Dead Loads and Idealization of Structural Members Steven Vukazich San Jose State University
What is a Dead Load? Dead Loads are Fixed Position Gravity Loads Examples are weights of the following: • Ceiling, • Flooring, • Façade, • Structural Members. Found from tables of weights of building materials (usually listed in weight/unit area)
Construct Dead Load Table for Roof Framing Dead Load 1 2 3 tables are 22’-0” 22’-0” 1’-6” usually 1’-6” 1’-6” constructed A W14x22 W18x46 using the load 1-1/2” 18 gauge W18x50 W18x50 path metal deck typ. W14x22 DO 18’-0” 6’-0” typ. Load Path DO W14x22 Dbl 6x6 B DO W18x46 Metal Deck Section on W18x50 W18x50 next slide DO W14x22 18’-0” Beams (e.g. W14x22) DO W14x22 C DO W18x46 Girders or Truss W18x50 W18x50 W18x50 (e.g. W18x50) DO W14x22 18’-0” Columns DO W14x22 W14x22 W18x46 D Foundation 1’-6”
Cross Section of Roof 3 ply felt tar and 2” rigid 1-1/2” 18 gauge gravel roofing fiberglass insulation metal deck W14x22 6’ - 0” 6’ - 0” 6’ - 0” spray-on fireproofing ceiling HVAC duct (mechanical)
Ceiling Support Hangers from Steel Framing at New Rec Center
Construct Dead Load Table Load Path → To metal To beams To girders, truss To columns Material deck (W14x22) (Lines 1-3) 1-1/2” 18 gauge metal 2.82 (A) 2.82 2.82 2.82 deck Fireproofing 0.5 0.5 0.5 0.5 2” Rigid fiberglass 3 (B) 3 3 3 insulation 3 ply felt tar and gravel 5.5 (B) 5.5 5.5 5.5 roofing Ceiling and Lighting 1 (B) 1 1 1 W14x22 @ 6 ft o.c. 3.7 (C) 3.7 3.7 Mechanical (plumbing, 4 4 4 HVAC) W18x50, truss 4 4 Weight of columns 1 Misc. 3 3 3 3 Total 15.82 23.52 27.52 28.52 Use 16 psf 24 psf 28 psf 29 psf Notes: A. From Vulcraft deck catalog. B. From AISC steel manual “Weights of Building Materials”. C. W14x22: (22 lb/ft)/(6 ft) = 3.7 psf.
Weights of Building Materials from AISC Manual of Steel Construction
Deck Carries Uniform Load to Beams Loads carried to the beam from the metal deck are uniformly distributed over the beam
Vertical (Gravity) Load Path Loads carried to the larger beam (girder) from the smaller beams are concentrated at the point of the connection and applied as point loads
Framing at Deck Overhang Framing at overhanging deck carries load to girder at edge
Idealization of Structural Members 1 2 3 22’-0” 22’-0” 1’-6” 1’-6” 1’-6” A W14x22 W18x46 Point dead load W18x50 W18x50 based on 28 psf W14x22 DO 18’-0” W14x22 B DO W18x46 6’-0” typ. W18x50 18’-0” C DO W18x46 W18x50 W18x50 W18x50 DO W14x22 18’-0” DO W14x22 W14x22 W18x46 D Uniformly distributed dead load based on 24 psf W14x22
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