Title:
Allowable Tensile Stress for Webs of Prestressed Segmental Concrete Bridges
Author(s):
Ayman M. Okeil
Publication:
Structural Journal
Volume:
103
Issue:
4
Appears on pages(s):
488-495
Keywords:
bridges; prestressed; reliability; tensile strength
DOI:
10.14359/16424
Date:
7/1/2006
Abstract:
Structural, economical, and aesthetic advantages have helped prestressed (PS) concrete segmental box girder bridges gain popularity. The long-term endurance of PS segmental bridges depends on being free of cracking. Designers limit structural cracking by ensuring that service stresses do not exceed the tensile strength of concrete. An allowable tensile stress, which is more stringent than tensile strength, is often used to account for the uncertainties in both capacity and demand. Design codes clearly provide the allowable tensile stress for top and bottom fibers. This paper investigates establishing an allowable tensile stress limit for consideration in webs, where research is currently lacking. The proposed limit is obtained through a reliability study where three expressions were calibrated to conform to HL-93 loading. The effect of the accompanying principal compressive stress is accounted for in two of the expressions. Six PS concrete bridge designs were used to demonstrate the importance of accounting for the biaxial state of stress. A parametric study shows that one of the proposed expressions provides a more uniform range of reliability index b than the other two, including the one currently used by designers.