tables 1 and 2: base mount capacity in landscape and ......jan 19, 2015 · re: quick mount pv...
TRANSCRIPT
January 19, 2015
Quick Mount PV 2700 Mitchell Drive, Building 2 Walnut Creek, CA 94598 Attn: Tom Hindmarsh, Senior Vice President of Engineering and Operations Re: Quick Mount PV Quick Rack V1.1 Base Mount Code Compliance Report MSD Job No. 2014,501.00 Dear Tom,
We have reviewed the Quick Rack V1.1 photovoltaic (PV) array mounting system (base mount) and determined that, for the configurations and criteria described below, it complies with the structural requirements of the 2012 International Building Code, the 2013 California Building Code, and both ASCE 7-05 and ASCE 7-10.
The Quick Rack base mount consists of a base extrusion (“QBlock Slider”) that fastens to a supporting roof rafter, and an adjustable height top extrusion (“Top Slider”) that connects to the QBlock Slider with a stainless steel machine bolt. The PV modules are connected to the Top Slider by a 5/16” stainless steel (grade 18/8) machine bolt that fits into a track in the Top Slider (“track”) and together with a two-part clamp (consisting of a “clamp base” and a lipped “panel clamp”) clamps the modules to the Top Slider. The QBlock Slider is anchored to the roof with a 5/16” nominal diameter “structural screw”, defined as either a 5/16” nominal diameter GRK RSS screw with Climatek coating or a 5/16” nominal diameter QMPV Dual-Drive screw. The typical horizontal (cross-slope) spacing of Quick Rack base mounts is four feet on center, with tighter spacing sometimes required in regions with extreme wind and snow loads. Larger spacing can be achieved in regions of low wind and snow loads.
The attached Figures 1 through 4 illustrate the assembly and nomenclature of the various parts of the Quick Rack base mount system. Figures 5 and 6 illustrate wind and snow considerations, and Figures 7 to 10 illustrate conventional base mount layouts (straight columns and rows) and staggered base mount layouts.
The attached tables define the range of roof slopes, wind speeds, wind exposure categories, roof wind zones, ground snow loads and seismic zones where particular configurations of Quick Rack installations are allowed. Base Mount Capacity: Tables 1 and 2 define permissible configurations based on the anchorage capacity of the base mounts themselves, for modules installed in landscape and portrait orientation, respectively. Roof Capacity: Table 3 examines the structural capacity of typical code-compliant roof framing, and shows where a conventional layout of base mounts can be used, and where a staggered pattern is recommended instead.
Tables 1 and 2: Base Mount Capacity in Landscape and Portrait Orientations
The allowable capacity of Quick Rack base mount installations are based on allowable upward, downward, lateral, and combined downward-lateral load values determined from tests on actual Quick Rack base mount specimens conducted at Applied Materials & Engineering in Oakland, CA on June 25-27, 2013, following ICC AC-13 and ICC AC-428 provisions.
Quick Rack V1.1 Base Mount Code Compliance Report January 19, 2015 Page 2 of 4
Table 3: Existing Roof Rafter Capacity
Typical base mount layouts concentrate loads on every second, third or fourth rafter. Assuming the existing roof can support code-required loads, Table 3 indicates where such concentrated loading is likely to be structurally acceptable, and shows where staggered layouts to create a more uniform distribution of loads are required. Table 3 is based on methods described in the structural technical appendix to the California Solar Permitting Guidebook (Second Edition).
General Requirements
The attached tables are subject to the requirements shown in the attached figures and table footnotes, and the criteria listed below:
Region and Site:
1. The roof is not in a special topographic region subject to wind speed-up effects, such as near or at the crest of a tall ridge or hill (i.e. ASCE 7 topographic factor of 1.00). Refer to ASCE 7-05 Sec. 6.5.7 or ASCE 7-10 Sec. 26.8 for determining if a roof is in a special wind speed-up zone.
2. The building is not a special occupancy structure such as a public school, public safety building or assembly building (i.e. ASCE 7-05 importance factor for wind, snow and seismic loads of 1.00, or Risk Category II building for ASCE 7-10).
3. In general, Quick Rack base mount capacity exceeds seismic lateral demands in almost all areas of the United States. The tables list minor limitations in unusual regions where combined high snow and seismic loads may occur.
Roof Characteristics:
1. The installation is on wood-framed roofs with composition shingle, wood sawn shingle, built-up roofing, or membrane roofs, underlain by plywood, oriented strand board or solid 1x sheathing.
2. The existing roof structure should be generally code-compliant, and should not show signs of decay, fire damage, significant added dead loads, structural modifications (such as removal of web members from carpenter trusses) or any other condition that may weaken its load-carrying capacity. If there is doubt about the suitability of the roof to carry the new PV array, a qualified licensed engineer should be retained to inspect and analyze the existing roof structure.
3. The PV array is installed on the roof of an enclosed building with a mean roof height less than or equal to 35 feet (see Figure 6). The mean roof height is defined as the average height of the roof eave and the highest point on the roof.
4. The roof pitch is between 2:12 (9.5 degrees) and 12:12 (45 degrees).
5. Rafters have a minimum nominal width of 2” (1.5” actual width), and have a specific gravity of 0.42 or greater, allowing lumber species groups that range from relatively lightweight, such as Spruce-Pine-Fir, Hem-Fir and Close Grain Redwood, to denser woods such as Douglas Fir and Southern Pine.
Quick Rack V1.1 Base Mount Code Compliance Report January 19, 2015 Page 3 of 4
6. In existing construction, rafters are dry and seasoned. In new construction, rafters are either Kiln-Dried (KD) or Surfaced Dry (S-DRY), or if Surfaced Green (S-GRN), have an in-field measured moisture content of 19% or less.
Installation Specifics:
1. The maximum short edge panel width for PV modules installed in landscape orientation is 40”.
2. The maximum long edge panel length for PV modules installed in portrait orientation is 66”.
3. Each Quick Rack base mount is fastened to the roof rafter with one 5/16” nominal diameter structural screw, defined as either a 5/16” nominal diameter GRK RSS screw with Climatek coating or a 5/16” nominal diameter QMPV Dual-Drive screw, each pre-drilled with an 1/8” pilot hole to prevent splitting. The structural screw shall be embedded at least 2.5” into the roof rafter. The structural screw shall be torqued to achieve a snug fit of the mount to the flashing (the QBlock Slider should not be able to rotate easily).
4. For all PV module orientations, the Quick Rack base mount Top Slider tracks are positioned parallel to roof slope and connect to the module edges that run perpendicular to the slope. Alternate mounts so that approximately 50% of the base mount “elevated seal regions” (toes) point in the nominal west (left cross-slope) direction with the remainder pointing in the opposite direction. Exceptions are allowed at cantilevers and at bridge clamps between modules.
5. The PV modules shall be clamped to the Quick Rack track using the provided two-part clamp (clamp base and panel clamp) and a 5/16” stainless steel (grade 18/8) machine bolt, torqued to no less than 13 ft-lbs and no more than 20 ft-lbs. The center of the machine bolt into the track shall be installed no more than 1.5” upslope or downslope from the center of the track. Machine bolts may be installed in any position along the slots in the clamp.
6. The maximum PV mount and module cantilevers are defined in Figure 4 and enumerated in Tables 1B, 1C, 2B and 2C.
7. Per AC-428, the edge of the PV array shall be no closer than 10” to any edge, eave, rake, hip, or ridge of the roof, unless Tables 1B, 1C, 2B and 2C require larger roof edge distances.
8. To prevent excessive snow build-up, where the ground snow load exceeds 10 psf, the top edge of the PV array shall be set no farther than 5 feet from the roof ridge, measured perpendicular to the ridge. Note that local fire jurisdictions sometimes require that the top edge of the array be set no closer than a certain distance (often 3 feet) to the ridge.
9. If a skirt is installed along the bottom and/or top edge of an array, the gap between bottom of skirt and top of roof surface shall be at least 1/2”. Nominal left and right edges of the array shall remain open.
10. The dead load of the PV array (sum of the PV modules and Quick Rack base mount hardware) shall not exceed 3.5 psf.
11. This code compliance report is limited to base mount structural performance. The modules installed in combination with Quick Rack shall also have UL 1703/2703 rated load capacities appropriate for the site’s wind and snow loads.
Quick Rack V1.1 Base Mount Code Compliance Report January 19, 2015 Page 4 of 4
Conditions outside the assumptions and limitations listed above and in the attached figures and tables may be feasible, but shall be investigated in consultation with Quick Mount PV, and, where appropriate, reviewed by a licensed professional engineer. Please call if you have any questions.
Sincerely,
John Wolfe, SE
Encl. Figures 1 to 10 Tables 1 to 3 Appendices 1 to 2 Glossary of Symbols 2015-01-19 Code Compliance Letter CA.docx
Qu
ick
Ra
ck M
ou
nt
Co
de
Co
mp
lia
nce
Re
po
rtJa
nu
ary
19
, 2
01
5
Ta
ble
1A
. Q
uic
k R
ack
Ba
se M
ou
nt
Ma
xim
um
Sp
aci
ng
, M
od
ule
s in
Landscape
Ori
en
tati
on
BC
DB
CD
BC
DB
CD
BC
D
2:1
2 t
o 6
:12
72
"7
2"
72
"6
4"
64
"6
4"
48
"4
8"
48
"3
2"
32
"3
2"
32
"3
2"
32
"
7:1
2 t
o 1
2:1
27
2"
72
"7
2"
48
"4
8"
48
"3
2"
32
"3
2"
32
"3
2"
32
"2
4"
24
"3
2"
2:1
2 t
o 6
:12
72
"7
2"
72
"6
4"
64
"6
4"
48
"4
8"
48
"3
2"
32
"3
2"
32
"3
2"
32
"
7:1
2 t
o 1
2:1
27
2"
72
"7
2"
48
"4
8"
48
"3
2"
32
"3
2"
32
"3
2"
32
"2
4"
24
"3
2"
2:1
2 t
o 6
:12
72
"7
2"
72
" *
/64
"6
4"
64
"6
4"
48
"4
8"
48
"3
2"
32
"3
2"
32
"3
2"
32
"
7:1
2 t
o 1
2:1
27
2"
72
"7
2"
48
"4
8"
48
"3
2"
32
"3
2"
32
"3
2"
32
"2
4"
24
"3
2"
2:1
2 t
o 6
:12
72
"7
2"
*/6
4"
72
" *
/48
"6
4"
64
"6
4"
*/4
8"
48
"4
8"
48
"3
2"
32
"3
2"
32
"3
2"
32
"
7:1
2 t
o 1
2:1
27
2"
72
"6
4"
48
"4
8"
48
"3
2"
32
"3
2"
32
"3
2"
32
"2
4"
24
"3
2"
2:1
2 t
o 6
:12
72
"7
2"
*/4
8"
64
" *
/32
"6
4"
6
4"
*/4
86
4"
*/3
2"
48
"4
8"
48
" *
/32
"3
2"
32
"3
2"
32
"3
2"
32
"
7:1
2 t
o 1
2:1
27
2"
64
"4
8"
48
"4
8"
48
"3
2"
32
"3
2"
32
"3
2"
32
"2
4"
24
"3
2"
Ta
ble
No
tes:
1.
