混凝土橋梁加寬改造的結(jié)構(gòu)可靠度分析
發(fā)布時間：2018-08-27 07:17
【摘要】：目前關于加寬改造后橋梁的可靠性分析很少,有必要對加寬改造后橋梁的可靠性進行深入的研究,本文結(jié)合國家自然科學基金“既有混凝土橋梁拓寬改造設計的基礎理論研究(51278182)”,依托實際工程項目,基于可靠性理論對一座四跨連續(xù)預應力T梁橋的加寬改造進行了研究,主要內(nèi)容如下:(1)采用《公路鋼筋混凝土及預應力混凝土橋涵設計規(guī)范》的收縮徐變模型進行分析,計算收縮徐變差和基礎沉降差在結(jié)構(gòu)內(nèi)產(chǎn)生的附加內(nèi)力。結(jié)果表明:收縮徐變差在舊橋外邊梁和新橋主梁梁內(nèi)產(chǎn)生軸拉力而舊橋中梁及內(nèi)邊梁則產(chǎn)生軸壓力,且越靠近拼接縫的主梁軸力值越大;收縮徐變差在橋墩內(nèi)產(chǎn)生的軸力較小,橫向彎矩較大;基礎沉降差在主梁內(nèi)產(chǎn)生的附加內(nèi)力較小,在主梁連接面處產(chǎn)生的剪力較大,且在橫隔板附近剪力變化較劇烈,在不同橋墩內(nèi)產(chǎn)生的軸力差別很大,內(nèi)邊梁側(cè)的橋墩是外邊梁側(cè)的3.37~4.38倍,墩內(nèi)產(chǎn)生的橫向彎矩最大值為310k N·m;(2)根據(jù)等超越概率原則確定加寬改造基準期和設計荷載的取值,并求得不同設計使用年限的汽車荷載折減系數(shù),考慮混凝土經(jīng)時強度變化、鋼筋銹蝕建立結(jié)構(gòu)抗力時變模型;(3)根據(jù)加寬改造后結(jié)構(gòu)受到的附加內(nèi)力計算主梁的抗彎承載力和橋墩的抗壓承載力。結(jié)果表明:在收縮徐變差及基礎沉降差的影響下,6#梁的抗彎承載力提高了13.6%,7#梁的抗彎承載力下降了7.19%;1#-2墩的抗壓承載力降低了18.79%,1#-3墩的抗壓承載力降低了36.27%;(4)基于JC法和串聯(lián)體系可靠指標計算方法對加寬橋梁進行時變可靠性分析,結(jié)果表明:加寬改造后到舊橋運營至100年時,考慮收縮徐變差和基礎沉降差的影響后,上部結(jié)構(gòu)的可靠指標提高了15.66%,下部結(jié)構(gòu)則下降了29.8%,組合結(jié)構(gòu)整體可靠指標則下降了2.20%;不加寬時,舊橋運營至30年后,可靠指標開始小于4.2,加寬后,舊橋運營至85年時可靠指標才開始小于4.2。
[Abstract]:At present, there is little analysis on the reliability of the bridge after widening and reconstruction, so it is necessary to carry out in-depth research on the reliability of the bridge after widening and reforming. Based on the National Natural Science Foundation of China "basic theoretical study on widening and rebuilding of existing concrete Bridges (51278182)", based on the reliability theory, the widening and rebuilding of a four-span continuous prestressed T-beam bridge is studied based on the actual engineering project. The main contents are as follows: (1) the shrinkage and creep model of highway reinforced concrete and prestressed concrete bridge and culvert design code is used to calculate the additional internal forces caused by shrinkage creep and foundation settlement difference in the structure. The results show that the axial tension is produced by the shrinkage and creep variation in the outer girder of the old bridge and the main beam of the new bridge, while the axial pressure is produced in the middle beam and the inner side beam of the old bridge, and the greater the axial force value of the main beam near the jointing joint, the smaller the axial force produced by the shrinkage and creep variation in the pier. The lateral bending moment is larger, the additional internal force produced by the foundation settlement difference in the main beam is smaller, the shear force generated at the junction surface of the main beam is larger, and the shear force changes sharply near the transverse partition, and the axial force produced in different piers is very different. The piers on the inner side of the beam are 3.37 ~ 4.38 times of the outside side, and the maximum transverse moment generated in the pier is 310k N m; (_ 2). According to the principle of equal transcendental probability, the reference period of widening and rebuilding and the value of the design load are determined. The vehicle load reduction coefficient with different design life is obtained, and the time-varying strength of concrete is taken into account. (3) the flexural bearing capacity of the main beam and the compressive capacity of the pier are calculated according to the additional internal force of the structure after widening and reforming. The results show that under the influence of shrinkage and creep variation and foundation settlement difference, the flexural bearing capacity of the beam is increased, and the flexural capacity of the beam decreases by 7.19% and 7.19% and the compressive capacity of the #-2 pier decreases by 36.27%; (4) based on the JC method, the compressive capacity of the #-2 pier decreases by 36.27; (4) based on the JC method, the flexural capacity of the #-2 pier decreases by 7.19% and that of the #-3 pier by 7.19%. And the calculation method of reliability index of series system is used to analyze the time-varying reliability of the widened bridge. The results show that the effects of shrinkage, creep and foundation settlement are taken into account when the old bridge is operated to 100 years after widening and reconstruction. The reliability index of the superstructure has increased by 15.66, the substructure has decreased by 29.8and the overall reliability index of the composite structure has decreased by 2.20.When the old bridge is not widened, the reliability index of the old bridge starts to be less than 4.2 after 30 years of operation, and the reliability index is widened. It was not until 85 years that the old bridge began to have a reliable index of less than 4. 2.
