STRUCTURAL ENGINEERING CALCULATIONS FOR PROPOSED ROOF MOUNTED SOLAR PV SYSTEM

Montville High School 100 Horseneck Road, Montville, NJ 07045
Prepared for:
Charlotte, NC 28273
April 25 th
Prepared by:
___________________________________
License No.: 24 GE 044993
Montville HS Roof, Montville – PowerPartners
Structural Analysis Report IEI Project Number # 12003.001
April 25 th
1. Code & Standards .................................................................................................................. 6
April 25 th
EXECUTIVE SUMMARY Power Partners MasTec, LLC. has procured Innovative Engineering, Inc. (IEI) to provide a detailed structural analysis
package for one school building with multiple flat roof sections to support the installation of roof mounted solar photovoltaic
(PV) systems at 100 Horseneck Road, Montville, NJ 07045. This analysis is to determine the capacity of the existing
structures and their components to support the proposed systems and to determine if structural reinforcements are required
due to the proposed solar PV and racking systems installation.
The total roof area of the subject facility is approximately 170,000
+/- SF in size and consists of classrooms, gymnasium, multi-
purpose room, auditorium, cafeteria, and library. The subject
facility currently serves as the public high school for the
Montville Board of Education in Morris County, NJ. The original
building was design and built circa 1968 by Raymond B. Flatt,
A.I.A. & William F. Poole, A.I.A. Architects with a subsequent
building expansion added in 2002 by USA Architects, Planners, &
Interior designers.
building containing previous roof replacement, structural plans
and details were provided. IEI engineers visited the site on
February 10 th
constructed in accordance with the drawings and have performed
detailed measurements required to determine the existing member sizes and their ultimate capacities in order to estimate the
residual capacities for the use to select proper and adequate
ballast solar PV systems.
residual capacity have been provided herein and performed in
accordance with NJ IBC 2009 and ASCE 7-05 and our
engineering judgment. Canadian Solar MaxPower CS6X 290M
Monocrystalline solar module and PanelClaw Grizzly Bear FR
Gen II 10 Degree racking systems have been provided by Power
Partners MasTec as the preferred products to be used. Based on
the provided panel properties and the racking system
recommended, the result of this analysis indicates that the
existing structural systems within both proposed roof sections
(cafeteria & section A) are adequate to support the proposed roof
solar PV systems without any repair and/or reinforcement.
I. PURPOSE AND SCOPE
Power Partners MasTec, LLC. requires a structural calculation report providing a description and residual capability of the
existing structural systems within the designated roof sections, located at 100 Horseneck Road, Montville, NJ 07045 to
support the additional weight and incurred building code applicable forces due to the proposed solar PV system installation.
In order to achieve these goals, the scope of this analysis and report include the following:
Observe the components of the existing roof and supporting members that were readily exposed to view.
To report on the existing roof structural condition if any deficiency has found leading to any insufficient capacity
to support the proposed PV solar system.
April 25 th
Perform engineering calculations based on provided information, field tests data and prepare a conclusion for the
analysis.
II. METHODOLOGY
The following methods were employed during the course of this analysis:
On site observation of components of the roof structural members including existing open web steel joists, steel
girders, spandrel beams, metal decks, and structural steel columns.
Review available existing construction documents.
Utilization of standard reference sources including, but not limited to, the NJ state adopted International Building
Code, AISC Structural Steel Specifications and the Steel Joist & Metal Deck manuals.
Professional engineering judgment
III. OBSERVATION
1. General
Based on the drawing provided to IEI, the original school building was designed and built circa 1968 with
additional classrooms and gymnasium added in 2002. The estimated footprint of the facilities proposed for the
roof mounted solar PV system installation is approximately 40,000 square feet totally in plan (28,000 ft 2 for
section A and 12,000 ft 2 for cafeteria). The roof heights of these two facilities are 20’-0” and 35’-0”, respectively,
measured approximately from top of existing slab on grade to the bottom of the 1 ½ inch metal deck.
The proposed non-penetrating solar PV system will be installed directly over the top of the roofing membrane and
will add approximately 8.0 psf additional load to the roof structure at affected areas. The recommendations of the
panel types were provided to IEI by Power Partners MasTec and PanelClaw Grizzly Bear FR Gen II 10 Degree
racking systems has been considered and recommended to us to accommodate the proposed panel efficiently. The
worst-case loading scenarios have been considered in the engineering calculation on the safe side.
2. Structural
Section A Roof
The roof diaphragm of the section A roof is composed of 1 ½ inch 20 gauge galvanized type B metal roof
decks, supported by 14 inch deep wide-flange steel filler beams located at 7’-0” maximum on center.
