## 1 Introduction  
Accidental explosions or terrorist attacks can have a devastating impact on structures. The blast resistance of structures can be tested and verified through experiments [1, 2, 3], which can help mitigate the damage caused by explosions. Blast pressure is influenced by the mass of the explosive and the distance from the explosion, and it can be predicted using the scaled distance. Additionally, blast pressure reaches its peak in the initial phase and then rapidly decreases within a short duration [4]. However, explosion tests conducted in open spaces often exhibit high variability in shock characteristics, making it challenging to achieve the required shock load within a limited number of tests. [PERSON] et al. [5] analyzed the Coefficients of Variation (COV) of various blast characteristics based on 325 explosion data, finding that the peak reflected pressure had a COV of 0.30, and the reflected impulse had a COV of 0.25. [PERSON] et al. [6] reported that COVs of the peak reflected pressure and the peak incident pressure were 0.23 and 0.28, respectively. In general, detonation tests exhibit a COV range of 0.23 to 0.30 in blast characteristics, which can pose reproducibility issues. To address these reproducibility issues, shock tube tests can be applied [7]. A shock tube consists of a driver section, which generates the initial pressure, and a driven section, where the shock propagates. Since the driver section is subjected to higher pressure than the driven section, it is often thicker. This thickness is one of the factors that determine the pressure generation capacity of the shock tube. If the target is larger than the diameter of the driven section, an expansion section may be used at the end of the driven section to expand the shock wave application area. Shock tube tests can be classified into three types based on how the shock is generated: releasing compressed gas [8; 9; 10; 11; 12; 13; 14; 15; 16; 17], detonating combustible gas [18; 19; 20], and detonating explosives [7; 21; 22]. The driver and driven sections were connected by a 200 mm nozzle, with a diaphragm located in front of the nozzle attached to the driver section. The diaphragm was made of 1.6 mm thick aluminum. The driven section had a length of 3300 mm and an internal diameter of 45 mm, and the generated peak reflected pressure ranged from 0.5 to 1.5 MPa. In shock tubes using gas explosions, the driver section contained combustible gas. A specific amount of combustible gas can be accumulated and then ignited to create an explosion. In the Virginia Tech Shock Tube Research Facility [18; 19; 20], the shock tube generates shock waves in the driver section using up to 40 cubic feet of oxy-acetylene gas. A plastic membrane was used. For tests requiring a gas volume of less than 3.75 cubic feet, plastic bags can be used without a membrane. The driver section gradually increased in cross-sectional area, eventually reaching a cross-section of 2143 \(\times\) 2440 mm. The maximum reflected pressure recorded was 0.2 MPa, and the maximum reflected impulse was 2 MPa\(\cdot\)ms [20]. [PERSON] et al. [21] conducted experiments using a shock tube with an internal diameter of 100 mm, a wall thickness of 10 mm, and a total length of 800 mm, without distinguishing between the driver and driven sections. The experiments used 10 g, 20 g, 30 g, and 50 g of C4 explosives, with peak reflected pressure and reflected impulse measurements taken only for 10 g and 20 g to avoid damage to the pressure sensors. The peak reflected pressure and reflected impulse were recorded as 15.3 MPa and 2.1 MPa\(\cdot\)ms for 10 g, and 32.3 MPa and 3.8 MPa\(\cdot\)ms for 20 g. [PERSON] et al. [7] used a shock tube with an internal diameter of 168.2 mm and a length of 1200 mm. C4 explosives weighing 5, 10, 15, 20, 30, and 40 g were used. At 20 g, the peak reflected pressure was recorded as 13 MPa, while data for 30 g and 40 g were not provided due to sensor saturation. The COV values for the shock tube used were reported to be between 0.1 and 0.15. [PERSON] et al.