發(fā)布時(shí)間：2019-07-05 17:46

【摘要】：隨著現(xiàn)代化交通需求、橋梁設(shè)計(jì)理念的推動(dòng)和箱形截面梁與預(yù)應(yīng)力技術(shù)的結(jié)合,箱形截面梁更加趨向于薄壁、長(zhǎng)懸臂的結(jié)構(gòu)形式,預(yù)應(yīng)力箱梁已經(jīng)成為橋梁建設(shè)的一種大趨勢(shì)。本論文在國(guó)家自然科學(xué)基金《PC箱梁考慮預(yù)應(yīng)力作用效應(yīng)的剪力滯行為研究(51208242)》資助下,針對(duì)預(yù)應(yīng)力混凝土箱梁,通過理論研究并結(jié)合數(shù)值模擬,系統(tǒng)研究了預(yù)應(yīng)力效應(yīng)下箱梁的剪力滯效應(yīng)理論分析中的關(guān)鍵問題。主要研究?jī)?nèi)容及成果如下:(1)為了回答軸向力是否引起剪力滯效應(yīng),分別針對(duì)無懸臂板和有懸臂板的單室箱梁,采用板殼有限元分析了軸向力分散于箱梁不同部位時(shí)的縱向應(yīng)力,引入軸向力剪力滯系數(shù)概念,研究了不同工況下的簡(jiǎn)支梁、懸臂梁和連續(xù)梁的軸向力剪力滯系數(shù)。結(jié)果表明,軸向力作用在箱梁時(shí),梁體總體不會(huì)產(chǎn)生剪力滯效應(yīng),僅在靠近軸向力作用點(diǎn)部位存在局部應(yīng)力集中區(qū),其區(qū)域約為1倍梁寬的長(zhǎng)度,其值與一般構(gòu)件承受局部壓力時(shí)的應(yīng)力非均勻傳遞長(zhǎng)度相等。(2)針對(duì)箱梁預(yù)應(yīng)力束在梁端通常是偏心錨固,并非錨固在形心軸位置,等效預(yù)應(yīng)力作用包括作用在形心軸的軸壓力和梁端集中彎矩。本文將單箱雙室箱梁預(yù)應(yīng)力束偏心錨固時(shí)的預(yù)應(yīng)力等效荷載中軸向力和集中彎矩分開計(jì)算,對(duì)集中彎矩作用下的箱梁剪力滯效應(yīng)計(jì)算時(shí),提出了在集中彎矩作用下能夠反映箱梁各翼板間剪力滯翹曲位移差異的剪力滯翹曲位移模式,建立了集中彎矩作用下的箱梁剪力滯效應(yīng)控制微分方程,得到解析解。系統(tǒng)的研究了集中彎矩作用部位不同時(shí),箱梁的剪力滯分布規(guī)律。經(jīng)本文解析解與ANSYS有限元數(shù)值解的對(duì)比分析,得到的結(jié)果基本規(guī)律和數(shù)值分析結(jié)果大小均基本相同,說明本文所取的翹曲位移函數(shù)是合理的,導(dǎo)出的控制微分方程和解析解計(jì)算公式是正確的,且計(jì)算精度較好。(3)對(duì)僅在集中彎矩作用下的簡(jiǎn)支單箱雙室箱剪力滯效應(yīng)分析,在集中彎矩作用部位的左右兩側(cè)各l/4范圍內(nèi)較大,剪力滯系數(shù)在集中彎矩作用部位取得最大值,當(dāng)在l/4跨部位作用集中彎矩時(shí),集中彎矩作用部位附近頂板與腹板交界處考慮剪力滯效應(yīng)后的應(yīng)力達(dá)到了初等梁理論值的2.24倍,而其余部位較小。并且剪力系數(shù)在各腹板之間存在差異,因此建議結(jié)構(gòu)設(shè)計(jì)中有必要考慮到不同腹板間翼板應(yīng)力差異。(4)針對(duì)預(yù)應(yīng)力束偏心錨固時(shí)的鋼束橫向布置方式不同,研究了不同剪力滯荷載效應(yīng)模式對(duì)箱梁截面的剪力滯效應(yīng)影響,采用ANSYS有限元軟件建立了簡(jiǎn)支梁、懸臂梁和連續(xù)梁分別在三腹板平均布束、兩邊腹板布束和僅中腹板布束時(shí),典型截面和沿跨度方向的剪力滯效應(yīng)。結(jié)果表明,不同偏心布束不同時(shí),箱梁剪力滯效應(yīng)分布不同,且差異較大,綜合三種布束方式下典型截面頂、底板的剪力滯系數(shù)分析,僅在中腹板布置預(yù)應(yīng)力束時(shí),截面頂?shù)装宓募袅�滯系�?shù)變化較大,頂板剪力滯系數(shù)從中腹板附近的1.22變化到了翼緣邊緣附近的0.531,剪力滯效應(yīng)明顯;在三個(gè)腹板均勻布束的情況下,截面的剪力滯效應(yīng)相對(duì)差異較小。同時(shí),不同布束方式對(duì)不同邊界條件下箱梁剪力滯效應(yīng)影響不同,對(duì)連續(xù)梁影響最大,簡(jiǎn)支梁次之,懸臂梁影響較小。(5)針對(duì)超靜定箱梁結(jié)構(gòu)預(yù)應(yīng)力次內(nèi)力對(duì)箱梁剪力滯效應(yīng)的影響進(jìn)行了理論分析。理論上,在預(yù)應(yīng)力錨固端部位因剪力滯效應(yīng)引起的附加彎矩值和預(yù)應(yīng)力初彎矩值同號(hào),且大小只與箱梁截面的幾何特性有關(guān),在中支點(diǎn)處的附加彎矩同時(shí)與箱梁的截面幾何參數(shù)、寬跨比有關(guān)。結(jié)合相關(guān)算例的有限元分析結(jié)果,得出理論與數(shù)值分析結(jié)果相符。(6)對(duì)于兩跨連續(xù)梁在實(shí)際預(yù)應(yīng)力束線形布置設(shè)計(jì)時(shí),一般是非吻合索布束方式。這些布束方式都會(huì)在梁內(nèi)產(chǎn)生次內(nèi)力,結(jié)合預(yù)應(yīng)力混凝土兩跨連續(xù)箱梁中鋼束不同線形布置方式,采用ANSYS有限元軟件建立板殼模型,研究了直線布束、折線布束和拋物線布束時(shí)的箱梁剪力滯效應(yīng)。得到,布束線形的改變對(duì)中支承截面的剪力滯效應(yīng)有一定影響,直線布束與拋物線布束時(shí),中支點(diǎn)截面上靠近邊腹板的剪力滯系數(shù)大小相差達(dá)到了23.68%;左側(cè)跨中截面靠近邊腹板處更是達(dá)到了33.45%;腹板與頂板交界處的剪力滯效應(yīng)沿跨度方向的分布趨勢(shì)基本一致,但在中支點(diǎn)截面頂板靠近邊腹板處的剪力滯系數(shù)差值達(dá)23.68%。從總體上看,截面剪力滯系數(shù)變化較大范圍基本是在中支承位置附近L/4長(zhǎng)度范圍,在其他較遠(yuǎn)區(qū)域影響很小。
[Abstract]:With the development of modern traffic demand, the promotion of bridge design concept and the combination of box-section beam and pre-stressed technology, the box-section beam is more inclined to the structure of thin-wall and long cantilever, and the prestressed box girder has become a big trend of the construction of the bridge. In this paper, under the study of the shear lag behavior of the NSFC , the prestressed concrete box girder is studied by theory and combined with the numerical simulation. The key problems in the