These steel filer beams, spanning 28’-0”, in turn are supported by the 14 and 16 inch deep wide flange
structural steel girders and steel columns. The existing roofing appeared to be a built-up roof composed
of rigid insulation and loose-laid ballast gravels on top. The exterior walls are concrete masonry (CMU)
non-load bearing walls.
Cafeteria Roof
The roof diaphragm of the cafeteria is composed of 1 ½ inch 20 gauge galvanized type B metal roof
decks, supported by 12 inch deep wide-flange steel filler beams located at 8’-1 ¾” maximum on center.
These filler beams, spanning 18’-0” maximum, in tern are supported by the 18 inch deep wide flange
structural steel girders and steel columns. The existing roofing appeared to be a built-up roof composed
April 25 th
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of rigid insulation and loose-laid ballast gravels on top. The exterior walls are concrete masonry (CMU)
non-load bearing walls.
April 25 th
1) International Building Code / New Jersey Edition 2009.
2) ASCE 7-05 Minimum Design Loads for Buildings and Other Structures.
B. Accepted Industrial Standards
1. Steel: AISC Specification for Structural Steel Buildings / AISC 360-05
April 25 th
2. Steel: AISC Specification for Structural Steel Buildings / Sixth Edition, published
on 4/1/1965. (for the use for the original building analysis.)
3. ASTM A 6 “General Requirements for Delivery of Rolled Steel Plates, Shapes,
Sheet Piling and Bars for Structural Use.”
4. 80-year steel joist manual – “A compilation of specifications and load tables since
1928.” Published by Steel Joist Institute, 3127 10 th
avenue north extension, Myrtle
Edition SJI Specifications of CANAM Joist & Deck –Design Manual and
Catalog of Steel Deck Products.
6. Specification for the Design of Cold-Formed Steel Structural Members, American
Iron & Steel Institute, Washington, DC, 1986 with 1989 Addendum.
2. Assumptions & Input
A. Occupancy Classification
B. Soil Conditions
C. Design Loads
1) Live Loads:
a. Ground Snow (Pg) 30.0 psf
b. Flat Roof Snow Load (Ps) 23.1 psf
Note: Ps= Cs x 0.7 x Ce x Ct x I x Pg
Cs = 1.0 Ce = 1.0 Ct = 1.0 I = 1.1
2. Snow Drift:
According to the proposed solar PV layout, the snow drifting
effect is not applicable due to shadow offset from the adjacent
roof projection at the section A roof within the subject site.
Snow drifting effect by the existing roof top units is included in
the roof live load consideration for the effective areas.
April 25 th
2. Rigid Insulation 1.0 psf
3. Deck
4. Mech./Elec./Plumb 4.0 psf
3.0 psf (Rest of Sections)
6. Estimated Solar Panel Load 8.0 psf –estimated conservatively
on the safe side.
7. Framing See Calculation
Note:
Self-weights of primary and secondary members shall be calculated and included
separately.
3) Lateral Loads:
b. Exposure (IBC 1609.4) B (estimated at site)
c. Importance Factor (IBC 1604.5) I = 1.15
(Category III)
e. Damping Ratio 0.05
Mean Roof Height
Cafeteria Roof 35’-0”
April 25 th
SEISMIC
Note: Use the USGS (US Geological Survey) program by inputting the ZIP code of the
job site to obtain the seismic parameters. (ZIP = 07045)
II. Building Main Frame:
a. Site Class D (Assumed)
Note: Per ASCE 7-05 11.4.2, Where the soil properties are not known in sufficient
detail to determine the site class, Site Class D shall be used.
Fa = 1.523
Fv = 2.400
S1 = 0.070 (1-second Period Spec. Response Acct.)
b. Seismic Design Category C
Note: IBC 2006 Table 1613.5.6 (1) & (2)
c. Importance Factor (IBC 1604.5) I = 1.25
(Category III)
d. Seismic Group III
Note: IBC 2006 Table 1604.5 Occupancy category of buildings and other structures:
For buildings and other structures except those listed in Occupancy Categories I,
III and IV, the occupancy category is IV.
e. Response modification Factor (R factor) 3
Note: ASCE 7-05 Table 12.2-1 Design Coefficients & Factors For Seismic Force-
Resisting Systems. The Seismic Force-Resisting System falls into the item H “
Steel Systems Not Specifically Detailed for Seismic Resistance, Excluding
Cantilever Column Systems.”
