S - Kam Ng PhD Dissertation Final.pdf - Digital Repository of CCEE ...

90design coordinates,( ) = cumulative distribution function of the standard normal distribution,( ) = probability density function of the standard normal distribution,β = reliability index,= directional cosines for i = 1, 2,….., n, and= given set of load factor refer to Table 2.15.2.7.3 Fitting to ASD approachThe fitting to allowable stress design (ASD) approach is always used as a referencewhenever there is a fundamental change in either design philosophy or design specificationformat (Allen, 2005). Barker et al. (1991) developed resistance factors using the statisticaldata and calibration by fitting to ASD approach based on Strength I which focuses only ondead load (Q D ) and live load (Q L ). The general formula used to calculate a resistance factorby fitting to ASD is given by Eq. (2.56). Based on the current AASHTO recommended loadfactors as listed in Table 2.14 and a dead load to live load ratio of 3.0 chosen by Allen(2005), Eq. (2.56) can be simplified to Eq. (2.57).. /. /(2.56)(2.57)where,γ Dγ LQ DQ LFS= dead load factor,= live load factor,= dead load, kN or kip,= live load, kN or kip, and= allowable stress design factor of safety.