Fire Resistance of RC columns ACI (216.1) Method – FPS Units Fire resistance provisions for RC columns exposed to fire on four faces as per ACI 216.1 Aggregate Type Minimum column dimension for fire resistance, in. 1h 1 ½ h 2h 3 h 4h Carbonate 8 9 10 11 12 Siliceous 14 Semi-lightweight 8 ½ 10 ½ Fire resistance rating is equal to an hour for every inch of concrete cover

Fire Resistance of RC columns Eurocode (EC2) Method – SI Units Franssen and Dotreppe (1997) where: for n = 4 (corner bars only) for n > 4

Fire Resistance of RC columns Eurocode (EC2) Method Contd. – SI Units = the ratio of the applied load to the load carrying capacity of the column at room temperature = the longitudinal reinforcement ratio at room temperature conditions where: = the area of steel, = the yield strength of reinforcing steel, = the characteristic strength of concrete. = the area of concrete = coefficient for compressive strength as per EN 1992-1-1

Fire Resistance of RC columns Eurocode (EC2) Method Contd. – SI Units = the axis distance to the longitudinal steel bars (mm); 25 mm 80 mm = the effective length of the column under fire conditions; 2 m 6 m Values corresponding to = 2 m give conservative estimates for columns with < 2 m 200 mm 450 mm where: h = longer dimension of the column b = shorter dimension of the column

Fire Resistance of RC columns Australian Code (AS 3600) Method – SI Units where: FRP = fire resistance in minutes k = a coefficient dependent on steel ratio = 1.5 when < 0.025 = 1.7otherwise where: = the area of reinforcing steel, = the gross area of cross section f′c = the characteristic compressive strength of concrete (MPa) Dc = the smaller column dimension of a rectangular column (mm) Dg = the greater column dimension of a rectangular (mm) N* = the design axial force for the fire limit state (KN) Le = the effective length of the column (mm)

Fire Resistance of RC columns Kodur VKR and Raut NK Proposed Method – SI Units where: R = fire resistance in minutes SR = slenderness ratio of the column LR = load ratio of the column Ct = a constant based on aggregate type used in concrete Ct = 1.0 for siliceous aggregate Ct = 1.1 for carbonate aggregate k = a constant based on the cover thickness and the percentage steel where: Ce = effective concrete cover thickness (mm) Sp = percentage of steel in column,

Example 1 305 mm (12 in.) 4  25 mm (#8 bars)  10 mm (#3 bars) stirrups 48 mm (2 in.) Figure shows the elevation and cross sectional details of an RC column, tested by Lie and Woolerton7, considered for analysis. The column, fabricated with siliceous aggregate concrete, had an applied load of 1178 KN (265 Kips). The column is made of concrete of strength 31 Mpa (4.5 Ksi) and the reinforcing steel is of 444 Mpa (65 Ksi) The measured fire resistance of the column, in the test is 183 minutes. Calculate the fire resistance of the column using the provisions of different codes of practice discussed earlier and also using the proposed equation by Kodur and Raut. (b) Cross Section P = 1178 KN (265 Kips) 3810 mm (12.5 ft.) P (a) Elevation

Example 1 ACI (216.1) Method The fire resistance of the column using the ACI provisions presented in Table for a 305 mm(12 in.) column made of siliceous aggregate concrete is 3 hours i.e. 180 min. Using the provisions based on concrete cover to the main reinforcement, the fire resistance for a 48mm (2 in.) cover is found to be 120min

Example 1 Eurocode (EC2) Method mm (12 in.) m (12.5 ft.) mm (2 in.)

Example 1 Eurocode (EC2) Method Contd.

Example 1 Australian Code (AS 3600) Method mm mm Kn mm

Example 1 Kodur VKR and Raut NK Proposed Method mm (2 in.) Radius of gyration = mm (3.5 in.)

Example 1 Kodur VKR and Raut NK Proposed Method Load carrying capacity = (720 Kips) Load Ratio = Here Ct =1.0 as siliceous aggregate is used

Example 1 Fire Resistance (min) Measured (test) Proposed Equation ACI Eurocode Australian Code Column III14 183 162 120 161 234