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Home My WebLink AboutLA209888 - APPROVED - Thooft Travis Letter SSVSE Project Number: U3356.0074.231 February 7, 2023 MN Solar and More LLC ATTENTION: Leah Johnson 310 Oak Street South New London, MN 56276 REFERENCE: Thooft Travis Residence: 16573 Elm Creek Lane, Lakeville, MN 55044 MN Solar and More LLC Project: 75 Solar Array Installation To Whom It May Concern: We have reviewed the existing structure at the above referenced site.The purpose of our review was to determine the adequacy of the existing structure to support the proposed installation of solar panels on the roof as shown on the panel layout plan. Based upon our review, we conclude that the existing structure is adequate to support the proposed solar panel installation. Design Parameters Code: 2020 Minnesota Residential Code (2018 IRC) Risk Category: II Design wind speed, Vult: 115 mph (3-sec gust) Wind exposure category: C Ground snow load, Pg: 50 psf Existing Roof Structure Roof structure: manufactured trusses @ 24" o.c. Roofing material: composite shingles Connection to Roof Mounting connection: (1) 5/16" lag screw w/ min. 2.5" threaded embedment into framing at max. 48" o.c. along rails Install (2) rails per row of panels, evenly spaced; panel length perpendicular to the rails shall not exceed 70 in Rail cantilever shall not exceed 33% of connection spacing Connections shall be staggered so as not to overload any existing structural member Conclusions Based upon our review,we conclude that the existing structure is adequate to support the proposed solar panel installation. The glass surface of the solar panels allows for a lower slope factor per ASCE 7,resulting in reduced design snow load on the panels.The gravity loads,and thus the stresses of the structural elements,in the area of the solar array are either decreased or increased by no more than 5%.Stress decreases or increases of no more than 5%are considered acceptable. Therefore, the structure is permitted to remain unaltered. 651 W. Galena Park Blvd., Ste. 101 / Draper, UT 84020 / T (801) 990-1775 / F (801) 990-1776 / www.vectorse.com VSE Project Number: U3356.0074.231 Thooft_Travis Residence 2/7/2023 The solar array will be flush-mounted (no more than 10"above the roof surface)and parallel to the roof surface.Thus,we conclude that any additional wind loading on the structure related to the addition of the proposed solar array is negligible. The attached calculations verify the capacity of the connections of the solar array to the existing roof against wind (uplift), the governing load case.Increases in lateral forces less than 10%are considered acceptable.Thus the existing lateral force resisting system is permitted to remain unaltered. Limitations Installation of the solar panels must be performed in accordance with manufacturer recommendations.All work performed must be in accordance with accepted industry-wide methods and applicable safety standards.The contractor must notify Vector Structural Engineering,LLC should any damage,deterioration or discrepancies between the as-built condition of the structure and the condition described in this letter be found.The use of solar panel support span tables provided by others is allowed only where the building type,site conditions,site-specific design parameters,and solar panel configuration match the description of the span tables.The design of the solar panels,solar racking (mounts,rails,etc.)and electrical engineering is the responsibility of others.Waterproofing around the roof penetrations is the responsibility of others.Vector Structural Engineering assumes no responsibility for improper installation of the solar array.Vector Structural Engineering shall be notified of any changes from the approved layout prior to installation. VECTOR STRUCTURAL ENGINEERING, LLC 02/07/2023 _______________________________________________________ Brett Veazie, P.E. Project Engineer Enclosures BDV/jss I hereby certify that this plan, specification or report was prepared by me or under my direct supervision and that I am a duly Licensed Professional Engineer under the laws of the State of Minnesota. Brett Veazie, License No. 56392, Expiration Date: 30-June-2024 02/07/2023 651 W. Galena Park Blvd., Ste. 101 / Draper, UT 84020 / T (801) 990-1775 / F (801) 990-1776 / www.vectorse.com Concept Approval ONLYSubject to Field Inspection Inspector Date 2020 MN Bldg Code 02/15/2023dpfannenstein Please provide a copy of the City Approved plans on