Transcript Solar roof engineering powerpoint

Standardized Load Tables Characterizing
Residential Solar Thermal and Solar Electric
Installations For Residential Structures in
Minnesota
Jason S. Hanlon, PE, MLSE
Braun Intertec Corporation
September 30, 2013
Overview
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Establishing Analysis/Review Criteria
Research and Analysis
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Pre-Manufactured Trusses
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Roof Rafters
Rafter Tables
Establishing Analysis/Review Criteria
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Closely match IRC content
Consider conditions common to MN
Consider Types of Roof Mounted Solar
Technologies
Establishing Analysis/Review Criteria
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Closely match IRC content
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Spans presented try to closely match
that shown in IRC Tables
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Wood Species
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Roof Pitches
Establishing Analysis/Review Criteria
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Closely match IRC content
Consider conditions common to MN
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Wood Species --- Old Doug-Fir
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Design Loading Criteria
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Based on 2007 MSBC, 2006
IRC/IBC and ASCE 7-05
Wind Load Exposure B, C, and D
Dead Weight
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One Layer ½-inch OSB/Plywood or
¾-inch plank board
One layer asphalt shingles
Establishing Analysis/Review Criteria
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Closely match IRC content
Consider conditions common to MN
Consider Types of Roof Mounted Solar
Technologies
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Photovoltaic Panels supplementing
electrical services
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Solar Thermal Panels supplementing
heating services
Research and Analysis
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Pre-Manufactured Wood Trusses
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Challenges
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Things to consider
Roof Rafters
Research and Analysis – Pre-Manufactured
Wood Trusses
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Challenges
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Common design layout hard to define
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Wood trusses are “efficiently”
designed.
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Controlling component will be the
nailer plates
Research and Analysis – Pre-Manufactured
Wood Trusses
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What to consider
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Common design throughout the
industry:
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Top Chord DL = 7 psf
Bottom Chord DL = 10 psf
Changes in Code prescribed Snow
Load
Research and Analysis – Pre-Manufactured
Wood Trusses
1998-Previous MSBC
2003-Current MSBC
Research and Analysis – Pre-Manufactured
Wood Trusses
- Roof snow load decreased by 5 psf
- Roof snow load increased by 5 psf
- Roof snow load increased by 12 psf
- Roof snow load increased by 2 psf
Summary of Design Load Adjustments
Research and Analysis – Roof Rafters
(Hand-Framed Construction)
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Framing Conditions
Snow Loading
Wind Loading
Material Selfweight
Allowable Stress Design
Research and Analysis – Roof Rafters
(Hand-Framed Construction)
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Framing Conditions
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Use of Ridge Nailer Plate (not a ridge
beam)
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Outward thrust is resolved at exterior
wall bearing
Research and Analysis – Roof Rafters
(Hand-Framed Construction)
Research and Analysis – Roof Rafters
(Hand-Framed Construction)
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Framing Conditions
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Use of Ridge Nailer Plate (not a ridge
beam)
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Outward thrust is resolved at exterior
wall bearing
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Allowable stress values taken from
NDS (National Design Standard) for
Wood Construction and Historical
Douglas Fir Use Book
Research and Analysis – Roof Rafters
(Hand-Framed Construction)
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Framing Conditions
Snow Loading
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Exposure Rating B, C and D
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Design for Snow Drifting not required
per IRC
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Limit installation angle of panel so
drifting is limited to design depth of
snow
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Tables presented for different
lengths between PV and Solar
Panels
Research and Analysis – Roof Rafters
(Hand-Framed Construction)
Table 1 - Maximum Allowable PV Panel Installation Angle
Ground Snow Load = 50 psf, Flat Roof Snow Load = 35 psf
Maximum Allowable PV Panel Installation Angle (deg)
Roof Pitch
PV Panel
Length
3:12
4:12
5:12
7:12
9:12
12:12
(in)
36
37.0
40.9
44.4
38
35.8
39.7
43.2
40
34.6
38.5
42.2
42
33.6
37.6
41.2
44
32.7
36.7
40.3
46
31.8
35.8
39.5
48
31.1
35.1
38.8
50
30.4
34.4
38.1
44.8
52
29.7
33.8
37.5
44.2
54
29.1
33.2
37.0
43.7
56
28.6
32.7
36.4
43.2
58
28.1
32.2
36.0
42.7
60
27.6
31.7
35.5
42.3
Note: dash indicates that the solar panel may be installed at any angle up to 45
degrees from horizontal
Research and Analysis – Roof Rafters
(Hand-Framed Construction)
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Framing Conditions
Snow Loading
Wind Loading
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Structures 30-ft. or less in height
(average)
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Not located near isolated hills or
ridges or other abrupt changes in
topography
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Followed ASCE 7-05. Slight changes
in ASCE 7-10 (decrease)
Research and Analysis – Roof Rafters
(Hand-Framed Construction)
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Framing Conditions
Snow Loading
Wind Loading
Material Selfweight
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Member DL based on wood species,
size, and spacing
Research and Analysis – Roof Rafters
(Hand-Framed Construction)
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Framing Conditions
Snow Loading
Wind Loading
Material Selfweight
Allowable Stress Design
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Shear
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Bending/Compression
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Deflection
Rafter Tables
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Info needed to determine which table to
use
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Wood Species
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Grade of Wood
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Spacing
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Ground Snow Design Requirement
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Exposure Classification
Rafter Tables
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Info needed to determine which table to
use
Rafter Tables
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Info needed to use the table
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Rafter Pitch
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Rafter Size
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Projected Rafter Span
Rafter Tables
Rafter Tables
Rafter Tables
Rafter Tables
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Reinforced Rafter Tables
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Similar Analysis approach
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Uses a sistered 2x4 member of equal
or greater species and grade
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Installed as follows:
Rafter Tables
Questions???