| External prestressing has shown to be advantageous in segmental construction and rehabilitation, but has not been introduced into general precast construction. A case study and comparative design was performed to determine the effectiveness of external prestressing in highway overpass design. The overpass uses precast-prestressed concrete girders as the main structural elements, made continuous through deck and diaphragms and longitudinally post-tensioned.; Deflections and strains in two girders were monitored from fabrication to service, and a comprehensive material testing program was done on the concrete mix. A model describing all relevant concrete properties was formulated from the testing program and a structural analysis method incorporating the concrete properties was validated through the field study. The method of analysis was expanded, using current literature, to predict the behaviour using external rather than internal tendons. Results show a decrease in weight and more efficient use of prestressing and post-tensioning is possible with external tendons. |
