【作者】 唐亚东；

【导师】 卢文良；

【作者基本信息】 北京交通大学 ， 土木工程（专业学位）， 2023， 硕士

【摘要】 旧桥的改造再利用在桥梁工程中越来越多。新旧线路距离较近时,将旧线路上梁体移至新建线路是我国既有铁路桥梁改造中的常见施工方法。移梁施工中经常对基础补桩,对桥墩进行帮宽。补桩会引起新老桩基与土体相互作用,桥墩帮宽存在新老混凝土交界面需要关注,顶推及横移梁体时,桥墩与梁体的受力情况也需要进行研究。本文依托国内某高铁线路移梁项目,通过试验与数值模拟的方法对各施工阶段桥梁结构不利受力状态进行分析研究。具体研究工作及结论如下:(1)使用有限元分析软件对梁体进行了不均匀顶升和不均匀横移的模拟,并通过最不利荷载组合来分析梁体的薄弱位置,以验证梁体的安全性。结果表明,箱梁底板受压,最大压应力出现在跨中,最大值为7.46MPa;梁体横移与正常使用时受力状态差别不大;(2)对桥墩帮宽前后的受力性能进行了数值模拟研究,以验证移梁过程中桥墩的安全性,证明桥墩帮宽与移梁方法的合理性。结果表明,墩身竖向拉应力最大为0.464MPa,交界面法向正应力与切向剪应力最大值分别为0.2MPa和0.178MPa,受力状态良好;(3)设计了新老混凝土Z型剪切试件,考虑到界面凿毛、植筋长度、植筋数量等因素,分析了新老混凝土交界面受力性能。试验结果表明,试件破坏形式均为脆性破坏。整浇试件抗剪强度最大,为7.22MPa,界面凿毛强度提高15.31%～23.29%,界面植筋强度提高43.60%～114.01%,但植筋深度过大并不能提高抗剪强度;(4)通过数值模拟分析了补桩前后基础的承载能力,将理论计算和有限元结果进行了对比,二者吻合较好。结果表明,补桩后群桩承载力大于补桩前,比原有承载力提高15%～25%,说明增加桩数桩基承载力有明显的提升效果。补桩后单桩承载力有所下降,为补桩前的88.93%～96.64%。(5)分析了新老承台交界面的受力状态,最大拉应力不超过0.6MPa,最大竖向剪应力不超过0.34MPa,受力状态良好,验证了其安全性。更多还原

【Abstract】 The reuse of old bridges for renovation is becoming more and more common in bridge engineering.When the old and new lines are close together,moving the girders on the old lines to the new lines is a common construction method in the renovation of existing railroad bridges in China.The number of piles is often added to the foundation and the piers are widened during the construction of the moved girders.Increasing the number of piles will cause the interaction between the old and new piles and soil,and the existence of new and old concrete intersection interface for pier widening needs attention,and the force situation of piers and girders needs to be studied when jacking and moving girders across.In this paper,based on a domestic high speed railway line girder shifting project,the unfavorable stress state of the bridge structure in each construction stage is analyzed and studied by means of experiments and numerical simulations.The specific research work and conclusions are as follows:(1)Simulations of uneven jacking and uneven traverse of the beam were carried out using finite element analysis software,and the weak locations of the beam were analyzed by the most unfavorable load combination to verify the safety of the beam.The results show that the maximum compressive stress is 28.66 MPa at the jacking pivot point position,and the bottom plate of the box girder is compressed;the beam traverse is not much different from the force state in normal use;(2)Numerical simulations were conducted to study the stress performance of the bridge pier before and after widening,in order to verify the safety of the pier in the process of beam removal and to prove the rationality of the pier widening and beam removal methods.The results show that the maximum vertical tensile stress of the pier is 0.464 MPa,and the maximum normal stress and tangential shear stress at the intersection are 0.2MPa and 0.178 MPa respectively,with good stress state;(3)Z-shear specimens of old and new concrete were designed,and the force performance of the intersection of old and new concrete was analyzed considering factors such as interface haircut,length of reinforcement and number of reinforcement.The test results show that the damage of the specimens is brittle damage.The shear strength of the whole cast specimens is the largest,7.22 MPa,and the strength of interface gouging is increased by 15.31%～23.29%,and the strength of interface reinforcement is increased by 43.60%～114.01%,but the depth of reinforcement planting is too large to improve the shear strength;(4)The bearing capacity of the foundation before and after increasing the number of piles was analyzed by numerical simulation,and the theoretical calculation and finite element results were compared,and the two were in good agreement.The results show that the group pile bearing capacity after increasing the number of piles is greater than that before pile replenishment,and it is 15%～25% higher than the original bearing capacity,which indicates that the bearing capacity of pile foundation with increasing the number of piles has an obvious effect of improvement.The bearing capacity of single pile after pile patching has decreased,which is 88.93%～96.64% of that before pile patching.(5)The stress state at the intersection of new and old bearing platform was analyzed,the maximum tensile stress did not exceed 0.6MPa,the maximum vertical shear stress did not exceed 0.34 MPa,and the stress state was good,which verified its safety.更多还原