Th
e Q
uic
k R
ack
ba
se m
ou
nt
ma
xim
um
all
ow
ab
le s
pa
cin
g l
iste
d i
n t
his
ta
ble
is
the
sp
aci
ng
be
twe
en
ba
se m
ou
nts
in
th
e r
oo
f cr
oss
-slo
pe
dir
ect
ion
fo
r m
od
ule
s in
la
nd
sca
pe
ori
en
tati
on
.
2.
Th
is t
ab
le i
s b
ase
d o
n a
n a
ssu
me
d P
V m
od
ule
siz
e n
o l
arg
er
tha
n 4
0"
x 6
6".
3.
* W
he
re t
wo
nu
mb
ers
are
sh
ow
n,
such
as
72
" *
/48
", t
he
fir
st n
um
be
r is
th
e m
axi
mu
m a
llo
wa
ble
sp
aci
ng
wh
en
th
e P
V a
rra
y i
s w
ith
in r
oo
f zo
ne
1,
an
d t
he
se
con
d n
um
be
r is
th
e m
axi
mu
m a
llo
wa
ble
spa
cin
g i
n z
on
es
2 a
nd
3 (
usu
all
y w
ith
in 3
6"
of
roo
f e
dg
e).
Fo
r b
uil
din
gs
wit
h n
arr
ow
sid
e w
ide
r th
an
30
fe
et,
in
cre
ase
36
" to
10
% o
f b
uil
din
g l
ea
st p
lan
(fo
otp
rin
t) d
ime
nsi
on
to
re
ma
in w
ith
in Z
on
e 1
.
4.
Se
e F
igu
re 4
an
d T
ab
les
1B
an
d 1
C f
or
the
ma
xim
um
mo
un
t ca
nti
leve
r (c
lam
p b
olt
to
en
d-o
f-m
od
ule
) a
t th
e n
om
ina
l e
ast
or
we
st e
dg
e o
f a
rra
y (
cro
ss-s
lop
e e
dg
e o
f ro
of)
.
5.
Se
ism
ic:
Ma
xim
um
sp
aci
ng
s su
bje
ct t
o t
he
fo
llo
win
g l
imit
ati
on
s o
n S
DS:
72
":
hig
h s
eis
mic
zo
ne
s (S
DS ≤
1.5
g)
64
":
hig
h s
eis
mic
zo
ne
s (S
DS ≤
1.5
g f
or
gro
un
d s
no
w l
oa
d g
rea
ter
tha
n 2
0 p
sf,
oth
erw
ise
SD
S ≤
1.7
5g
)
48
" a
nd
sm
all
er
: h
igh
se
ism
ic z
on
es
(SD
S ≤
2.0
g)
6.
Th
is t
ab
le i
s su
bje
ct t
o t
he
co
nd
itio
ns
sta
ted
in
th
e a
tta
che
d C
od
e C
om
pli
an
ce L
ett
er,
an
d s
ho
wn
in
th
e a
tta
che
d s
ke
tch
es.
7.
Th
is t
ab
le i
s b
ase
d o
n A
SC
E 7
-05
an
d A
SC
E 7
-10
. A
SC
E 7
-10
win
d s
pe
ed
s a
re b
ack
-ca
lcu
late
d f
rom
AS
CE
7-0
5 w
ind
sp
ee
ds
to p
rod
uce
th
e s
am
e w
ind
pre
ssu
res
on
a R
isk
Ca
teo
gy
II
bu
ild
ing
.
8.
Se
e T
ab
le 3
fo
r re
gio
ns
of
hig
h w
ind
or
sno
w l
oa
d w
he
re a
sta
gg
ere
d b
ase
mo
un
t la
yo
ut
is r
eco
mm
en
de
d.
12
0 m
ph
15
0 m
ph
90
mp
h1
15
mp
h
10
0 m
ph
12
5 m
ph
11
0 m
ph
14
0 m
ph
Win
d S
pe
ed
Ro
of
Pit
ch
AS
CE
7-0
5 (
Se
rvic
e
Leve
l)
AS
CE
7-1
0
(Str
en
gth
Le
ve
l)
85
mp
h1
10
mp
h
Gro
un
d S
no
w L
oa
d
0 -
20
psf
21
- 3
0 p
sf3
1 -
40
psf
41
- 5
0 p
sf5
1 -
60
psf
Win
d E
xpo
sure
Ca
teg
ory
Qu
ick
Ra
ck V
1.1
Ba
se M
ou
nt
Co
de
Co
mp
lia
nce
Re
po
rtJa
nu
ary
19
, 2
01
5
Ta
ble
1B
. Q
uic
k R
ack
Ba
se M
ou
nt
Ma
xim
um
Ea
st a
nd
We
st C
an
tile
ve
rs,
Mo
du
les
in L
an
dsc
ap
e O
rie
nta
tio
n w
ith
Ty
pic
al
Ba
cksp
an
fro
m T
ab
le 1
A
BC
DB
CD
BC
DB
CD
BC
D
2:1
2 t
o 6
:12
72
"7
2"
72
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
~/2
1"
24
" ~
/21
"2
4"
~/2
1"
24
" ~
/ 1
8"
24
" ~
/ 1
8"
24
" ~
/ 1
8"
7:1
2 t
o 1
2:1
27
2"
72
"7
2"
24
"2
4"
24
"2
4"
24
"2
4"
24
" ~
/21
"2
4"
~/2
1"
24
" ~
/21
"2
4"
~/
18
"2
4"
~/
18
"2
4"
~/
18
"
2:1
2 t
o 6
:12
72
"7
2"
72
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
~/2
1"
24
" ~
/21
"2
4"
~/2
1"
24
" ~
/ 1
8"
24
" ~
/ 1
8"
24
" ~
/ 1
8"
7:1
2 t
o 1
2:1
27
2"
72
"7
2"
24
"2
4"
24
"2
4"
24
"2
4"
24
" ~
/21
"2
4"
~/2
1"
24
" ~
/21
"2
4"
~/
18
"2
4"
~/
18
"2
4"
~/
18
"
2:1
2 t
o 6
:12
72
"7
2"
7
2"
*/6
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
" ~
/21
"2
4"
~/2
1"
24
" ~
/21
"2
4"
~/
18
"2
4"
~/
18
"2
4"
~/
18
"
7:1
2 t
o 1
2:1
27
2"
72
"7
2"
24
"2
4"
24
"2
4"
24
"2
4"
24
" ~
/21
"2
4"
~/2
1"
24
" ~
/21
"2
4"
~/
18
"2
4"
~/
18
"2
4"
~/
18
"
2:1
2 t
o 6
:12
72
"
72
" *
/64
"7
2"
*/4
8"
24
"2
4"
22
"2
4"
24
"1
4"
24
" ~
/21
"2
4"
~/2
1"
12
"2
4"
~/
18
"2
4"
~/
18
"9
"
7:1
2 t
o 1
2:1
27
2"
72
"6
4"
24
"2
4"
24
"2
4"
24
"2
1"
24
" ~
/21
"2
4"
~/2
1"
18
"2
4"
~/
18
"2
4"
~/
18
"1
5"
2:1
2 t
o 6
:12
72
"7
2"
*/4
8"
64
" *
/32
"2
4"
22
"2
0"
~/1
5"
24
"1
4"
12
" ~
/ 7
"2
4"
~/2
1"
12
"1
0"
~/6
"2
4"
~/
18
"9
"8
" ~
/4"
7:1
2 t
o 1
2:1
27
2"
64
"4
8"
24
"2
4"
22
"2
4"
21
"1
4"
24
" ~
/21
"1
8"
12
"2
4"
~/
18
"1
5"
9"
Ta
ble
No
tes:
1.
Th
e Q
uic
k R
ack
ba
se m
ou
nt
ma
xim
um
ca
nti
lev
er
list
ed
in
th
is t
ab
le i
s th
e d
ista
nce
fro
m c
en
ter
of
cla
mp
bo
lt t
o e
nd
of
mo
du
le (
see
Fig
ure
4).
2.
Th
e "
ba
cksp
an
" is
th
e f
irst
sp
an
(i.
e.
mo
un
t sp
aci
ng
) in
wa
rd f
rom
th
e c
an
tile
ve
r (s
ee
Fig
ure
4).
In
th
is t
ab
le (
Ta
ble
1B
), b
ack
spa
n m
atc
he
s ty
pic
al
spa
n f
rom
Ta
ble
1A
.
3.
Se
e T
ab
le 1
C ,
no
tes
3 t
hro
ug
h 9
, w
hic
h a
lso
ap
ply
to
th
is t
ab
le.
