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Home My WebLink AboutSTRUCTURAL LETTER OF APPROVAL - 23-00799 - 351 S 3rd E - Solar PanelsDate: 30 October 2023 Big Dog Solar Energy 620 Pheasant Ridge Dr Chubbuck, ID 83202 Layne Dearden Residence: 351 South 3rd Street East, Rexburg, ID 83440 Dear Sir/ Madam, Conclusion Structural Letter of Approval Terra Engineering Consulting (TEC) has performed a structural analysis for the existing roof based on the existing and proposed load conditions, and determined that the structure can support the additional weight of the proposed solar panel system. The attached calculations are based off the assumptions that the existing structural components are in good condition and that they meet industry standards. The existing structure information is assumed based on the survey and information provided by the client. The design information and assumptions that the calculations are based off are located in the attached References page. The design of the solar panel’s mounting hardware is to be provided by others. This engineering analysis was performed in accordance with ASCE 7-16 and 2018 IBC/IRC design methods. The total additional roof load of the solar panels system is 3 psf, and the typical 20 psf live load will not be present in the area of the panels, as defined per Section 1607.13.5.1 in 2018 IBC. The structural evaluation shows that existing framing is able to withstand the additional load while meeting current standards, allowing the structure to remain unaltered; see calculations and span table attached. Regarding lateral wind loads, the solar panel structure is considered to be partially enclosed due to the low profile of the panels (3 to 6 inches) and airflow restrictions below the panels caused by the pv frame, wiring, conduit, and frame brackets. Because the system is considered to be 'partially enclosed' additional wind pressure on the structure is considered negligible. The addition of total PV system weight result in an increase under 10% of the total roof weight, and meets the seismic requirements in Section 502.5 of 2018 IEBC. See the attached calculations for further details. TEC concludes that the installation of solar panels on existing roof will not affect the structure, and allows it to remain unaltered under the applicable design standards. The calculations performed to support these conclusions are attached to this letter. 8470 W MAGNA MAIN ST UNIT 311, MAGNA, UT 84044 / T (801) 739-0117 General Instructions 2. Contractor shall keep an accurate set of As-Built plans Best Regards, TEC Solar, PLLC Ahmad Alshakargi, PE Civil Engineer 1. Contractor shall comply with all Federal, State, County, City, local and OSHA mandated regulations and requirements. The most stringent shall govern. 3. The solar panel's racking system and mounting hardware shall be mounted in accordance with the manufacturer's most recent installation manual. 4. Connection: 5/16'' lag screws 2.5'' minimum penetration at 48'' maximum spacing. 5. Panel supports connections shall be staggered to distribute load to adjacent trusses. 6. If during solar panel installation, the roof framing members appear unstable or deflect non-uniformly, our office should be notified before proceeding with the installation. 7. Structural observation or construction inspections will not be performed by TEC, Engineer-of-Record (EOR) nor their representatives. 10/30/2023 8470 W MAGNA MAIN ST UNIT 311, MAGNA, UT 84044 / T (801) 739-0117 References Design Parameter Risk Category: II Ground Snow load: 50 psf Roof Snow load: 35 psf Design Wind Speed: 115 mph (3 sec gust) per ASCE 7-16 Seismic Design Category: D Wind Exposure Category: C Existing Roof Structure Roof framing: 2x6 Rafters at 24” O.C. Roof material: Metal seam Roof slope: 20°, 34° Solar Panels Weight: 3 psf Code: 2018 International Building Code/ International Existing Building Code, ASCE 7-16, and National Design Specification for Wood Construction (NDS) 2015 Edition 8470 W MAGNA MAIN ST UNIT 311, MAGNA, UT 84044 / T (801) 739-0117 Date:10/30/2023 Client:Layne Dearden Subject:Gravity load Gravity load calculations Snow load (S)Existing w/ solar panels Roof slope (°):20 20 Ground snow load, pg (psf):50 50 ASCE 7-16 C7.2 Terrain category:C C ASCE 7-16 table 7.3-1 Exposure of