(IBC Table 1604.5)
h. Building Period Coefficient (Ct) 0.028
Note: ASCE 7-05 Table 12.8-2 Values of Approximate Period Parameters Ct and x
3. Material
A. Steel
2. Structural Steel Plate: ASTM A572 or A36
3. Cold Formed Light Gage Shapes: ASTM A570
4. High Strength Bolts ASTM A325N
April 25 th
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V. SUMMARY OF RESULTS
No reinforcement to the section A and cafeteria roof areas within the subject building is required due to the
installation of the proposed PV solar system. The conclusions reached by IEI in this report are only applicable for
the Canadian Solar MaxPower CS6X 290M Monocrystalline solar module and PanelClaw Grizzly Bear FR Gen II
10 Degree racking systems information provided to us and the observation from our visit on February 10 th
, 2012.
These results are also based on the estimated code-applicable loads for the geographic location of the site and the
additional loads from the proposed solar systems. It should be noted that IEI shall be informed of any additional
load other than the proposed systems mentioned above; e.g. any additional roof membrane to be installed prior to
the Solar PV and racking systems installation.
See the following for detailed descriptions for items checked:
1. The existing 20 gauge 1 ½ -inch roof metal decks of the subject facility roofs have been checked adequate to
support the current code applicable loads and the panels support reactions. The result is based on the
calculations using the proposed Canadian Solar MaxPower CS6X 290M Monocrystalline solar module and
PanelClaw Grizzly Bear FR Gen II 10 Degree racking systems and the ideal layout for performance. The
worst case loading scenario has been considered in the calculation for the existing roof deck to support the
largest reactions located at the center of the deck span. Both the stress and deflection of the existing metal
deck has been verified meeting the current building code requirements.
2. The typical existing wide flange steel girders and filler beams have been verified to be adequate and sufficient
to support the existing loads including code applicable dead and live load as well as the effects from the
proposed Canadian Solar MaxPower CS6X 290M Monocrystalline solar module and PanelClaw Grizzly Bear
FR Gen II 10 Degree racking systems installation at the subject flat roof. The worst case loading scenario has
been considered; i.e. the support reactions from the solar panel mounts line up and fall into the vicinities of
one single span steel filler beam. The results from our analysis have also indicated that the existing structural
steel wide flange columns within the areas proposed to support the solar PV system are adequate to support
the additional loads from the solar PV panel and racking systems by inspection and our engineering
judgment.
3. The building foundations are deemed to be adequate to support the additional loads by inspection based on
our professional engineering judgments, considering the relative small additional weight from the solar panels
+ racking systems in oppose to the high capacity building column foundations.
4. The increased seismic loads due to the additional weight from the proposed PV and its racking systems have
been verified to be small than the tolerance set forth in the current building code requirement. Therefore the
existing lateral load resisting system (LLRS) is deemed to be adequate and no seismic reinforcement to the
LLRS is required.
VI. DETAILED ENGINEERING CALCULATIONS
Synopsis & Existing Building Anatomy
Based on the existing drawings provided and the site visits made on February 10 th
, the subject facilities including
the section A and gymnasium roof have been maintained in a good condition. No signs of deterioration and/or
structural distresses were found from the accessible areas. The existing building systems are divided into multiple
sections by building expansion joints. Majority of the lateral system have been designed as ordinary moment
frames. Curtain walls with brick veneer system are installed around the building perimeter.
For the 1968 built building where the solar PV system is proposed, the roof structure is comprised of steel filler
beams spanning in between the structural steel columns and wide flange girders. A 20 gauge 1 ½ inch Type B
April 25 th
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metal deck is present and supported by these steel filler beams located at a maximum 8’-1 ¾” spacing throughout
the original building facility.
The following items have been checked with the addition of the proposed roof mounted solar PV system:
1. Properties of proposed PV solar and Racking System operating weight estimate.
2. Wind pressure calculation based on the geographic location of the subject site and the criteria set forth in the
wind load provision of the currently NJ adopted building code, IBC 2009, Chapter 6.
3. Existing 1 ½” roof deck panels to support existing and additional loads. The existing roof deck has been
verified to be a 1 ½ - inch 20 gauge Type B metal decks within the original building based on the existing
drawings. A worst case load scenario and longest span observed was used for the engineering calculations.
4. The typical interior structural wide flange steel girders & beams have been checked per the current AISC
steel manual to satisfy the building code requirements. The calculation below uses the worst cases within the
roof sections of the subject building.
5. Lateral Load Resisting System* – To verify if current lateral systems shall be reinforced due to add’l
seismic forces from additional panel mass.