Ta
ble
1C
. Q
uic
k R
ack
Ba
se M
ou
nt
Ma
xim
um
Ea
st a
nd
We
st C
an
tile
ve
rs,
Mo
du
les
in L
an
dsc
ap
e O
rie
nta
tio
n w
ith
Aty
pic
al
16
" o
r 2
4"
Ba
cksp
an
BC
DB
CD
BC
DB
CD
BC
D
2:1
2 t
o 6
:12
72
"7
2"
72
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"
7:1
2 t
o 1
2:1
27
2"
72
"7
2"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
2:1
2 t
o 6
:12
72
"7
2"
72
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"
7:1
2 t
o 1
2:1
27
2"
72
"7
2"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
2:1
2 t
o 6
:12
72
"7
2"
7
2"
*/6
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
7:1
2 t
o 1
2:1
27
2"
72
"7
2"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
2:1
2 t
o 6
:12
72
"
72
" *
/64
"7
2"
*/4
8"
24
"2
4"
24
"2
4"
24
"1
6"
24
"2
4"
14
"2
4"
24
"1
3"
7:1
2 t
o 1
2:1
27
2"
72
"6
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
4"
24
"2
1"
2:1
2 t
o 6
:12
72
"7
2"
*/4
8"
64
" *
/32
"2
4"
24
"2
0"
~/
17
"2
4"
16
"1
3"
~/
11
"2
4"
14
"1
2"
~/
10
"2
4"
13
"1
1"
~/9
"
7:1
2 t
o 1
2:1
27
2"
64
"4
8"
24
"2
4"
24
"2
4"
24
"1
6"
24
"2
4"
14
"2
4"
21
"1
3"
Ta
ble
No
tes:
1.
Th
e Q
uic
k R
ack
ba
se m
ou
nt
ma
xim
um
ca
nti
lev
er
list
ed
in
th
is t
ab
le i
s th
e d
ista
nce
fro
m c
en
ter
of
cla
mp
bo
lt t
o e
nd
of
mo
du
le (
see
Fig
ure
4).
2.
Th
e "
ba
cksp
an
" is
th
e f
irst
sp
an
(i.
e.
mo
un
t sp
aci
ng
) in
wa
rd f
rom
th
e c
an
tile
ve
r (s
ee
Fig
ure
4).
In
th
is t
ab
le (
Ta
ble
1C
), b
ack
spa
n i
s o
ne
ra
fte
r sp
aci
ng
(1
6"
or
24
").
3.
Th
e "
mo
du
le c
an
tile
ve
r" i
s m
ea
sure
d f
rom
en
d o
f m
od
ule
to
clo
sest
ed
ge
of
cla
mp
(se
e F
igu
re 4
). I
nst
all
er
sha
ll v
eri
fy t
ha
t m
od
ule
ca
nti
lev
er
do
es
no
t e
xce
ed
ma
nu
fact
ure
r re
com
me
nd
ati
on
s.
4.
Th
e "
roo
f e
dg
e d
ista
nce
" is
th
e d
ista
nce
fro
m g
ab
le e
nd
, h
ip o
r o
the
r ro
of
ed
ge
, to
en
d o
f p
eri
me
ter
mo
du
le (
see
Fig
ure
4).
F
or
bu
ild
ing
s n
o w
ide
r th
an
30
fe
et
(le
ast
pla
n d
ime
nsi
on
),
a 3
6"
ed
ge
dis
tan
ce m
ea
ns
the
arr
ay
is
full
y w
ith
in r
oo
f zo
ne
1 a
s d
efi
ne
d b
y A
SC
E 7
-10
, C
ha
pte
r 3
0,
wit
h l
ow
er
ass
oci
ate
d w
ind
up
lift
pre
ssu
res.
5.
Th
is t
ab
le i
s b
ase
d o
n a
n a
ssu
me
d P
V m
od
ule
siz
e n
o l
arg
er
tha
n 4
0"x
66
".
6.
Hig
h s
no
w l
oa
d r
eg
ion
s: a
bo
ve
20
psf
gro
un
d s
no
w l
oa
d,
the
ma
xim
um
mo
un
t ca
nti
lev
er
sha
ll b
e h
alf
th
e t
yp
ica
l sp
an
sh
ow
n i
n T
ab
le 1
A,
un
less
Ta
ble
s 1
B o
r 1
C i
nd
ica
te a
sh
ort
er
can
tile
ve
r .
7.
+
Fo
r b
uil
din
gs
wit
h t
he
na
rro
w s
ide
wid
er
tha
n 3
0 f
ee
t, i
ncr
ea
se 3
6"
to 1
0%
of
bu
ild
ing
le
ast
pla
n (
foo
tpri
nt)
dim
en
sio
n t
o r
em
ain
wit
hin
Zo
ne
1 a
s d
efi
ne
d b
y A
SC
E 7
-10
, C
ha
pte
r 3
0.
8.
*
Un
de
r th
e "
Ty
pic
al
Sp
an
" co
lum
ns,
wh
ere
tw
o n
um
be
rs a
re s
ho
wn
, su
ch a
s 4
8"
*/3
2",
th
e f
irst
nu
mb
er
is t
he
ma
xim
um
all
ow
ab
le s
pa
cin
g w
he
n t
he
PV
arr
ay
is
wit
hin
ro
of
zon
e 1
, a
nd
th
e s
eco
nd
nu
mb
er
is t
he
ma
xim
um
all
ow
ab
le s
pa
cin
g i
n z
on
es
2 a
nd
3 (
usu
all
y w
ith
in 3
6"
of
roo
f e
dg
e).
9.
~
Un
de
r th
e "
Ma
xim
um
Ca
nti
lev
er"
co
lum
ns,
wh
ere
tw
o n
um
be
rs a
re s
ho
wn
, su
ch a
s 2
4"
~/1
8",
th
e f
irst
nu
mb
er
is t
he
ma
xim
um
all
ow
ab
le c
an
tile
ve
r b
ase
d o
n t
he
ca
pa
city
of
the
Qu
ick
Ra
ck s
yst
em
an
d i
ts a
tta
chm
en
t to
th
e r
oo
f, w
hil
e t
he
se
con
d n
um
be
r is
th
e c
an
tile
ve
r th
at
en
sure
s th
at
the
en
d r
aft
ers
un
de
r th
e a
rra
y a
re l
oa
de
d n
o m
ore
he
av
ily
th
an
in
teri
or
raft
ers
.
If t
he
fir
st n
um
be
r (e
.g.
24
" ~
) is
use
d,
en
gin
ee
rin
g r
ev
iew
of
the
lo
ad
ed
en
d r
aft
ers
is
req
uir
ed
, fo
r b
oth
up
wa
rd a
nd
do
wn
wa
rd l
oa
ds.
10
0 m
ph
12
5 m
ph
11
0 m
ph
14
0 m
ph
12
0 m
ph
15
0 m
ph
Win
d E
xpo
sure
Ca
teg
ory
85
mp
h1
10
mp
h
Win
d E
xpo
sure
Ca
teg
ory
Win
d E
xpo
sure
Ca
teg
ory
Ro
of
Pit
ch
AS
CE
7-0
5
(Se
rvic
e L
ev
el)
AS
CE
7-1
0
(Str
en
gth
Le
ve
l)
Win
d E
xpo
sure
Ca
teg
ory
Win
d E
xpo
sure
Ca
teg
ory
Ro
of
Ed
ge
Dis
tan
ce =
36
"+R
oo
f E
dg
e D
ista
nce
= 2
4"
Ro
of
Ed
ge
Dis
tan
ce =
18
"T
yp
ica
l S
pa
n
(se
e T
ab
le 1
A)
Ro
of
Ed
ge
Dis
tan
ce =
12
"
14
0 m
ph
12
0 m
ph
15
0 m
ph
90
mp
h1
15
mp
h
Win
d S
pe
ed
Ma
xim
um
Mo
un
t C
an
tile
ve
r w
ith
Aty
pic
al
Ba
cksp
an
= 1
6"
or
24
"
Win
d S
pe
ed
Ro
of
Pit
ch
AS
CE
7-0
5
(Se
rvic
e L
ev
el)
AS
CE
7-1
0
(Str
en
gth
Le
ve
l)
Win
d E
xpo
sure
Ca
teg
ory
85
mp
h1
10
mp
h
Win
d E
xpo
sure
Ca
teg
ory
Win
d E
xpo
sure
Ca
teg
ory
10
0 m
ph
12
5 m
ph
90
mp
h1
15
mp
h
11
0 m
ph
Ma
xim
um
Mo
un
t C
an
tile
ve
r w
ith
Ba
cksp
an
= T
yp
ica
l S
pa
n
Ty
pic
al
Sp
an
(se
e T
ab
le 1
A)
Win
d E
xpo
sure
Ca
teg
ory
Ro
of
Ed
ge
Dis
tan
ce =
12
"
Win
d E
xpo
sure
Ca
teg
ory
Ro
of
Ed
ge
Dis
tan
ce =
36
"+R
oo
f E
dg
e D
ista
nce
= 2
4"
Ro
of
Ed
ge
Dis
tan
ce =
18
"
Qu
ick
Ra
ck V
1.1
Ba
se M
ou
nt
Co
de
Co
mp
lia
nce
Re
po
rtJa
nu
ary
19
,20
15
Ta
ble
2A
. Q
uic
k R
ack
Ba
se M
ou
nt
Ma
xim
um
Sp
aci
ng
, M
od
ule
s in
Portrait
Ori
en
tati
on
BC
DB
CD
BC
D
2:1
2 t
o 6
:12
48
"4
8"
48
"3
2"
32
"3
2"
24
"2
4"
24
"
7:1
2 t
o 1
2:1
24
8"
48
"4
8"
32
"3
2"
32
"2
4"
24
"2
4"
2:1
2 t
o 6
:12
48
"4
8"
48
"3
2"
32
"3
2"
24
"2
4"
24
"
7:1
2 t
o 1
2:1
24
8"
48
"4
8"
32
"3
2"
32
"2
4"
24
"2
4"
2:1
2 t
o 6
:12
48
"4
8"
48
" *
/32
"3
2"
32
"3
2"
24
"2
4"
24
"
7:1
2 t
o 1
2:1
24
8"
48
"4
8"
32
"3
2"
32
"2
4"
24
"2
4"
2:1
2 t
o 6
:12
48
"4
8"
*/3
2"
48
" *
/32
"3
2"
32
"3
2"
24
"2
4"
24
"
7:1
2 t
o 1
2:1
24
8"
48
"3
2"
32
"3
2"
32
"2
4"
24
"2
4"
2:1
2 t
o 6
:12
48
"4
8"
*/3
2"
32
" *
/24
"3
2"
32
"3
2"
*/2
4"
24
"2
4"
24
"
7:1
2 t
o 1
2:1
24
8"
32
"3
2"
32
"3
2"
32
"2
4"
24
"2
4"
Ta
ble
No
tes:
1.
