The safety level of a structural system designed per code specifications can not be inferred directly from the reliability of members due to the load redistribution and nonlinear inelastic structural behavior. Comparison of the system and member reliability, which is scarce in the literature, is likely to indicate any possible inconsistency of design codes in providing safe and economical designs. Such a comparative study is presented in this study for moment resisting two-dimensional steel frames designed per AISC LRFD Specifications. The member reliability is evaluated using the resistance of the beam-column element and the elastic load effects that indirectly accounts for the second-order effects. The system reliability analysis is evaluated based on the collapse load factor obtained from a second-order inelastic analysis. Comparison of the system and member reliability is presented for several steel frames. Results suggest that the failure probability of the system is about one order of magnitude lower than that of the most critically loaded structural member, and that the difference between the system and member reliability depends on the structural configuration, degree of redundancy, and dead to live load ratio. Results also suggest that the system reliability is less sensitive to initial imperfections of the structure than the member reliability. Therefore, the system aspect should be incorporated in future design codes in order to achieve more reliability consistent designs.
Zhou, W. and Hong, H.P. (2000),"Reliability analysis of steel frames", Proc. of 28th Annual Conf. of the Canadian Society for Civil Engineering, London, Ontario (in press).
Ziemian, R.D. (1990),"Advanced methods of inelastic analysis in the limit states design", PhD Thesis, Cornell University, Ithaca, N.Y.
Zimmerman, J.J., Ellis, J.H. and Corotis, R.B. (1993),"Stochastic optimization models for structural reliability analysis", J. of Struct. Eng., ASCE, 119(1), 223-239.
Bennett, R.M. and Ang, A.H.-S. (1987),""Formulation of structural system reliability", J. of Eng. Mech., ASCE, 112(11), 1135-1151.
Chen, W.F., Goto, Y. and Liew, J.Y.R. (1996), Stability Design of Semi-rigid Frames. John Wiley & Sons, Inc., New York.
Chen, W.F. and Lui, E.M. (1985),"Columns with end restraint and bending in load and resistance factor design", Eng. J., AISC, 22(3), 3rd Otr., 105-132.
Ellingwood, B., Galambos, T.V., MacGregor, J.G. and Cornell, C.A. (1980),"Development of a probability based load criterion for American national standard A58", Spec. Pub. No. 577, National Bureau of Standards, Washington, D.C.
Ellingwood, B. and Reinhold, T.A. (1981),"Reliability analysis of steel beam-columns", J. of the Struct. Div., ASCE, 106(12), 2560-2564.
Galambos, T.V. and Ravindra, M.K. (1978),"Properties of steel for use in LRFD", J. of the Struct. Div., ASCE, 104(9), 1459-1468.
Haldar, A. and Zhou, Y. (1991),"An efficient SFEM algorithm for nonlinear structures", Computational Stochastic Mechanics, Computational Mechanics Publications, Southampton, 851-862.
Hong, H.P. (1999a),"An approximation to bivariate and trivariate normal integrals", Civil Engineering and Environmental Systems, 16, 115-127.
Hong, H.P. (1999b),"Simple approximations for improving second-order reliability estimates", J. of Eng. Mech., ASCE, 125(5), 592-595.
Kam, T.Y., Corotis, R.B. and Rossow, E.C. (1983),"Reliability of nonlinear framed structures", J. of Struct. Eng., ASCE, 109(7), 1585-1601.
LeMessurier, W.J. (1977),"A practical method for second order analysis. Part II-Rigid frames", Eng. J., AISC, 14(2), 2nd Qtr., 49-67.
Liew, J.Y.R. (1992),"Advanced analysis of frame design", PhD Thesis, Purdue University, West Lafayette, IN.
Madsen, H.O., Krenk, S. and Lind, N.C. (1986), Methods of Structural Safety. Prentice-Hall, Englewood Cliffs, N.J.
Mendell and Elston (1974),"Multifactorial qualitative traits: Genetic analysis and prediction of recurrence risks", Biometrics, 30, 41-57.
Ravindra, M.K. and Galambos, T.V. (1978),"Load and resistance factor design for steel", J. of the Struct. Div., ASCE, 104(9), 1337-1353.
Terada, S. and Takahashi, T. (1988),"Failure-conditioned reliability index", J. of Struct. Eng., ASCE, 114(4), 942-952.
Throft-Christensen, P. and Murotsu, Y. (1986), Application of Structural Systems Reliability Theory. Springer- Verlag, Berlin.
Yura, J.A., Galambos, T.V. and Ravindra, M.K. (1978),"The bending resistance of steel beams", J. of the Struct. Div., ASCE, 104(9), 1355-1371.
Zhao, Y.G. and Ono, T. (1997),"System reliability evaluation of ductile frame structures", J. of Struct. Eng., ASCE, 124(6), 678-685.
Bjorhovde, R., Galambos, T.V. and Ravindra, M.K. (1978),"LRFD criteria for steel beam-columns", J. of the Struct. Div., ASCE, 104(9), 1371-1387.
"Load and Resistance Factor Design Specifications for Structural Steel Buildings", (1986) American Institute of Steel Construction, Chicago.