b'TECHNICAL ARTICLE1.6 Small Scale Ratio System Ratio1.411.4 1.241.21 1 1Wood:Steel Ratio0.80.60.40.20Mod. Bit EPDM40 ksiFigure 5: Ratios of small-scale and system testing for 5/8 plyw Figure 5:Ratios of small scale and system testing for 5/8 plywoodood.probabilityofrepeatability.BasedonFrom this comparison, one can establishshowingthatsmall-scaleratioswere this, it is not recommend to use OSBtherequirementsforsubstitutingsteelalways higher than the system ratios. In asadeckcomponentincommercialdeck from atested system with woodthe case of mod bit, the ratios were 1.0 roof applications. deckandhowmuchthesubstitutionvs. 1.4, whereas with EPDM, they were Respectivesmall-scaleandsystemaffects the tested wind uplift resistance.1.0 vs. 1.24.data obtained fromplywood set isWood vs. steel relative ratios were calcu- Based on the above summarized data compared with steel deck ones in Fig.latedbothforsmall-scaleandsystemand in consultation with the SIGDERS 4. Both the fastener pullout and winddata, as shown in Fig. 4 (c). There is amembership, the following recommen-upliftresistancearehigherwithsteelclose resemblance between the respec- dations are presented for the commercial deck compared to wood deck, irrespec- tiveratios(small-scalevssystem).Inapplication of wood deck with mechani-tive of the membrane type, or the higherthe case of the TPO system, both ratioscally fastened membrane roofs:fastenerpulloutresistanceresultedwere 0.67, whereas in the case of EPDMFor commercial applicationinhigherwindupliftresistance.Itisand mod bit, there was a small variation worth mentioning that the only differ- betweentheratios.Fig.5showsthewith mechanically fastened encebetweenthetwosetsofdataislimiteddatafromthe5/8plywoodmembrane roofs, the use ofthe decking component: wood vs. steel.comparingwith40ksisteeldeck,OSB as a decking component is not suitable.To obtain wind resistance of aroof assembly with wood deck (CSA ) without performing woodsystem testing and only doing small-scale testing, the tested wind resistance data with steel deck (CSA ) should be modified as Steelfollows. If the small-scale ratio (SS ) is:R-SS 1.0, then CSA=R woodCSASteel-0.5SS 1.0, then CSA R wood= 0.5CSASteel -SS 0.5, then full-scale Rmock-ups should be tested with a wood deckAreportdescribingtheexperi-mentalproceduresandallmeasured dataisavailableuponrequestforfurther reading.32 lROOFINGBClSPRING 2025'