# Numerical Analysis of a Moderate Fire inside a Segment of a Subway Station
## 2 Experimental Results from a Scaled Fire Test
### Results from Structural Monitoring  
The thermocouples and the strain gauges undertook readings every 20 s. Thus, the first 30 min of the fire test were documented by 90 readings of each sensor.  
The temperature close to the inner surface of the top slab, at the midspan of the right cell, rose by approximately 90 \({}^{\circ}\)C during the first 30 min of the fire test; see Figure 8a. The temperature decreased with increasing distance from the heated inner surface (see the four graphs in Figure 8a), which shows the measured evolutions of temperature changes at distances of 2 mm, 30 mm, 68 mm and 106 mm from the heated inner surface. At a depth equal to or greater than 106 mm, the temperature remained practically constant throughout the analyzed part of the fire test. A qualitatively similar, but quantitatively different behavior was measured at the other measurement positions of the top slab, the right wall and the bottom slab; see Figure 8d,e. At the center of the right wall, e.g., the temperature close to the inner surface rose by about 80 \({}^{\circ}\)C, while no temperature increase was measured at depths equal to or greater than 105 mm. The temperature of the right column was measured at its core, at a distance of 80 mm to the nearest heated surface. Notably, the core temperature of the column rose significantly more than that at the same depth in the slabs and the right wall. The measured temperature evolution is, in fact, comparable with that at a depth of some 30 mm in the top slab.  
The strain gauges measured deformations resulting from the mechanical loading (see the values labeled as 0-min readings in Figure 9) and the progressive thermomechanical loading (see the evolution of the total strains after 0 min in Figure 9). For instance, at the outer reinforcement layer of the top slab, the strains resulting from the mechanical loading amounted to approximately \(-50\times 10^{-6}\); see the ordinate of the dash-dotted curve at \(t=0\) min. During the subsequent 30 min of the fire test, the reading increased by approximately \(150\times 10^{-6}\) to approximately \(100\times 10^{-6}\); see the dashed-dotted graph in Figure 9. This underlines that strains resulting from the thermal loading became the dominant part of the total strains soon after the start of the fire test. Notably, strain changes of the inner rebar resulted from both the eigenstrains, caused by the temperature increase, and the structural load redistributions, induced by the thermal loading. The strain changes of the outer rebar, where the temperature remained constant throughout the analyzed part of the fire test, resulted exclusively from redistribution of the structural load.  
Figure 7: Temperature history of the air inside the tested structure.  
Figure 8: Measured evolutions of temperature changes: (**a**) top slab, at the midspan of the right cell, (**b**) top slab, at the midspan of the middle cell, (**c**) top slab, at the midspan of the left cell, (**d**) center of the right wall, (**e**) bottom slab, at the midspan of the middle cell, and (**f**) core of the right column.