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CR LAURENCE Z-SERIES GLASS CLAMPS (03/27/2014) Page 12 of 19 <br /> GLASS STRENGTH FULLY TEMPERED INFILL PANELS <br /> All glass is fully tempered glass conforming to the specifications of ANSI Z97.1,ASTM C <br /> 1048-97b and CPSC 16 CFR 1201. The average Modulus of Rupture for the glass Fr is 24 ksi. <br /> In accordance with IBC 2407.1.1 glass used in guards shall be designed for a safety factor of 4. <br /> For wind loads and loads other than human impact the glass used in guardrails may be designed <br /> in accordance with ASTM E1300-12a. Recommend using a maximum allowable bending stress <br /> of 8,000 psi for the wind loads because the glass is point supported. Higher glass stress may <br /> cause excessive glass deflection and failure at a stress less than the modulus of rupture. <br /> Values for the modulus of rupture,Fr, modulus of Elasticity,E and shear modulus,G for glass <br /> based on AAMA CW-12-84 Structural Properties of Glass (values are consistent with those used <br /> in ASTM E1300) are typically taken as: <br /> Fr=24,000 psi <br /> E= 10,400 ksi is used as the standard value for common glass. While the value of E for <br /> glass varies with the stress and load duration this value is typically used as an average value for <br /> the stress range of interest. <br /> G=3,800 ksi: The shear component of the deflection tends to be very small,under 1% <br /> of the bending component and is therefore ignored. <br /> p =0.22 Typical value of Poisson's ratio for common glasses. <br /> v =5x10-6 in/(inF°) Typical coefficient of thermal expansion. <br /> The shear strength of glass tracks closely to the modulus of rupture because failure under shear <br /> load will be a tensile failure with strength limited by the modulus of rupture. Thus shear loads <br /> are transformed using Mohr's circle to determine the critical tension stress to evaluate the failure <br /> load. The safety factor of 4 is applicable to this case same as the bending case. Thus the shear <br /> stress is limited based on principal stresses of 0 and 6,000 psi to 6,000/2 =3,000 psi. <br /> Bearing stress can be derived in a similar fashion with the principal stresses being—6,000 psi and <br /> 6,000 psi so the bearing stress = 6,000 psi. <br /> Bending strength of glass for the given thickness: <br /> I = 12"*(t)3/12= (t)3 in3/ft <br /> S = 12"*(t)2/6= 2*(t)2 in3/ft <br /> EDWARD C.ROBISON,PE <br /> 10012 Creviston Dr NW <br /> Gig Harbor,WA 98329 <br /> 253-858-0855/Fax 253-858-085&elrobison@narrows.com <br />