Grain elevators (which that building is) can undergo fairly extreme loading so they are constructed from thick, steel-reinforced concrete. Depending on the deta

Grain elevators (which that building is) can undergo fairly extreme loading so they are constructed from thick, steel-reinforced concrete. Depending on the details, the walls can be a substantial fraction of a meter in thickness. Additionally, there was tens of meters of standoff distance between the explosive and the grain elevators, which significantly reduces the peak stress it needs to endure. Due to the height of the grain column, they are designed to withstand enormous pressures induced by having extremely tall columns of grain concurrent with undergoing lateral stresses from typhoon/tornado velocity winds. While they are not designed to be resistant to the shock wave characteristic of large detonations per se, being built with so much reinforced concrete lends some of that property naturally.