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SHORT-TERM TEST RESULTS <br />Short-term buckling tests demonstrate that <br />lnsituform design is conservative In terms of <br />both the enhancement factor, K, and the predicted <br />buckling pressures using the following ASTM <br />F-1216 design model: <br />where, P <br />= Buckling pressure, psi (MPa) <br />K <br />= Enhancement factor <br />EL <br />= Long-term (time -corrected) <br />modulus of elasticity, psi (MPa) <br />,f <br />= Poisson's ratio <br />RR= Dimension ratio (outside diameter <br />divided by thickness) <br />C <br />= Ovality factor =1 (for test program) <br />N <br />= Safety factor =1 (for analysis <br />of test data) <br />The enhancement factor, K, is a measure of the <br />restraining action of the host pipe that encases <br />the lnsituform product and greatly increases <br />the allowable external buckling pressure. A <br />conservative enhancement factor of 7 Is <br />typically recommended for design. The tests <br />measured the average enhancement factor, <br />K, of the lnsituform Standard at 9.8 and the <br />lnsituform Enhanced product at 10.5. <br />GREET' FACTOR <br />Creep factor reflects the reduction in buckling resistance of a plastic pipe over <br />time, typically 50 years. The creep factor, CL, is the ratio of Experimental ELto <br />the measured flexural modulus reported in Table 1 and represents the retention <br />of buckling resistance at 50 years (Le., EL = CL E). A value of CL greater than <br />the manufacturer's recommended value is desirable. As shown in Table 2, <br />the reported creep factor confirms the conservative nature of the 50% creep <br />reduction factor applied to flexural modulus in the lnsituform product design, <br />Table 2 <br />Creep Factor <br />LONG-TERM TEST RESULTS <br />Regression analysis was used to extrapolate long-term buckling pressures <br />beyond the 10,000-hour test period to 50 years. (See Figure 3, next page). <br />�fp�l <br />Test results supported the flexural modulus reduced to account for <br />long-term effects, Er, used In the lnsituform product design, by comparing <br />it to the experimentally derived apparent long-term flexural modulus for a <br />50-year design life. The tested value greatly exceeded the conservative <br />value used in the lnsituform product design. (See Table 3). <br />Table 3 <br />Flexural Modulus (tong -term) <br />Tic Ex0etimuntal EL : <br />M, nulaclerer°s <br />psl (MPe) i, <br />aecommenalad Design PL <br />PSI (MPa) <br />lnsituform Standard 259,990 <br />150,000 <br />(1:7 4)� . <br />(1030). <br />lnsituform Enhanced 393,265 <br />200,000 <br />(2720) <br />(1330) <br />From TMeOnleal Report 43R, Tablo 9•8 <br />