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Home My WebLink AboutRevision Loyd W. Martin Professional Engineer, Inc. 9924 Universal Boulevard #224-406 Orlando, FL 32819 Tel:1 .310.464.1804 Email: loydwmartin@gmail.com www.loydwmartin.com Structural Calculations for a Roof Mounted Solar Photovoltaic System for: Chris Berg QRO\N. 1 y9l 74320 Aster Dr 6 Q) LU Palm Desert, CA 92260 No. C58724 Exp.3-31-25 Applicable Codes: w �T9'FOFcA_\F 2022 California Building Code, 2022 California Electric Code, 2022 California Mechanical Code, American Society of Civil Engineers Standard ASCE 7-16 Minimum Design Loads for Buildings and Other Structures, American Wood Council 2018 National Design Specification for Wood Construction, Local Municipal Code, and all other codes which are adopted by reference or enacted by law. Assumed Design Parameters: The existing structure has been built under a building permit and is in its original condition. The existing roof structure is capable of its code required live load and the ability of the roof structure to support live loads has not been substantially reduced by the age of the structure, termites or mold, or unauthorized modifications to the existing structure. Solar Energy Contractor shall make an inspection of the existing roof framing system prior to installation of the roof mounted solar energy system to verify that the existing roof is capable of supporting minimum roof live loads. Assumed Design Parameters: All 2x members are grade Douglas Fir #2 or better All 4X members are grade Douglas Fir #1 or better All Roof Connectors are Simpson Strong-Tie or Equal All Concrete Foundations are f'c = 2500 psi or stronger Original Structure was built to the Type-V Wood Framed Standards of the Applicable Building Code at the time of Construction. Sht # 1 of 7 2023-4735 Vision CE Chris Berg September 6, 2023 Loyd W. Martin Professional Engineer, Inc. 9924 Universal Boulevard #224-406 Orlando, FL 32819 Tel:1 .310.464.1804 Email: loydwmartin@gmail.com www.loydwmartin.com Note to Building Official: Based upon a review of the proposed plans I am confident that the existing roof framing system is capable of safely supporting the additional loads caused by the new solar photovoltaic energy system. The contractor shall field verify that the existing roof structure is in its original permited condition and verify that it can support the normal code required roof live loads. Attached in this package are several calculations showing that the roof members can support the additional weight of the solar array. Furthermore, an analysis of the solar array's support for wind forces and a seismic analysis of the existing structure are also included. Check Existing 2X6 Roof Rafters (D- 16" O.C.: (Assume max rafter span = 11 .75 ft.) W DL+ LL I I w = 30 psf x 1 .33 ft. = 39.9 plf R1 R2 11.75' �oQ�OF ESS/04// W. Total load on rafters = 39.9 plf x 11 .75 ft. = 469 Ibs U m Of No. C58724 Exp.3-31-25 ��9TF I OF C AL FO��\P Sht # 2of7 2023-4735 Vision CE Chris Berg September 6, 2023 Loyd W. Martin Professional Engineer, Inc. 9924 Universal Boulevard #224-406 Orlando, FL 32819 Tel:1 .310.464.1804 Email: loydwmartin@gmail.com www.loydwmartin.com