【正文】 （ 4） 這里： 和 為與基體和鋼纖維特性有關(guān)的參數(shù)。 邊界條件為： 1) X=0， Y=0； 2) X=0， dy／ dx=E0 ／ Ep； 3)X=1， Y=1， dy／ dx=0． 由邊界條件可得公式 (5)可以簡(jiǎn)化為： （ 5） 系數(shù) 可 以通過試驗(yàn)數(shù)據(jù)回歸獲得 (6) 式中： E0 為圓點(diǎn)切線模量； EP 為峰值應(yīng)力點(diǎn)割線模量 (第一峰值 )。 因此公式 (6)可以轉(zhuǎn)換為： (7) 下降段公式 下降段數(shù)學(xué)的模型為： （ 8） 式中： 和 為與基體和鋼纖維特性有關(guān)的參數(shù)。 下降段表達(dá)式中系數(shù)值選取 。邊界條件 x=l和 y=1自然滿足。系數(shù)的取 值通過最小二乘法回歸獲得： （ 9） 可見基體強(qiáng)度和纖維參量對(duì)軸拉曲線下降段的下降速率的影響是相反的。 五、 理論曲線與試驗(yàn)結(jié)果的比較 鋼纖維高強(qiáng)混凝土軸拉應(yīng)力一應(yīng)變理論曲線和試驗(yàn)曲線的比較如圖 l2所示 (以試件 F3— 6010為例 )?？梢姡碚摻Y(jié)果與試驗(yàn)結(jié)果符合較好。 六、實(shí)驗(yàn)結(jié)論 (1)試驗(yàn) 結(jié)果表明：鋼纖維高強(qiáng)混凝土劈拉強(qiáng)度略高于軸拉強(qiáng)度，兩者有較好的相關(guān)性，鋼纖維高強(qiáng)混凝土軸拉強(qiáng)度可取為劈拉強(qiáng)度的 倍。 (2)在摻入同種同量鋼纖維時(shí)，隨著基體強(qiáng)度的增加，鋼纖維高強(qiáng)混凝土與同配比素混凝土的初裂強(qiáng)度的比值基本不變；軸拉極限強(qiáng)度的比值有 所變化，且該變化對(duì)不同的纖維類型有所不同，鋼纖維與基體黏結(jié)性能好，且破壞時(shí)不被拉斷，則增強(qiáng)效果好。 (3)提高鋼纖維摻量對(duì)鋼纖維高強(qiáng)混凝土的抗拉強(qiáng)度特性的改善作用比對(duì)普通強(qiáng)度混凝土的改善作用明顯。 (4)鋼纖維高強(qiáng)混凝土的初裂應(yīng)變和峰值應(yīng)變要比素混凝土的增幅隨基 體強(qiáng)度和纖維摻量的升高而增大。 (5)引入了軸拉韌性指數(shù)來評(píng)價(jià)鋼纖維高強(qiáng)混凝土的韌性，鋼纖維混凝土的軸拉韌性要大大優(yōu)于同配比的索混凝土，并且受基體強(qiáng)度和鋼纖維特性和 摻量的影響。 (6)基體強(qiáng)度越高，鋼纖維高強(qiáng)混凝土的軸拉應(yīng)力應(yīng)變曲線在峰值過后下降得越快；纖維摻量的提高可以大大改善曲線的豐滿程度，鋼纖維類型對(duì)曲線形狀也有一定的影響。通過對(duì)實(shí)驗(yàn)曲線的分析與回歸，給出了考慮上述影響因素的鋼纖維高強(qiáng)混凝土軸拉應(yīng)力應(yīng)變?nèi)€表達(dá)式。 (7)綜合而言，四種鋼纖維中， F3 型鋼纖維的增強(qiáng)效果最好，而 Fl 型鋼纖維的增韌效果 最好。 外文翻譯原文 Concrete stress test 1 Test Introduction The tensile properties of concrete can be enhanced substantially by incorporating high strength and small diameter short steel fibers． which leads to the steel fiber reinforced concrete(SFRC)． In conventional SFRC， the steel fiber content is usually within the range of 0． 2％ —2％ by volume． At such a low 6her content． the tensile response of SFRC would assume a nonhardening type． which is characterized by the widening of a single crack， similar to an unreinforced concrete ． The contribution of fibers is apparent in the post—cracking response, represented by an increase in post—cracking ductility due to the work associated with pullout of fibers bridging a failure crack. However， improvements in some other properties are insignificant ． Moreover，the softening segment of the stress—strain curve of SFRC with such a low fiber content under uniaxial tension is difficult to be got with normal experimental methods． Many works have been done to find a suitable and relatively easy way to analyze the tensile characteristics ． And it was reported that the whole curve could be got on a normal testing machine with stiffening ponents added. In this article， the stress—strain behavior of SFRC under uniaxial tension Was analyzed for different types of fiber． The tensile characteristics of SFRC influenced by the matrix strength and the steel fiber content were studied also． In addition， the stress—strain curves of high strength SFRC with different factors were well acquired． The mechanism of fiber reinforced concrete to enhance research, to obtain steel fiber reinforced concrete in tension curve of the whole process, using the most appropriate method of axial tension, but to make sure the testing methods improved, and the testing machine must have enough stiffness to ensure the testing process stability. Is well known in engineering practice, process, technology and economic conditions due to construction constraints, SFRCdoped fiber volume in the rate of generally not more than 2%, while most of the engineering example, the fiber fraction are about 1%. In this paper the design of the axial tension SFRC material testing, fiber dosage to take 1%, and using different types of fiberreinforced forms, were analyzed. 2 Experimental Content The specimens were tested on a 60 kN universal testing machine． Four high steel bars were added to enhance the stiffness of the testing machine． In addition， spherichinges were used to abate the initial axial eccentricity of the specimens．． It was ensured that specimens should be pulled under uniaxial tension by adjusting the four high strength bolts which connect the specimens to the crossbeam． And the difference between the tensile strains of the opposite sides of the specimen should be less than 1 5％ of their mean value． When the fiber content was low (0 and ％ by volume)， the cyclic quire the whole stress—strain. 2． 1 Materials Four types of steel fibers shown in Table were chosen for this test． Three of these fibers (F1， F2 and F3) were hooked—end and the other one(F4)was smooth． Three concrete mixtures， shown in Table 2， were investigated． Water reducing agents were used in C60 and C80 mixes(DK 一 5 made by Dalian Structure Research Institute and Sika made in Switzerland respectively). The pressive strengths of these C30， C60， C80 mixes were determined according to “Test Methods Used for Steel Fiber Reinforced Concrete”(CECS 13： 89)8 3 at 28 days using 150 mm150 mm 150 mm cube s． Averaged results for 3 specimens are given in Table 2． 0rdinary Portland cement(yielded by Dalian Huaneng Onoda Cement Company)of 32． 5 and 52