast wall design, they exhibit the following limitations: First, both the diagram and the curve present only a single structural response (usually the maximum displacement of the blast wall) for a given blast load, making it difficult to assess localized failures. Individually, the P-I diagram presents multiple iso-damage curves; however, drawing these curves requires a substantial number of simulations. Since performing such simulations using the Finite Element Method (FEM) is computationally inefficient, the Single Degree of Freedom (SDOF) method is generally adopted to predict the structural response, which could reduce the validity of the iso-damage curves. Moreover, highly unrealistic blast load scenarios might be included in the diagram to draw the curves. Although the resistance curve provides a more intuitive representation of structural response by presenting displacement under applied loads, it is generally derived for specific loading conditions, such as static loads or nominal blast loads. Consequently, its applicability becomes limited in hydrogen explosions, which could involve highly nonlinear structural responses of blast walls. To overcome these limitations, a new type of diagram was proposed in this study. Figure 12 illustrates the proposed diagram, which integrates the structural responses analyzed in the previous paragraphs. The x-axis presents the ratio between the residual  
Figure 11: Dynamic structural responses depending on nondimensionalized time and peak overpressure: (**a**) maximum and (**b**) residual strain energies of corrugated panel. and maximum strain energies that occurred at the corrugated panel, and the y-axis presents the ratio between the permanent and maximum displacements at the mid-span of the target structure. Each data point represents the dynamic structural response characteristics for a single blast load scenario. This diagram is similar to the resistance curve but has the advantages of including the structural response for diverse blast load scenarios and enabling assessment of the degree of damage in a specific structural member. The analysis based on this diagram is as follows. In the case of load scenarios with peak overpressures of 0.2 MPa or less, plastic deformation mostly occurred at supports, and a linearly proportional trend between the ratios was observed. When the peak overpressure increased to 0.3 MPa, plastic deformation at the corrugated panel began to occur in earnest, and all blast load scenarios for hydrocarbon were exhausted. A trend in which plastic deformations of the panel and supports increased nonlinearly was observed in blast load scenarios with peak overpressures of 0.4 MPa or greater. In this stage of structural response, the blast loads absorbed by the corrugated panel increased significantly. However, when the peak overpressure reached 0.5 MPa, it was observed that the plastic deformations of the panel and supports increased together. Ultimately, this significant increase led to fracture and structural collapse of the target structure. Figure 13a-c present the von Mises stress (left column) and effective plastic strain (right column) distributions at the moment when the blast wall reaches its maximum displacement for locations 2, 6, and 3 in Figure 12, respectively.