文档介绍：附录: A 科技文献翻译
原文
Construction and Building Materials
Volume 21, Issue 5 , May 2007, Pages 1052-1060
An approach to determine long-term behavior of concrete members prestressed with FRP tendons
Abstract
bined effects of creep and shrinkage of concrete and relaxation of prestressing tendons cause gradual changes in the stresses in both concrete and prestressing tendons. A simple method is presented to calculate the long-term prestress loss and the long-term change in concrete stresses in continuous prestressed concrete members with either carbon fiber reinforced polymer (CFRP) or aramid fiber reinforced polymer (AFRP) tendons. The method satisfies the requirements of equilibrium patibility and avoids the use of any empirical multipliers. A simple graph is proposed to evaluate the reduced relaxation in AFRP tendons. It is shown that the prestress loss in FRP tendons is significantly less than that when using prestressing steel, mainly because of the lower moduli of elasticity of FRP tendons. The long-term changes in concrete stresses and deflection can be either smaller or greater than those parable girders prestressed with steel tendons, depending on the type of FRP tendons and the initial stress profile of the cross-section under consideration.
Keywords: Creep; FRP; Long-term; Prestress loss; Prestressed concrete; Relaxation; Shrinkage
Nomenclature
A area of cross section
d vertical distance measured from top fiber of cross section
E modulus of elasticity
age-adjusted elasticity modulus of concrete
fpu ultimate strength of prestressing tendon
h total thickness of concrete cross section
I second moment of area
O centroid of age-adjusted transformed section
t final time (end of service life of concrete member)
t0 concrete age at prestressing
y coordinate of any fiber measured downward from O
χ aging coefficient
χr reduced relaxation coefficient
α ratio of modulus of elasticity of FRP or steel to that of concrete
Δεc(t,t0) change