site at final inspection. JOB NO.:U3356.0074.231 SUBJECT:WIND PRESSURE PROJECT:Thooft Travis Residence Label:Note: Calculations per ASCE 7-10 SITE-SPECIFIC WIND PARAMETERS: Basic Wind Speed [mph]:115 Notes: Exposure Category:C Risk Category:II Importance Factor, I: ADDITIONAL INPUT & CALCULATIONS: Height of Roof, h [ft]:30 (Approximate) Comp/Cladding Location:No Enclosure Classification: Zone 1 GCp:1.0 Figure 30.4-2C (enter negative pressure coefficients) Zone 2 GCp:1.2 Zone 3 GCp:1.2 α:9.5 Table 26.9-1 zg [ft]:900 Table 26.9-1 Kh:0.98 Table 30.3-1 Kzt:1 Equation 26.8-1 Kd:0.85 Table 26.6-1 Velocity Pressure, qh [psf]:28.3 Equation 30.3-1 GCpi:0 Table 26.11-1 PRESSURES:Equation 30.9-1 Zone 1, p [psf]:27.9 psf (1.0 W, Interior Zones, beyond 'a' from roof edge) Zone 2, p [psf]:33.5 psf (1.0 W, End Zones, within 'a' from roof edge) Zone 3, p [psf]:33.5 psf (1.0 W, Corner Zones, within 'a' from roof corner) (a= 3 ft) Solar Panel Array Gable Roofs 27° < θ ≤ 45° Enclosed Buildings Components and Cladding Wind Calculations ()()piphGCGCqp−= JOB NO.:U3356.0074.231 SUBJECT:CONNECTION PROJECT:Thooft Travis Residence Calculate Uplift Forces on Connection Pressure (0.6 Dead -0.6 Wind) (psf) Max Trib. Width1 (ft) Max Trib. Area2 (ft2) Max Uplift Force (lbs) Zone 1 14.9 4.0 11.7 174 Zone 2 18.3 4.0 11.7 214 Zone 3 18.3 4.0 11.7 214 Calculate Connection Capacity Lag Screw Size [in]:5/16 Cd:1.6 NDS Table 2.3.2 Embedment3 [in]:2.5 Grade: Nominal Capacity [lbs/in]:205 NDS Table 12.2A Number of Screws:1 Prying Coefficient:1.4 Total Capacity [lbs]:586 Determine Result Maximum Demand [lbs]:214 Lag Screw Capacity [lbs]:586 Result:Capacity > Demand, Connection is adequate. Notes 1. 'Max Trib. Width' is the width along the rails tributary to the connection. 3. Embedment is measured from the top of the framing member to the beginning of the tapered tip of the lag screw. Embedment in sheathing or other material is not effective. The length of the tapered tip is not part of the embedment length. 2. 'Max Trib Area' is the product of the 'Max. Trib Width' and 1/2 the panel width/height perpendicular to the rails. (2) rails per row of panels. Length of panels perpendicular to the rails shall not exceed 70". SPF (G = 0.42) VECTOR STRUCTURAL ENGINEERS JOB NO.:U3356.0074.231 SUBJECT:GRAVITY LOADS PROJECT:Thooft Travis Residence GRAVITY LOADS Roof Pitch: 8.0 :12 ROOF DEAD LOAD (D) Increase due to pitch Material weight [psf] Composite Shingles 1.20 2.0 1/2" Plywood 1.20 1.0 Framing 1.00 3.0 Insulation 1.00 0.5 1/2" Gypsum Clg.1.20 2.0 M, E & Misc 1.00 6.5 Total Existing Roof DL PV Array DL 1.20 3 DL:1.20 ROOF LIVE LOAD (Lr) Existing Design Roof Live Load [psf]20 ASCE 7-10 Table 4.3-1 Roof Live Load With PV Array [psf]0 SNOW LOAD (S):w/ Solar Array Roof Slope [x:12]:8.0 Roof Slope [°]:34 Ground Snow Load, pg [psf]:50 ASCE 7-16, Section 7.2 Terrain Category:C ASCE 7-16, Table 7.3-1 Exposure of Roof:Fully Exposed ASCE 7-16, Table 7.3-1 Exposure Factor, Ce:0.9 ASCE 7-16, Table 7.3-1 Thermal Factor, Ct:1.1 ASCE 7-16, Table 7.3-2 Risk Category:II ASCE 7-16, Table 1.5-1 Importance Factor, Is:1.0 ASCE 7-16, Table 1.5-2 Flat Roof Snow Load, pf [psf]:35 ASCE 7-16, Equation 7.3-1 Minimum Roof Snow Load, pm [psf]:0 ASCE 7-16, Section 7.3.4 Unobstructed Slippery Surface?Yes ASCE 7-16, Section 7.4 Slope Factor Figure:Figure 7-2b ASCE 7-16, Section 7.4 Roof Slope Factor, Cs:0.61 ASCE 7-16, Figure 7.4-1 Sloped Roof Snow Load, ps [psf]:21 ASCE 7-16, Equation 7.4-1 Design Snow Load, S [psf]:2135 8.0 34 50 C Fully Exposed 0.9 1.1 II 1.0 35 0 No Figure 7-2b 1.00 35 Design material weight [psf] 2.4 1.2 3.0 0.5 2.4 6.5 16.0 3.6 #VALUE! 2020 MRC, Section R324.4.1.1 Existing JOB NO.:U3356.0074.231 SUBJECT:LOAD COMPARISON PROJECT:Thooft Travis Residence Summary of Loads Existing With PV Array D [psf]16 20 Lr [psf]20 0 S [psf]35 21 Maximum Gravity Loads: Existing With PV Array (D + Lr) / Cd [psf]29 22 ASCE 7-10, Section 2.4.1 (D + S) / Cd [psf]44 35 ASCE 7-10, Section 2.4.1 Maximum Gravity Load [psf]:44 35 Ratio Proposed Loading to Current Loading:80%OK The gravity loads, and thus the stresses of the structural elements, in the area of the solar array are either decreased or increased by no more than 5%. Stress decreases or increases of no more than 5% are considered acceptable. Therefore, the structure is permitted to remain unaltered. (Cd = Load Duration Factor = 0.9 for D, 1.15 for S, and 1.25 for Lr) VECTOR STRUCTURAL ENGINEERS JOB NO.:U3356.0074.231 SUBJECT:SOLAR LAYOUT PROJECT:Thooft Travis Residence