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Home My WebLink AboutENGINEER LETTER - 18-00287 - 671 S 5th W - Solar Panels651 W. Galena Park Blvd, Suite 101 / Draper, UT 84020 / T (801) 990-1775 / www.vectorse.com Project Number: U2456-003-181 March 9, 2018 Skyline Attention: Pierson Watts 309 E. State Road America Fork, UT 84003 REFERENCE: Ivie Dorthy Residence: 671 South 5th west, Rexburg, ID 83440 Ground-Mount Solar Array Installation To whom it may concern: We have reviewed the requirements for the ground-mount solar array installation at the above-referenced site. The proposed array will be supported by the Ironridge framing & concrete pier foundation as shown on the drawing dated 03/02/18. Based upon our review, the footings shall be a concrete pier that has a diameter of 1’-0” and a depth of 4’-0” for all piers. The design of supporting framing system and connections is by the manufacturer and/or installer. The adopted building code in this jurisdiction is the International Building Code, 2015 Edition and ASCE 7-10. Appropriate design parameters used in design of the footings and which must be used in the design of the supporting members and connections are listed below: • Ground snow load: 50 psf per the IBC • Design wind speed for risk category I structures: 105 mph (3-sec gust) • Wind exposure: Category C • Foundation concrete shall have a minimum compressive strength of 3000 psi at 28 days. Cement for all concrete shall be Type II with a minimum of 6% entrained air with water/cement ratio of 0.5. Maximum aggregate size shall be 3/4". • Footings are designed based on an allowable soil pressure of 1,500 psf, skin friction of 250 psf, and lateral bearing pressure of 150 psf. Vector Structural Engineering strongly recommends independent soils testing be performed by a licensed geotechnical engineer to verify soil bearing capacity, slope stability, and any other related soil parameters, as required. All ground mounts are to be installed per manufacturer’s recommendations. The use of solar panel support span tables provided by the manufacturer is allowed only where the site conditions and solar panel configuration match the description of the span tables. Electrical engineering is beyond our scope. All work performed must be in accordance with accepted industry-wide methods and applicable safety standards. Vector Structural Engineering assumes no responsibility for improper installation of the solar panels. Please note that a representative of Vector Structural Engineering has not physically observed the site conditions. Very truly yours, VECTOR STRUCTURAL ENGINEERING, LLC Well Holmes, P.E. Project Manager WLH/wic Enclosures 03/12/2018 JOB NO.:U2456-003-181 DESIGNED:wic DATE:03/06/18 PROJECT:Dorthy Ivie - Ground Mount SUBJECT:Dead Load Design Weight: Individual Panel Weight [lb]:41.9 Panel Transverse Length (T5) [in]:65.0 Panel Transverse Length (T5) [ft]:5.4 Panel Longitudinal Length (L2) [in]:39.1 Panel Longitudinal Length (L2) [ft]:3.3 Individual Panel Area [ft2]:17.6 Individual Panel Weight [psf]:2.4 # of Panels in