Th
e Q
uic
k R
ack
ba
se m
ou
nt
ma
xim
um
all
ow
ab
le s
pa
cin
g l
iste
d i
n t
his
ta
ble
is
the
sp
aci
ng
be
twe
en
ba
se m
ou
nts
in
th
e r
oo
f cr
oss
-slo
pe
dir
ect
ion
fo
r m
od
ule
s in
po
rtra
it o
rie
nta
tio
n.
2.
Th
is t
ab
le i
s b
ase
d o
n a
n a
ssu
me
d P
V m
od
ule
siz
e n
o l
arg
er
tha
n 4
0"
x 6
6".
3.
*
Wh
ere
tw
o n
um
be
rs a
re s
ho
wn
, su
ch a
s 7
2"
*/4
8",
th
e f
irst
nu
mb
er
is t
he
ma
xim
um
all
ow
ab
le s
pa
cin
g w
he
n t
he
PV
arr
ay
is
wit
hin
ro
of
zon
e 1
, a
nd
th
e s
eco
nd
nu
mb
er
is t
he
ma
xim
um
all
ow
ab
le
spa
cin
g i
n z
on
es
2 a
nd
3 (
usu
all
y w
ith
in 3
6"
of
roo
f e
dg
e).
Fo
r b
uil
din
gs
wit
h n
arr
ow
sid
e w
ide
r th
an
30
fe
et,
in
cre
ase
36
" to
10
% o
f b
uil
din
g l
ea
st p
lan
(fo
otp
rin
t) d
ime
nsi
on
to
re
ma
in w
ith
in Z
on
e 1
.
4.
Se
e F
igu
re 4
an
d T
ab
les
2B
an
d 2
C f
or
the
ma
xim
um
mo
un
t ca
nti
lev
er
(cla
mp
bo
lt t
o e
nd
-of-
mo
du
le)
at
the
no
min
al
ea
st o
r w
est
ed
ge
of
arr
ay
(cr
oss
-slo
pe
ed
ge
of
roo
f).
5.
Se
ism
ic:
Ma
xim
um
sp
aci
ng
s su
bje
ct t
o t
he
fo
llo
win
g l
imit
ati
on
s o
n S
DS:
72
":
hig
h s
eis
mic
zo
ne
s (S
DS ≤
1.5
g)
64
":
hig
h s
eis
mic
zo
ne
s (S
DS ≤
1.5
g f
or
gro
un
d s
no
w l
oa
d g
rea
ter
tha
n 2
0 p
sf,
oth
erw
ise
SD
S ≤
1.7
5g
)
48
" a
nd
sm
all
er
: h
igh
se
ism
ic z
on
es
(SD
S ≤
2.0
g)
6.
Th
is t
ab
le i
s su
bje
ct t
o t
he
co
nd
itio
ns
sta
ted
in
th
e a
tta
che
d C
od
e C
om
pli
an
ce L
ett
er,
an
d s
ho
wn
in
th
e a
tta
che
d s
ke
tch
es.
7.
Th
is t
ab
le i
s b
ase
d o
n A
SC
E 7
-05
an
d A
SC
E 7
-10
. A
SC
E 7
-10
win
d s
pe
ed
s a
re b
ack
-ca
lcu
late
d f
rom
AS
CE
7-0
5 w
ind
sp
ee
ds
to p
rod
uce
th
e s
am
e w
ind
pre
ssu
res
on
a R
isk
Ca
teo
gy
II
bu
ild
ing
.
8.
Se
e T
ab
le 3
fo
r re
gio
ns
of
hig
h w
ind
or
sno
w l
oa
d w
he
re a
sta
gg
ere
d b
ase
mo
un
t la
yo
ut
is r
eco
mm
en
de
d.
11
0 m
ph
11
5 m
ph
11
0 m
ph
12
0 m
ph
85
mp
h
90
mp
h
10
0 m
ph
Win
d E
xpo
sure
Ca
teg
ory
12
5 m
ph
14
0 m
ph
15
0 m
ph
Ro
of
Pit
ch
Gro
un
d S
no
w L
oa
d
31
- 4
5 p
sf0
- 1
5 p
sf1
6 -
30
psf
Win
d S
pe
ed
AS
CE
7-0
5
(Se
rvic
e L
ev
el)
AS
CE
7-1
0
(Str
en
gth
Le
ve
l)
Qu
ick
Ra
ck V
1.1
Ba
se M
ou
nt
Co
de
Co
mp
lia
nce
Re
po
rtJa
nu
ary
19
, 2
01
5
Ta
ble
2B
. Q
uic
k R
ack
Ba
se M
ou
nt
Ma
xim
um
Ea
st a
nd
We
st C
an
tile
ve
rs,
Mo
du
les
in Portrait
Ori
en
tati
on
wit
h T
yp
ica
l B
ack
spa
n f
rom
Ta
ble
2A
BC
DB
CD
BC
DB
CD
BC
D
2:1
2 t
o 6
:12
48
"4
8"
48
"2
4"
~/2
2"
24
" ~
/22
"2
4"
~/2
2"
24
" ~
/14
"2
1"
~/1
4"
21
" ~
/14
"2
4"
~/1
2"
18
" ~
/12
"1
8"
~/1
2"
24
" ~
/ 9
"1
5"
~/
9"
15
" ~
/ 9
"
7:1
2 t
o 1
2:1
24
8"
48
"4
8"
24
" ~
/22
"2
4"
~/2
2"
24
" ~
/22
"2
4"
~/1
4"
21
" ~
/14
"2
1"
~/1
4"
24
" ~
/12
"1
8"
~/1
2"
18
" ~
/12
"2
4"
~/
9"
15
" ~
/ 9
"1
5"
~/
9"
2:1
2 t
o 6
:12
48
"4
8"
48
"2
4"
~/2
2"
24
" ~
/22
"2
2"
24
" ~
/14
"2
1"
~/1
4"
14
"2
4"
~/1
2"
18
" ~
/12
"1
2"
24
" ~
/ 9
"1
5"
~/
9"
9"
7:1
2 t
o 1
2:1
24
8"
48
"4
8"
24
" ~
/22
"2
4"
~/2
2"
22
"2
4"
~/1
4"
21
" ~
/14
"1
4"
24
" ~
/12
"1
8"
~/1
2"
12
"2
4"
~/
9"
15
" ~
/ 9
"9
"
2:1
2 t
o 6
:12
48
"4
8"
48
" *
/32
"2
4"
~/2
2"
22
"1
5"
21
" ~
/14
"1
4"
7"
18
" ~
/12
"1
2"
6"
15
" ~
/ 9
"9
"4
"
7:1
2 t
o 1
2:1
24
8"
48
"4
8"
24
" ~
/22
"2
2"
22
"2
1"
~/1
4"
14
"1
4"
18
" ~
/12
"1
2"
12
"1
5"
~/
9"
9"
9"
2:1
2 t
o 6
:12
48
"
48
" *
/32
"
48
" *
/32
"2
4"
~/2
2"
15
"1
5"
21
" ~
/14
"7
"7
"1
8"
~/1
2"
6"
6"
15
" ~
/ 9
"4
"4
"
7:1
2 t
o 1
2:1
24
8"
48
"3
2"
24
" ~
/22
"2
2"
15
"2
1"
~/1
4"
14
"7
"1
8"
~/1
2"
12
"6
"1
5"
~/
9"
9"
4"
2:1
2 t
o 6
:12
48
"
48
" *
/32
"
32
" *
/24
"2
2"
15
"1
21
4"
7"
41
2"
6"
4"
9"
4"
3"
7:1
2 t
o 1
2:1
24
8"
32
"3
2"
22
"1
5"
15
"1
4"
7"
7"
12
"6
"6
"9
"4
"4
"
Ta
ble
No
tes:
1.
Th
e Q
uic
k R
ack
ba
se m
ou
nt
ma
xim
um
ca
nti
lev
er
list
ed
in
th
is t
ab
le i
s th
e d
ista
nce
fro
m c
en
ter
of
cla
mp
bo
lt t
o e
nd
of
mo
du
le (
see
Fig
ure
4).
2.
Th
e "
ba
cksp
an
" is
th
e f
irst
sp
an
(i.
e.
mo
un
t sp
aci
ng
) in
wa
rd f
rom
th
e c
an
tile
ve
r (s
ee
Fig
ure
4).
In
th
is t
ab
le (
Ta
ble
2B
), b
ack
spa
n m
atc
he
s ty
pic
al
spa
n f
rom
Ta
ble
2A
.
3.
Se
e T
ab
le 2
C ,
no
tes
3 t
hro
ug
h 9
, w
hic
h a
lso
ap
ply
to
th
is t
ab
le.
