Beam Design

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Discussion Topics--Beam Types 1--Solid timber beam 2--Built-up dimensional lumber beam 3--Glued Laminated beam 4--Parallel strand lumber beam (PSL) 5--Laminated veneer lumber beam (LVL) 6--Truss I-Joist beam 7--Box or Plywood beam 8--Flitch beam (wood and steel) 9--Steel beams

Beam Type—Solid Lumber Beam

Beam Type—Built-up Dimensional Lumber Beam Dimensional lumber (2x6, 2x8, 2x10, 2x12) nailed, screwed, and/or glued together Vertical placement— Large size placed vertical

Example: Beam and Joist Attached with joist hangers Joist are attached to beams with metal joist hangers What type of beam is shown?

Beam Type—Glued Laminated Dimensional lumber placed horizontally and glued together

Beam Type—Parallel Strand (Parallam) Lumber Beam

Beam Type—Laminated Veneer Lumber Beam Laminated Veneer Lumber (LVL) Made of ultrasonically graded douglas fir veneers with exterior adhesives under heat and pressure 1 3/4” wide x (5 1/2 to 18”) depth

Beam Type—Truss I-Joist Beam Laminated or Solid wood (top and bottom chords) OSB or Plywood web

Beam Type—Box or Plywood Beam 2x @ 12” or 16” structure with plywood skin Designed by architect or engineer

Beam Type—Flitch Beam A sandwich of wood and steel An architect/engineer designed beam

Beam Type—Steel Beams S shape (American Standard shape) Often called an I-beam W & M shapes Wide flange design C shape Channel shape S-- I Shape W or M Shape C- Channel

Beam Type—Steel Beams Drawing Callouts: Shape, Nominal height x Weight/foot Example: W10x25 WEIGHT PER FOOT OF BEAM NOMINAL HEIGHT SHAPE

Reaction Reaction is the portion of the load that is transferred to the bearing points of the beam A simple beam reaction to a load would be at the end supports. Each end would support or be required to carry half the total load

Calculating the Reactions of a Beam Total load on beam should equal reaction loads: 25 x 900 = 22500# R1 = 15/2 x 900# = 6750# R2 = 10/2 x 900# = 4500# R3 = (15/2 + 10/2) x 900 =11250# Reaction formula R = wl 2 W = uniform load l = length of span R2 R3 R1 W = 900 #/ linear foot Span = 15’-0” Span = 10’-0”

Simple Beam Design Simple beam has a uniform load evenly distributed over the entire length of the beam and is supported at each end. Uniform load = equal weight applied to each foot of beam.

Simple Beam Design Terminology Conditions of Design Joist/Rafter Beam/Girder Post/Column Span Tributary area Conditions of Design Uniform load over length of beam Beam supported at each end Beam span 15’-0” Tributary area of beam

Simple Beam Design Tributary area Total Load on Beam 16’ x 15’ = 240 sq ft Total Load on Beam 240 x 50#/sq ft = 12,000# Load at each supporting end 12,000/2 = 6000# Tributary area of beam 15’-0” Beam span

Table Design Considerations Total lbs of load and span Lbs of load per (lineal) foot Deflection Allowances (Stiffness) Floor = 1/360: Meaning an allowance of 1” deflection for every 360” span, structure is solid with little deflection Roof = 1/240: Meaning an allowance of 1” deflection for every 240” span, structure springs or deflects more than floors

Determine the size of a Solid Wood Beam using Span Table 1)Determine the tributary area and calculate the total load (W) for the beam, LL = 50#, DL = 13#, therefore TL = 63# 10 x 12 x 63 = 7560 TLD Select beam size from table 12’-0” 10’-0” BEAM 20’-0”

Solution = 4 x 14 Beam 7560 TLD w/ span of 12’ Roof Design Area 1/240 Floor Design Area 1/360 Solution = 4 x 14 Beam

Crawl Space Floor Joist, Beam/Post

Reading the Steel Table Table values of load are given in kips 1 kip = 1000 lbs Shape and nominal size across the top Weight per foot is given below designation Span is located along the left side of table

Example of Using Steel Table 30’-0” 18’-0” BEAM Calculate load: 18 x 30 x 60 = 32400 TLD = 32.4 KIPS Selected Beam S18 x 54.7

Glued-Laminated Beam Table Design Data: Span 18’, Load per linear feet = 674#

Columns and Post

Reading Column Tables Determine the column load Establish the height of column Set the column size by height and load

Steel Column Table Conditions: Height = 4.5’, Load = 19.4 kips Solution: 2 ½ Dia x 5.79 PIPE COLUMN

Wood Post Table Conditions: Height = 4 feet, Load = 23,000 Solution: 4x6 WOOD POST

Load Considerations First floor loads (DL + LL) = 50#/sq ft First floor partitions (DL) = 10#/sq ft Second floor loads (DL + LL) = 50#/sq ft Second floor partitions (DL) = 10#/sq ft If Truss design no loads on interior structure(DL) If rafter/ceiling joist design (DL) = 20#/sq ft Roof load regionally varies (LL) = 20-50#/sq ft

Beam Sizing and Post Spacing Trial & Error Method 1--Locate tributary area 2--Determine various conditions placing post to shorten the beam span 3--Go to tables & choose beam 4--Smaller beams are less expensive and usually better

Handout on Structural Analysis #2 Before doing calculations sketch problem to visualize conditions Calculate the tributary loads for beams and columns conditions Use Handout charts and tables and select beams and columns for conditions