Reducing cambers and prestress losses by including fully tensioned top prestressing strands and mild reinforcing steel

摘要

This paper investigates the effects of fully tensioned top strands and inclusion of mild reinforcing steel on prestress losses and camber of pretensioned bridge girders. The results show that the inclusion of both fully tensioned top strands and mild reinforcing steel in the precompression zone reduced both short-term and long-term camber by 72% in the prestressed concrete bridge designs that were studied. Furthermore, the inclusion of both fully tensioned top strands and mild reinforcing steel have small but beneficial reduction in prestress losses. Prestress losses were estimated for a prestressed concrete bridge made with Type IV bridge girders spanning 103.33 ft (31.5 m). Five methods were used to estimate losses, including both the AAS-HTO LRFD Bridge Design Specifications approximate method and relined method. The newly developed Jayaseelan time-step method is presented and compared with other methods. The results show that all live methods estimate prestress losses that were within 2% of one another.