Figure 2.6 Progressive collapse separated into two parts. The UAF team used a consistent method for modeling the connections in all floor story modeling and included nonlinear deformation and failure behavior in the connections. The calculated nonlinear connections were defined in our building model by using rotational and axial nonlinear springs. It may be argued that pin connections may be stiffer than a spring and, in some cases, depending on loading with moment transfer, it may be less stiff. In either case, not accounting for how the structure was built when evaluating a possible collapse is not appropriate. 2.1.3.3 Heat Transfer Analysis We also reviewed the principle of heat transfer analysis. Heat transfer occurs between different physical systems at different temperatures. Thermal energy is always transferred from physical systems with high temperature to physical systems with low temperature and can be transferred by three different mechanisms: conduction, convection, and radiation. Thermal conduction happens when different physical systems with different temperatures are in direct contact. Thermal convection is the transfer of thermal energy due to bulk fluid movements. Thermal radiation is the transfer of energy by the emission of electromagnetic radiation, which
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