【正文】 條典型曲線作為代表 )，表述了軸拉曲線隨基體強(qiáng)度的變化規(guī)律；表述了軸拉曲線隨鋼纖維 (F3 型 )摻量的變化規(guī)律。另外，鋼纖維摻量的提高可以大大地改善曲線的豐滿程度。 當(dāng)基體強(qiáng)度較高時(shí)，由于纖維拔斷的出現(xiàn)使得 F2 和 F3 型鋼纖維試件的軸拉曲線下降端呈階梯狀。 曾經(jīng)有許多鋼纖維混凝土軸拉應(yīng)力一應(yīng)變?nèi)€模型提出大多數(shù)為分段函數(shù)，以應(yīng)力峰值點(diǎn)為分界點(diǎn)。 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)。 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 )。 (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。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。 and when the matrix strength is high， fiber breaking occurs． Therefore， the toughness modulus falls down continually as the matrix strength rises. The toughness modului of fibers F3 and F4 rise together with the matrix strength． Both the two kinds of fiber are snipped and their surfaces are coarse． Therefore． the friction is dominant in the proportions of bond stress． Because the friction between fiber and matrix increases along with the matrix strength， and the whole pulling out of these kinds of bond status is a continuous process， the rising of matrix strength plays a positive role in improving the toughness of SFRC containing these two kinds of fiber． The difference between the two kinds of fibers is that fiber F3 has hooked ends，which makes fiber F3 have better toughening effects than fiber F4 when the matrix strength is paratively low(C30 and C60)． When the matrix strength is high(C80)， fiber breaking impaires the toughening effect of fiber F3． And the function of fiber F4 exceeds that of fiber F3 in reverse． 3． 3 Stressstrain curves of SFRC under uniaxial tension The typical stressstrain curves of SFRC under uniaxial tension are shown in Figs． 4—11(one curve is chosen for each group of specimen to keep the graphs orderly)． Figs． 4—8 express the variation of curves along with the increasing of the matrix strength， and Figs． 9 一 l1 express the variation along with the change of the fiber content of fiber F3． The curve consists of elastic section． elastic—plastic section and falling section(softening section)． Points of contra flexure exit in the falling section of the curve． It can be seen from these figures that the matrix strength is higher， the stress—strain curves fall down faster， and the rising of the fiber content can much improve the chubbiness of these curves． Moreover， the type of steel fiber has some effect on the shape of the stress—strain curve． The curves of fiber F1 are the plumpiest of them al1． The second peak was observed in the curves of fiber F1 at the strain of about 10 000 ue． This phenomenon expresses a good toughening effect of fiber F1． The curves of fibe1s F2 and F3 are ladder—like when the matrix strength is high because of fiber breaking． The curves of fiber F4 ale smooth and like those of plain concrete in shape ． That is because the pullout process of smooth steel fiber is rather gentle． 4 Analytical Investigation Four kinds of typical steel fiber concrete tensile stress strain curves can be seen: in axial tension conditions, the 1% dosage of the steel fiber is far short of strain hardening of the concrete materials to the point where most of the experimental curves are in reach After the peak, there loads sag section. However, as deformation increases, there are two curves have a clear second peak appeared, while the other two do not, it is the basis of this phenomenon can be divided into two major categories of strengthening and toughening of steel fiber reinforced concrete, there is a second peak for the toughening class, no second peak to enhance the class. Many tensile stress—strain models have been brought forward 一 10， Most of their formats are sectiona1． taking the peak load as the divisional point． In this paper， the formula of the rising section and that of the fa11ing section are different． In the formulas： （ 3） 4． 1 Formula of rising section The digital model for the rising section is （ 4） where， are parameters related to the characters of matrix an d steel fibers． The boundary conditions are as following： 1) X=0， Y=0； 2) X=0， dy／ dx=E0 ／ Ep； 3)X=1， Y=1， dy／ dx=0． It can be drawn from the boundary39。 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