The URL can be used to link to this page

Home My WebLink AboutLA200293-Approved Raway Engineering Letter SS (1)VSE Project Number: U1922.1366.221 March 17, 2022 Powerfully Green 2010 E Hennepin Ave Minneapolis, MN 55413 REFERENCE: Raway Residence: 20501 Granville Lane, Lakeville, MN 55044 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 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: 2x4 manufactured trusses @ 24" o.c. Roofing material: composite shingles Roof slope: 24° Connection to Roof Mounting connection: (1) 5/16" lag screw w/ min. 2.5" threaded embedment into framing at max. 48" o.c. (portrait and landscape) along rails Install (2) rails per row of panels, evenly spaced Maximum panel dimension: 68.5x41 in Rail cantilever shall not exceed 33% of connection spacing Conclusions Based upon our review,we conclude that the existing structure is adequate to support the proposed solar panel installation. 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: U1922.1366.221 Raway Residence 3/17/2022 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.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 shall be notified of any changes from the approved layout prior to installation. VECTOR STRUCTURAL ENGINEERING, LLC 03/17/2022 _______________________________________________________ Brett Veazie, P.E. Project Engineer Enclosures BDV/ryl 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 03/17/2022 651 W. Galena Park Blvd., Ste. 101 / Draper, UT 84020 / T (801) 990-1775 / F (801) 990-1776 / www.vectorse.com JOB NO.:U1922.1366.221 SUBJECT:WIND PRESSURE PROJECT:Raway 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]:25 (Approximate)Hip? Comp/Cladding Location:No Enclosure Classification: Zone 1 GCp:0.9 Figure 30.4-2B (enter negative pressure coefficients) Zone 2 GCp:1.7 Zone 3 GCp:2.6 α:9.5 Table 26.9-1 zg [ft]:900 Table 26.9-1 Kh:0.95 Table 30.3-1 Kzt:1 Equation 26.8-1 Kd:0.85 Table 26.6-1 Velocity Pressure, qh [psf]:27.2 Equation 30.3-1 GCpi:0 Table 26.11-1 PRESSURES:Equation 30.9-1 Zone 1, p [psf]:24.4 psf (1.0 W, Interior Zones, beyond 'a' from roof edge) Zone 2, p [psf]:45.5 psf (1.0 W, End Zones, within 'a' from roof edge) Zone 3, p [psf]:69.8 psf (1.0 W, Corner Zones, within 'a' from roof corner) (a= 3 ft) Solar Panel Array Gable/Hip Roofs 7° < θ ≤ 27° Enclosed Buildings Components and Cladding Wind Calculations ()()piphGCGCqp−= JOB NO.:U1922.1366.221 SUBJECT:CONNECTION PROJECT:Raway 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 12.8 4.0 11.4 146 Zone 2 25.5 4.0 11.4 291 Zone 3 40.1 4.0 11.4 457 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]:457 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. 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 69". 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.:U1922.1366.221 SUBJECT:GRAVITY LOADS PROJECT:Raway Residence GRAVITY LOADS Roof Pitch: 5.3 :12 ROOF DEAD LOAD (D) Increase due to pitch Material weight [psf] Composite Shingles 1.09 2.0 1/2" Plywood 1.09 1.0 Framing 1.00 3.0 Insulation 1.00 0.5 1/2" Gypsum Clg.1.09 2.0 M, E & Misc 1.00 6.5 Total Existing Roof DL PV Array DL 1.09 3 DL:1.09 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]:5.3 Roof Slope [°]:24 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?No ASCE 7-16, Section 7.4 Slope Factor Figure:Figure 7-2b ASCE 7-16, Section 7.4 Roof Slope Factor, Cs:1.00 ASCE 7-16, Figure 7.4-1 Sloped Roof Snow Load, ps [psf]:35 ASCE 7-16, Equation 7.4-1 Design Snow Load, S [psf]:35 1.00 35 Design material weight [psf] 2.2 1.1 3.0 0.5 2.2 6.5 15.5 3.3 #VALUE! 2020 MRC, Section R324.4.1.1 Existing 35 5.3 24 50 C Fully Exposed 0.9 1.1 II 1.0 35 0 No Figure 7-2b VECTOR STRUCTURAL ENGINEERS JOB NO.:U1922.1366.221 SUBJECT:MEMBER FORCES PROJECT:Raway Residence DESIGN LOADS [PSF]:Load Types:Snow Live Dead Existing Roof 35 20 15 Proposed PV Array 35 0 19 (Cd = Load Duration Factor = 0.9 for D, 1.15 for S, and 1.25 for Lr) Label Length 35.9 Existing Proposed Check M (ft-lb)14043 13871 99%OK Existing Proposed Check V (lb)1565 1528 98%OK Existing Loads (Distributed) Cond Roof Trib (ft) Add'l Live Load (plf) Add'l Dead Load (plf) Bm wt (plf)wLL (plf)wDL (plf) 1 2.00 0 0 0 60.3 26.9 Proposed Loads (Distributed) Cond Dist to Load 'a' (ft) Length of Load 'b' (ft) Δ wLL (plf)Δ wDL (plf) 2 2.3 5.7 -14.1 5.7 3 11.0 5.7 0.0 5.7 4 24.4 11.4 -14.1 5.7 5 0.0 5.7 6 0.0 5.7 Proposed Loads as Point Loads Cond Dist 'a' (ft) Point Live Load 'PLL' (lb) Point Dead Load 'PDL' (lb) 7 0.0 0.0 8 0.0 0.0 9 0.0 0.0 10 0.0 0.0 11 0.0 0.0 manufactured trusses 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. (D+Lr)/Cd(D+S)/Cd Max Load 28 21 44 46 44 46 0 5000 10000 15000 0 5 10 15 20 25 30 35 40 MOMENT (FT-LB) EXISTING PROPOSED -2000 -1000 0 1000 2000 0 10 20 30 40 SHEAR (LB) EXISTING PROPOSED 0 50 100 0 10 20 30 40 LOAD (LB) EXISTING PROPOSED