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Il'U N I RAC Unirac Code-Compliant Installation Manual SolarMount <br />Part II. Procedure to Select Rail Span and Rail Type <br />[2.1.] Using Standard Beam Calculations, Structural Engineering Methodology <br />The procedi fre to determine the Unirac SolarMotint series <br />rail type and rail span uses standard beam calculations and <br />structural engineerbig methodology. The beam calculations <br />nre based on, a simply supported beam conservatively·, ignoring <br />the reductions allowed for supports of continue.us beams over <br />multiple supports. Please refer to Part I for more inform ation <br />on beam calculations, equations and assumptions. If beams <br />are installed perpendicular to the eaves on a roof steeper than <br />a 4/12 pitch in an area with a ground snow load greater [han <br />30psf, then additional. analysis is required for side loading on <br />the roof attachmeht and beam, <br />In using this document, obtaining correct results is <br />dependent upon the following: <br />1. Obtain the Snow Load for your area from your local building <br />official. <br />2. Obtain the Design Wind Load, pnet. See 'Part I (Procedure <br />to Determine the Design Wind Load) for more information on <br />calculating the Design Wind Load. <br />3. Please Note: The terms rail span and footing spacing <br />are interchangeable in this document. See Figure 3 for <br />illustrations. <br />4. To use Table 8 and Table 9 the Dearl Load foryourspecific <br />installation must be;less than 5 psf, including modules and <br />Unirac facking systems. If the Dead Load is greater than 5 <br />psf, see your Unirae distributor, a local structural engineer or <br />contactI Unirac. <br />The following protedum-will guirle you in selecting a Unirac <br />rail for a flush mount installation. It will also help determine <br />the design loading imposed by the Uii i rae PVMounting <br />Assembly that the building structure must be capable of <br />supporting. <br />Step 1: Determine the Total Design Load <br />*5-Figure 3. Rail span andfooting <br />spacing are;interchangeable. <br />Woes )- <br />The Total Design Load, P (ps,0 is determined using ASCE 7-05 <br />2.4.1 (ASD Method equations 3,5,6 and 7) by adding the Snow <br />Loadi, S (psID, Design Wind Load, pnel (ps.0 from Part I, Step 9 <br />and the Dead Load (psD. Both Uplift and Down.Force Wind <br />Loads calculated iii Step 9 of Part 1 must be investigated. Use <br />Table 7 to calculate the Total Design Load for the load cases. <br />Use the maximum absolute value of the three downfarce cases <br />and the uplift case for sizing the rail. Use the uplift case only <br />for sizing lag bolts pull out capacities (Part II, Step 6). Use the <br />following equations or Table 7. <br />P (psD = 1.OD + 1.081 (downforce caseill) <br />P (ps.0 = 1.OD + 1.0pnet (downforce case 2) <br />P (psy) = 1.00 + 0.75St + 0.75pnet (downforce case 3) <br />P 0,0 = 0.69 + 1.Opnet (uplift) - <br />D = Dead Load (psD <br />S = Snow Load @sf) <br />pnet = Design Wind Load (psD (Positive for downforce, negative <br />for uplifO <br />The maximum Dead Load, D (ps/9, is 5 psfbased on market <br />research and internal data. <br />1 Snow Load Reducrion - The snow load can be reduced according <br />to Chapter 7 ofASCE 7-05. The reduction is a.function of- the roof <br />slope, Exposure Factor, Importance Factor and 77?ennal Factor. <br />Please refer to Chapter 7 ofASCE 7-05 for more information. <br />B <br />de <br />Sfc <br />?- .,10 <br />Note: Modules must be centered symmetrically onPaze ----the rails (+/- 2*), as shown infigure-3:- <br />1 <br />10