Transverse Direction:2 Approximate Transverse Length (T4) [ft]:10.8 # of Panels in Longitudinal Direction:6 Approximate Longitudinal Length (L1) [ft]:19.6 ILLUSTRATION ONLY Transverse Column Spacing (T1) [ft]:5.5 Longitudinal Column Spacing (L3) [ft]:9.0 # of Columns in Longitudinal Direction:3 # of Columns in Transverse Direction:2 Total Number of Columns:6 Panel Slope from Horizontal (a) [°]:18.0 Short Column Height (H1) [ft]:2.3 Approximate Tall Column Height (H2) [ft]:4.1 Transverse Brace between Columns :No Approximate Brace Length (B1) [ft]:0.0 Weight of Columns [plf]:3.7 Weight of Cross Pipe [plf]:3.7 Weight of Brace [plf]:0.0 Tributary Transverse Length per Column [ft]:5.4 ILLUSTRATION ONLY Tributary Longitudinal Length per Column [ft]:9.0 Tributary Area per Column [ft2]:48.8 Rail Weight [plf]:1.0 Transverse Rail Weight per Column [lb]:32.5 Longitudinal Rail Weight per Column [lb]:33.3 Tall Column Weight [lb]:15.1 Panel Weight per Column [lb]:115.7 Rail Weight per Column [lb]:32.5 Cross Pipe Weight per Column [lb]:33.3 Brace Weight per Column [lb]:0.0 Total Weight per Column (1.0 D) [lb]:196.7 ILLUSTRATION ONLY Assumptions: • T2 = T3 JOB NO.:U2456-003-181 DESIGNED:wic DATE:03/06/18 PROJECT:Dorthy Ivie - Ground Mount SUBJECT:Snow Load SNOW LOAD (S): ASCE 7 Standard:10 Panel Slope from Horizontal [°]:18.0 Snow Ground Load, pg [psf]:50.0 (Section 7.2) Terrain Category:C (Table 7-2) Exposure of Roof:Fully Exposed (Table 7-2) Exposure Factor, Ce:0.9 (Table 7-2) Thermal Factor, Ct:1.2 (Table 7-3) Risk Category:I (Table 1.5-1) Importance Factor, IS:0.8 (Table 1.5-2) Flat Roof Snow Load, pf [psf]:30 (Equation 7.3-1) Minimum Roof Snow Load, pm [psf]:0 (Section 7.3.4) Unobstructed Slippery Surface?Yes (Section 7.4) Slope Factor Figure:Figure 7-2c (Section 7.4) Roof Slope Factor, Cs:1.000 (Figure 7-2) Sloped Roof Snow Load, ps [psf]:30 (Equation 7.4-1) Design Snow Load, S [psf]:30 Tributary Transverse Length [ft]:5.2 Tributary Longitudinal Length [ft]:9 Tributary Area per Column [ft2]:46.4 Snow Load per Column (1.0 S) [lb]:1402.0 JOB NO.:U2456-003-181 DESIGNED:wic DATE:03/06/18 PROJECT:Dorthy Ivie - Ground Mount SUBJECT:Wind Pressure Design Wind Load: ASCE 7 Standard:10 Basic Wind Speed, V [mph]:105 Risk Category:I Exposure Category C (Section 26.7.3) Velocity Pressure Exposure Coefficient, Kh:0.85 (Table 27.3-1) Topographic Factor, Kht:1.0 (Section 26.8.2) Wind Directionality Factor, Kd:0.85 (Table 26.6-1) Internal Pressure Coefficient, GCpi :0.00 (Table 26.11-1) Velocity Pressure, qh [psf]:20.4 (Equation 27.3-1) Gust Effect Factor, G:0.85 (Section 26.9.1) Panel Slope [degrees]:18.0 Net Pressure Coefficients (CN) per:(Figure 27.4-4) Clear Wind Flow CNW CNL Case 1 (g = 0°, Load Case A)-1.14 -1.42 Case 2 (g = 0°, Load Case B)-2.10 -0.12 Case 3 (g = 180°, Load Case A)1.46 1.68 Case 4 (g = 180°, Load Case B)1.96 0.64 Design Wind Pressures (p) [psf] per:(Equation 27.4-3) Clear Wind Flow qhGCNW qhGCNL Case 1 (g = 0°, Load Case A)-19.8 -24.6 Case 2 (g = 0°, Load Case B)-36.4 -2.1 Case 3 (g = 180°, Load Case A)25.3 29.1 Case 4 (g = 180°, Load Case B)34.0 