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Engineering and Construction
Pages 12 (3012 words)
FIRE DYNAMICS by Student’s name Code+ course name Professor’s name University name City, State Date Detrimental Effects. The greatest effect of subjecting this structure to this heat source over a long period is creep. Creep strain results from the movement of dislocations in the slip plane.
At 250-300 degrees room temperature, creep has little effect on the performance on the steel structure since the amount and distribution of the effects of steel remain uniform hence any deformations occur at a slow pace. As the fire crib is set to temperatures of 0.25/0.5 MegaWatt, recorded by a thermal imaging camera, creep starts to become a dominating factor (Totten, 2007). Deformation starts to occur as the vacancies in the crystal structure diffuse to the location of a dislocation hence the dislocations move faster to an adjacent slip plane. As the temperature of steel increases so does the creep deformations. Depending on its material composition, steel’s melting point stands at 1400 degrees Celsius. Therefore, creep deformations will become noticeable at temperatures corresponding to 30% of its melting point. Creep strain has three phases which include: Primary creep/ Initial phase Steady-state creep/ Secondary creep Tertiary creep At the initial phase, the strain rate is high and increases at a steady rate, that is, it is directly proportional to temperature. On almost entering the secondary creep phase, it decreases gradually. At the steady state creep, the strain rate reaches a minimum and is almost constant. At the tertiary creep phase, the strain rate increases exponentially as temperature increases. ...
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