Ta
ble
2C
. Q
uic
k R
ack
Ba
se M
ou
nt
Ma
xim
um
Ea
st a
nd
We
st C
an
tile
ve
rs,
Mo
du
les
in Portrait
Ori
en
tati
on
wit
h A
typ
ica
l 1
6"
or
24
" B
ack
spa
n
BC
DB
CD
BC
DB
CD
BC
D
2:1
2 t
o 6
:12
48
"4
8"
48
"2
4"
24
"2
4"
24
" ~
/16
"1
9"
~/1
6"
19
" ~
/16
"2
4"
~/1
4"
19
" ~
/14
"1
9"
~/1
4"
24
" ~
/13
"2
0"
~/1
3"
20
" ~
/13
"
7:1
2 t
o 1
2:1
24
8"
48
"4
8"
24
"2
4"
24
"2
4"
~/1
6"
19
" ~
/16
"1
9"
~/1
6"
24
" ~
/14
"1
9"
~/1
4"
19
" ~
/14
"2
4"
~/1
3"
20
" ~
/13
"2
0"
~/1
3"
2:1
2 t
o 6
:12
48
"4
8"
48
"2
4"
24
"2
4"
24
" ~
/16
"1
9"
~/1
6"
16
"2
4"
~/1
4"
19
" ~
/14
"1
5"
~/1
4"
24
" ~
/13
"2
0"
~/1
3"
13
"
7:1
2 t
o 1
2:1
24
8"
48
"4
8"
24
"2
4"
24
"2
4"
~/1
6"
19
" ~
/16
"1
6"
24
" ~
/14
"1
9"
~/1
4"
15
" ~
/14
"2
4"
~/1
3"
20
" ~
/13
"1
3"
2:1
2 t
o 6
:12
48
"4
8"
48
" *
/32
"2
4"
24
"1
7"
19
" ~
/16
"1
6"
11
"1
9"
~/1
4"
14
"1
0"
20
" ~
/13
"1
3"
9"
7:1
2 t
o 1
2:1
24
8"
48
"4
8"
24
"2
4"
24
"1
9"
~/1
6"
16
"1
6"
19
" ~
/14
"1
4"
14
"2
0"
~/1
3"
13
"1
3"
2:1
2 t
o 6
:12
48
"
48
" *
/32
"
48
" *
/32
"2
4"
17
"1
7"
19
" ~
/16
"1
1"
11
"1
9"
~/1
4"
10
"1
0"
20
" ~
/13
"9
"9
"
7:1
2 t
o 1
2:1
24
8"
48
"3
2"
24
"2
4"
17
"1
9"
~/1
6"
16
"1
1"
19
" ~
/14
"1
4"
10
"2
0"
~/1
3"
13
"9
"
2:1
2 t
o 6
:12
48
"
48
" *
/32
"
32
" *
/24
"2
4"
17
"1
2"
16
"1
1"
4"
14
"1
0"
4"
13
"9
"3
"
7:1
2 t
o 1
2:1
24
8"
32
"3
2"
24
"1
7"
17
"1
6"
11
"1
1"
14
"1
0"
10
"1
3"
9"
9"
Ta
ble
No
tes:
1.
Th
e Q
uic
k R
ack
ba
se m
ou
nt
ma
xim
um
ca
nti
lev
er
list
ed
in
th
is t
ab
le i
s th
e d
ista
nce
fro
m c
en
ter
of
cla
mp
bo
lt t
o e
nd
of
mo
du
le (
see
Fig
ure
4).
2.
Th
e "
ba
cksp
an
" is
th
e f
irst
sp
an
(i.
e.
mo
un
t sp
aci
ng
) in
wa
rd f
rom
th
e c
an
tile
ve
r (s
ee
Fig
ure
4).
In
th
is t
ab
le (
Ta
ble
2C
), b
ack
spa
n i
s o
ne
ra
fte
r sp
aci
ng
(1
6"
or
24
").
3.
Th
e "
mo
du
le c
an
tile
ve
r" i
s m
ea
sure
d f
rom
en
d o
f m
od
ule
to
clo
sest
ed
ge
of
cla
mp
(se
e F
igu
re 4
). I
nst
all
er
sha
ll v
eri
fy t
ha
t m
od
ule
ca
nti
lev
er
do
es
no
t e
xce
ed
ma
nu
fact
ure
r re
com
me
nd
ati
on
s.
4.
Th
e "
roo
f e
dg
e d
ista
nce
" is
th
e d
ista
nce
fro
m g
ab
le e
nd
, h
ip o
r o
the
r ro
of
ed
ge
, to
en
d o
f p
eri
me
ter
mo
du
le (
see
Fig
ure
4).
F
or
bu
ild
ing
s n
o w
ide
r th
an
30
fe
et
(le
ast
pla
n d
ime
nsi
on
),
a 3
6"
ed
ge
dis
tan
ce m
ea
ns
the
arr
ay
is
full
y w
ith
in r
oo
f zo
ne
1 a
s d
efi
ne
d b
y A
SC
E 7
-10
, C
ha
pte
r 3
0,
wit
h l
ow
er
ass
oci
ate
d w
ind
up
lift
pre
ssu
res.
5.
Th
is t
ab
le i
s b
ase
d o
n a
n a
ssu
me
d P
V m
od
ule
siz
e n
o l
arg
er
tha
n 4
0"x
66
".
6.
Hig
h s
no
w l
oa
d r
eg
ion
s: a
bo
ve
15
psf
gro
un
d s
no
w l
oa
d,
the
ma
xim
um
mo
un
t ca
nti
lev
er
sha
ll b
e h
alf
th
e t
yp
ica
l sp
an
sh
ow
n i
n T
ab
le 2
A,
un
less
Ta
ble
s 2
B o
r 2
C i
nd
ica
te a
sh
ort
er
can
tile
ve
r .
7.
+
Fo
r b
uil
din
gs
wit
h t
he
na
rro
w s
ide
wid
er
tha
n 3
0 f
ee
t, i
ncr
ea
se 3
6"
to 1
0%
of
bu
ild
ing
le
ast
pla
n (
foo
tpri
nt)
dim
en
sio
n t
o r
em
ain
wit
hin
Zo
ne
1 a
s d
efi
ne
d b
y A
SC
E 7
-10
, C
ha
pte
r 3
0.
8.
*
Un
de
r th
e "
Ty
pic
al
Sp
an
" co
lum
ns,
wh
ere
tw
o n
um
be
rs a
re s
ho
wn
, su
ch a
s 4
8"
*/3
2",
th
e f
irst
nu
mb
er
is t
he
ma
xim
um
all
ow
ab
le s
pa
cin
g w
he
n t
he
PV
arr
ay
is
wit
hin
ro
of
zon
e 1
, a
nd
th
e s
eco
nd
nu
mb
er
is t
he
ma
xim
um
all
ow
ab
le s
pa
cin
g i
n z
on
es
2 a
nd
3 (
usu
all
y w
ith
in 3
6"
of
roo
f e
dg
e).
9.
~
Un
de
r th
e "
Ma
xim
um
Ca
nti
lev
er"
co
lum
ns,
wh
ere
tw
o n
um
be
rs a
re s
ho
wn
, su
ch a
s 2
4"
~/1
8",
th
e f
irst
nu
mb
er
is t
he
ma
xim
um
all
ow
ab
le c
an
tile
ve
r b
ase
d o
n t
he
ca
pa
city
of
the
Qu
ick
Ra
ck s
yst
em
an
d i
ts a
tta
chm
en
t to
th
e r
oo
f, w
hil
e t
he
se
con
d n
um
be
r is
th
e c
an
tile
ve
r th
at
en
sure
s th
at
the
en
d r
aft
ers
un
de
r th
e a
rra
y a
re l
oa
de
d n
o m
ore
he
av
ily
th
an
in
teri
or
raft
ers
.
If t
he
fir
st n
um
be
r (e
.g.
24
" ~
) is
use
d,
en
gin
ee
rin
g r
ev
iew
of
the
lo
ad
ed
en
d r
aft
ers
is
req
uir
ed
, fo
r b
oth
up
wa
rd a
nd
do
wn
wa
rd l
oa
ds.
Ma
xim
um
Mo
un
t C
an
tile
ve
r w
ith
Ba
cksp
an
= T
yp
ica
l S
pa
n
Ty
pic
al
Sp
an
(se
e T
ab
le 2
A)
Ma
xim
um
Mo
un
t C
an
tile
ve
r w
ith
Aty
pic
al
Ba
cksp
an
= 1
6"
or
24
"
Win
d E
xpo
sure
Ca
teg
ory
Win
d E
xpo
sure
Ca
teg
ory
Win
d E
xpo
sure
Ca
teg
ory
Win
d E
xpo
sure
Ca
teg
ory
Win
d E
xpo
sure
Ca
teg
ory
Ro
of
Ed
ge
Dis
tan
ce =
18
"R
oo
f E
dg
e D
ista
nce
= 1
2"
12
5 m
ph
11
0 m
ph
14
0 m
ph
Win
d S
pe
ed
Ro
of
Ed
ge
Dis
tan
ce =
12
"T
yp
ica
l S
pa
n
(se
e T
ab
le 2
A)
Ro
of
Ed
ge
Dis
tan
ce =
36
"+R
oo
f E
dg
e D
ista
nce
= 2
4"
12
0 m
ph
15
0 m
ph
Win
d E
xpo
sure
Ca
teg
ory
85
mp
h1
10
mp
h
Win
d E
xpo
sure
Ca
teg
ory
Win
d E
xpo
sure
Ca
teg
ory
Win
d E
xpo
sure
Ca
teg
ory
Win
d E
xpo
sure
Ca
teg
ory
90
mp
h1
15
mp
h
Ro
of
Pit
ch
AS
CE
7-0
5
(Se
rvic
e
AS
CE
7-1
0
(Str
en
gth
Ro
of
Ed
ge
Dis
tan
ce =
18
"
10
0 m
ph
85
mp
h1
10
mp
h
Ro
of
Ed
ge
Dis
tan
ce =
36
"+R
oo
f E
dg
e D
ista
nce
= 2
4"
90
mp
h1
15
mp
h
Ro
of
Pit
ch
AS
CE
7-0
5
(Se
rvic
e
AS
CE
7-1
0
(Str
en
gth
Win
d S
pe
ed
11
0 m
ph
14
0 m
ph
12
0 m
ph
15
0 m
ph
10
0 m
ph
12
5 m
ph
Qu
ick
Ra
ck V
1.1
Ba
se M
ou
nt
Co
de
Co
mp
lia
nce
Re
po
rtJa
nu
ary
19
,20
15
Ta
ble
3.
