Time-Dependent Deflections of Prestressed Concrete Beams

T w o p rocedures , the " r a t e o f c r e e p " and the " supe rpos i ton" methods, a r e used f o r comput ing creep of concre te under v a r i a b l e s t r e s s f r o m known r e l a t i ons f o r c reep under constant s t r e s s and r o u t i n e n u m e r i c a l p rocedures a r e presented f o r these methods . These n u m e r i c a l methods a r e app l i ed t o t w o s e r i e s o f sus ta ined load tes ts on p r e s t r e s s e d concrete beams c a r r i e d out under l a b o r a t o r y condi t ions . Measu red def lec t ions a r e c o m pa red w i t h computed def lec t ions and found to be i n good ag ree ment . The r a t e o f c r e e p method i s then app l i ed to a f u l l s i ze b r idge beam and measu red and computed def lec t ions a r e again compared . I n the f i n a l sec t ion , the methods presented i n the f i r s t p a r t of the paper a re used to inves t iga te the poss ib le ranges of t i m e def lec t ions i n f i v e r ep resen ta t ive composi te highway b r i d g e s . A p rocedure i s ou t l ined f o r m v e s t i g a t i n g the t ime-dependent def lec t ions of p r e s t r e s s e d concrete beams.