Length (ft) At 2. Penthouse At 3 (roof) : DL = 30 psf

Transcription

1 SUBJECT: INTERIOR (underneath penthouse) SHEET 40 of 131 Design Columns for the lightest W10's and W12's section. Columns are to be sized for two options: Option I Continuous, Option II with Splices. Then prices are to be compared to select most economical option. Both explicit calculations or Column Design Tables may be used. COLUMN B-2 LOAD TAKEOFF Dead load (psf) Penthouse Roof = 30 Penthouse Floor = 100 Roof = 30 3 rd Floor = 61 2 nd Floor = 61 Tributary Areas (At): At 1 = At 2 = Width (ft) Live load (psf) 20 KLL= 80 Fy (ksi)= Bold Numbers are 80 Roof Live Loads Length (ft) At 3 = At 1 - At 2 = Plan View At 1 (floors) : At 2 (penthouse floor) : DL = 61 psf DL = 100 psf At 1 At 3 LL = 80 psf LL = 80 psf At 2 Penthouse At 3 (roof) : DL = 30 psf LL = 20 psf Note: Live load reduction can be applied in accordance with ASCE 7-02 section (see ASCE 7-02 Eq. 4-1) L = L o *( /AI^0.5) ASCE 7-02 Eq. 4-1 Use the larger of: L = reduced design live load value in psf L > 0.5*Lo (columns supporting one floor) L o = unreduced live load in psf L > 0.4*Lo (columns supporting two or more floors) A I = influence area A I = Tributary area *KLL if AI > 400 ft^2 live load reduction is allowed AI (1) = >400 ft^2 AI (2) = >400 ft^2 L (2nd floor) = psf > 32 psf, thus use = L (3rd floor) = psf > 32 psf, thus use = L (penthouse floor) = psf > 40 psf, thus use = Note: Roof Live loads are NOT allowed to be Reduced

2 SUBJECT: INTERIOR (underneath penthouse) SHEET 41 of 131 METHOD 1 - EXPLICIT CALCULATIONS METHOD 2 - USE TABLES CONTINUOUS - L =13 FEET Notation: φpn - design compressive strength, Fcr - critical design force λc - width-thickness ratio Ag - gross area of member, in 2 Fy - specified yield strength, ksi E - modulus of elasticity, ksi K - effective length factor l - Laterally unbraced length of member, in r - governing radius of gyration about the axis of buckling, in Begin Load Takeoff from roof and proceed downward: From Ground floor to 2nd floor: Pnth Roof Pnth Floor Roof 3 rd Floor 2 nd Floor dead loads (psf) live loads (psf) P u = [1.2*dead load + 1.6*live load] P u = [1.2*dead load + 1.6* roof live load] Pu (Pnth Roof) = Pu (Pnth Floor) = Pu (Roof) = Pu (3rd Floor) = Pu (2nd Floor) = psf * A2 = psf * A2 = psf * A3 = psf * A1 = psf * A1 = sum = PU = Note: Use column B2 for ALL Interior Columns.

3 SUBJECT: INTERIOR (underneath penthouse) SHEET 42 of 131 From Ground floor to 2nd floor: Note: For small axial loads the smallest section from the column design Tables (Table 4-2 LRFD) may not be the lightest. If this is the case, do explicit calculations and then try a section from the Table 1-25 LRFD. Use W8x24 as the smallest size (do not use W10 s or W12 s with a nominal weight less than 24 lb/ft). If the column tables are used you only need to write down the section selected and its capacity. φpn = 0.85 * Ag * Fcr Fcr = (.658 λc^2 ) * Fy when λc < 1.5 Fcr = (0.877 / λc 2 ) * Fy when λc > 1.5 λc = (K * L/π r) * (Fy / E) 0.5 (Equation E2-1 LRFD p ) (Equation E2-2 LRFD p ) (Equation E2-3 LRFD p ) (Equation E2-4 LRFD p ) Fy = 50 ksi K = Pu = L = ft E = ksi Assume KL/r = 60 to start λc = Fcr = ksi Ag = in 2 LRFD p.4-25 Check W 12: LRFD p.4-26 Check W 10:

4 SUBJECT: INTERIOR (underneath penthouse) SHEET 43 of 131 METHOD 1 - EXPLICIT CALCULATIONS METHOD 2 - USE TABLES CONTINUOUS - L =13 FEET Notation: φpn - design compressive strength, Fcr - critical design force λc - width-thickness ratio Ag - gross area of member, in 2 Fy - specified yield strength, ksi E - modulus of elasticity, ksi K - effective length factor l - Laterally unbraced length of member, in r - governing radius of gyration about the axis of buckling, in From Ground 2nd floor to 3rd floor: dead loads (psf) live loads (psf) Pnth Roof Pnth Floor Roof 3 rd Floor 2 nd Floor - - P u = [1.2*dead load + 1.6*live load] P u = [1.2*dead load + 1.6* roof live load] Pu (Pnth Roof) = Pu (Pnth Floor) = Pu (Roof) = Pu (3rd Floor) = psf * A2 = psf * A2 = psf * A3 = psf * A1 = sum = PU =