Exi
stin
g R
oo
f R
aft
er
Ca
pa
city
Ass
ess
me
nt
Win
d S
pe
ed
Ro
of
Pit
chn
= 1
n =
2n
= 3
n =
4n
= 1
n =
2n
= 3
n =
4n
= 1
n =
2n
= 3
n =
4
Fla
t to
6:1
2O
KO
KO
KO
KO
KO
KO
KO
KO
KO
KO
KS
A
7:1
2 t
o 1
2:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
**
Fla
t to
6:1
2O
KO
KO
KO
KO
KO
KO
KS
AO
KO
KO
KS
A
7:1
2 t
o 1
2:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
**
Fla
t to
6:1
2O
KO
KO
KO
KO
KO
KO
KS
AO
KO
KS
AS
A
7:1
2 t
o 1
2:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
**
Fla
t to
6:1
2O
KO
KO
KS
AO
KO
KS
AS
AO
KO
KS
AS
A
7:1
2 t
o 1
2:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
**
Fla
t to
6:1
2O
KO
KO
KS
AO
KO
KS
AS
AO
KS
AS
A*
SA
**
7:1
2 t
o 1
2:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
**
Fla
t to
6:1
2O
KO
KS
AS
AO
KO
KS
AS
AO
KO
KS
AS
A
7:1
2 t
o 1
2:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
**
Fla
t to
6:1
2O
KO
KS
AS
AO
KO
KS
AS
AO
KO
KS
AS
A
7:1
2 t
o 1
2:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
**
Fla
t to
6:1
2O
KO
KS
AS
AO
KO
KS
AS
AO
KO
KS
AS
A
7:1
2 t
o 1
2:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
**
Fla
t to
6:1
2O
KO
KS
AS
AO
KO
KS
AS
AO
KO
KS
AS
A
7:1
2 t
o 1
2:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
**
Fla
t to
6:1
2O
KO
KS
AS
AO
KO
KS
AS
AO
KS
AS
A*
SA
**
7:1
2 t
o 1
2:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
**
Fla
t to
6:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
**
7:1
2 t
o 1
2:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
**
Fla
t to
6:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
**
7:1
2 t
o 1
2:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
**
Fla
t to
6:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
**
7:1
2 t
o 1
2:1
2O
KS
AS
A*
SA
**
OK
SA
SA
*S
A*
*O
KS
AS
A*
SA
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Appendix 1: Quick Rack Base Mount Allowable Load Values The purpose of this Appendix is to document the allowable load values used to generate Tables 1 and 2 enclosed in the “Quick Mount PV Quick Rack V1.1 Base Mount Code Compliance Report” dated January 19, 2015.
The allowable Quick Rack base mount installations are based on allowable upward, downward, lateral, and combined downward-lateral load values determined from tests on actual Quick Rack specimens conducted at Applied Materials & Engineering (AME) in Oakland, CA on June 25-27, 2013, following ICC-AC13 and ICC-AC428 provisions. The allowable loads are determined from ultimate load values reduced by factors of safety that vary according to failure mode and design load duration.
Test Description
Tests were performed on Quick Rack base mounts installed in 2x4 Douglas-Fir rafters of nominal length with one 5/16” nominal diameter GRK RSS screw with Climatek coating pre-drilled with an 1/8” pilot hole and installed with 2.5” embedment into the rafter. The mount top extrusion was attached to the base in the highest possible configuration to capture the worst effects. The mounts were installed with the aluminum flashing and over two layers of composition shingle roofing over 1/2” nominal thickness plywood to simulate a typical installed condition.
Tests were conducted to investigate the effect of the following three primary parameters on the behavior of the base mount under ultimate loads: (1) load direction, (2) position of the application of load on the top slider, and (3) roof slope (pitch). See Figure A1.1.
Figure A1.1 Load directions and top slider loading positions.
Appendix 1: January 19, 2015 Quick Rack Base Mount Allowable Load Values Page 2 of 11
1. Load Direction
Load tests were conducted in each primary load direction to investigate the behavior of the base mount under pure loading. The four pure load directions are:
(1) Upward load from the top slider track,
(2) Downward load on the top slider track,
(3) Down-slope lateral load in the direction of the slope of the roof, and
(4) Cross-slope lateral load the direction of the elevated seal region.
2. Top Slider Loading Position
The application of load on the top slider and its effect on the behavior of the base mount was investigated for certain load direction tests where the behavior was expected to be significantly different depending on the location from which the top slider was loaded. The top slider positions that were investigated are:
• Position A: Centered on the top slider.
• Position B: Down-slope-most position on the top slider, defined as 1.5” down-slope from base mount centerline.
• Position C: Up-slope-most position on the top slider, defined as 1.5” up-slope from the base mount centerline.
3. Roof Slope
A series of downward load tests (load direction 2) were conducted on base mounts that were set on test beds sloped with a 6:12 pitch (~27 degree roof angle) to investigate the effect of combined downward and lateral parallel to roof loading on the base mount. The 6:12 slope was tested because, under ASCE 7 snow design loads, the parallel-to-roof force component is greatest at this slope.
Table A1.1 summarizes the tests that were performed at AME (note that the “G” represents that the base mount was anchored to the rafter with a GRK RSS screw as described above). In all tests, the top slider was allowed to rotate freely. However, in actual installations, the top slider is firmly clamped to the PV modules. The flexural stiffness of the modules will tend to reduce moments imposed on the base mount. This means the allowable values from these tests are likely to be conservative, especially for the lateral and combined downward and lateral load cases.
Appendix 1: January 19, 2015 Quick Rack Base Mount Allowable Load Values Page 3 of 11
Table A1.1. Testing plan summary.
Test Series Name
Primary Test Parameters
Load Direction Top Slider Loading Position Roof Slope
1 2 3 4 A B C Flat 6:12
1-A-0-G X X X
1-C-0-G X X X
2-A-6-G X X X
2-B-0-G X X X
2-B-6-G X X X
3-C-0-G X X X
4-A-0-G X X X
4-C-0-G X X X
Load Testing Summary
Upward Load Tests (Load Direction 1)
Two series of upward load tests were conducted, where in the first series the top rail was loaded from position “A”, and the second series from position “C”. From testing, it was determined that top rail position “C” produced smaller ultimate values, and was therefore taken as the controlling configuration for the allowable upward load.
The ultimate behavior of the Quick Rack base mount subject to upward loading from top slider position “C” was characterized by rotation of the base mount toward the elevated seal region (toe) with associated uplift of the slider region, slight rotation of the base mount in the down-slope direction, bending of the base mount, bending and denting of the base flashing, moderate bending of the GRK screw (due to the rotation of the base mount) and screw pull-out. Bending of the base mount was concentrated at the interface between the bottom and slider section of the QBlock slider. Furthermore, the elevated seal region creates a quasi-fixed condition on the screw end and causes it to bend and follow the base mount as it rotates. This rotation is enabled by denting of the flashing, compression of the composition shingle roofing, and pull-out of the screw. Puncturing of the flashing was observed under the down-slope-most edge of the elevated seal region. However, because the flashing was not punctured at Ultimate Load/Factor of Safety, this serviceability limit state did not define the allowable load.
Downward Load Tests (Load Direction 2)
One downward load test series was conducted in top slider position “B”. Position “A” was not tested and was assumed not to control since loading from position “B” would have a tendency to rotate the base mount more than loading from position “A”.
The dominant ultimate behavior of the base mount subject to pure downward loading was bending and cracking of the plywood directly beneath the base mount slider region. Other behavior included
Appendix 1: January 19, 2015 Quick Rack Base Mount Allowable Load Values Page 4 of 11
moderate rotation of the base mount toward the slider region accompanied by screw rotation, slight bending of the base mount at the slider region of the QBlock slider, and denting and crippling of the base flashing under the base mount slider region. After a series of three tests had been conducted to ultimate failure, a fourth test was conducted up to the approximate allowable load. The base mount was then un-installed to check for puncturing of the base flashing and crushing of the plywood. At the allowable load, there was no puncturing of the base flashing, nor was there evidence of damage to the plywood or composition shingle roofing. Thus, the allowable downward load is not controlled by a serviceability limit state.
Down-Slope Lateral Load Tests (Load Direction 3)
One down-slope lateral load test series was conducted in the “C” top slider position. Due to the direction of loading, top slider position was not viewed as an influential variable, and top slider position “C” was chosen due to ease of testing.
The ultimate behavior of the base mount in this load direction was typically characterized by moderate rotation of the base mount in the down-slope direction and uplift of the up-slope edge, moderate screw rotation and pull-out, moderate bending of the base flashing, and denting and puncturing of the base flashing under the down-slope edge. In some instances, tests from this series ended prematurely due to “end of travel” limitations, where the machine test head exceeded the expected travel distance (due to larger than expected rotations of the base mount) and disengaged from the intended loading surface. In these cases, the ultimate load was taken as the applied load when this occurred. Observations at the allowable load showed no sign of excessive base mount rotation, screw bending or pullout, or base flashing puncture, so those serviceability limit states do not control.
Cross-Slope Lateral Toward Elevated Seal (Toe) Load Tests (Load Dir. 4)
Base mount tests in this load direction were conducted in the “A” and “C” top slider positions. Due to the relatively short moment resisting arm between the GRK screw and the edge of the base mount as compared to the overturning arm, the base mount exhibits relatively low strength and stiffness in this load direction, and there was no appreciable difference in ultimate load between the two top slider positions.
The behavior at ultimate load is characterized by moderate rotation of the base mount toward the elevated seal region and uplift of the slider region, moderate screw bending and pull-out, bending of the QBlock slider, and slight bending and denting of the base flashing. Observations at the allowable load level indicate significant rotation of the base mount. However, since the primary action that causes loading in this direction is due to seismic events, such rotations were deemed acceptable. Other serviceability limit states were not considered.
