The URL can be used to link to this page

Home My WebLink AboutPATIO ENGINEERING LETTER - 22-00816 - 491 Morgan Dr - Solar Panels.pdfDate: 24 October 2022 Big Dog Solar Energy 620 Pheasant Ridge Dr Chubbuck, ID 83202 Christina Allred (Patio): 491 Morgan Drive, Rexburg, ID 83440 Dear Sir/ Madam, Conclusion Page 1 of Christina Allred letter Structural Letter of Approval Terra Engineering Consulting (TEC) has performed a structural analysis for the existing framing and load conditions and determined that the structure can support the additional load of the proposed solar panel system. TEC has reviewed the site survey, photographs of the existing framing, and the proposed PV array. The attached calculations are based off the assumptions that the existing structural components are in good condition, that they meet industry standards, and that the site survey provided by the client is accurate. The design assumptions the calculations are based off are located in the attached References page. The contractor shall notify TEC of any damage to the roof system encountered at the time of installation. The design of the solar panel’s mounting hardware is to be provided by the manufacturer or installer. Structural observation or construction inspections will not be performed by TEC or their representatives. The total load of the solar panels is assumed to not exceed 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 loads, the wind load controls, and due to the low profile of the panels (3” to 6”) as well as PV frame, wiring, conduit, and structural component below the module causing restriction in airflow which allow it to be considered as “partially enclosed structure”; thus the additional 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. 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. These conclusions are based on the attached calculations. 1863 GOLDENROD WAY / NORTH SARATOGA SPRINGS, UT 84045 / T (801)-616-6204 General Instructions Best Regards, Terra Engineering Consulting, PLLC Ahmad Alshakargi, PE Civil Engineer Page 2 of Christina Allred letter The solar array mounting system shall be connected to every other truss/rafter (48" maximum penetration spacing) in order to distribute the load evenly. The installer shall stagger the connections into the roof framing to not overload any existing structural members. Installation and waterproofing shall be performed within accepted industry standards. 10/24/2022 1863 GOLDENROD WAY / NORTH SARATOGA SPRINGS, UT 84045 / T (801)-616-6204 References Page 3 of Christina Allred letter 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: C Wind Exposure Category: C Existing Roof Structure Roof framing: 2x6 Rafters at 24” O.C. Roof material: Composite shingles Roof slope: 8° Roof type: Gable 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 Connections: (1) 5/16” Lag screw with 2.5” min. embedment into the framing at 48” O.C. spaced along the rail 1863 GOLDENROD WAY / NORTH SARATOGA SPRINGS, UT 84045 / T (801)-616-6204 Date:10/24/2022 Client:Christina Allred Subject:Gravity load Gravity load calculations Snow load (S)Existing w/ solar panels Roof slope (°):8 8 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):20 20 ASCE 7-16, equation 7.3-4 Roof Surface type:Other Other ASCE 7-16, C7.4 Roof slope factor, Cs: 1 1 ASCE 7-16, C7.4 Sloped roof snow load, ps [psf]: 35.0 35.0 Roof dead load (D) Roof pitch/12 1.7 Composite shingles 1.5 psf 1/2" Gypsum clg.psf 1/2" plywood 1 psf Insulation 0.5 psf Framing 3 psf M, E & Misc 0.5 psf Roof DL without PV arrays 6.6 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]6.6 9.6 ASCE 7-16, Section 2.4.1 D+L [psf]6.6 9.6 ASCE 7-16, Section 2.4.1 D+[Lr or S or R] [psf]41.6 44.6 ASCE 7-16, Section 2.4.1 32.9 35.9 ASCE 7-16, Section 2.4.1 Maximum gravity load [psf]:41.6 44.6 ASCE 7-16, equation 7.4-1, Design Snow Load (S) D+0.75L+0.75[Lr or S or R] [psf] Date:10/24/2022 Client:Christina Allred 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 0.9 (ASCE 7-6 Table 26.10-1) Kd 0.85 (ASCE 7-16 Table 26.6-1) Velocity Pressure,qh (psf)25.90 (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]-23.31 -44.03 -67.34 W Pressure, (pos) [psf]12.95 12.95 12.95 W Pressure, (Abs. max) [psf]23.31 44.03 67.34 Connection calculations Capacity Connection type:Lag screw Lag screw diameter:5/16 Embedment (in):2.5 Framing grade:SPF#2 G:0.42 Capacity [lbs/in]:205 (2015 NDS table 12.2A) Number of screws:1 Total capacity [lbs]:512.50 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 14.0 11 153.8 2 26.4 11 290.6 3 40.4 11 444.4 (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:10/24/2022 Client:Christina Allred Subject:Beam calculator Beam Design (Roof)2x6 Rafters at 24 in o.c., span 10 ft max. Load Combination Combo DL LL W SL LLR E Sum 1 1.4 9.6 0 0 0 0 0 35 0 0 0 13.44 2 1.2 9.6 1.6 0 0 0 0.5 35 0 0 0 29.02 3 1.2 9.6 1 0 1 0 1.6 35 0 0 0 67.52 4 1.2 9.6 1 0 1 0 0.5 35 0 0 0 29.02 5 1.2 9.6 0 0 0 0 0.2 35 0 1 0 18.52 6 0.9 9.6 0 0 1 0 0 35 0 0 0 8.64 7 0.9 9.6 0 0 0 0 0 35 0 1 0 8.64 Roof DL 9.6 psf (see Gravity load roof DL) S 35 psf W E LL 0 psf RLL 0 psf (see Gravity load LL with PV arrays) U 67.52 psf beam spacing 2 ft o.c. uniform load 135.04 plf span 10 ft Mu = w(l^2)/8 1428.7232 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 326565.3 2267.815 20.8 purlin size λ (Table N3, NDS 2015 p184)F'bn (psi) Fbu Fbu < F'bn 2x6 0.8 2323.9476 2267.815 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 44.6 lb Uniform load 89.2 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 0.038333333 1600000 89.2 9.2 19.53534 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 135.04 plf Vu 621.184 lb Vu = wl/2 Framing cross section 8.25 in^2 fvu 112.94 psi Fv 180 psi (for DFL#2) F'vn 311.04 psi F'vn > fvu Works Beam works