Preliminary Design of Post-Tensioned Transfer Girders

Abstract

Posttensioned transfer girders offer elegant solutions to support vertical members that do not extend below lower levels of high-rise buildings. The design of a posttensioned transfer girder involves selection of a preliminary section, and then optimization of girder size and the prestressing force to satisfy serviceability and ultimate design requirements. In practice, typical span-to-depth ratios are used for preliminary sizing of structures. However, in the case of transfer girders, it is not easy to set a rule-of-thumb because the depth of the member depends on the transferred load and many other parameters. Herein, a simple approach is suggested to practicing engineers for determining the depth of simply supported transfer girders with minimal trial and error. It is shown that the proposed expression gives reasonable preliminary dimensions to achieve an acceptable design in terms of serviceability.