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Home My WebLink AboutSTRUCTURAL CALCS -18-00145 - 561 Park St - Solar Array___________________________________________________________________________________________ Domus Structural Engineering, LLC P.O. Box 6986 Broomfield, CO 80021 530‐864‐7055 Domusstructural@gmail.com To: Blue Raven Solar 1220 S. 630 E. Ste. 430 American Fork, UT. 84003 Subject: Certification Letter El‐kher Residence 561 Park Street Rexburg, ID. 83440 To Whom It May Concern, Design Criteria: ● Applicable Codes = 2012 IBC/IRC, ASCE 7‐10, and NDS‐12 ● Roof Dead Load = 9 psf (MP1) ● Roof Live Load = 20 psf ● Wind Speed = 115 mph, Exposure C, Risk Category II ● ● Attachments: S5! ProteaBracket, at spacing shown above. Sincerely, John Calvert, P.E. Project Engineer March 20, 2018 The roof structure of (MP1) consists of metal roofing on roof plywood that is supported by 2x8 rafters @ 24"o.c.. The rafters support a vaulted ceiling and have a max projected horizontal span of 11'‐6", with a slope of 6 degrees. The rafters are supported at the ridge by a ridge beam and at the eave by a load bearing wall. The existing roof framing system of (MP1) is judged to be adequate to withstand the loading imposed by the installation of the solar panels. No reinforcement is necessary. Ground Snow Load = 50 psf ‐ Roof Snow Load = 35 psf The spacing of the solar standoffs should be kept at 32" o.c. for landscape and 32" o.c. for portrait orientation, with a staggered pattern to ensure proper distribution of loads. A jobsite observation of the condition of the existing framing system was performed by an audit team of Blue Raven Solar as a request from Domus Structural Engineering. All review is based on these observations and the design criteria listed below and only deemed valid if provided information is true and accurate. On the above referenced project, the roof structural framing has been reviewed for additional loading due to the installation of the solar PV addition to the roof. The structural review only applys to the section of the roof that is directly supporting the solar PV system and its supporting elements. The observed roof framing is described below. If field conditions differ, contractor to notify engineer prior to starting construction. The scope of this report is strictly limited to an evaluation of the fastener attachment, underlying framing and supporting structure only. The attachment's to the existing structure are required to be in a staggered pattern to ensure proper distribution of loading. All panels, racking and hardware shall be installed per manufacturer specifications and within specified design limitations. All waterproofing shall be provided by the manufacturer. Domus Structural Engineering assumes no responsibility for misuse or improper installation of the solar PV panels or racking. Please contact me with any further questions or concerns regarding this project. El-kher Residence, Rexburg, ID 1 ____________________________________________________________________________________ Domus Structural Engineering, LLC P.O. Box 6986 Broomfield, CO 80021 530‐864‐7055 Domusstructural@gmail.com 50 psf (ASCE7 - Eq 7-1) 1 (ASCE7 - Table 7-2) 1 (ASCE7 - Table 7-3) 1 35.0 psf (ASCE7 - Eq 7-2) 1 35.0 psf 3.0 psf 2.67 ft 2.67 ft 7.12 sft 21 lb 1.00 2.00 1.52 4.00 0.48 9.0 psf 9.0 psf Gravity Loading PV System Weight Weight of PV System (Per Blue Raven Solar) X Standoff Spacing = Y Standoff Spacing = Note: PV standoffs are staggered to ensure proper distribution of loading 2x8 Rafters @ 24"o.c. I = Importance Factor = Cs = Slope Factor = Standoff Tributary Area = ps = Cspf ps = Sloped Roof Snow Load = pf = Flat Roof Snow Load = Roof Snow Load Calculations pg = Ground Snow Load = Ce = Exposure Factor = pf = 0.7 Ce Ct I pg Ct = Thermal Factor = Roof Live Load = 20 psf Roof Plywood Roof Dead Load (MP1) Metal Roofing Note: Roof live load is removed in area's covered by PV array. DL Adjusted to 6 Degree Slope Point