【正文】 uction Fiberreinforced polymer
FRP reinforcing bars are currently available as a substitute for steel reinforcement in concrete structures that may be vulnerable to attack by aggressive corrosive agents. In addition to superior durability, FRP reinforcing bars have a much higher strength than conventional mild steel. However, the modulus of elasticity of FRP is typically much lower than that of steel. This leads to a substantial decrease in the stiffness of FRP reinforced beams after cracking. Since deflections are inversely proportional to the flexural stiffness of the beam, even some FRP overreinforced beams are susceptible to unacceptable levels of deflection under service conditions. Hence, the design of FRP reinforced concrete
（FRPRC） is typically governed by serviceability requirements and a method is needed that can calculate the expected service load deflections of FRP reinforced members with a reasonable degree of accuracy. The objective of this paper is to point out the inconsistencies in existing deflection formulas. Only instantaneous deflections will be discussed in this paper.Effective Moment of Inertia Approach ACI 318
（ACI 1999）and CSA
(CSA 1998) remend the use of the effective moment of inertia, Ie, to calculate the deflection of cracked steel reinforced concrete members. The procedure entails the calculation of a uniform moment of inertia throughout the beam length, and use of deflection equations derived from linear elastic analysis. The effective moment of inertia, Ie, is based on semiempirical considerations, and despite some doubt about its applicability to conventional reinforced concrete members subjected to plex loading and boundary conditions, it has yielded satisfactory results in most practical applications over the years. In North American codes, deflection calculation of flexural members are mainly based on equations derived from linear elastic analysis, using the effective moment of inertia, Ie, given by Branson’s formula
(1965) （1）=cracking moment。這些構件與芳綸玻璃鋼鋼筋、玻璃玻璃鋼或碳纖維塑料筋配筋率、幾何和材料屬性不同。本文只討論瞬時撓度。=鋼筋的彈性模量。
CSA S80602（CSA 2002）表明，在計算撓度時彎矩曲率法非常適合FRP構件，因為彎矩曲率圖分為兩個線性近似區(qū)域:第一個是在混凝土破壞前的區(qū)域,第二個是混凝土破壞之后的區(qū)域。整個曲率圖可由三對坐標組成:開裂時,開裂瞬間，開裂后。它建議今后使用進行修改過的有效慣性矩方程，如下所示: （6）=未破壞截面處的慣性矩 方程式（6）取自CEBFIP MC90（CEBFIP 1990）加利等（2001）。這個過程需要一個適用于整個梁長的慣性矩計算,并使用由線性彈性分析所得的撓度方程。本文分析的目的是確定FRPRC構件撓度的計算方法,也是確定最適用的可靠性的準則。 =moment of inertia of the cracked section transformed to concrete。 Curvature。（通訊作者）摘 要： 纖維復合材料包覆鋼筋混凝土（FRPRC）的設計通常是由正常使用極限狀態(tài)的要求控制,而不是像由傳統的鋼筋混凝土極限狀態(tài)要求控制。由于變形量和梁的抗彎剛度是成反比的,甚至一些纖維復合材料超鋼筋加固梁在使用情況下容易受到不可接受的水平偏轉。他們發(fā)現方程的順序取決于FRP的彈性模量和配筋率。因此通過慣性矩加載點和方程（1）中的有效慣性矩可導出撓度方程。對記錄進行分析，可由試驗所得的比率得出計算撓度的比率，所得值為最大值與最小值的平均值。由于出版物中統計樣本的范圍有限，所以用于此試驗的梁的材料和幾何性質不能在出版物中找到,但可以在莫塔（2005）找到。α =相關系數。=毛截面慣性矩,=破壞截面混凝土慣性矩。撓度彎曲。 Toutanji and Saafi 2000) argue that the basic form of the effective moment of inertia equation should remain as close to the original Branson’s equation as possible, because it is easy to use and designers are familiar with modified equation is presented in the following equation: （3） A further investigation of the effective moment of inertia was performed