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PLASTIC SECTIONAL MODULUS . Shape Property, Independent of material Higher indicates more bending strength. PNA. PNA. PNA. TOTAL. PNA (Plastic Neutral Axis). TOTAL. PNA (Plastic Neutral Axis). FULLY LOADED. FORCE X LEVERARM. For rectangular sections=. FORCE X LEVERARM.

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## PLASTIC SECTIONAL MODULUS

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**PLASTIC SECTIONAL MODULUS**• Shape Property, Independent of material • Higher indicates more bending strength PNA**TOTAL**PNA (Plastic Neutral Axis)**TOTAL**PNA (Plastic Neutral Axis)**FULLY LOADED**FORCE X LEVERARM For rectangular sections=**LATERAL SUPPORT OF STEEL BEAMS**47 kip-ft CASE II CASE III CASE I W10X12 28.5 kip-ft CASE II CASE III CASE I**W10X12**BRACING DISTANCE CASE I if lateral brace is spaced 0-2.75’ CASE II if lateral brace is spaced 2.75’-8’ CASE III if lateral brace is spaced more than 8’ CASE I BRACES W10X12 Design Moment Strength = = 47 kip-ft**CASE II**LATERAL BRACES W10X12 Design Moment Strength reduces as increases kip-ft AT AT kip-ft Linear variation in &**CASE III**Should be avoided for load bearing floor beams. Design Moment Strength reduces as increases kip-ft AT AT kip-ft**CASE I CONSTRUCTION DETAILS**x CONCRETE STEEL STUDS W-SHAPE X-X x Most Common Current Practice Using Metal Deck and Shear Studs. Steel and Concrete Deck can be designed as Composite or Non-Composite**Use 50 ksi and select a shape for a typical floor beam**AB. Assume that the floor slab provides continuous lateral support. The maximum permissible live load deflection is L/180. The service dead loads consist of a 5-inch-thick reinforced-concrete floor slab (normal weight concrete), a partition load of 20 psf, and 10 psf to account for a suspended ceiling and mechanical equipment. The service live load is 60 psf.**Fy = 50ksi**• Case 1 GIRDER not to exceed • DEAD LOADS • 1) 5” Slab • 2) Partition = 20psf • 3) Ceiling, HVAC = 10psf • LIVE LOAD = 60psf GIRDER (PRIMARY BEAMS) Figure 1**DESIGN LOAD (kips/ft) on AB = wux TRIBUTORY AREA**LENGTH OF BEAM x = 1.242 kips/ft 12” of Slab = 150 psf 6” of Slab = 75 psf 1” of Slab = 12.5 psf 5” of Slab = 62.5 psf (12.5 psf for every inch of concrete thickness) *5 x 12.5 = 62.5**wu = 1.242 kips/ft**Mu = = = 139.7 ft-kips CASE 1**Page # 3-127**STRENGTH OF W14 X 26 = 150.7 ft-kips STRENGTH OF W16 X 26 = 165.7 ft-kips 139.7**Page # 1-21**SELECT W16X26**EXTRA SELF WEIGHT MOMENT =**= 3.3 ft-kips MOMENT STRENGTH APPLIED MOMENT 165.7 139.7 + 3.3 W16X26 is OK = 2” = = = Page # 3-211**= 360 lb/ft**w = = 0.360 kips/ft kips/in = 0.03 kips/in = = 0.75” 2” OK = in = ; =**Note that duct holes have to be strengthened by plates.**Also, holes are at third point where shear & moment are not maximum. Typical Copes for a shear connection of a large girder to column web.**Cantilever construction for projected balcony.**If shear studs are noticed on beams and column then those members have to be encased in concrete for increasing fire resistance of steel.

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