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Home My WebLink AboutLA210237-APPROVED - TOMSHEALetterSS63a52ab571329Engineering Alliance, Inc https://www.eng-alliance.com 23 December 2022 UNIRAC 1411 Broadway Blvd. NE Albuquerque, NM 87102 REFERENCE: Tom Shea: 16163 Logarto Ln, Lakeville, MN 55044 USA Solar Array Installation Design Parameter Code: International Residential Code 2018 (IRC 2018) Risk Category: II Design wind speed: 115 MPH Wind exposure category: B Ground snow load: 50 PSF Seismic design category: A Existing Roof Structure Roof Structure: 2"x6" rafters @24" o.c. Roofing material: Comp Shingle Connection to Roof Mounting connection: One 5/16 in lag screw w/ min. 2.5 in embedment into framing at max. 48 in o.c. along rails Two rails per row of panels, evenly spaced; panel length perpendicular to the rails not to exceed 74 in Conclusions 4603 April Meadow Way, Sugar Land, TX 77479. Ph: 832 865 4757 To Whom It May Concern: We have reviewed the existing structure referenced above. The purpose of the review was to evaluate its adequacy to support the proposed installation of solar panels on the roof as shown on the panel layout plan drawings. Based upon our review, we conclude that the existing structure is adequate to support the proposed solar panel installation. Based upon our evaluation, we conclude that the existing structure is adequate to support the proposed solar panel installation. In the area of the solar array, other live loads will not be present or will be greatly reduced . 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 stresses of the structural elements, resulting from the altered gravity loads in the area of the solar array are either decreased or increased by no more than 5%. Therefore, the structure is permitted to remain unaltered. Engineering Alliance, Inc https://www.eng-alliance.com Limitations Please feel free to call for any questions or clarifications. Prepared by Engineering Alliance, Inc Sugar Land, TX Phone: 832 865 4757 4603 April Meadow Way, Sugar Land, TX 77479. Ph: 832 865 4757 The solar array will be flush-mounted (not more than 5 in 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. Regarding seismic loads, we conclude that any additional forces will be small. As per ASCE 7-16, Section 11.1.2, detached one- and two-family dwellings with Seismic Design Category A, B or C or located where the mapped short- period spectral response acceleration, Ss, is less than 0.4 g are exempted from seismic load. Therefore the existing lateral force resisting system can remain unaltered. 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 Engineering Alliance Inc. 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 are 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. Engineering Alliance Inc assumes no responsibility for improper installation of the solar array. Professional Engineer 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. Signature: Typed or Printed Name: Saddam Ahmad Date: License Number: 5538123-DEC-2022 Concept Approval ONLY Subject to Field Inspection Inspector Date 2020 MN Bldg Code 03/06/2023dpfannenstein Please provide a copy of the City Approved plans on site at final inspection. Project: Location: Designer:NH Date: Calculations per ASCE 7-16 International Residential Code 2018 (IRC 2018) ROOF DEAD LOAD (D): Material Design material weight (psf) Increase due to pitch Material weight (psf) Comp Shingle 2.31 1.15 2 1/2" Plywood 1.2 1.15 1 Framing 3 3 Insulation 0.5 0.5 1/2" Gypsum Clg.2.3 1.15 2 M, E & Misc 1.5 1.5 Total Dead Load 10.8 PV Array Dead Load 3.5 1.15 3 ROOF LIVE LOAD (Lr): Existing Design Roof Live Load [psf]16 2018 IRC, Table R301.6 Roof Live Load With PV Array [psf]0 2018 IRC, Table R301.6 SEISMIC LOAD, (E): Risk category:II Table 1.5-1 Seismic Design Category:A Table 11.6-2 Ip:1 Table 1.5-2 Site Class:D Rp:1.5 Table 13.6-1 Ss:0.048 S1:0.032 ap:1 Table 13.6-1 z:1 ft h:1 ft z/h:1 Fa:1.6 Table 11.4-1 Fv:2.4 Table 11.4-2 SMS:0.077 Eqs. 11.4-1 SM1:0.077 Eqs. 11.4-2 SDS:0.051 Eqs. 