theoretical analysis of the shear lag effect of the box girder under the prestress effect are studied. The main research contents and results are as follows: (1) In order to answer whether the axial force causes the shear lag effect, the longitudinal stress in different parts of the box girder is analyzed by the finite element method of the plate shell for the single-chamber box girder without the cantilever plate and the cantilever plate, The axial force shear lag coefficient of simply-supported beam, cantilever beam and continuous beam under different working conditions is studied by introducing the concept of axial force shear lag coefficient. The results show that, when the axial force acts on the box girder, there is no shear lag effect in the beam body, and only the local stress concentration area exists near the point of action of the axial force, and the area is about 1 times the length of the beam width. The value is equal to the non-uniform transfer length of the general component under the local pressure. (2) The pre-stressed beam of box girder is usually eccentrically anchored at the beam end and is not anchored in the position of the mandrel, and the equivalent pre-stress includes the shaft pressure acting on the mandrel and the concentrated bending moment of the beam end. In this paper, the axial force and the concentrated bending moment of the pre-stressed equivalent load of a single-box double-chamber box-girder pre-stressed beam are calculated separately, and the shear lag effect of the box girder under the action of concentrated bending moment is calculated. In this paper, the shear lag-warping displacement model, which can reflect the difference of the shear lag and the difference of the shear lag between the flanges of the box girder under the action of concentrated bending moment, is put forward, and the differential equation of the shear lag effect of the box girder under the action of concentrated bending moment is established to obtain the analytical solution. The shear lag distribution of the box girder is not the same at the same time in the system. The result of the comparison between the analytical solution and the finite element numerical solution of ANSYS is that the basic law of the results and the size of the numerical analysis result are basically the same, and the warping displacement function as taken in this paper is reasonable, and the derived control differential equation and the analytical solution are correct. And the calculation accuracy is good. (3) The shear lag effect of a simply-supported single-box double-chamber box under the action of a concentrated bending moment is analyzed, The stress after the shear lag effect is considered to be 2.24 times the theoretical value of the primary beam, while the rest is smaller. And the shear coefficient is different between the web plates, and therefore, it is necessary to take into account the stress difference of the wing plates between the different web plates in the structural design. (4) The effect of different shear lag load effect mode on the shear lag effect of the section of the box girder is studied. The average distribution of the beam, the cantilever beam and the continuous beam on the three-web is established by using the finite element