本文選題：雙室箱梁　切入點(diǎn)：剪力滯效應(yīng)　出處：《長安大學(xué)》2015年碩士論文

【摘要】：隨著我國鐵路、公路等基礎(chǔ)交通設(shè)施建設(shè)的迅猛發(fā)展,橋梁工程逐步向大跨度、寬體薄壁方向改進(jìn),研究人員經(jīng)過行業(yè)實(shí)踐經(jīng)驗(yàn)及理論論證,發(fā)現(xiàn)箱形截面梁與其他截面梁相比具有較為優(yōu)異的受力特性,倍受橋梁設(shè)計(jì)師的青睞。但是大跨度、寬體薄壁箱梁仍然存在理論計(jì)算盲點(diǎn)及誤區(qū),在承受豎向荷載時,由于其翼緣板剪切變形在橫向的不均勻分布所引起的剪力滯效應(yīng)問題,平截面假設(shè)已不在成立,運(yùn)用初等梁理論計(jì)算縱向正應(yīng)力已無法表征箱形梁的實(shí)際受力狀況。大量的理論論證和現(xiàn)場試驗(yàn)調(diào)查發(fā)現(xiàn),很多箱形梁出現(xiàn)裂縫的原因就是設(shè)計(jì)中未考慮剪力滯效應(yīng),造成設(shè)計(jì)應(yīng)力與實(shí)際應(yīng)力狀態(tài)不相符,為箱形截面梁的安全耐久運(yùn)營造成隱患。箱形梁剪力滯效應(yīng)問題已經(jīng)引起廣大研究人員的重視。通過能量變分法的最小勢能原理,推導(dǎo)帶翼緣板雙室矩形截面梁在簡支、懸臂體系下分別作用集中荷載和均布荷載的應(yīng)力應(yīng)變計(jì)算式。引入附加彎矩概念,考慮軸力自平衡條件,推導(dǎo)豎向撓度計(jì)算式。剪力滯效應(yīng)影響下的雙室矩形箱梁豎向撓度有兩部分組成,即初等梁彎曲撓度和剪力滯效應(yīng)附加撓度的疊加。運(yùn)用有限元分析軟件Midas/FEA板單元結(jié)構(gòu)建立數(shù)學(xué)模型,將計(jì)算結(jié)果與理論分析計(jì)算結(jié)果加以對比,相互驗(yàn)證,并將計(jì)算結(jié)果與初等梁彎曲理論做對比。不同的結(jié)構(gòu)形式、加載方式對箱形梁剪力滯效應(yīng)的影響是不同的,分別選取簡支結(jié)構(gòu)、懸臂結(jié)構(gòu)的雙室箱形梁,分別作用集中荷載和均布荷載,且每種荷載考慮三種荷載工況,用有限元分析軟件建立數(shù)學(xué)計(jì)算模型,得出最不利截面的縱向正應(yīng)力值,與初等梁彎曲理論計(jì)算的縱向正應(yīng)力值相除,所得的結(jié)果就是箱梁剪力滯系數(shù)。對剪力滯系數(shù)進(jìn)行論證分析總結(jié),得出不同加載方式對箱形梁剪力滯效應(yīng)的影響作用,以及縱向正應(yīng)力的橫向分布規(guī)律,以此找出箱形梁危險截面的最不利點(diǎn)和最不利的荷載工況,作為結(jié)構(gòu)設(shè)計(jì)的控制點(diǎn)。選取跨度為40m的鋼筋混凝土帶懸臂板雙室矩形等截面箱梁為計(jì)算算例,采用通用有限元分析程序MIDAS/FEA建立箱形梁橋梁單元數(shù)學(xué)模型,分析其在不同荷載作用下簡支、懸臂梁的正應(yīng)力的橫向分布和撓曲變形規(guī)律。
[Abstract]:With the rapid development of railway, highway and other basic transportation facilities in our country, the bridge engineering is gradually improved in the direction of large span and thin-walled body. It is found that box section beam has more excellent mechanical characteristics than other section beams, and is favored by bridge designers. However, there are still theoretical blind points and misunderstandings in theory calculation for large-span, wide-body thin-walled box girder, which are subjected to vertical load. Due to the shear lag effect caused by the transverse inhomogeneous distribution of the flange plate shear deformation, the plane section hypothesis is no longer valid. Using the elementary beam theory to calculate the longitudinal normal stress can no longer represent the actual stress state of the box beam. A large number of theoretical arguments and field tests have found that the reason for the cracks in many box beams is that the shear lag effect is not taken into account in the design. As a result, the design stress does not accord with the actual stress state, which causes hidden trouble for the safe and durable operation of the box section beam. The shear lag effect of the box beam has attracted the attention of the majority of researchers. Through the principle of minimum potential energy of the energy variational method, The formulas for calculating stress and strain of double-chamber rectangular section beams with flange plates acting on concentrated load and uniform load respectively under simply supported and cantilever systems are derived. The concept of additional bending moment is introduced and the self-equilibrium condition of axial force is considered. A formula for calculating vertical deflection is derived. The vertical deflection of a double-chamber rectangular box girder under the influence of shear lag is composed of two parts. That is, the superposition of the bending deflection of elementary beam and the additional deflection of shear lag effect. The mathematical model of Midas/FEA plate element structure is established by using the finite element analysis software, and the calculated results are compared with the calculated results of theoretical analysis, and the results are verified by each other. The results are compared with the bending theory of elementary beam. The effects of different structural forms and loading modes on the shear lag effect of box beam are different. The concentrated load and uniform load are acted on respectively, and each load takes into account three load conditions. The mathematical calculation model is established by using finite element analysis software, and the longitudinal normal stress of the most unfavorable section is obtained. Divided from the longitudinal normal stress value calculated by the elementary beam bending theory, the result obtained is the box girder shear lag coefficient. The effect of different loading modes on the box girder shear lag effect is obtained by the demonstration, analysis and summary of the shear lag coefficient. And the transverse distribution of longitudinal normal stress, so as to find out the most disadvantageous point and the most unfavorable load condition of the dangerous section of box beam. As the control point of structural design, the box girder with double room and rectangular section with cantilever slab with span of 40 m is selected as an example, and the mathematical model of bridge element of box beam is established by using the general finite element analysis program MIDAS/FEA. The normal stress distribution and flexural deformation of simply supported cantilever beam under different loads are analyzed.
【學(xué)位授予單位】：長安大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：U441

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