11.4-3 SD1:0.051 Eqs. 11.4-4 Engineering Alliance, Inc Tom Shea 23 December 2022 16163 Logarto Ln, Lakeville, MN 55044 USA Project: Location: Designer:NH Date: Engineering Alliance, Inc Tom Shea 23 December 2022 16163 Logarto Ln, Lakeville, MN 55044 USA SITE-SPECIFIC WIND PARAMETERS: Basic Wind Speed [mph]:115 Exposure Category:B Sec. 26.7.3 Risk Category:II Table 1.5-1 Height of Roof, h [ft]:25 (Approximate) Roof Slope [°]:30 Site Elevation [ft]:958 Comp/Cladding Location:FIGURE_30.3_2D Enclosure Classification:Enclosed Buildings Zone 1, 2e 1.8 (enter largest abs. value) Zone 2n, 2r, 3e 2.0 (enter largest abs. value) Zone 3r 3.2 (enter largest abs. value) α:7 Table 26.11-1 zg [ft]1200 Table 26.11-1 Kh:0.67 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]:18.49 Equation 26.10-1 ɣE:1.5 ɣa:0.8 Figure 29.4-8 PRESSURES: p = qh(GCp)(ɣE)(ɣa)(lb/ft2)Equation 29.4-7 Zone 1, 2e :39.9 psf (1.0 W) Zone 2n, 2r, 3e :44.4 psf (1.0 W) Zone 3r :71.0 psf (1.0 W) a [ft] =3.2 Gable Roofs, 27° < θ ≤ 45° Project: Location: Designer:NH Date: Engineering Alliance, Inc Tom Shea 23 December 2022 16163 Logarto Ln, Lakeville, MN 55044 USA COMPARE WIND & SEISMIC LOADS FOR CONNECTION (1 Sq. Ft. Section) Wind Load, W: Wind pressure, p:24.0 psf (Zone 1: 0.6 W from wind pressure calculation) Height, h:1 ft Width, w:1 ft Fperp:24.0 lb (Uplift) Seismic Load, E: 0.7 * Fp ,min:0.032 lb Equation 13.3-2 0.7 * Fp ,max:0.172 lb Equation 13.3-3 0.7 * Fp ,vert:0.022 lb Sec 13.3.1.2 0.7 * Fp ,long:0.086 lb Equation 13.3-1 0.7*Fp ,perp:0.062 lb (uplift) Wind (uplift) Controls Connection Design CHECK INCREASE IN OVERALL SEISMIC LOADS SEISMIC: Seismic Design Category: A As per ASCE 7-16, Section 11.1.2, Seismic load is Exempted. Project: Location: Designer:NH Date: Engineering Alliance, Inc Tom Shea 23 December 2022 16163 Logarto Ln, Lakeville, MN 55044 USA Lag Screw Connection Tributary Length (in): 74 Max Tributary Width (in): 48 Capacity: Lag Screw Size[in] : 5/16 Cd:1.6 NDS Table 2.3.2 Embedment1 [in]:2.5 Grade: SPF (G = 0.42) Capacity [lbs/in]: 205 NDS Table 12.2A Number of Screws in tension: 1 Prying Coefficient: 1.4 Total Capacity [lbs]: 586 Demand: Zone 1, 2e : 21.0 4.0 3.1 12.3 258 Zone 2n, 2r, 3e : 23.6 4.0 3.1 12.3 291 Zone 3r : 39.6 4.0 3.1 12.3 488 Total Tension Force(lbs): 488 Demand< Capacity:83.4%, OK Notes 1. Embedment is measured from the top of the framing member to the beginning of the tapered tip of the 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. Tributary Width' (along the rails) and 1/2 the panel width/height (perpendicular to the rails). Max. Trib. Length (ft) Pressure (0.6 Wind) (psf) Max Tributary Width (ft) Max. Trib. Area2 (ft2) Max. Uplift Force (lbs)Zone Project: Location: Designer:NH Date: Engineering Alliance, Inc Tom Shea 23 December 2022 16163 Logarto Ln, Lakeville, MN 55044 USA SNOW LOAD (S): Existing w/ Solar Panel Array Roof Slope [x:12]:6.9 6.9 Roof Slope [°]:30 30 Snow Ground Load, pg [psf]:50 50 Section 7.2 Surface Roughness Category: B B Sec. 26.7.2 Exposure of Roof:Fully Exposed Fully Exposed Table 7.3-1 Exposure Factor, Ce:0.9 0.9 Table 7.3-1 Thermal Factor, Ct:1.1 1.1 Table 7.3-2 Risk Category:II II Table 1.5-1 Importance Factor, Is:1 1 Table 1.5-2 Flat Roof Snow Load, pf [psf]:35 35 Equation 7.3-1 Minimum Roof Snow Load, pm [psf]:0 0 Section 7.3.4 Unobstructed Slippery Surface? NO YES Section 7.4 Slope Factor Figure:Figure 7-2b Figure 7-2b Section 7.4 Roof Slope Factor, Cs:1.00 0.67 Figure 7.4-1 Sloped Roof Snow Load, ps [psf]:35 23 Equation 7.4-1 Design Snow Load, S [psf]: 35 23 Summary of Loads Existing With PV Array D [psf] 11 14 Lr [psf] 16 0 S [psf] 35 23 Maximum Gravity Loads: Existing With PV Array (D + Lr) / Cd [psf]21 16 ASCE 7-16, Section 2.4.1 (D + S) / Cd [psf]39 32 ASCE 7-16, Section 2.4.1 (Cd = Load Duration Factor = 0.9 for D, 1.15 for S, and 1.25 for Lr) Maximum Gravity Load [psf]: 39 32 82% OKRatio Proposed Loading to Current Loading: 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 structure is permitted to remain unaltered.