software of ANSYS. The shear lag effect in the typical cross-section and in the span direction is typical when both the web of the web and the web of the middle web are deployed. The results show that the shear lag effect of the box girder is different and the difference is large, and the shear lag coefficient of the top and bottom plate of the cross-section is larger when the prestressed beam is arranged in the middle web. The shear lag coefficient of the top plate is changed from 1.22 to 0.531 near the edge of the flange, and the shear lag effect is obvious; in the case of uniform distribution of three webs, the shear lag effect of the section is relatively small. At the same time, the effect of different beam patterns on the shear lag effect of box girder under different boundary conditions is different, the effect on the continuous beam is the largest, the simple-supported beam is the second, and the influence of the cantilever beam is small. (5) The influence of the internal force of the pre-stressed secondary internal force on the shear lag effect of the box girder is analyzed. In theory, the additional bending moment value and the pre-stress initial bending moment value which are caused by the shear lag effect at the position of the prestressed anchorage end are the same as the original bending moment value, and the size is only related to the geometric characteristics of the section of the box girder, and the additional bending moment at the middle supporting point is related to the cross-sectional geometric parameter and the width-span ratio of the box girder. The results of the finite element analysis of the relevant examples are given, and the results are in agreement with the numerical results. (6) For the design of the two-span continuous beam in the linear arrangement of the actual pre-stressed beam, the non-staple fiber bundle mode is generally used. In this paper, the internal force is generated in the beam, and the shear lag effect of the box girder is studied by using the ANSYS finite element software to establish the plate shell model in combination with the different linear arrangement of the steel beam in the two-span continuous box girder of the pre-stressed concrete. The results show that the change of the beam alignment has a certain effect on the shear lag effect of the middle bearing section, and the shear lag coefficient in the cross section of the middle supporting point near the side web is 23.68% when the straight-line cloth bundle and the parabolic distribution beam are arranged, and the cross-section of the left side is more than 33.45% near the edge web; The shear lag effect at the interface between the web and the top plate is generally consistent with the distribution trend in the span direction, but the difference of the shear lag coefficient at the top of the mid-pivot section near the edge web is 23.68%. In general, that large extent of the shear lag coefficient of the section is basically the L/4 length range near the middle support position, and the effect on the other remote areas is very small.
【學(xué)位授予單位】：蘭州交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：U441.5

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本文編號(hào)：2510704

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