高墩大跨径刚构桥的设计与施工监控研究

【作者】 陈素君；

【导师】 邹银生； 王力力；

【作者基本信息】 湖南大学 ， 结构工程， 2003， 硕士

【摘要】 本文以一座最大跨径160m，最大墩高100m的预应力混凝土连续刚构桥为背景，结合本人负责其设计审查和施工监控项目的实施过程，对桥梁总体设计、结构内力计算、承载能力验算、稳定性验算及施工监控的内容与方法等进行了研究。重点论述了高墩大跨径刚构桥设计应考虑的主要因素、结构分析的基本理论、计算内容、程序、方法等，并编制了相应的计算机程序用于背景工程的设计计算。论文研究的主要内容和结论如下： 高墩大跨刚构桥桥墩的结构形式可选择双肢薄壁墩或空心单柱墩；当墩高大于80m时，选用空心单柱墩更为合适，因为此时双肢薄壁墩的稳定安全系数急剧降低，空心单柱墩的稳定安全系数是双肢薄壁墩的4～5倍，若仍用双肢薄壁墩，必须增加横撑以减小桥墩的自由高度；墩梁合适的刚度比是在稳定、安全的前提下，使桥墩具有较大的抗弯刚度和较小的抗推刚度；箱梁横向计算时，荷载沿顺桥向的有效分布宽度应加以修正，修正后的应力值比按规范计算的高20％～60％。 在技术创新方面，本文提出了预应力真空压浆技术的实验参数和桥墩复合基础的设计方法，通过现场实验和专家会议认可，已用于小关特大桥。真空压浆技术既是通过一定的真空度(＞80％)消除预应力孔道和浆体中的气泡，使压浆饱满、密实，与之配套的塑料波纹管密封性好、强度高、耐腐蚀，且摩擦系数小，能减小预应力的摩阻损失，提高预应力效应约10％；复合基础的设计方法是按基桩与承台共同受力并满足变形协调条件的方法进行桩基承载力计算，综合考虑承台底地基加固、承台内桩顶钢筋的构造处理、上部结构计入不均匀沉降等方法进行设计。小关大桥4#墩处岩石较软，不满足支承桩的承载力要求，采用了复合基础设计方法，经现场检测，其效果很好。 本文进行结构分析的理论基础是有限单元法的基本原理和大跨径桥梁的计算理论。结构分析的基本步骤是：首先划分结构单元和施工阶段，逐阶段建立结构的力学模型、刚度矩阵、荷载列阵和位移列阵，然后根据各单元之间的几何条件和平衡条件，建立单元刚度方程和整体刚度方程，求解任意施工(营运)阶段的内力和位移。在营运阶段，用动态规划法对影响线加载计算汽车荷载的内力，并按最不利荷载组合原则，计算最大荷载效应和最终应力状态。最后按规范公式进行配筋设计、承载力验算和稳定性验算。更多还原

【Abstract】 The background of this paper is a prestressed concrete continuous rigid-frame bridge ,which maximum span of is 160m and maximum pier height of is 100m. In the process of design checking and the construction control 1 ing, the author makes a research of bridge global design, internal force calculation, bearing capacity checking computation, stability checking computation and construction controlling methods etc. . The author focus on main factors that should be taken into account in design, basic theories of structural analysis,calculation content, calculation procgram, calculation methods ,etc.. The relevant program has been worked out and put into practice in the background project. The main results of this Paper are included below:Pier structural configuration in high-pier and long-span rigid-frame bridge could be choiced with double-limb thin-wall pier or hollow single pier; It is more suitable that hollow single pier is adopted when the pier height is beyond 80m, because the stability factor of hollow single pier will be over 3~4 times more safety than the one of double-limb thin-wall pier; If double-limb thin-wall pier is adopted when the pier height is beyond 80m, lateral brace must to be added to decrease the unsupported height of piers; The appropriate stiffness ratio of pier beams is the value that the bridge piers have higher flexural rigidity and the lower compressive stiffness under the premise of satisfying stability and safety; When the box girder is transversely calculated, the effective distributed width of the loading along longitudinal bridge should be modified. The modified stress value is 20-60 percent higher than the one by normative calculation.As far as innovation is concerned, experimental parameters of prestressed vacuum grouting technique and design methods of compound foundation of bridge piers are presented. The results, which have beenverified in field experiment and have achieved admission of experts, areutilized in Xiaoguan Bridge. By eliminating air bubbles in the prestressed passage and paste at certain degree of vacuum (>80%), the vacuum grouting technique can make grouting satiable and compact.So it can make equipped corrugated-plastic-tubes airtight, corrosion-resistant , high strength and small frictional coefficient, reducing the frictional loss of prestress and increasing prestress effect about 10 percent. Bearing capacity of pile foundation is calculated by compound foundation design method, given that foundation pile and base slab bear force collectively and that compatibility of deformation condition is satisfied. Compound foundation is devised by means of strengthening groundsill at the bottom of base slab , tectonic treatment of reinforcing pile butt in the base slab, and accounting for non-uniform settlement of the upper configuration. The rock under the No. 4 pier in Xiaoguan Bridge is a little soft and is dissatisfied with bearing capacity of bracing pile. Good results have been obtained by adopting the method of compound foundation design.Structural analysis of this paper is based on the finite element method (FEM) and calculation theory of long span bridge. At first, structure units and construction phases are divided into. Mechanical model, stiffness matrix, load matrix and displacement matrix of the structure are built stage by stage. Then, unit stiffness equations and integrated stiffness equations are established respectively according to geometric conditions and equilibrium conditions among the units. Internal force and displacement in any construction (service) phase are resolved. By means of influence line loading of dynamic planning, the internal force of the service phase produced by automobile load are computed, maximum load effect and final stress state of the service phase are calculated under the worst loading combination. In the end, reinforcement design, bearing capacity checking computation and stability checking computation are carried out according to the normative formulas.更多还原