Loads 40 LL 10 DL 1-Lumber type 2-Lumber grade 3-Spacing 4-Span Solution: DF 16” OC will span 14’-11” See Text Problem #1: Span = 11’-8” Hem-Fir 1st Step-find E: E = 1.6 Joist Sizing & Spacing 1 2nd Step-Use E and find size to fit span 2 * 3rd Step-find Fb value (2x8): Fb = 1,380 Value is under 1,380 so it works! 4th Step-determine if Fb works with E Solution = (E controls failure-all fits) 4ġ9 Joist Sizing & Spacing See Text Problem #2: Span = 14’-9” Douglas Firġst Step-find E: E = 1.6 1 2nd Step-Use E and find sizes to fit span 3rd Step-find Fb value (2x10): Fb = 1,045 2 4th Step-determine if Fb works with E Value is over 1045 it 4 doesn’t work! 5th Step-using Fb find working column Solution: 16 OC(Fb is tendency to failure) 4 5 Modulus of Elasticity of a 2x10 Hemlock-Fir for grade No.1/No.2 Hem-Fir Fb Eġ8 Joist Sizing & Spacing Problem #1: Span = 11’-8” Hem-Fir Modulus of Elasticity of a 2x8 Douglas fir-Larch for grade No.1/No.2 (see text) E Fb DOUGLAS FIR-LARCHġ7 Hem-Fir Fb E Required: Find the Fiber Stress in Bending and the 3 (Worst)ġ6 E Fb Required: Find the Fiber Stress in Bending and the Wood Type Available in Area Douglas Fir-Larch (North) Hemlock-Fir (North) Spruce-Pine-Fir (North) Southern Pine Wood Quality or Grade Value Select Structural (Best) No. Normal Duration for fiber stress (Fb) Typical consideration for floor loads Modulus of Elasticity (E) See Text Fb = fiber stress in bending E = Modulus of Elasticity (Stiffness)ġ5 Construction Lumber Considerations - Wood Type & Quality Deflection Allowances (Stiffness) Floor = 1/360 Roof = 1/240ġ4 Table Values Look up values for lumber type & grade See Text Loading reactions of wood members For every action there is an equal and opposite reaction, creates a “state of rest” Two types of actions or stresses Fiber Bending Stress (Fb)-a bending stress Modulus of Elasticity (E)-stiffness of structure considered as the deflection or amount of sag when structural members are given a load. Wind loads Shear wall design used to resist wind pressure Uplift forces placed upon the roof Earthquake loads Seismic loads causing lateral forces on entire structureġ0 Typical Loads for Residential ConstructionĬode based, acceptance varies Spacing Options 12” OC 16” OC 19.2” OC 24” OC Common SpacingĬonsidering 12” OC joist spacing Considering 16” OC joist spacing Considering 19.2” OC joist spacing Considering 24” OC joist spacing 12” 15’-0” SPAN 1’ X 15’ = 15 SQFT X 50 = 750# 16” 12’-0” SPAN 1.33’ X 12’ = SQFT X 50 = 798# 19.2” 18’-0” SPAN 1.6’ X 18’ = 28.8 SQFT X 50 = 1440# 24” 10’-0” SPAN 2’ X 10’ = 20 SQFT X 50 = 1000# Codes differ, common residential LL = 40#/sq ftĩ Dynamic Loads Definition: loads imposed on the structure by outside natural forces, such as wind and earthquake. Building codes specify the amount of live load upon type of use or occupancy. These loads include: people, furniture, and exterior weather related items such as, ice, snow, rain, etc.
Building codes specify a minimum of 10#/sq ft for floors and ceilings, DL = 10#/sqftĨ Live Loads Definition: (LL) loads that are fluctuating and changing through the use of the building. Materials that make up the walls, such as, studs, plywood, insulation, sheet rock, nails, glue, etc. Load Types Dead loads Live loads Dynamic loadsħ Dead Loads Definition: (DL) loads that make up the actual weight of the structure, such as walls, floors, roofs and any permanently fixed loads such as furnace, air conditioner or other service equipment. 2 Floor System Types - Conventional Dimensional Lumber Framingģ Floor System Types - Open Web Floor JoistĤ Floor System Types - Truss Joist Floor Framingĥ Floor System Types - Post and Beam Floor Framing
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