Reliability Assessment of the Tie-down Cables Resisting Negative Reactions in Cable-stayed Bridges Yu Jin Lee
ABSTRACT This paper suggests the reliability analysis of the tie-down cables for negative reactions in the bridge for the bridge design based on Load and Resistance Factor Design(LRFD). Bridge design concepts have been changed from Allowable Stress Design (ASD) method to LRFD method. ASD method is simplified the design applied a factor of safety based on empirical method. LRFD design method is rational method based on reliability assessment that applies probabilistic and statistical information of the design variables. For the design of the Tie-down cables resisting negative reactions in cable-stayed bridges, it is important to set the limit state function. The limit state function of negative reactions is specified by the ultimate strength of the tie-down cables and the reactions at supports. The reliability index and the most probable failure point are obtained by the advanced first-order second-moment reliabiblity method (AFOSM). The sensitivity of the reactions have to be evaluated using the finite element model of a cable-stayed bridge. The reliability analysis are performed by AFOSM through four ways. First Analysis is based on the AASHTO LRFD bridge design specification and the post-tensioning institute (PTI) recommendation for three cable-stayed bridge in service in Korea. And other two analysis are subjected to tie-down cables at the three cable-stayed bridge in service in Korea. Tie-down cables are usually pre-tensioned to prevent uplift displacements of supports under the normal operation condition. So the reliability analysis is performed by normal operation condition and ultimate condition that failure of the tie-down cables. This proposed method could be a meaningful information for the LRFD design method.
Key Word SI(System Identification), EEE(Equation Error Estimation), Bias, 1-Norm Error Function, 1-Norm Regularization in L1
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