Combined Downward and Down-Slope Lateral Tests
Two test series used 6:12 sloped test beds to study the interaction of downward and down-slope lateral loads on the base mount, first in the “A” position and then in the “B” position. Because of the tendency of the mount to rotate due to downward load when loaded in the “B” position, the base mounts were typically weaker and more flexible in the “B” position than in the “A” position. Therefore, the controlling ultimate values were determined from the “B” series tests.
Appendix 1: January 19, 2015 Quick Rack Base Mount Allowable Load Values Page 5 of 11
The behavior at ultimate load was characterized by rotation of the base mount in the down-slope direction and uplift of the up-slope edge, slight screw bending and pull-out, bending of the base flashing, and denting of the base flashing under the down-slope edge. For some tests, the ultimate load was taken as the load at the point when the test head slipped off the intended loading surface and no longer loaded the base mount in the correct location. The load-displacement curves from this test series were characterized by several cycles of load increase to a certain level followed by an immediate drop in load, caused by stick-slipping of the test head against the loading surface. Several measures were taken to prevent further stick-slipping in subsequent tests, including changing test heads, but this phenomenon was not eliminated completely. Serviceability limit states were not considered.
Allowable Load Adjustments
Per ICC-AC 13, for failure modes associated with failure of wood or attachments into wood (such as GRK RSS screw withdrawal and bending), the ultimate load is determined as the minimum of three test load values where each test load does not deviate from the average by more than +/- 20%, or the average of six test load values. The allowable decade-long duration load (i.e. with a wood load duration factor of 1.00) is the ultimate load divided by a Factor of Safety (FOS) of three. The allowable load for other duration loads, such as dead load (permanent), snow (duration of two months or less), and wind or seismic (duration of 10 minutes or less), are adjusted from the decade-long allowable load by multiplying by their load duration factors of 0.90, 1.15, and 1.60, respectively (the load duration factors are listed in Appendix B of both the 2005 and 2012 National Design Specifications for Wood Construction, NDS-2005 & NDS-2012). Alternatively, the FOS for these load durations is divided by its respective load duration factor. Table A1.2 summarizes the load duration factors and factors of safety for each load duration type.
Table A1.2. Load duration factors and factors of safety for the pertinent load types.
Load Type Load Duration Factor Factor of Safety (FOS)
Dead (permanent) 0.90 3 / 0.90 = 3.33
Snow (two months or less) 1.15 3 / 1.15 = 2.61
Wind or Seismic (10 minutes or less) 1.6 3 / 1.60 = 1.88
As described above, tests of Quick Rack base mounts were conducted in rafters of species Douglas-Fir, which has a nominal specific gravity G = 0.49. Douglas-Fir was chosen as the testing wood because of its availability on the West Coast of the United States. In order to extend the applicability of Quick Rack base mount installations to other parts of the United States, where the typical wood stock is less dense than Douglas-Fir (i.e. the specific gravity is lower than 0.49), the allowable load values need to be adjusted to correspond to wood with a lower specific gravity. Spruce-Pine-Fir, with a nominal specific gravity of G = 0.42, was chosen as the target wood species. For each test series, the average specific gravity of the wood specimens from the applicable tests was determined. The ultimate load was then adjusted for specific gravity by the following relation:
Appendix 1: January 19, 2015 Quick Rack Base Mount Allowable Load Values Page 6 of 11
𝑃𝑢𝑙𝑡,𝑎𝑑𝑗 = (0.42
𝐺𝑡𝑒𝑠𝑡)1.5
⋅ 𝑃𝑢𝑙𝑡,𝑡𝑒𝑠𝑡 ⩽ 𝑃𝑢𝑙𝑡,𝑡𝑒𝑠𝑡
where
Gtest = average specific gravity from the applicable tests Pult,test = ultimate load determined from testing Pult,adj = specific gravity adjusted ultimate load
The Quick Rack base mount allowable load value is then calculated by the following relation:
𝑃𝑎𝑙𝑙𝑜𝑤 =𝑃𝑢𝑙𝑡,𝑎𝑑𝑗
𝐹𝑂𝑆𝐶𝐷
where 𝐹𝑂𝑆𝐶𝐷 = applicable factor of safety for the load duration from Table A1.2
Pallow = allowable load value for a specific load duration
The Quick Rack base mount allowable load values for each load direction are summarized in Table A1.3. These loads are the basis for the Quick Rack allowable installation tables in the Code Compliance Letter.
Table A1.3. Quick Rack allowable load values.
Load Direction Governing Test
Series Failure Mode
Specific Gravity Adjusted Ultimate
Load
Allowable Load
Dead Snow Wind or Seismic
Upward 1-C-0-G GRK screw bending and pull-out, base
mount bending Avg. of 6 1188 lb. 356 lb. 455 lb. 633 lb.
Downward 2-B-0-G Plywood bending Min. of 3 3165 lb. 950 lb. 1214 lb. 1689 lb.
Down-Slope Lateral
3-C-0-G GRK screw bending
and pull-out, excessive base mount rotation†
Avg. of 6 282 lb. 85 lb. 108 lb. 150 lb.
Cross-Slope Lateral toward Elevated Seal
Region
4-A-0-G GRK screw bending and pull-out, base
mount bending Min. of 3 50 lb. n/a n/a 80 lb.
Combined Downward and
Down-Slope Lateral
2-B-6-G Excessive base mount
rotation‡ Avg. of 6 955 lb. 286 lb. 366 lb. 509 lb.
† = In some tests, the test ended when the machine test head disengaged from the intended loading surface due to excessive rotation of the base mount. In these instances, the test load was taken as the load when this occurred.
‡ = Large rotation of base mount. Test ended when test head slipped off of loading surface.
Appendix 1: January 19, 2015 Quick Rack Base Mount Allowable Load Values Page 7 of 11
Determination of Base Mount Demand-to-Capacity Ratio
The allowable Quick Rack base mount installations summarized in Tables 1 and 2 are based on a demand-to-capacity ratio analysis, in which the load demand from the controlling (largest) load combination of dead, snow, wind, and/or seismic loads is divided by the controlling (lowest) capacity of the base mount, to produce a demand-to-capacity ratio (DCR). DCR’s less than or equal to 1.0 indicate that the base mount has adequate strength to resist the applied loads, and that use of the base mount is acceptable. The load demands and determination of the Quick Rack base mount capacity is described next.
Load Demands
The following basic load types were considered:
D = dead load S = snow load W(down) = ASD wind load toward the roof W(up) = ASD wind load away from the roof E =seismic
Each basic load type acts in a unique direction, as defined by ASCE 7-05, and shown visually in Figure A1.2. Each load type is decomposed into its parallel and normal to the plane of the roof components. These basic loads are then combined using the applicable ASD load combinations from ASCE 7-05 Sec 2.4:
1) 1.0*D 2) 1.0*D + 1.0*S 3) 1.0*D + 1.0*W(down) 4) 1.0*D + 0.75*W(down) + 0.75*S 5) (1.0 + 0.14*SDS)*D + 0.525*E + 0.75*S 6) 0.6*D + 1.0*W(up)
For each load combination, the magnitude of the load parallel (P||) and normal (P⊥) to the roof is determined, and the resultant load, P, and load angle, α, is calculated.
𝑃 = √𝑃∥2 + 𝑃⊥
2𝛼 = arctan(𝑃⊥𝑃∥)
Quick Rack Base Mount Capacity
The capacity of the Quick Rack base mount is defined by the weakest of the following five capacities:
1) Combined parallel and normal to the roof allowable load capacity of the Quick Rack base mount itself, based on test results,
2) Combined withdrawal and lateral load capacity of the GRK RSS screw based on allowable capacities published in ICC-ESR 2442,
Appendix 1: January 19, 2015 Quick Rack Base Mount Allowable Load Values Page 8 of 11
3) A minimum clamping force provided by the 5/16” stainless steel (grade 18/8) machine bolt of two times the wind uplift demand (per UL 2703),
4) A minimum slip resistance between the PV array and the top slider of two times the load demand parallel to the roof (per UL 2703), and
5) The axial capacity of the machine bolt.
For the allowable installations presented in Table 1 and 2 in the Code Compliance Letter, capacity 1 or 2 always controlled.
Capacity of the Quick Rack Base Mount Itself
The capacity of the Quick Rack base mount itself under combined parallel and normal to the roof loads is determined through the use of a load interaction diagram based on the allowable loads in Table 3. Figure A1.3 shows the interaction diagram for snow load duration (CD = 1.15). The capacity of the Quick Rack base mount is a function of the load angle, α, of the load demands from the controlling load combination. The point of intersection of a line through the origin with angle α and the interaction diagram defines the capacity of the Quick Rack base mount for load parallel and normal to the roof. The Quick Rack load capacity, RQR, is the resultant of the parallel and normal load capacities. The DCR of the Quick Rack base mount is calculated:
𝐷𝐶𝑅𝑄𝑅 =𝑃
𝑅𝑄𝑅
Figure A1.2. Basic load types (dead, snow and wind) and definitions for load parallel (P||) and
normal (P⊥) to roof, load angle (α), and resultant load (P).
Appendix 1: January 19, 2015 Quick Rack Base Mount Allowable Load Values Page 9 of 11
Figure A1.3. Quick Rack base mount interaction diagram using allowable load values determined from testing. This interaction diagram is adjusted for a snow load duration (CD = 1.15). Similar interaction diagrams are defined for dead load (CD = 0.90) and wind/seismic (CD = 1.60).