Since the overall surface of building subject to current code applicable wind pressure has not changed, the
wind effect on the existing Main Wing Force Resisting System (MWFRS) shall remain the same. However,
the roof deck and girder members shall be checked against existing loads plus wind components and
claddings along with the additional weight from the proposed solar PV system installation.
Analysis & Calculations
1. Properties of proposed PV solar and racking system operating weight estimate are as following:
April 25 th
Width = 3.23 feet / each panel Length = 6.41 feet / each panel
Self weight = 61.73 lbs / each panel (i.e. 2.99 psf)
Racking: Based on the information provided to us, the PanelClaw Grizzly Bear FR Gen II 10 Degree
racking systems has been provided to us for the calculation & analysis purpose. The
proposed racking system consists of three major parts – a module support with integrated
ballast, a claw for module attachment and a wind deflector.
2. Wind pressure calculation based on the geographic location of the subject site and the proposed the solar PV
& racking systems.
In order to estimate the applied loads at various roofs within the subject site, wind pressure calculations based
on the geographic location of the subject site and the existing flat roof. It should be noted that the proposed
solar panel will be installed to the existing flat roof with 10 tilted degree.
In order to estimate applicable wind pressure, calculate the velocity pressure per ASCE 7-05 Sect. 6.5.10:
Velocity pressure = qh = 0.00256 Kz x Kzt x Kd x V 2 x I
= 0.00256 x 0.73 x 1.0 x 0.85 x 90 2
x 1.15
= 14.8 psf
Kz = the velocity pressure exposure coefficient defined in ASCE 7-05 Sect 6.5.6.6 = 0.73
For the proposed panels with no degree tilted on a gable roof, the worst case net Pressure Coefficients for
windward and leeward are as follow (ASCE 7-05 Figure 6-5 & 6-11B):
Net internal pressure coefficient = GCpi = -0.18 & +0.18 per ASCE 7-05, Figure 6-5
Net external pressure coefficient = GCp = -0.8 & +0.3 per ASCE 7-05, Figure 6-11C
PU = Calculate design wind uplift (psf):
qh x [(GCp) - (GCpi)] = 14.80 x [(-0.8) - (+0.18)] = -14.5 psf
(Design net uplift wind pressure estimate)
PD = Calculate design wind downward (psf):
qh x [(GCp) - (GCpi)] = 14.80 x [(+0.3) - (-0.18)] = +7.10 psf
Estimate wind pressures:
Wind uplift pressure
Apply net wind uplift pressure to the proposed PV system to calculate wind load force in uplift case. The
uplift pressure in vertical direction (local coordination) shall be:
-14.5 x COS (10 tilted degree) = -14.28 psf
Wind downward pressure
Apply net wind downward pressure to the proposed PV system to calculate wind load force in downward
case. The downward pressure in vertical direction shall be:
+7.10 x COS (10 tilted degree) = +6.99 psf.
April 25 th
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Since the code applicable roof snow load is greater than 75 percent of wind downward pressure plus roof
snow load, the controlling load combination shall be existing dead load plus the roof snow load.
Therefore, load combination of existing dead load plus the code applicable roof snow load will be
considered as the worst case loading scenario for the components and cladding check below.
3. Existing 1 ½” 20 GA roof deck check - Per field measurement and existing drawings, the existing 20 gauge
cold formed roof deck is supported on top of the steel filler beams in a spacing of 8’-1 ¾” o/c. The properties
of the existing roof deck are:
20 33 2.1 0.2 0.23 0.23 0.24
SECTION PROPERTIES
Gauge
Fy
The Canadian Solar MaxPower CS6X-290M Monocrystalline Solar Module and PanelClaw Grizzly Bear FR Gen
II 10 Degree racking systems or equivalent will used in the analysis based on the information provided to us. With
a 10° panel tilt, the proposed panel sizes, and the ideal racking systems provided to us, the existing metal deck
with a tributary width equals to the panel support spacing in the longitudinal direction = 6’-5” was check as
following:
Per existing drawings and current governing codes, the existing Dead & Live loads used for analysis are:
Existing DL = 17.1 psf (Estimated Dead Load over Metal Deck only)
Total Existing Load= 17.1 psf + 23.1 psf = 40.2 psf
Note: Existing dead & live loads has been estimated as following:
Roofing = 7.0 psf (per existing drawings)
Rigid…

STRUCTURAL ENGINEERING CALCULATIONS FOR PROPOSED ROOF MOUNTED SOLAR PV SYSTEM

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