【摘要】：近幾十年來,世界上大量經(jīng)過多年運營使用的混凝土箱梁橋出現(xiàn)跨中下?lián)线^大和梁體開裂現(xiàn)象,嚴重影響了結(jié)構(gòu)的安全性和適用性。本文依托國家自然科學(xué)基金項目“在役混凝土箱梁橋時變承載力的分析理論及試驗研究(51178416)”,以混凝土箱梁結(jié)構(gòu)為研究對象,探索了其短期和長期剪力滯效應(yīng)的分析方法,主要研究內(nèi)容及成果如下:(1)在箱梁位移場中引入箱梁腹板的縱向位移函數(shù),以消除傳統(tǒng)剪力滯分析方法假定箱梁截面中性軸與形心軸重合引起的計算誤差,據(jù)此提出了考慮中性軸變化及剪切變形的剪力滯效應(yīng)分析方法。通過算例分析,將所提方法計算值與文獻試驗值、有限元值及傳統(tǒng)分析方法計算值對比,表明所提方法能較為準確地計算箱梁的剪力滯效應(yīng)。(2)運用所提出的方法,探討了寬跨比、懸臂板寬與頂板半寬比、底板與頂板寬度比、高寬比及板厚比四個幾何參數(shù)對箱梁翼板應(yīng)力差值比的影響,結(jié)果表明,寬跨比、懸臂板寬與頂板半寬比、底板與頂板寬度比對箱梁集中荷載作用截面和中支點截面上翼板與腹板交界處的應(yīng)力差值比影響較大,而高寬比與板厚比則僅對連續(xù)箱梁集中荷載作用截面和中支點截面上翼板與腹板交界處的應(yīng)力差值比影響顯著。(3)基于虛功原理及齡期調(diào)整有效模量法,提出了考慮剪力滯效應(yīng)和混凝土收縮徐變的RC箱梁長期性能分析方法,通過與典型簡支RC箱梁的有限元模型和初等梁理論計算結(jié)果對比,驗證了所提方法的有效性和精度。此外,詳細分析了收縮和徐變對RC箱梁長期性能的影響,指出混凝土徐變及收縮是影響RC箱梁長期撓度和混凝土應(yīng)力的主要因素,其同樣也影響RC連續(xù)箱梁的支反力和內(nèi)力分布。(4)基于預(yù)應(yīng)力等效荷載法與Timoshenko梁理論,提出了考慮剪切變形的預(yù)應(yīng)力作用下箱梁剪力滯分析方法,該法能考慮軸向力引起的剪力滯效應(yīng)。通過算例分析,將該法計算值與文獻試驗值、有限元值比較,驗證了提出方法的精度。通過對典型預(yù)應(yīng)力布束方式的簡支梁和兩跨連續(xù)箱梁的分析,表明剪切變形對預(yù)應(yīng)力作用下箱梁撓度計算影響很大;預(yù)應(yīng)力等效軸向力會在鋼束錨固端引起顯著的剪力滯效應(yīng)。(5)引入混凝土材料的時變性,采用不同的有限單元(梁、實體單元)數(shù)值模擬方法,分別建立了考慮懸臂施工階段的典型懸臂施工PC連續(xù)箱梁橋的分析模型,比較研究了在非均勻及均勻收縮徐變作用下,考慮剪力滯效應(yīng)的PC連續(xù)箱梁橋的時變變形、混凝土應(yīng)力和鋼束應(yīng)力。結(jié)果表明,忽略剪力滯效應(yīng)會嚴重低估大跨PC箱梁橋的跨中下?lián)?非均勻收縮徐變對跨中長期撓度影響較小,而對鋼束應(yīng)力和混凝土應(yīng)力影響較大。
[Abstract]:In recent decades a large number of concrete box girder bridges which have been used for many years in the world have appeared the phenomenon of excessive span deflection and beam body cracking which seriously affected the safety and applicability of the structure. In this paper, based on the National Natural Science Foundation project "Analysis theory and experimental study of time-varying bearing capacity of in-service concrete box girder bridge (51178416)", this paper takes concrete box girder structure as the research object, and probes into the analysis method of its short-term and long-term shear lag effect. The main research contents and results are as follows: (1) the longitudinal displacement function of the box girder web is introduced in the displacement field of the box girder to eliminate the calculation error caused by the assumption that the neutral axis of the box girder section coincides with the centroid axis of the box girder by the traditional shear lag analysis method. Based on this, a method for analyzing the shear lag effect considering the variation of neutral axis and shear deformation is proposed. Through the example analysis, the calculated value of the proposed method is compared with the experimental value, the finite element value and the calculated value of the traditional analysis method. It shows that the proposed method can calculate the shear lag effect of the box girder more accurately. (2) the proposed method is applied to the calculation of the shear lag effect of the box girder. The effects of four geometric parameters, the ratio of width to span, the ratio of cantilever width to roof width, the ratio of bottom to roof width, the ratio of height to width and the ratio of plate to thickness, on the stress difference ratio of box girder wing plate are discussed. The results show that the ratio of width to span, the ratio of cantilever plate width to roof width, The ratio of the width of the bottom plate to the top plate has a great influence on the stress difference ratio between the flange and the web at the interface of the central fulcrum section and the concentrated load section of the box girder. However, the ratio of height to width to the thickness of the plate has a significant effect on the stress difference ratio between the flange and web at the junction of the flange and the web on the central support section and the concentrated load section of the continuous box girder. (3) based on the virtual work principle and the age adjustment effective modulus method, A long-term performance analysis method for RC box girder considering shear lag effect and concrete shrinkage and creep is proposed. The effectiveness and accuracy of the proposed method are verified by comparing with the finite element model of typical simply supported RC box girder and the theoretical calculation results of elementary beam. In addition, the effects of shrinkage and creep on the long-term performance of RC box girder are analyzed in detail. It is pointed out that concrete creep and shrinkage are the main factors affecting the long-term deflection and concrete stress of RC box girder. It also affects the distribution of the supporting reaction force and internal force of RC continuous box girder. (4) based on the prestressing equivalent load method and Timoshenko beam theory, the shear lag analysis method of box girder considering shear deformation is proposed. The shear lag effect caused by axial force can be considered by this method. The accuracy of the proposed method is verified by comparing the calculated value with the experimental value and the finite element value. Through the analysis of simple supported beam and two-span continuous box girder in typical prestressing beam distribution mode, it is shown that shear deformation has great influence on the deflection calculation of box girder under prestressing force. The equivalent axial force of prestressing force will cause significant shear lag effect at the end of steel bundle anchoring. (5) introducing the time variation of concrete material, different finite element (beam, solid element) numerical simulation methods are used. The analytical models of typical cantilever construction PC continuous box girder bridge are established, and the time-varying deformation of PC continuous box girder bridge considering shear lag effect under the action of non-uniform and uniform shrinkage and creep is compared. Concrete stress and steel bundle stress. The results show that ignoring the shear lag effect will seriously underestimate the mid-span deflection of long-span PC box girder bridge, and the effect of non-uniform shrinkage and creep on the mid-long span deflection is small, but on the steel beam stress and concrete stress is greater.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：U441

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