How does fire affect structural analysis and design?

Fire analysis considers: (1) Temperature distribution through members using heat transfer analysis or parametric fire curves, (2) Material property degradation - steel loses 50% strength at 550C, concrete cover spalls, (3) Thermal expansion causing additional stresses and buckling, (4) Restrained members develop high compression then tension during cooling. Analysis methods range from prescriptive (fire ratings) to performance-based using zone models or CFD for fire, then coupled thermal-structural FEA. Design includes fire protection, member sizing for fire resistance, and alternate load paths.