Structural system reliability with applications to bridge analysis, design, and optimization

Material behavior, correlations, variabilities of loads and resistances, and structural damage, affects the reliability level of a structural system. The effects of the above factors on structural system reliability are investigated in this study using both a theoretical multi-member parallel system and a realistic hybrid plate girder bridge system.; Safety levels with respect to ultimate flexural and shear stresses for composite hybrid plate girders are determined using reliability methods. Different composite hybrid plate girder bridges are analyzed and designed according to the U.S. bridge code. Time-invariant and time-variant reliability-based analysis, design, and optimization formulations for composite plate girder bridge systems are proposed and used to study the effect of environment (corrosion) on the design reliability and optimum weight.; In reliability-based optimal design of structural systems, some of the quantities used are modeled as stochastic variables. A general purpose computer program is used to evaluate the component as well as the system reliability with respect to any performance function. This program is linked to a general purpose optimization program to be used in reliability-based optimization of systems. Plate girder bridge optimizations are performed for both reserve and residual system constraints.; A girder bridge system is modeled as a series system in which the occurrence of any limit state in any girder will cause failure of the bridge. This model is used to evaluate and optimize different girder bridges. The effects of various factors such as span length, girder spacing, and corrosion location on the reliability and optimum weight of girder bridges are studied. Another bridge system model is developed. A general series-parallel system is considered in which the failure of the bridge requires the failure of more than one girder. This model is used to evaluate the reliability of bridges designed using the series system model. The effects of various factors on the reliability of the bridge are investigated. A comparison between the two models results is made. A bridge system redundancy factor is defined based on these results.; Finally, conclusions and recommendations for future research are indicated.