【學位授予單位】：湖南大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：U445.6
本文編號：2206523
[Abstract]:At present, there is little analysis on the reliability of the bridge after widening and reconstruction, so it is necessary to carry out in-depth research on the reliability of the bridge after widening and reforming. Based on the National Natural Science Foundation of China "basic theoretical study on widening and rebuilding of existing concrete Bridges (51278182)", based on the reliability theory, the widening and rebuilding of a four-span continuous prestressed T-beam bridge is studied based on the actual engineering project. The main contents are as follows: (1) the shrinkage and creep model of highway reinforced concrete and prestressed concrete bridge and culvert design code is used to calculate the additional internal forces caused by shrinkage creep and foundation settlement difference in the structure. The results show that the axial tension is produced by the shrinkage and creep variation in the outer girder of the old bridge and the main beam of the new bridge, while the axial pressure is produced in the middle beam and the inner side beam of the old bridge, and the greater the axial force value of the main beam near the jointing joint, the smaller the axial force produced by the shrinkage and creep variation in the pier. The lateral bending moment is larger, the additional internal force produced by the foundation settlement difference in the main beam is smaller, the shear force generated at the junction surface of the main beam is larger, and the shear force changes sharply near the transverse partition, and the axial force produced in different piers is very different. The piers on the inner side of the beam are 3.37 ~ 4.38 times of the outside side, and the maximum transverse moment generated in the pier is 310k N m; (_ 2). According to the principle of equal transcendental probability, the reference period of widening and rebuilding and the value of the design load are determined. The vehicle load reduction coefficient with different design life is obtained, and the time-varying strength of concrete is taken into account. (3) the flexural bearing capacity of the main beam and the compressive capacity of the pier are calculated according to the additional internal force of the structure after widening and reforming. The results show that under the influence of shrinkage and creep variation and foundation settlement difference, the flexural bearing capacity of the beam is increased, and the flexural capacity of the beam decreases by 7.19% and 7.19% and the compressive capacity of the #-2 pier decreases by 36.27%; (4) based on the JC method, the compressive capacity of the #-2 pier decreases by 36.27; (4) based on the JC method, the flexural capacity of the #-2 pier decreases by 7.19% and that of the #-3 pier by 7.19%. And the calculation method of reliability index of series system is used to analyze the time-varying reliability of the widened bridge. The results show that the effects of shrinkage, creep and foundation settlement are taken into account when the old bridge is operated to 100 years after widening and reconstruction. The reliability index of the superstructure has increased by 15.66, the substructure has decreased by 29.8and the overall reliability index of the composite structure has decreased by 2.20.When the old bridge is not widened, the reliability index of the old bridge starts to be less than 4.2 after 30 years of operation, and the reliability index is widened. It was not until 85 years that the old bridge began to have a reliable index of less than 4. 2.
【學位授予單位】：湖南大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：U445.6
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