Check Existing 2X6 Roof Rafters (cb- 16" O.C.: P P P P WLLIIIIIIIIIIIIIIH6 6 b b W DL WDL+ LL = 30 psf x 1 .33 ft. = 39.9 plf WDL = 14 psf x 1 .33 ft. = 18.6 plf R1 R2 11.75' 3' 3.4' 1.5' 3.4' 0.45 Total load on rafters = ( 39.9 plf x4.95ft ) + ( 18.6 plf x6.8ft ) + ( 5.33' x1 .7' x3 psf x4 ) = 433 Ibs < 469 Ibs OK Check attachment of Support to Existing Structure for Wind Uplift CHECK SOLAR STRUCTURE ATTACHMENTS PER ASCE 7-16 WIND LOADS ON BUILDING APPURTENANCES AND OTHER STRUCTURES Section 29.4.4 THEREFORE CHECK ATTACHMENT FOR TYPICAL CRITICAL LOAD WHICH IS THE EDGE ZONE - ZONE 2. NOTE: PER DEFINITION ON SHEETS 246 & 247 OF ASCE 7-16 EFFECTIVE WIND AREA: FOR ROOFTOP SOLAR ARRAYS, THE EFFECTIVE WIND AREA IN FIG. 29.4-7 IS EQUAL TO THE TRIBUTARY AREA FOR THE STRUCTURAL ELEMENT BEING CONSIDERED, EXCEPT THAT THE WIDTH OF THE EFFECTIVE WIND AREA NEED NOT BE LESS THAN ONE-THIRD ITS LENGTH. �OQRpFESS/olv W. 114 EFFECTIVE AREA = 15 SQ FT w o M No. C58724 Exp. 3-31-25 LPT9rF OF l CAL\F��\P Sht # 3of7 2023-4735 Vision CE Chris Berg September 6, 2023 Loyd W. Martin Professional Engineer, Inc. 9924 Universal Boulevard #224-406 Orlando, FL 32819 Tel:1 .310.464.1804 Email: loydwmartin@gmail.com www.loydwmartin.com Check attachment of Support to Existing Structure for Wind Uplift - Cont'd Tributary Area to Each Solar Mount = 6 ft. x 3.15 ft. = 18.9 sq. ft. ( Max ) Calculate Design Wind Pressure at each support (Wind Speed 130 mph Exposure C): p = q h (GCp)(YE)(Y J Eq'n 29.4-7 ASCE 7-16 qh = 0.00256KZ KZt Kd Ke V2 Eq'n 26.10-1 ASCE 7-16 Note: KZ = velocity pressure coefficient Section 29.10.1 ASCE 7-16 KZ = 0.9 (Exposure C, Height = 20 ft or less) KZt = Topographical Factor = 1 .0 oQROFEsSIOli,1 Kd = Wind Directionality Factor = 0.85 114 CO o Ke = Ground Elevation Factor = 1 .0Of No. C58724 V = 130 mph ; VASB = 101 mph * Exp.3-31-25 qh = 0.00256 (0.9) (1 .0) (0.85) (1 .0) (101)2 cj�x civic �Q q h = 19.98 psf 9�F OF C GCp = -2.0 (Zone 2 ; Effective Area = 15 sq. ft. ) Y E = Exposure Factor = 1 .5 Ya = Solar Array Pressure Equalization Factor = 0.7 Fig. 29.4-8 ASCE 7-16 p = qh (GC p)(YE)(Ya) p = 19.98 psf(-2.0) (1.5) (0.7) = 42 psf Sht # 4of7 2023-4735 Vision CE Chris Berg September 6, 2023 Loyd W. Martin Professional Engineer, Inc. 9924 Universal Boulevard #224-406 Orlando, FL 32819 Tel:1 .310.464.1804 Email: loydwmartin@gmail.com www.loydwmartin.com Check attachment of Support to Existing Structure for Wind Uplift - Cont'd Nominal (Unfactored) Uplift at each support = 42 psf x 18.9 sq. ft. = 793.8 Ibs Note: Section 2.4.1 of ASCE 7-16, Basic Load Combinations for Allowable Stress Design. Note: Applicable Load Combination #5 (D + 0.6W) Design (Factored) Uplift at each support = 0.6 x 793.8 Ibs = 476 Ibs Load per lag screw = 476 Ibs / 1 = 476 Ibs Determine allowable load per 5/16" lag screw w/ 2.5" embedment into wood below according to the 2018 NDS. �oQROFESSIO4,, w. W ' = W x Cd x Ct Table 10.3.1 2018 NDS ' m �where No. C58724 � Exp.3-31-25 W = 266 Ibs / in. of embedment per Table 12.2a sT civi\� �P Cd = 1 .6 per Table 2.3.2 of 2018 NDS 9rFOF Ca��F°�� Ct = 1 .0 per Table 2.3.3 of 2018 NDS W' = 266 Ibs/ in. x 2.5 in. x 1 .6 x 1 .0 = 1 ,064 Ibs > 476 