Abstract
The combined 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 and compatibility and avoids the use of any empirical multipliers. A simple graph is proposed to eva luate 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 of comparable girders prestressed with steel tendons, depending on the type of FRP tendons and the initial stress profile of the cross-section under consideration.
在過去的十年，纖維增強(qiáng)聚合體筋作為預(yù)應(yīng)力鋼筋的使用已經(jīng)被提議，并且已經(jīng)用FRP筋建造了一些混凝土橋。與傳統(tǒng)的預(yù)應(yīng)力鋼筋相比，F(xiàn)RP筋有許多優(yōu)點(diǎn)，其中包括它們有無腐蝕性和絕緣性的良好性能，質(zhì)輕，還有較高的抗拉強(qiáng)度。大多數(shù)關(guān)于用FRP筋的預(yù)應(yīng)力混凝土梁的研究工作都集中在預(yù)應(yīng)力構(gòu)件的短期行為；在文獻(xiàn)里面關(guān)于配有FRP筋的混凝土構(gòu)件的長(zhǎng)期行為的研究成果是缺乏的。最近ACI委員會(huì)在關(guān)于用FRP筋的預(yù)應(yīng)力混凝土結(jié)構(gòu)的報(bào)告中指出“關(guān)于預(yù)應(yīng)力的長(zhǎng)期損失和隨時(shí)間變化的彎曲度和變形的研究是必要的…?！被炷两Y(jié)構(gòu)中大多數(shù)的FRP筋的研究和應(yīng)用要么是碳纖維增強(qiáng)聚合體或者是芳族聚酸胺纖維增強(qiáng)的聚合體。玻璃纖維增強(qiáng)聚合體的應(yīng)用大多數(shù)都局限在傳統(tǒng)的配筋中，因?yàn)樗目估瓘?qiáng)度相對(duì)較低，而且抵抗徐變的能力差。因此，這篇論文集中在CFRP 和AFRP筋的預(yù)應(yīng)力構(gòu)件的研究上。