roof:Fully exposed Fully exposed ASCE 7-16 table 7.3-1 Exposure factor, Ce:0.9 0.9 ASCE 7-16 table 7.3-1 Thermal factor, Ct:1.1 1.1 ASCE 7-16 table 7.3-2 Risk Category:II II ASCE 7-16 table 1.5-1 Importance Factor, Is:1 1 ASCE 7-16 table 1.5-2 Flat roof snow load, pf (psf):35.0 35.0 ASCE 7-16, equation 7.3-1 Minimum roof snow load, pm (psf):0 0 ASCE 7-16, equation 7.3-4 Roof Surface type: Unobstructed Slippery surface Unobstructed slippery surface ASCE 7-16, C7.4 Roof slope factor, Cs:0.83 0.83 ASCE 7-16, C7.4 Sloped roof snow load, ps [psf]:29.1 29.1 Roof dead load (D) Roof pitch/12 4.4 Metal seam 0.8 psf 1/2" Gypsum clg.0 psf 1/2" plywood 1 psf insulation 0.8 psf Framing 3 psf M, E & Misc 1.5 psf Roof DL without PV arrays 7.6 psf PV Array DL 3 psf Roof live load (Lr)Existing w/ solar panels Roof Live Load 20 0 2018 IBC, Section 1607.13.5.1 ASD Load combination: Existing With PV array D [psf]7.6 10.6 ASCE 7-16, Section 2.4.1 D+L [psf]7.6 10.6 ASCE 7-16, Section 2.4.1 D+[Lr or S or R] [psf]36.7 39.7 ASCE 7-16, Section 2.4.1 29.4 32.4 ASCE 7-16, Section 2.4.1 Maximum gravity load [psf]:36.7 39.7 ASCE 7-16, equation 7.4-1 Design Snow Load (S) D+0.75L+0.75[Lr or S or R] [psf] Date:10/30/2023 Client:Layne Dearden Subject: Wind Pressure Calculations Basic wind speed (mph)115 Risk category II Exposure category C Roof type Gable Figure for GCp values ASCE 7-16 Figure 30.3-2A-I Zone 1 Zone 2 Zone 3 GCp (neg)-0.9 -1.7 -2.6 GCp (pos)0.5 0.5 0.5 zg (ft)900 (ASCE 7-16 Table 26.11-1) α 9.5 (ASCE 7-16 Table 26.11-1) Kzt 1 (ASCE 7-16 Equation 26.8-1) Kh 0.94 (ASCE 7-6 Table 26.10-1) Kd 0.85 (ASCE 7-16 Table 26.6-1) Velocity Pressure,qh (psf)27.05 (ASCE 7-16 Equation 26.10-1) Gcpi 0 (ASCE 7-16 Table 26.13-1)(0 for enclosed buildings) Zone 1 Zone 2 Zone 3 W Pressure, (neg) [psf]-24.35 -45.99 -70.33 W Pressure, (pos) [psf]13.53 13.53 13.53 W Pressure, (Abs. max) [psf]24.35 45.99 70.33 Connection Calculations Lag screw diameter:5/16 Capacity Connection type:Lag screw Embedment (in):2.5 Framing grade:DFL#2 G:0.5 Capacity [lbs/in]:266 (2015 NDS table 12.2A) Number of screws:1 Total capacity [lbs]:665.00 Demand Anchor spacing:48 in Anchor spacing in roof corners:48 in Zone ( 0.6 W Pressure, psf), see Note 1 Max. tributary area (ft^2)Max Uplift force (lbs) 1 14.6 11 160.7 2 27.6 11 303.5 3 42.2 11 464.2 (only changes if structure located on a hill or ridge) Connection Meets Demand Wind load and Connection Note 1: 0.6W results from dominant ASD combo [0.6D+ 0.6W] (ASCE 7-16 2.4.1). Date:10/30/2023 Client:Layne Dearden Subject:Beam calculator Beam Design (Roof)2x6 Rafters at 24 in o.c., span 9 ft max. Load Combination Combo DL LL W SL LLR E Sum 1 1.4 10.6 0 0 0 0 0 29.1 0 0 0 14.84 2 1.2 10.6 1.6 0 0 0 0.5 29.1 0 0 0 27.27 3 1.2 10.6 1 0 1 0 1.6 29.1 0 0 0 59.28 4 1.2 10.6 1 0 1 0 0.5 29.1 0 0 0 27.27 5 1.2 10.6 0 0 0 0 0.2 29.1 0 1 0 18.54 6 0.9 10.6 0 0 1 0 0 29.1 0 0 0 9.54 7 0.9 10.6 0 0 0 0 0 29.1 0 1 0 9.54 Roof DL 10.6 psf (see Gravity load roof DL) S 29.1 psf W E LL 0 psf RLL 0 psf (see Gravity load LL with PV arrays) U 59.28 psf beam spacing 2 ft o.c. uniform load 118.56 plf span 9 ft Mu = w(l^2)/8 1200.42 lb-ft Number of joists 1 Flexure design Cr 1.15 (2015 NDS Supp, p32) Timber grade DFL#2 (2015 NDS Supp, table 4A) Fb 900 psi (set SPF#2 as default) Kf 2.54 (2015 NDS, table 2.3.5) bending fact.0.85 (2015 NDS, table 2.3.6) dimension Cf (table 4A, NDS supp 2015, p32) S in^3 (table1B, NDS supp 2015) Fbu = Mu/S (psf)Fbu (psi) moment of inertia in^4 (table 1B, NDS supp) 2x6 1.3 7.56 274381.7 1905.429 20.8 purlin size λ (Table N3, NDS 2015 p184)F'bn (psi)Fbu Fbu < F'bn 2x6 0.8 2323.9476 1905.429 Works Design for deflection we going to assume these calculations for U1 only since its clearly higher we use the following equation to calculation max deflection, minimum interia, and deflection service load combination:D+S U 39.7 lb Uniform load 79.4 plf *convert all the units in the equaion to inch max def. (ft) E psi(Table 4A)w (plf)l (ft) I (min) (in^4) Imin< Ipurlin 0.0375 1600000 79.4 9 16.27948 Works Design for Shear fvu = 1.5V/A V is shear Vu, and A cross sectional area of purlin found in table 1B uniform load 118.56 plf Vu 533.52 lb Vu = wl/2 Framing cross section 8.25 in^2 fvu 97.00 psi Fv 180 psi (for DFL#2) F'vn 311.04 psi F'vn > fvu Works Beam works