id	author	title	date	pages	extension	mime	words	sentence	flesch	summary	cache	txt
ap-642	Wald, F.; Studecká, P.; Kroupa, L.	Temperature of Steel Columns under Natural Fire	2004	9	.pdf	application/pdf	4821	169	61	The accurate and simple step-by-step calculation proce- dure is based on the principle that the heat entering the steel over the exposed surface area in a small time step � t (taken as 30 seconds maximum) is equal to the heat required to raise the temperature of the steel by �a,t (at time t) assuming that the steel section is a lumped mass at uniform temperature, so that � , ,�� �q F t c Va a t a t� �� � , (1) where �a is the unit mass of steel, ca,t is the temperature de- pendent specific heat of steel, V is the volume of the member per unit length, and ���q is the heat transfer at the surface, given by � ( ) ( ), , , ,�� � � � �q hc g t a t g t a t� � � �� � � � � �4 4 , (2) where hc is the convective heat transfer coefficient, � is the Stefan-Bolzman constant (56.7 10�12 kW m�2 K�4), � is the resultant emissivity, and �� g t, is the increase of the ambient gas temperature during the time interval � t. Eqs (1) and (3) may be rearranged to give � �� � � � � �� � � � �� � �a t m a a c g t a t g t a t A V c h t, , , , ,( ) ( )� � � �4 4 , (3) where Am/V is the section factor for unprotected steel mem- bers, Am is the surface area of the member per unit length. i, ,� �2 , where Ai is the cross-section area of the insulating material and A is the cross-section area of the steel.	cache/ap-642.pdf	txt/ap-642.txt