Loads of Standoffs Miscellaneous Vaulted Ceiling Total Roof DL (MP1) PV Dead Load = 3 psf (Per Blue Raven Solar) El-kher Residence, Rexburg, ID 2 ___________________________________________________________________________________________ Domus Structural Engineering, LLC P.O. Box 6986 Broomfield, CO 80021 530‐864‐7055 Domusstructural@gmail.com 115 mph C Gable/Hip 6 degrees 20 ft 19.3 ft (Eq. 30.3-1) 0.9 (Table 30.3-1) 1 (Fig. 26.8-1) 0.85 (Table 26.6-1) 115 mph (Fig. 26.5-1A) II (Table 1.5-1) qh = 25.90 15.54 Zone 1 Zone 2 Zone 3 Positive GCp = -0.98 -1.67 -2.48 0.28 (Fig. 30.4-1) Uplift Pressure = -15.24 psf -25.91 psf -38.49 psf 10.0 psf (Minimum) X Standoff Spacing = 2.67 2.67 1.78 Y Standoff Spacing = 2.67 2.67 2.67 Tributary Area = 7.12 7.12 4.75 Footing Uplift = -109 lb -184 lb -183 lb Zone 1 Zone 2 Zone 3 Positive GCp = -0.98 -1.67 -2.48 0.28 (Fig. 30.4-1) Uplift Pressure = -15.24 psf -25.91 psf -38.49 psf 10.0 psf (Minimum) X Standoff Spacing = 2.67 2.67 1.78 Y Standoff Spacing = 1.67 1.67 1.67 Tributary Area = 4.45 4.45 2.97 Footing Uplift = -68 lb -115 lb -114 lb -184 lb 220 lb Therefore, OK Wind Calculations Maximum Design Uplift = Standoff Uplift Capacity = 220 lb capacity > 184 lb demand Standoff Uplift Check Kz (Exposure Coefficient) = Kzt (topographic factor) = Kd (Wind Directionality Factor) = V (Design Wind Speed) = Risk Category = qh = 0.00256 * Kz * Kzt * Kd * V^2 Wind Pressure P = qh*G*Cn Exposure Category Per ASCE 7‐10 Components and Cladding Mean Roof Height Roof Slope 0.6 * qh = Standoff Uplift Calculations-Landscape Input Variables Wind Speed Effective Wind Area Design Wind Pressure Calculations Roof Shape Standoff Uplift Calculations-Portrait El-kher Residence, Rexburg, ID 3 ___________________________________________________________________________________________ Domus Structural Engineering, LLC P.O. Box 6986 Broomfield, CO 80021 530‐864‐7055 Domusstructural@gmail.com (MP1)PASS Dead Load 9.0 psf PV Load 3.0 psf Snow Load 35.0 psf Governing Load Combo = DL + SL Total Load 47.0 psf Fb (psi) = f'b x Cd x Cf x Cr (NDS Table 4.3.1) 900 x 1.15 x 1.2 x 1.15 Allowed Bending Stress = 1428.3 psi (wL^2) / 8 = 1555.577 ft# = 18666.92 in# Actual Bending Stress = (Maximum Moment) / S = 1420.6 psi L/180 (E = 1600000 psi Per NDS) = 0.766 in Deflection Criteria Based on = (5*w*L^4) / (384*E*I) = = L/284 > L/180 Therefore OK Allowed Deflection (Live Load) =L/240 0.575 in (5*w*L^4) / (384*E*I) L/382 > L/240 Therefore OK Member Area = Fv (psi) = 180 psi (NDS Table 4A) Allowed Shear = Fv * A = Max Shear (V) = w * L / 2 = 541 lb Framing Check 2x8 Rafters @ 24"o.c. Member Span = 11' - 6" 10.9 in^2 Check Shear w = 94 plf (True Dimensions) 1958 lb Allowed > Actual -- 27.7% Stressed -- Therefore, OK DF#2 Member Spacing @ 24"o.c. Maximum Moment = Check Deflection I (in^4) 47.63 Lumber Sp/Gr Actual Deflection (Live Load) = Allowed Deflection (Total Load) = Actual Deflection (Total Load) = Allowed > Actual -- 99.5% Stressed -- Therefore, OK Member Properties Member Size 2x8 S (in^3) 13.14 0.362 in Check Bending Stress Simple Span 0.486 in El-kher Residence, Rexburg, ID 4 ___________________________________________________________________________________________ _ Domus Structural Engineering, LLC P.O. Box 6986 Broomfield, CO 80021 530‐864‐7055 Domusstructural@gmail.com Level Area Weight (psf) Weight (lb) Roof 1400 sf 9.0 psf 12669 lb Ceiling 1400 sf 0.0 psf 0 lb Wood Siding 100 ft 5.0 psf 2000 lb (8'-0" Wall Height) Int. Walls 100 ft 6.4 psf 2560 lb 17229 lb 3.0 psf 289 sf 867 lb 1723 lb 867 lb 5.0% Lateral Check 1723 lb > 867 lb, Therefore OK Per 2012 IBC Chapter 34 Existing Weight of Effected Building Existing Weight of Effected Building Proposed Weight of PV System Weight of PV System (Per Blue Raven Solar) Approx. Area of Proposed PV System Approximate Total Weight of PV System 10% Comparison 10% of Existing Building Weight (Allowed) Approximate Weight of PV System (Actual) Percent Increase El-kher Residence, Rexburg, ID 5