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Home My WebLink AboutLA186700 - Approved plansVSE Project Number: U3759.0005.201 December 3, 2020 I Solar 2676 47th Street East Inver Grove Heights, MN 55076 REFERENCE: Stephanie & Matt Steinbron Residence: 17117 Frazer Path, Farmington, MN 55024 Solar Array Installation To Whom It May Concern: Per your request,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 Building Code (2018 IBC) Risk Category: II Design wind speed: 109 mph (3-sec gust) per ASCE 7-16 Wind exposure category: C Ground snow load: 50 psf Existing Roof Structure Roof structure: 2x6 rafters @ 24" O.C. Roofing material: composite shingles Roof slope: 19° Connection to Roof Mounting connection: (1) 5/16" lag screw w/ min. 3" embedment into framing at max. 48" o.c. along rails (2) rails per row of panels, evenly spaced; panel length perpendicular to the rails not to exceed 67 in 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%.Therefore,the requirements of Section 806.2 of the 2020 Minnesota Conservation Code for Existing Buildings are met and 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: U3759.0005.201 Stephanie Matt Steinbron Residence 12/3/2020 The solar array will be flush-mounted (no more than 6"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.Because the increase in lateral forces is less than 10%,this addition meets the requirements of the exception in Section 806.3 of the 2020 Minnesota Conservation Code for Existing Buildings.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.Connections to existing roof framing must be staggered,except at array ends,so as not to overload any existing structural member.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 panel 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, LLC 12/03/2020 _______________________________________________________ Brett Veazie, P.E. Project Engineer Enclosures BDV/jsl 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-2022 12/03/2020 651 W. Galena Park Blvd., Ste. 101 / Draper, UT 84020 / T (801) 990-1775 / F (801) 990-1776 / www.vectorse.com JOB NO.:U3759.0005.201 SUBJECT:WIND PRESSURE PROJECT:Stephanie & Matt Steinbron Residence Label:Note: Calculations per ASCE 7-16 SITE-SPECIFIC WIND PARAMETERS: Basic Wind Speed [mph]:109 Notes: Exposure Category:C Risk Category:II Importance Factor, I: ADDITIONAL INPUT & CALCULATIONS: Height of Roof, h [ft]:15 (Approximate) Comp/Cladding Location:Hip?Yes Enclosure Classification: Zone 1 GCp:1.80 Figure 30.3-2E (enter negative pressure coefficients) Zone 2r GCp:2.36 Zone 2e, 3 GCp:2.56 α:9.5 Table 26.11-1 zg [ft]:900 Table 26.11-1 Kh:0.85 Table 26.10-1 Ke:0.97 Table 26.9-1 Kzt:1 Equation 26.8-1 Kd:0.85 Table 26.6-1 Velocity Pressure, qh [psf]:21.2 Equation 26.10-1 PRESSURES:p = qh (GCp)(γE)(γa)Equation 29.4-5 Zone 1, p [psf]:45.8 psf (1.0 W) Zone 2r, p [psf]:60.1 psf (1.0 W) Zone 2e, 3, p [psf]:65.1 psf (1.0 W) (a =3 ft) Solar Panel Array Hip Roofs 7° < θ ≤ 20° Enclosed Buildings Components and Cladding Wind Calculations JOB NO.:U3759.0005.201 SUBJECT:CONNECTION PROJECT:Stephanie & Matt Steinbron Residence Calculate Uplift Forces on Connection Pressure (0.6 Dead -0.6 Wind) (psf) Max Connection Spacing1 (ft) Max Trib. Area2 (ft2) Max Uplift Force (lbs) Zone 1 27.5 4.0 11.2 286 Zone 2r 36.0 4.0 11.2 381 Zone 2e, 3 39.0 4.0 11.2 415 Calculate Connection Capacity Lag Screw Size [in]:5/16 Cd:1.6 NDS Table 2.3.2 Embedment3 [in]:3 Grade: Nominal Capacity [lbs/in]:205 NDS Table 12.2A Number of Screws:1 Prying Coefficient:1.4 Total Capacity [lbs]:703 Determine Result Maximum Demand [lbs]:415 Lag Screw Capacity [lbs]:703 Result:Capacity > Demand, Connection is adequate. Notes 1. 'Max Connection Spacing' is the spacing between connections along the rails. 2. 'Max Trib Area' is the product of the 'Max Connection Spacing' 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 67". SPF (G = 0.42) 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. VECTOR STRUCTURAL ENGINEERS JOB NO.:U3759.0005.201 SUBJECT:GRAVITY LOADS PROJECT:Stephanie & Matt Steinbron Residence CALCULATE ESTIMATED GRAVITY LOADS Roof Pitch: 4.1 :12 ROOF DEAD LOAD (D) Increase due to pitch Material weight [psf] Composite Shingles 1.06 2.0 1/2" Plywood 1.06 1.0 Framing 1.00 3.0 Insulation 1.00 0.0 1/2" Gypsum Clg.1.06 0.0 M, E & Misc 1.00 0.0 Total Original Roof DL PV Array DL 1.06 3 DL:1.06 ROOF LIVE LOAD (Lr) Existing Design Roof Live Load [psf]20 ASCE 7-16, Table 4-1 Roof Live Load With PV Array [psf]0 SNOW LOAD (S):w/ Solar Array Roof Slope [x:12]:4.1 Roof Slope [°]:19 Snow Ground Load, pg [psf]:50 ASCE 7-16, Section 7.2 Terrain Category:C ASCE 7-16, Table 7-2 Exposure of Roof:Fully Exposed ASCE 7-16, Table 7-2 Exposure Factor, Ce:0.9 ASCE 7-16, Table 7-2 Thermal Factor, Ct:1.1 ASCE 7-16, Table 7-3 Risk Category:II ASCE 7-16, Table 1-1 Importance Factor, Is:1.0 ASCE 7-16, Table 7-4 Flat Roof Snow Load, pf [psf]:35 ASCE 7-16, Equation 7-1 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:0.85 ASCE 7-16, Figure 7-2 Sloped Roof Snow Load, ps [psf]:29 ASCE 7-16, Equation 7-2 Design Snow Load, S [psf]:29 1.00 35 Design material weight [psf] 2.1 1.1 3.0 0.0 0.0 0.0 6.2 3.2 #VALUE! 2020 MBC, Section 1607.13.5 Existing 35 4.1 19 50 C Fully Exposed 0.9 1.1 II 1.0 35 0 No Figure 7-2b JOB NO.:U3759.0005.201 SUBJECT:LOAD COMPARISON PROJECT:Stephanie & Matt Steinbron Residence Summary of Loads Existing With PV Array D [psf]6 9 Lr [psf]20 0 S [psf]35 29 Maximum Gravity Loads: Existing With PV Array (D + Lr) / Cd [psf]21 10 ASCE 7-16, Section 2.4.1 (D + S) / Cd [psf]35 34 ASCE 7-16, Section 2.4.1 Maximum Gravity Load [psf]:35 34 Ratio Proposed Loading to Current Loading:95%OK (Cd = Load Duration Factor = 0.9 for D, 1.15 for S, and 1.25 for Lr) 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%. Therefore, the requirements of Section 806.2 of the 2020 Minnesota Conservation Code for Existing Buildings are met and the structure is permitted to remain unaltered. VECTOR STRUCTURAL ENGINEERS JOB NO.:U3759.0005.201 SUBJECT:SOLAR LAYOUT PROJECT:Stephanie & Matt Steinbron Residence 1 2