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Home My WebLink AboutENGINEERING LETTER - 17-00774 - 1080 Washington Blvd - Solar PanelsTo: Blue Raven Solar 1220 S. 630 E Ste. 430 American Fork, UT 84003 Subject: Certification Letter Siepert Residence 1080 Washington Blvd. Rexburg, ID. 83440 To Whom It May Concern, Design Criteria: ● Applicable Codes = 2012 IBC/IRC, ASCE 7‐10 ● Roof Dead Load = 7 psf (MP1) ● Roof Live Load = 20 psf ● Wind Speed = 115 mph, Exposure C, Risk Category II ● Sincerely, Paul Zacher, P.E. Project Engineer The spacing of the solar standoffs should be kept at 48" o.c. with a staggered pattern to ensure proper distribution of loads. December 6, 2017 A jobsite observation of the condition of the existing framing system was performed by an audit team from Blue Raven Solar. All attached structural calculations are based on these observations and the design criteria listed below. 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, including the plans and calculations only apply to the section of the roof that is directly supporting the solar PV system and its supporting elements. The observed roof framing is described as follows. The roof structure of (MP1) consists of composition shingle on roof plywood that is supported by pre‐manufactured trusses that are spaced at @ 24"o.c.. The top chords, sloped at 27 degrees, are 2x4 sections, the bottom chords are 2x4 sections and the web members are 2x4 sections. The truss members are connected by steel gusset plates. The max unsupported projected horizontal top chord span is approximately 6'‐3''. 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 Please contact me with any further questions or concerns regarding this project. 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 requirements. All waterproofing shall be provided by the manufacturer. PZSE, Inc. assumes no responsibility for misuse or improper installation of the solar PV panels or racking. Siepert Residence, Rexburg, ID 1 R E E NI REHCAZK.LUAP GNELANOISSEFORP 2762 FOETATS OHADI DESNECIL EXP. 08/31/2018 Gravity Loading 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 4.00 ft 2.67 ft 10.68 sft 32 lb 4.00 2.00 0.73 0.00 (Ceiling Not Vaulted) 0.27 7.0 psf 7.9 psf PV Dead Load = 3 psf (Per Blue Raven Solar) DL Adjusted to 27 Degree Slope Point Loads of Standoffs Miscellaneous Vaulted Ceiling Roof Live Load = 20 psf Roof Plywood Roof Dead Load (MP1) Composition Shingle Note: Roof live load is removed in area's covered by PV array. Roof Snow Load Calculations pg = Ground Snow Load = Ce = Exposure Factor = pf = 0.7 Ce Ct I pg Ct = Thermal Factor = I = Importance Factor = Cs = Slope Factor = Standoff Tributary Area = ps = Cspf ps = Sloped Roof Snow Load = pf = Flat Roof Snow Load = 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 2x4 Top Chords @ 24"o.c. Total Roof DL (MP1) Siepert Residence, Rexburg, ID 2 Wind Calculations 115 mph C Gable/Hip 27 degrees 20 ft 17.4 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 = -0.85 -1.45 -2.30 0.40 (Fig. 30.4-1) Uplift Pressure = -13.20 psf -22.48 psf -35.68 psf 10.3 psf X Standoff Spacing = 4.00 4.00 2.67 Y Standoff Spacing = 2.67 2.67 2.67 Tributary Area = 10.68 10.68 7.12 Footing Uplift = -141 lb -240 lb -254 lb -254 lb 400 lb Therefore, OK Fastener =1 - 5/16" dia Lag Number of Fasteners = 1 Embedment Depth = 2.25 Pullout Capacity Per Inch = 250 lb Fastener Capacity = 563 lb w/ F.S. of 1.5 = 376 lb Therefore, OK Input Variables Wind Speed Effective Wind Area Design Wind Pressure Calculations Roof Shape Standoff Uplift Calculations Roof Slope 376 lb capacity > 254 lb demand 0.6 * qh = Maximum Design Uplift = Standoff Uplift Capacity = 400 lb capacity > 254 lb demand Fastener Capacity Check 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 Siepert Residence, Rexburg, ID 3 Framing Check (MP1)PASS Dead Load 7.9 psf PV Load 3.0 psf Snow Load 35.0 psf Governing Load Combo = DL + SL Total Load 45.9 psf Fb (psi) = f'b x Cd x Cf x Cr (NDS Table 4.3.1) 900 x 1.15 x 1.5 x 1.15 Allowed Bending Stress = 1785.3 psi (wL^2) / 8 = 447.815 ft# = 5373.78 in# Actual Bending Stress = (Maximum Moment) / S = 1754.8 psi L/180 (E = 1600000 psi Per NDS) = 0.416 in Deflection Criteria Based on = (w*L^4) / (185*E*I) = = L/491 > L/180 Therefore OK Allowed Deflection (Live Load) =L/240 0.312 in (w*L^4) / (185*E*I) L/642 > L/240 Therefore OK Member Area = Fv (psi) = 180 psi (NDS Table 4A) Allowed Shear = Fv * A = Max Shear (V) = w * L / 2 = 287 lb Check Bending Stress Continuous Span 0.153 in 0.117 in Member Properties Member Size 2x4 S (in^3) 3.06 DF#2 Member Spacing @ 24"o.c. Maximum Moment = Check Deflection I (in^4) 5.36 Lumber Sp/Gr Actual Deflection (Live Load) = Allowed Deflection (Total Load) = Actual Deflection (Total Load) = Allowed > Actual -- 98.3% Stressed -- Therefore, OK 945 lb Allowed > Actual -- 30.4% Stressed -- Therefore, OK (True Dimensions) 5.3 in^2 Check Shear w = 92 plf 2x4 Top Chords @ 24"o.c. Member Span = 6' - 3" Siepert Residence, Rexburg, ID 4 Lateral Check Level Area Weight (psf) Weight (lb) Roof 2500 sf 7.9 psf 19641 lb Ceiling 2500 sf 6.0 psf 15000 lb Wood Siding 100 ft 5.0 psf 2000 lb (8'-0" Wall Height) Int. Walls 100 ft 6.4 psf 2560 lb 39201 lb 3.0 psf 209 sf 627 lb 3920 lb 627 lb 1.6% 3920 lb > 627 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 Siepert Residence, Rexburg, ID 5