Steel-reinforced concrete pillars are used in the construction of large buildings. Structural failure can occur at high temperatures due to a fire because of softening of the metal core. Consider a 200-mm-thick composite pillar consisting of a central steel core (50 mm thick) sandwiched between two 75-mm-thick concrete walls. The pillar is at a uniform initial temperature of Ti 27 C and is suddenly exposed to combustion products at T 900 C, h 40 W/m2 K on both exposed surfaces. The surroundings temperature is also 900 C. (a) Using an implicit finite difference method with x 10 mm and t 100 s, determine the temperature of the e