A Study on the Decrease of Load Factor of Direct Dead Load for Design of Long-span Cable Bridge Ho Hyun Lee
ABSTRACT This thesis suggests a way to calculate load factor of direct dead load less than the dead load factor of ordinary bridges for reasonable bridge design. For safety of cable bridge, this reduced load factor should guarantees same reliability level provided by design based on existing bridge design code. In case of cable bridge, portion of factory made member is relatively large and construction process is controlled strictly. Therefore, it is valid to say that dead load of cable bridge has less variability than that of ordinary bridge and load factor of direct dead load which provide same reliability index with bridges designed to meet existing design code can be evaluated using approximate equation of AASHTO LRFD design code. Since it is hard to say that the result reflect properties of cable bridge well, reliability analysis considering nonlinearity of cable bridge is necessary for more accurate load factor evaluation of direct dead load. Thus, load factor for direct dead load which guarantees same reliability level when a bridge is designed to coincide existing design code using result of nonlinear reliability analysis of cable bridge. In addition, reliability index of cable bridge can be differ due to various reason. Therefore, reduction amount of load factor is calculated for various reliability index range and reduction effect is compared with other results.
Key Word Long-span cable bridge, Limit state design, Non-linear reliability analysis, Direct dead load, Load factor
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