Capacity of the GRK RSS Screw
Per ICC-ESR 2442, the capacity of the GRK RSS screw under combined withdrawal and lateral loads is determined by NDS-05 Sec. 11.4.1. The capacity of the GRK RSS screw, Z’α, is also a function of the load angle. The DCR of the GRK RSS screw is:
𝐷𝐶𝑅𝐺𝑅𝐾 =𝑃
𝑍𝛼′
Appendix 1: January 19, 2015 Quick Rack Base Mount Allowable Load Values Page 10 of 11
Minimum Clamping Force
The clamping force provided by the machine bolt can be related to torque through the relation:
𝑊 =𝑇
𝜇𝑏𝐷
where: W = clamping force T = torque μb = bolt coefficient of friction = 0.25 (per UL 2703) D = bolt diameter = 0.3125 inches
For the load combination including upward wind loads (wind loads away from the roof), the DCR for clamping is calculated:
𝐷𝐶𝑅𝑐𝑙𝑎𝑚𝑝 =2 ⋅ 𝑃⊥ +𝑊+𝛥𝑇
𝑊
where: P⊥ = load demand normal to the roof W+Δ T = increase in clamping force due to the differential strains between the PV modules
and the machine bolt because of an increase in temperature
Slip Resistance
Resistance to slip is provided by the friction force that acts between the panels, the clamp, and the top slider. The friction force is calculated as:
𝑅𝑓 = 𝜇𝑝(𝑃⊥ +𝑊 −𝑊−𝛥𝑇)
where: μb = coefficient of friction between the panel and the top slider = 0.30 (per UL 2703) P⊥ = load demand normal to the roof W = clamping force W-Δ T = decrease in clamping force due to the differential strains between the PV modules
and the machine bolt because of a decrease in temperature
The DCR for resistance to slip is calculated:
𝐷𝐶𝑅𝑠𝑙𝑖𝑝 =2 ⋅ 𝑃∥𝑅𝑓
where: P|| = load demand parallel to the roof
Appendix 1: January 19, 2015 Quick Rack Base Mount Allowable Load Values Page 11 of 11
Axial Capacity of the Machine Bolt
From in-house testing performed at Quick Mount PV, the strength of the machine bolt was determined by incrementally increasing the torque on the machine bolt until failure. Failure consistently occurred around 40 ft-lb. Thus, a maximum torque of 20 ft-lb on the machine bolt is recommended.
Controlling DCR
The controlling DCR of the Quick Rack base mount for a given combination of basic loads is the largest DCR from the individual components above:
𝐷𝐶𝑅𝑚𝑎𝑥 = 𝑚𝑎𝑥(𝐷𝐶𝑅𝑄𝑅 , 𝐷𝐶𝑅𝐺𝑅𝐾, 𝐷𝐶𝑅𝑐𝑙𝑎𝑚𝑝, 𝐷𝐶𝑅𝑠𝑙𝑖𝑝)
2015-01-14 Appendix 1 Allowable Load Values.docx
Appendix 2: Quick Rack Base Mount Code Compliance Report Technical Notes The purpose of this Appendix is to expand on the loading assumptions used to generate the tables enclosed in the “Quick Mount PV Quick Rack V1.1 Base Mount Code Compliance Report” dated January 19, 2015. Enclosed in that letter are three tables: Tables 1 and 2 present allowable Quick Rack base mount installations for PV modules oriented in landscape and portrait, respectively; and Table 3 shows when an existing code-compliant roof rafter is likely to be able to support the addition of a PV array with the base mount spacing indicated, and when staggering base mounts to create a more uniform distribution of load is recommended.
In addition to the conditions described in the Code Compliance Letter, additional assumptions and limitations common to all three tables are described in Section A of this Appendix. Tables 1 and 2 are further subject to the assumptions and limitations described in Section B of this Appendix, and Table 3 to those described in Section C of this Appendix. Sections A, B, and C are presented next.
Section A. Technical Notes Common to All Tables
● Load Criteria:
◦ Wind Loads:
▪ Calculation of code wind load demands is per ASCE 7-05 Chapter 6 for Components and Cladding (Sec 6.5.12.4.1) modified for an internal pressure coefficient, GCpi = 0, per ICC-AC 428. The basic wind speed (V), wind directionality factor (Kd), velocity pressure exposure coefficient (Kz), topographic factor (Kzt), importance factor (I), and exposure categories (B, C & D) are as defined by ASCE 7-05.
▪ External pressure coefficients for uplift zones 1 (interior), 2 (edge), and 3 (corner) and roof downward zone are as defined by ASCE 7-05 for a given roof geometry and slope (Figures 6-11B thru 6-11D).
▪ ASCE 7-10 wind speeds are back-calculated from ASCE 7-05 wind speeds so that the pressures are nearly identical for a Risk Category II building. See Table C26.5-6 in the ASCE 7-10 commentary.
◦ Snow Loads:
▪ Calculation of code snow load demands is per ASCE 7-05 Chapter 7. The ground snow load (pg), exposure factor (Ce), thermal factor (Ct), roof slope factor (Cs), importance factor (I), and terrain categories (B, C & D) are as defined by ASCE 7-05. Applicable snow load provisions in ASCE 7-10 remain unchanged.
▪ Since the site will generally be open to the south for solar exposure, the roof snow exposure condition is assumed to be either “partially exposed” or “fully exposed”.
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▪ The PV array is not located in an area of the roof subject to snow drift or where excessive amounts of snow can accumulate.
Section B. Technical Notes to the Allowable Quick Rack Base Mount Installation Tables (Tables 1 & 2)
Tables 1 and 2 identify the allowable Quick Rack base mount installations for landscape and portrait PV module orientations, respectively, for various base mount spacings given roof slope, wind speed, ground snow load, seismic load, and exposure category. The allowable Quick Rack base mount installations are based on allowable upward, downward, lateral, and combined downward-lateral load values determined from tests on actual Quick Rack base mount specimens conducted at Applied Materials & Engineering in Oakland, CA on June 25-27, 2013, following ICC-AC 13 and ICC-AC 428 provisions. Tables 1 and 2 are subject to the conditions described in the Code Compliance Letter, Section A of this Appendix, and the additional criteria below:
● Load Criteria:
◦ Snow Loads:
▪ The roof thermal condition after installation of the PV array is “unheated”; thus the thermal factor is equal to 1.2.
◦ Seismic Loads:
▪ Calculation of code seismic load demands is per ASCE 7-05 Chapter 13. The spectral acceleration at short period (SDS), component amplification factor (ap), component response modification factor (Rp), component importance factor (I), height of point of attachment (z), and mean roof height (h) are as defined by ASCE 7-05. Applicable seismic load provisions in ASCE 7-10 remain unchanged.
▪ The component amplification factor is equal to 1.0 and the component response modification factor is equal to 1.5 per ICC-AC 428.
● Other Considerations:
◦ The installer is responsible for verifying that all assumptions and limitations are met when applying the allowable Quick Rack base mount installation tables.
◦ The adequacy of the supporting roof structure is to be determined by others. Table 3 may be used as a guideline for determining whether the roof structure is likely to be able to support the addition of a PV array without staggering.
Section C. Technical Notes to the Existing Roof Rafter Capacity Table (Table 3)
PV arrays are often attached to every second, third, or fourth rafter. The roof rafters that support the PV array see a concentration of dead, wind, and snow loads due to this larger load span. Table 3 of the Code Compliance Letter provides guidance when an existing code compliant roof rafter is likely to be able to support the addition of a PV array given an attachment spacing (i.e. to every rafter, every second, every third, or every fourth). When a rafter is not likely to be able to support a
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PV array with a given attachment spacing, then staggering the attachment rows between rafters is often a viable option. Typically, staggering allows for the same (or a nominal increase) in the number of PV array attachments to the roof, but requires determining the location of more roof rafters, as the attachments are distributed more evenly across the roof. If staggering cannot be accommodated, then an engineering assessment is recommended to determine more precisely the load carrying ability of the roof structure and to design supplemental strengthening when appropriate. In all cases, the Quick Rack base mount allowable installations from Tables 1 or 2 still need to be satisfied. The analysis used to generate Table 3 is based on the methods described in the Structural Technical Appendix to the Structural Toolkit in the California Solar Permitting Guidebook, Second Edition. Table 3 is subject to the conditions described in the Code Compliance letter, Section A of this Appendix, and the additional criteria below:
● General Requirements:
◦ The roof rafters must run in the direction of the roof slope (i.e. from eave to ridge).
● Load Criteria:
◦ Roof Live Loads:
▪ Roof live loads are assumed to be displaced by the installation of the PV array.
▪ Prior to installation of the PV array, the roof was designed for roof live loads determined from ASCE 7-05, including reductions considering roof slope. Applicable roof live load provisions in ASCE 7-10 remain unchanged.
◦ Wind Loads:
▪ The wind area tributary to the rafter, as defined by ASCE 7-05 and ASCE 7-10 (“Effective Wind Area”) is at least 50 ft2.
▪ The rafter is subject to zone 1 (interior) uplift and downward pressures only, both for its original design and for evaluation of new PV module loads. Zone 2 (edge), and 3 (corner) pressures are not considered.
▪ The 10 psf minimum design wind pressure is ignored.
◦ Snow Loads:
▪ The roof structure was originally designed as an “unheated roof”, and remains “unheated” after installation of the PV array.
▪ Before installation of the PV array, the roof surface classification is rough (“all other surfaces” in ASCE 7-05 and ASCE 7-10 Fig. 7-2). After installation of the PV array, the roof surface classification is “unobstructed slippery”.
2015-01-19 Appendix 2 Technical Notes.docx
Quick Rack V1.1 Base Mount Code Compliance Report January 19, 2015
Glossary of Symbols
a = plan width of roof zone 2 or zone 3 from roof edge, eave, rake, hip, or ridge = larger of
3’-0” or L / 10.
b = required width of roof zone 2 or zone 3 measured along the slope of the roof.
See Sketch 5.
g = acceleration due to gravity.
hr = mean roof height, taken as the average height of the roof eave and the highest point on the roof.
L = least building plan dimension.
n = number of rafter spaces between Quick Rack base mounts = SM / SR.
SDS = spectral acceleration response parameter at short periods, see ASCE 7-05 or ASCE 7-10 Sec. 11.4.4 for more information.
SM = maximum allowable Quick Rack base mount spacing per Table 1 or Table 2.
SR = rafter spacing.
Ф = diameter symbol.
θ = roof slope with horizontal in degrees.