11.1 Clear Wind Flow Short Col. Pressure Long Col. Pressure Case 1 (g = 0°, Load Case A)-24.6 -19.8 Case 2 (g = 0°, Load Case B)-2.1 -36.4 Case 3 (g = 180°, Load Case A)25.3 29.1 Case 4 (g = 180°, Load Case B)34.0 11.1 Wind Pressure on Each Side of Panels [psf] JOB NO.:U2456-003-181 DESIGNED:wic DATE:03/06/18 PROJECT:Dorthy Ivie - Ground Mount SUBJECT:Wind Load ASCE 7 Standard:10 Tributary Transverse Length per Column:5.4 Tributary Longitudinal Length per Column:9.0 Panel Slope [degrees]:18.0 Projected Height [ft]:1.7 Projected Width [ft]:5.2 Short Column Height (H1) [ft]:2.3 Approximate Tall Column Height (H2) [ft]:4.1 Average Column Height (HA) [ft]:3.2 Projected Vertical Wind Surface [ft2]:46.4 Projected Horizontal Wind Surface [ft2]:15.1 (Figure 27.4-4) Vertical Horizontal Moment Vertical Horizontal Moment Case 1 (g = 0°, Load Case A)-1141.2 -370.8 -852.8 -916.1 -297.7 -1216.6 Case 2 (g = 0°, Load Case B)-96.4 -31.3 -72.1 -1687.6 -548.3 -2241.1 Case 3 (g = 180°, Load Case A)1173.3 381.2 876.8 1350.1 438.7 1792.9 Case 4 (g = 180°, Load Case B)1575.1 511.8 1177.1 514.3 167.1 683.0 Max:1575.1 511.8 1177.1 1350.1 438.7 1792.9 Min:-1141.2 -370.8 -852.8 -1687.6 -548.3 -2241.1 Moment [ft-lb]Short Col.Long Col.Short Col.Long Col. Case 1 (g = 0°, Load Case A)0.0 0.0 0.0 -1141.2 -916.1 Case 2 (g = 0°, Load Case B)0.0 0.0 0.0 -96.4 -1687.6 Case 3 (g = 180°, Load Case A)0.0 0.0 0.0 1173.3 1350.1 Case 4 (g = 180°, Load Case B)0.0 0.0 0.0 1575.1 514.3 Max:1575.1 1350.1 Load Combos Considered:Min:-1141.2 -1687.6 D D+S D+0.6W D+0.75S+0.45W 0.6D+0.6W Envelope Reactions (DL, S, & W) Short Col.Long Col. Uplift [lb]734.7 894.6 Axial [lb]1957.0 1855.7 Shear [lb]307.1 263.2 Moment [ft-lb]706.3 1344.7 Short Column Long Column Forces from Wind (1.0 W) [lb], [ft-lb] Final (W) Vertical [lb]Extra Vertical Due to Global Moment [lb] JOB NO.:U2456-003-181 DESIGNED:wic DATE:03/06/18 PROJECT:Dorthy Ivie - Ground Mount Drilled Pier Design Max. Shear, V [k]:0.3 Max. Down, Pd [k]:1.9 Max. Moment, M [k-ft]:1.3 Max. Uplift, Pu [k]:0.9 Pier Properties: Pier Diameter, b [ft]:1.0 Volume of Concrete [ft3]:3 Min. Pier Diameter, bmin (opt'l) [ft]:Volume of Concrete [yd3]:0.1 Top of Pier Elevation [ft]:0.00 Weight of Concrete [k]:0.5 Pier Depth, d [ft]:4.0 Min. Pier Depth, dmin (opt'l) [ft]: Max. Pier Depth, dmax (opt'l) [ft]: Soil Properties: Allow. Bearing Pressure [psf]:1,500 1/3 increase for short term loads?No Skin Friction [psf]:250 (IBC 1810.3.3.1.4) Lateral Bearing, S [pcf]:150 Top Length to Ignore [ft]:0.0 Max. Lateral Bearing (opt'l) [psf]: Top Depth to Ignore [ft]:0.0 No 1/3 increase for short term loads?No Combine w/ Bearing:No 1/2" deflection at t/o pier allowed:Yes Check Bearing: Bearing Capacity [k]:3.1 Check Uplift: Uplift Capacity [k]:3.6 Check Lateral Bearing: Applied Lateral Force, P [lb]:263 Point of Application, h [ft]:5.1 S1_max [psf]: S1 [psf]:400 A = 2.34*P/(S1b):1.54 Required Pier Depth, dreqd [ft]:4 Lateral bearing capacity OK. Design Loads: Optional Parameters for Uplift: 1/3 increase for short term loads? Bearing capacity OK. Uplift capacity OK.