【正文】 時(shí)，它將會(huì)產(chǎn)生持續(xù)的應(yīng)變。在空氣溫度為 25攝氏度的條件下，AFRP 筋中 a和 b的關(guān)系建議如下： (2)。正如以后部分所述，在實(shí)際用途中假定 Ω 在 和 之間變化， χ r = 22 (20K) 圖 1 AFRP 的松弛減少系數(shù) 3. 分析的理論方法 這種分析遵循了 Ghali 等人提議的一般的四個(gè)步驟。在這種情況下，可以通過(guò) t0時(shí)刻混凝土的土的彈性模量來(lái)劃分應(yīng)力的值進(jìn)而得到在 t0時(shí)刻應(yīng)變的圖表。 步驟 4：人為施加力的消除。 ?? 連續(xù)預(yù)應(yīng)力梁或是框架產(chǎn)生超靜定的彎矩（認(rèn)為是次彎矩），正如之前敘述， 9 里的 ε 1(t0)和 ψ (t0)代表由于恒載產(chǎn)生的彎矩和預(yù)應(yīng)力產(chǎn)生的次彎矩在某截面的應(yīng)變參數(shù)。不連續(xù)處的變化 Δ D1是按每一跨 兩端 的 和。典型的后張拉 DT截面的幾何系數(shù)的輔助設(shè)計(jì)如圖6a,6b,6c,7a,7b,7c,7d 分別是配有 CFRP 筋和 AFRP 筋。同那些用預(yù)應(yīng)力鋼筋制作的梁相比，混凝土內(nèi)的應(yīng)力變化和偏差要么變小，要么變大，這取決于所用的 FRP 筋的類(lèi)型和預(yù)應(yīng)力構(gòu)件中跨橫截面 的初始應(yīng)力。這種方法能夠容易的用計(jì)算機(jī)總分析表編程。所以有(Δ M)A = (Δ M)B = Δ F1/2 和 Δ MB = Δ F1。 (14K) 圖 .（ a）索結(jié)構(gòu)剖面及尺寸 。預(yù)應(yīng)力鋼筋中應(yīng)力隨時(shí)間的變化是 EpΔ ε p和減少的松弛的和。所以，Δ ψ free= ψ (t0) (9)。除了橫截面的初始應(yīng)力外，這個(gè)方程僅僅是四個(gè)容易計(jì)算出的無(wú)因次系數(shù)，徐變系數(shù)和收縮的函數(shù)。以下是之前 Ghali 和 Trevino 建議的估算預(yù)應(yīng)力鋼筋 χ r的一種方法， AFRP 筋的 χ r 可以這樣計(jì)算(4)，其中 (5)， ζ 是無(wú)量綱的時(shí)間函數(shù)，定義了鋼筋的應(yīng)力與時(shí)間關(guān)系的曲線的形狀。 AFRP 筋的松弛水平取決于許多因素，包括周?chē)h(huán)境的溫度，外界因素（例如，空氣，堿度，酸度或者是鹽含量），初應(yīng)力 σ p0與極限強(qiáng)度 fpu的比，還有初始應(yīng)力之后的時(shí)滯。由于松弛或者是由于徐變，收縮，和松弛的聯(lián)合作用引起的預(yù)應(yīng)力鋼筋內(nèi)拉力的損失為負(fù)值。這種方法滿足了平衡性和兼容性的要求，避免了經(jīng)驗(yàn)公式的使用，一般來(lái)說(shuō)精確的表明了損失。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。建議用簡(jiǎn)單的圖表來(lái)評(píng)估 AFRP 筋減少的松弛。 research findings on the longterm behavior of concrete members with FRP tendons are scarce in the literature. The recent ACI Committee report on prestressing concrete structures with FRP tendons (ACI [1]) has pointed out that: “Research on the longterm loss of prestress and the resultant timedependent camber/deflection is needed …” Most of the research and applications of FRP tendons in concrete structures have adopted either carbon fiber reinforced polymer (CFRP) or aramid fiber reinforced polymer (AFRP) tendons. The use of glass fiber reinforced polymers (GFRP) has mostly been limited to conventional reinforcing bars due to their relatively low tensile strength and poor resistance to creep. Therefore, this paper focuses on prestressed members with either CFRP or AFRP tendons. Creep and shrinkage of concrete, and relaxation of prestressing tendons, cause longterm deformations in concrete structures. While it is generally accepted that longterm losses do not affect the ultimate capacity of a prestressed concrete member, a reasonably accurate prediction of these losses is important to ensure satisfactory performance of concrete structures in service. If prestress losses are underestimated, the tensile strength of concrete can be exceeded under full service loads, causing cracking and unexpected excessive deflection. On the other hand, overestimating prestress losses can lead to excessive camber and uneconomic design. The error in predicting the longterm prestress losses can be due to: (1) inaccuracy in estimation of the longterm material characteristics (creep and shrinkage of concrete and relaxation of prestressing tendons)。附錄 A 科技文獻(xiàn)翻譯 原文 Construction and Building Materials Volume 21, Issue 5 , May 2020, Pages 10521060 An approach to determine longterm behavior of concrete members prestressed with FRP tendons Abstract The 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 longterm prestress loss and the longterm 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 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 longterm changes in concrete stresses and deflection can be either smaller or greater than those of parable girders prestressed with steel tendons, depending on the type of FRP tendons and the initial stress profile of the crosssection under consideration. Keywords: Creep。 and (2) inaccuracy of the method of analysis used. The objective of this paper is to address the second source of inaccuracy by presenting a simple analytical method to estimate the timedependent strains and stresses in concrete members prestressed with FRP tendons. The method satisfies the requirements of equilibrium and patibility and avoids the use of empirical equations, which in general show loss in accuracy to enable generality. The 5 inaccuracy in the material characteristics used can be mitigated by varying the input material parameters and establishing upper and lower bounds on the analysis results. For the purpose of this paper, and to avoid confusion, a consistent sign convention is used. Axial force N is positive when it is tensile. Bending moment, M, that produces tension at the bottom fiber of a cross section and the associated curvature ψ are positive. Stress, σ, and strain, ε, are positive for tension and elongation, respectively. Downward deflection is positive. It follows that shrinkage, εcs, is negative quantity. The loss in tension in prestressing reinforcement due to relaxation Δσpr or due to the bined effects of creep, shrinkage, and relaxation, Δσp, is negative quantity. The analysis considered herein focuses on a prestressed concrete section with its centroidal principal yaxis in vertical direction with the coordinate y of any concrete fiber or steel layer being measured downward from a given reference point. 2. Relaxation of FRP prestressing tendons Similar to concrete and steel, AFRP prestressing tendons exhibit some creep if subjected to sustained strains. CFRP tendons typically display insignificant amount of creep, w