發(fā)布時(shí)間：2018-05-09 22:05

  本文選題：裂縫 + 剛度折減�。� 參考：《武漢理工大學(xué)》2014年碩士論文

【摘要】：我國橋梁眾多，但是隨著時(shí)間的流逝及現(xiàn)代交通量的不斷上升，這些橋梁呈現(xiàn)出各種病害，使得結(jié)構(gòu)的功能不斷退化。在我國公路橋梁中，以鋼筋混凝土梁橋居多，而病害在該橋型中是最為普遍的。在鋼筋混凝土梁橋長期運(yùn)營的過程中，會出現(xiàn)開裂。隨著裂縫的發(fā)展，會使結(jié)構(gòu)的剛度下降，在同等荷載作用下結(jié)構(gòu)撓度變大，而撓度的增加又會使裂縫發(fā)展的更為迅速，使得結(jié)構(gòu)的使用性能下降，并且很可能導(dǎo)致結(jié)構(gòu)在一定的使用期后將成為危橋而面臨損毀、垮塌的危險(xiǎn)，因此必須對在役的鋼筋混凝土梁橋的承載力進(jìn)行分析。本文的研究工作主要有： (1)本文針對裂縫這一病害，歸納總結(jié)混凝土結(jié)構(gòu)的裂縫種類，分析各種裂縫形成機(jī)理及其特征，，并選取裂縫中的正裂縫進(jìn)行深入分析。通過正裂縫的寬度、高度、開裂范圍，建立裂縫的特征參數(shù)，根據(jù)截面分析方法計(jì)算各開裂段的有效剛度，并求得剛度折減系數(shù)。然后根據(jù)開裂范圍，對不同特征參數(shù)的裂縫分段折減剛度。 (2)在對混凝土空心板的實(shí)體建模中，研究了鋼筋混凝土建模的幾種方法，深入探討混凝土的本構(gòu)關(guān)系模型和破壞準(zhǔn)則及鋼筋的本構(gòu)關(guān)系，研究了鋼筋混凝土模型在開裂時(shí)的模擬方式，介紹了solid65單元和link8單元在模擬鋼筋混凝土結(jié)構(gòu)的方法。對帶裂縫的混凝土空心板進(jìn)行破壞性試驗(yàn)，對試驗(yàn)結(jié)果整理分析求得極限承載力；通過對該混凝土空心板的非線性全過程模擬，對比了折減不同項(xiàng)后承載力，得到有效的剛度折減方法。將有限元計(jì)算得到的撓度和應(yīng)變隨荷載變化的規(guī)律與試驗(yàn)結(jié)果對比，論證本文采用的對初始裂縫模擬方法準(zhǔn)確性和合理性。 (3)選取一預(yù)應(yīng)力空心板，在建模時(shí)研究初始預(yù)應(yīng)力如何施加，選取不同的裂縫寬度建立模型，進(jìn)行非線性全過程分析，對比不同裂縫寬度時(shí)的荷載—撓度曲線和極限承載力，分析得出隨著裂縫寬度的增加，結(jié)構(gòu)的剛度減小，在極限荷載下?lián)隙仍黾�，而裂縫對結(jié)構(gòu)的極限承載力并沒有影響。通過對帶裂縫的預(yù)應(yīng)力空心板梁進(jìn)行承載能力的非線性分析，對比不同裂縫寬度下有限元計(jì)算結(jié)果，定性的分析了裂縫對結(jié)構(gòu)的影響。 通過以上研究的內(nèi)容可知,在模擬初始裂縫對結(jié)構(gòu)的影響時(shí),采用剛度折減的方法是有效可行的，并且所采用的鋼筋和混凝土的本構(gòu)關(guān)系在進(jìn)行極限承載力分析時(shí)是合理的；不同裂縫參數(shù)的有限元計(jì)算結(jié)果表明裂縫會降低結(jié)構(gòu)的剛度，隨著裂縫寬度的增加，極限承載力不變，撓度增加。
[Abstract]:There are many bridges in our country, but with the passage of time and the rising of modern traffic volume, these bridges show various diseases, which make the function of the structure degenerate. The reinforced concrete beam bridge is the most common highway bridge in China, and the disease is the most common in the bridge type. In the long-term operation of reinforced concrete beam bridge, cracking will occur. With the development of cracks, the stiffness of the structure will decrease, the deflection of the structure will become larger under the same load, and the increase of the deflection will make the crack develop more rapidly, and the performance of the structure will decline. And it is very likely that the structure will become a dangerous bridge after a certain period of service and face the danger of damage and collapse. Therefore the bearing capacity of the existing reinforced concrete beam bridge must be analyzed. The main research work of this paper is as follows: In this paper, the types of cracks in concrete structures are summarized, the formation mechanism and characteristics of various cracks are analyzed, and the positive cracks in the cracks are selected for further analysis. According to the width, height and crack range of the normal crack, the characteristic parameters of the crack are established, and the effective stiffness of each crack segment is calculated according to the section analysis method, and the stiffness reduction coefficient is obtained. Then, according to the crack range, the stiffness of cracks with different characteristic parameters is reduced. 2) in the solid modeling of concrete hollow slab, several methods of reinforced concrete modeling are studied, and the constitutive relation model and failure criterion of concrete and the constitutive relation of steel bar are discussed in depth. The simulation method of reinforced concrete model during cracking is studied, and the methods of simulating reinforced concrete structure by solid65 element and link8 element are introduced. The ultimate bearing capacity of concrete hollow slabs with cracks is obtained by finishing and analyzing the test results, and the ultimate bearing capacity is compared by simulating the whole nonlinear process of the concrete hollow slabs with different items. An effective stiffness reduction method is obtained. By comparing the variation of deflection and strain with the experimental results obtained by finite element method, the accuracy and rationality of the initial crack simulation method used in this paper are demonstrated. 3) choose a prestressed hollow slab, study how to apply initial prestress in modeling, choose different crack width to establish model, carry out nonlinear whole process analysis, compare load-deflection curve and ultimate bearing capacity with different crack width. It is concluded that with the increase of crack width, the stiffness of the structure decreases and the deflection increases under the ultimate load, but the crack has no effect on the ultimate bearing capacity of the structure. Through nonlinear analysis of the bearing capacity of prestressed hollow slab beams with cracks, the effect of cracks on the structure is analyzed qualitatively by comparing the finite element results under different crack widths. The results show that the stiffness reduction method is effective and feasible when simulating the effect of initial crack on the structure, and the constitutive relation of steel bar and concrete is reasonable in the analysis of ultimate bearing capacity. The finite element calculation results of different crack parameters show that the crack will reduce the stiffness of the structure. With the increase of the crack width, the ultimate bearing capacity is unchanged and the deflection is increased.
【學(xué)位授予單位】：武漢理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：U441

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