5 SUBJECT: INTERIOR (underneath penthouse) SHEET 44 of 131 From Ground 2nd floor to 3rd floor: Note: For small axial loads the smallest section from the column design Tables (Table 4-2 LRFD) may not be the lightest. If this is the case, do explicit calculations and then try a section from the Table 1-25 LRFD. Use W8x24 as the smallest size (do not use W10 s or W12 s with a nominal weight less than 24 lb/ft). If the column tables are used you only need to write down the section selected and its capacity. φpn = 0.85 * Ag * Fcr Fcr = (.658 λc^2 ) * Fy when λc < 1.5 Fcr = (0.877 / λc 2 ) * Fy when λc > 1.5 λc = (K * L/π r) * (Fy / E) 0.5 (Equation E2-1 LRFD p ) (Equation E2-2 LRFD p ) (Equation E2-3 LRFD p ) (Equation E2-4 LRFD p ) Fy = 50 ksi K = Pu = L = ft E = ksi Assume KL/r = 60 to start λc = Fcr = ksi Ag = in 2 LRFD p.4-25 Check W 12: LRFD p.4-26 Check W 10:

6 SUBJECT: INTERIOR (underneath penthouse) SHEET 45 of 131 METHOD 1 - EXPLICIT CALCULATIONS METHOD 2 - USE TABLES CONTINUOUS - L =13 FEET Notation: φpn - design compressive strength, Fcr - critical design force λc - width-thickness ratio Ag - gross area of member, in 2 Fy - specified yield strength, ksi E - modulus of elasticity, ksi K - effective length factor l - Laterally unbraced length of member, in r - governing radius of gyration about the axis of buckling, in From 3rd floor to roof level: dead loads (psf) live loads (psf) Pnth Roof Pnth Floor Roof 3 rd Floor nd Floor - - P u = [1.2*dead load + 1.6*live load] P u = [1.2*dead load + 1.6* roof live load] Pu (Pnth Roof) = Pu (Pnth Floor) = Pu (Roof) = psf * A2 = psf * A2 = psf * A3 = sum = PU =

7 SUBJECT: INTERIOR (underneath penthouse) SHEET 46 of 131 From 3rd floor to roof level: Note: For small axial loads the smallest section from the column design Tables (Table 4-2 LRFD) may not be the lightest. If this is the case, do explicit calculations and then try a section from the Table 1-25 LRFD. Use W8x24 as the smallest size (do not use W10 s or W12 s with a nominal weight less than 24 lb/ft). If the column tables are used you only need to write down the section selected and its capacity. φpn = 0.85 * Ag * Fcr Fcr = (.658 λc^2 ) * Fy when λc < 1.5 Fcr = (0.877 / λc 2 ) * Fy when λc > 1.5 λc = (K * L/π r) * (Fy / E) 0.5 (Equation E2-1 LRFD p ) (Equation E2-2 LRFD p ) (Equation E2-3 LRFD p ) (Equation E2-4 LRFD p ) Fy = 50 ksi K = Pu = L = ft E = ksi Assume KL/r = 60 to start λc = Fcr = ksi Ag = in 2 LRFD p.4-25 Check W 12: LRFD p.4-26 Check W 10:

8 SUBJECT: INTERIOR (underneath penthouse) SHEET 47 of 131 From roof level to penthouse: dead loads (psf) live loads (psf) Pnth Roof Pnth Floor - - Roof rd Floor nd Floor - - P u = [1.2*dead load + 1.6*live load] P u = [1.2*dead load + 1.6* roof live load] Pu (Pnth Roof) = psf * A2 = sum = PU =

9 SUBJECT: INTERIOR (underneath penthouse) SHEET 48 of 131 From roof level to penthouse: Note: For small axial loads the smallest section from the column design Tables (Table 4-2 LRFD) may not be the lightest. If this is the case, do explicit calculations and then try a section from the Table 1-25 LRFD. Use W8x24 as the smallest size (do not use W10 s or W12 s with a nominal weight less than 24 lb/ft). If the column tables are used you only need to write down the section selected and its capacity. φpn = 0.85 * Ag * Fcr Fcr = (.658 λc^2 ) * Fy when λc < 1.5 Fcr = (0.877 / λc 2 ) * Fy when λc > 1.5 λc = (K * L/π r) * (Fy / E) 0.5 (Equation E2-1 LRFD p ) (Equation E2-2 LRFD p ) (Equation E2-3 LRFD p ) (Equation E2-4 LRFD p ) Fy = 50 ksi K = Pu = L = ft E = ksi Assume KL/r = 60 to start λc = Fcr = ksi Ag = in 2 LRFD p.4-25 Check W 12: LRFD p.4-26 Check W 10: Lab Note: When beams and girders are framed to columns with simple shear connections, the columns are usually designed as concentrically loaded members.

10 SUBJECT: INTERIOR (underneath penthouse) SHEET 49 of 131 SPLICED vs CONTINOUS Steel Prices per ton = $1,600 Wt of additional splice (lb) b = 500 W10's Continous: Member Length (ft) Weight (tons) Cost W10x49 Total cost = All columns spliced: Member Length (ft) Weight (tons) Cost W10x49 W10x39 W10x30 W8x24 splice = Total cost = TOTAL COST = Answer: b -- indicates general value according to Modern Steel Construction. April 2000.

11 SUBJECT: INTERIOR (underneath penthouse) SHEET 50 of 131 SPLICED vs CONTINOUS W12's Continous: Member Length (ft) Weight (tons) Cost W12x53 Total cost = Steel Prices per ton = $1,600 Wt of additional splice (lb) b = 500 All columns spliced: Member Length (ft) Weight (tons) Cost W12x53 W12x40 W12x26 W8x24 splice = Total cost = TOTAL COST = Answer: Use : Total cost = b - indicates general value according to Modern Steel Construction, April 2000