Ibs OK Use Support connected to 2x Min. Roof Member w/ (1) 5116" x 3.5" lag screws per connection minimum. Sht # 5of7 2023-4735 Vision CE Chris Berg September 6, 2023 Loyd W. Martin Professional Engineer, Inc. 9924 Universal Boulevard #224-406 Orlando, FL 32819 Tel:1 .310.464.1804 Email: loydwmartin@gmail.com www.loydwmartin.com Free Body Diagram of Reverse-tilt Sub Array �oQROF ESSIp�,9l W. No. C58724 Exp.3-31-25 `" CIV1 �Q 9TF OF C AL�FO�� Shear Reaction Uplift Reaction Uplift Reaction Shear Reaction = (5.33 ft x 6.3 ft x 42 psf x sin 10) = 244.9 Ibs (Note: Angle between Roof and Panels is 10 degrees) Allowable lateral Load at 5/16" diameter lag screw w/ 2.5" embedment Allowable Load = 200 Ibs x 1 .6 x 1 = 320 Ibs > 244.9 Ibs OK See plans for connection details. Sht # 5.1 of 2023-4735 Vision CE Chris Berg September 6, 2023 Loyd W. Martin Professional Engineer, Inc. 9924 Universal Boulevard #224-406 Orlando, FL 32819 Tel:1 .310.464.1804 Email: loydwmartin@gmail.com www.loydwmartin.com Check Seismic load due to added dead load of photovoltaic system. Determine Seismic Weight of Existing Building: Effective Existing Seismic Weight Area of (E) Building = Approximately 1 ,700 Sq. ft Approximate Effective = 1 ,700 sq. ft. x 30 psf ave. = 51 ,000 LBS Seismic Weight �oQROF ESS1049 DETERMINE BASE SHEAR W No. C58724 V = CS W EQ'N 12.8-1 ASCE 7-16 * Exp.3-31-25 LP�9TF ' AL�FO��\P CS — S DS EQ'N 12.8-2 ASCE 7-16 OF C [R] Ie R = THE RESPONSE MODIFICATION FACTOR IN TABLE 12.2-1 R = 6.5 WOOD SHEAR WALLS le = 1 .0 IMPORTANCE FACTOR SDS = 2/3 X SMS SMS = FAX SS SMS = 1 .2x1 .5 = 1 .8 SDS = 2/3 x 1 .8 = 1 .2 CS = SRS = 0.185 EQ'N 12.8-2 ASCE 7-16 LIeJ Sht # 6of7 2023-4735 Vision CE Chris Berg September 6, 2023 Loyd W. Martin Professional Engineer, Inc. 9924 Universal Boulevard #224-406 Orlando, FL 32819 Tel:1 .310.464.1804 Email: loydwmartin@gmail.com www.loydwmartin.com EXISTING BASE SHEAR V = 0.185 x 51 ,000 LBS = 9,435 LBS DETERMINE NEW BASE SHEAR �oQROFESSIO l w. Determine Seismic Weight of Building with Solar Array: o �% No. C58724 70 EXISTING * Exp.3-31-25 SEISMIC = 51 ,000 LBS LP WEIGHT �9TFOF'CAL F��\P NEW SOLAR ARRAY = 3 PSF x 31 PANELS x 6.3' x 3.4' = 1 ,993 LBS NEW SEISMIC = 51 ,000 LBS + 1 ,993 LBS = 52,993 LBS WEIGHT THEREFORE NEW BASE SHEAR: V = 0.185 x 52,993 = 9,804 LBS EQ'N 12.8-1 ASCE 7-16 % CHANGE = 9,804 LBS - 9,435 LBS , 100 = 3.9 % < 10 % OK 9,435 LBS OK. PER ASCE 7-16 SECTION 11 B.4 ALTERATIONS EXISTING LATERAL FORCE RESISTING SYSTEM IS EXEMPT FROM ANALYSIS SINCE NEW SEISMIC FORCE IS LESS THAN 10% GREATER THAN EXISTING SEISMIC FORCE "Alterations may be made to any structure without requiring the existing structure to comply with this standard, provided that the alterations comply with the requirements for a new structure. Alterations that increase the seismic force in any existing structural element by more than 10% or decrease the design strength of any existing structural element to resist seismic forces by more than 10% shall not be permitted unless the entire seismic force-resisting system is determined to comply with this standard for a new structure." End of Calculations Sht # 7of7 2023-4735 Vision CE Chris Berg September 6, 2023