外置耗能式自定心混凝土桥墩抗震性能研究

发布时间：2019-02-19 13:52

【摘要】：作为桥梁的下部结构,钢筋混凝土桥墩起着支承上部结构、传递荷载的作用。基于现行延性设计方法得到的桥墩在地震中通过自身的塑性变形来耗散能量,因此震后往往存在较大残余变形而影响桥梁的正常使用,并给修复带来困难。鉴于此,本文提出了一种“含外置耗能装置的自定心混凝土桥墩”,桥墩在震后的残余变形可以消除或大大减少,而损伤集中在易于更换的附加耗能件上,同时耐腐蚀材料的应用提高了桥墩在氯离子环境下的耐久性。围绕这一新型桥墩,本文先后展开了其构造形式、力学行为的理论分析、低周反复加载试验、数值模拟研究以及地震作用下的易损性分析,完成的主要工作如下：(1)自定心混凝土桥墩的构造形式研究。其中,钢筋混凝土桥墩和承台由工厂预制,在现场通过后张法无粘接预应力筋进行拼接。桥墩下部设有牛腿以固定耗能件,并可方便地进行耗能件的拆卸和替换。当桥墩所受倾覆弯矩超过墩柱-基础接触面的临界张开弯矩时,接触面张开,在桥墩发生刚体转动时耗能件出现塑性变形耗能；震后,墩柱-基础接触面在预应力的作用下重新闭合。为避免桥墩转动时混凝土的局部受压破坏,桥墩底部预先埋置在套筒内。套筒、预应力筋和耗能件分别采用玻璃纤维管、玄武岩纤维棒和改性铝棒提高其耐腐蚀性。(2)自定心混凝土桥墩力学行为的理论分析研究。针对桥墩的顶点侧向力-侧向位移关系,进行了理论分析,分别基于精细模型和简化模型,推导了结构在各受力阶段的变形、位移、抗侧刚度以及等效粘滞阻尼系数的计算公式。理论分析和实验结果吻合较好,为自定心桥墩后续的设计提供了参考。(3)自定心混凝土桥墩的低周反复加载试验研究。设计了15组试验,对自定心混凝土桥墩在循环荷载下的抗震性能进行了研究。考察了预应力大小、耗能件构造、预应力筋材料、有无GFRP套筒等因素对结构抗侧刚度、耗能能力和构件损伤的影响。试验结果表明,本文提出的自定心桥墩具有震后自复位、主体结构基本无损等优点。(4)自定心混凝土桥墩的数值模拟。在理论分析和试验研究的基础上,利用开源有限元软件OpenSees对自定心混凝土桥墩的数值模拟方法进行了研究,涉及墩柱-基础接触面的张开与闭合、预应力筋提供的自定心及铝棒耗能等。数值模拟结果与实验数据吻合良好,表明了该数值模拟方法的有效性。(5)自定心混凝土桥墩的易损性分析。建立了一个钢筋混凝土桥墩和自定心混凝土桥墩的有限元模型,进行增量动力分析并考察结构的弹塑性响应和地震动强度之间的关系。由易损性曲线可知,以最大位移角作为抗震性能指标时,所设计的自定心桥墩的超越概率接近但稍高于钢筋混凝土桥墩;而以残余位移角为性能指标时,自定心桥墩的超越概率显著小于钢筋混凝土桥墩。
[Abstract]:As the substructure of the bridge, the reinforced concrete pier acts as the supporting superstructure to transfer the load. Based on the existing ductility design method, the piers dissipate energy through their own plastic deformation in earthquake, so there is often a large residual deformation after the earthquake, which affects the normal use of the bridge, and brings difficulties to repair. In view of this, a kind of self-centered concrete pier with external energy dissipation device is proposed in this paper. The residual deformation of the pier after the earthquake can be eliminated or greatly reduced, while the damage is concentrated on the additional energy dissipation parts which are easy to replace. At the same time, the application of anticorrosive material improves the durability of bridge piers in chloride environment. Around this new pier, this paper has carried out the structural form, the theoretical analysis of mechanical behavior, the low cycle repeated loading test, the numerical simulation study and the vulnerability analysis under earthquake action. The main works are as follows: (1) study on the structure of self-centered concrete pier. Among them, reinforced concrete piers and caps are prefabricated by the factory. The lower part of the pier is provided with a corbel to fix the energy consuming parts, and the disassembly and replacement of the energy consuming parts can be carried out conveniently. When the overturning moment of the pier exceeds the critical opening moment of the pier-foundation interface, the contact surface is open, and the energy dissipation part appears plastic deformation when the rigid body rotates on the pier. After the earthquake, the contact surface between pier and foundation was reclosed under the action of prestress. In order to avoid the local compressive failure of concrete when the pier rotates, the bottom of the pier is embedded in the sleeve. The sleeve, prestressed tendons and energy dissipation parts are respectively used glass fiber tube, basalt fiber rod and modified aluminum bar to improve their corrosion resistance. (2) theoretical analysis and study on mechanical behavior of self-centered concrete pier. According to the relationship between lateral force and lateral displacement of piers, the deformation and displacement of the structure in each stress stage are deduced based on fine model and simplified model, respectively. The formula of lateral stiffness and equivalent viscous damping coefficient. The theoretical analysis is in good agreement with the experimental results, which provides a reference for the subsequent design of self-centered concrete piers. (3) low cycle repeated loading test of self-centered concrete piers. Fifteen groups of tests were designed to study the seismic behavior of self-centered concrete pier under cyclic load. The effects of prestress size, energy dissipation structure, prestressed tendons and GFRP sleeve on the lateral stiffness, energy dissipation capacity and damage of the structure are investigated. The experimental results show that the self-centered pier presented in this paper has the advantages of self-reposition after earthquake and non-damage of the main structure. (4) numerical simulation of self-centered concrete pier. On the basis of theoretical analysis and experimental study, the numerical simulation method of self-centered concrete pier is studied by using open source finite element software OpenSees, which involves the opening and closing of pier-foundation interface. Self-centring provided by prestressed tendons and energy dissipation of aluminum bars and so on. The numerical simulation results are in good agreement with the experimental data, which shows the effectiveness of the numerical simulation method. (5) vulnerability analysis of self-centered concrete pier. A finite element model of reinforced concrete pier and self-centered concrete pier is established. The incremental dynamic analysis is carried out and the relationship between elastic-plastic response and ground motion strength of the structure is investigated. According to the vulnerability curve, when the maximum displacement angle is taken as the seismic performance index, the transcendental probability of the self-centered pier is close to, but slightly higher than that of the reinforced concrete pier. When the residual displacement angle is taken as the performance index, the surpassing probability of self-centered pier is significantly smaller than that of reinforced concrete pier.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U442.55

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