HW5Solutions - UNIVERSITY OF CALIFORNIA BERKELEY Spring...

UNIVERSITY OF CALIFORNIA, BERKELEY
Spring 201 6
Department of Civil and Environmental Engineering
Instructor: J. P. Moehle
CE 120 - Structural Engineering
Solutions of Assignment No. 5
Due: February 2 6 , 201 6
Solution:
! Dead Load from ASCE-7-10 (Table C-3-1):
Component Load(psf)
Four ply felt and gravel 5.5psf
Mechanical Duct 4psf
¾ ” Subflooring (plywood) 3psf
! Live loads 20psf
! Material Density: Douglas fir 34pcf
Fig: Schematic Drawing of the Roof.
(a) Loads Supported by Plywood:
¾ in plywood carries weight from everything above it and it’s self weight.
Table 1: Loads carried by plywood
Dead load Live load
Four ply felt and gravel =5.5psf Roof Live load =20psf
¾ ” Plywood
=3psf
Total
= 8.5 psf
[ = 7.9psf]
=20psf
(b) Loads Supported by Joist:
Joist supports loads that are on the plywood (from part a) , mechanical duct and its self-weight.
• Self-weight of joist: Actual dimensions of 2X10 Douglas Fir roof joist are 1.5”X 9.25”
Therefore self-weight= (34pcf)*(1.5/12 ft)*(9.25/12 ft) = 3.27plf
[OR: ¾” Plywood =0.4psf/(1/8")*(3/4")=2.4psf]

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