【作者】 刘振宇；

【导师】 李乔；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2008， 博士

【摘要】 桥梁在朝着更大跨度发展的同时,出现越来越多的深水桥梁。目前为止,已建或在建的深水桥梁其桥墩入水深度最深已达168米。深水桥梁在地震作用下,桥墩自身的运动会引起周围水体的辐射波浪运动,而波浪运动也反过来影响桥墩的运动,这样桥梁结构的水下部分便产生了动水压力,而使桥梁的结构动力特性发生改变并影响结构的动力响应水平。从当前深水桥梁抗震研究的文献来看,国内外对深水桥梁的计算理论及地震响应特性的研究仍较少。本文在查阅大量国内外文献的基础上,评述了当前关于水与结构相互作用的计算理论、水中结构地震响应的分析方法及相关的研究成果,并针对深水桥梁在地震作用下的响应特性开展了以下几个方面详细研究:1.采用辐射波浪理论推导了圆形空心墩内域水体附加动水压力的计算解析式;采用相同理论,同时利用矩形截面的主轴与桥的纵轴和横轴相重合的特点,推导了矩形空心墩内、外水域的附加动水压力的计算解析式;采用流固耦合有限元分析的位移—压力格式(u—p)进行了有限元分析,对本文推导的附加动水压力的求解公式的计算精度进行了验证。结果表明,本文的解析式具有较高的精确度。2.将动水附加压力表达为动水附加质量和动水附加阻尼,在此基础上建立了深水桥梁在地震激励下的运动方程,并对其求解方法进行了研究。3.对圆形空心墩和矩形空心墩的动水附加质量沿墩高的分布规律进行了分析,研究了自由表面波、总淹没水深、桥墩几何尺度等因素对动水附加质量的影响:提出了临界水深的概念,并指出临界水深以上部分的动水附加质量成抛物线分布,临界水深以下的部分动水附加质量的分布与水深无关(大小保持不变);对于高频振动的结构自由表面波的影响可忽略;相同水深时几何尺度越大动水附加质量越大,桥墩形状是影响动水附加质量的重要因素;4.将上述研究成果与实际工程相结合,对大跨度深水连续刚构桥进行了地震响应时程分析,分析了深水连续刚构桥在纵向、横向地震作用下响应的特点。研究表明,墩—水耦合振动使主梁和桥墩的内力响应、位移响应大幅增加,是深水连续刚构桥地震响应分析中必须考虑的因素。对内、外墩水域附加质量和总淹没水深对桥墩地震响应的影响进行了分析,结果表明,内、外域水的影响必须同时计入,总淹没水深越深,墩—水耦合振动的不利影响越大;将本文方法的计算结果与欧洲规范、日本规范的计算结果进行了对比,指出欧洲规范对于总淹没水深较浅的桥梁其计算结果过于保守,而日本规范对于总淹没水深较深的桥梁,其计算结果偏于不安全。更多还原

【Abstract】 Nowdays more and more deep-water bridges are built with the devolpment of larg span bridges to cross water areas, and the deepest underwater foundation of deep-water bridges constructed had reached 168m. Under the effect of the earthquake, hydrodynamic pressure of structures will be occurred because of the relative movement between a structure and water induced by radiation wave movement of fluid around the structure. The dynamic characteristics and the dynamic responses of the structures will be changed due to the effects of the hydrodynamic pressure. However, the effects of hydrodynamic pressure induced by the earthquake on the deep water structures, such as underwater foundation of large span bridges have received relatively little attention in exiting literaturea.In this dissertation, the dynamic responses of deep-water bridges under the earthquake are studied based on extensive analysis. The main achievements of this dissertation are as follows:1. Based on the radiation wave theory, an analytical solution of additional hydrodynamic pressure of inner liquid of circular hollow piers is deduced, and by using the characteristic the main axis of a retangle section is coincided with the longitudinal axis and lateral axis of the bridge, and an analytical solution of addditional hydronamic pressure induced by inner and outer waters of the retangle hollow piers is also given. Using displacement-pressure model (u-p) of fluid-solid coupling, the finit element analysis (FEA) is carried out, and comparing with the analytical solution, the accuracy of the semi-analytic approach of additioanl hydrodynamic mass in this dissertation is verified.2. In this dissertation, the hydrodynamic additional pressure is expressed as the hydrodynamic additional mass and the hydrodynamic additional damping. Moreover, a motion equation of deep-water bridges induced by earthquake is presented and its solution method is extensivly investigated. 3. The distribution characteristics of hydrodynamics additional mass along the depth of circle hollow piers and retangle hollow piers are analyzed .The effect of free surface wave, whole depth of submerged water and geometry dimensions on hydrodynamic additional mass are studied and also summarized: a critical depth is found.The hydrodynamic additional mass distributes is a parabola when above the critical depth and the distribution of hydrodynamic additional mass is not effected by the water depth when below the depth. The effect caused by vibration of free-surface wave of structure at a high frequency can be ignored. The hydrodynamic additional mass will increase as the geometry dimensions increase if at the same depth. The shape of piers is the main factor which affects hydrodynamic additional mass.4. According to the preceding thoeries, a time-history analysis of the earthquake responses of long-span continuous rigid frame bridges is carried out and the characteristics of responses of continuous steel frame bridges in deep water under the effect of the longitudinal and lateral earthquake excitation are analyzed. It is indicated that the pier-water coupling vibration increases inner force responses and displacement responses of the main beam and piers, which should be considered in an analysis of earthquake response of continuous steel frame bridges in deep water. The effect of additional mass arising from waters inner and outer piers and whole depth of submerged water on the earthquake responses of piers is invesitigated, and the result shows that the effect of inner water and outer water should be considered. The disadvantages of pier-water coupling vibration increase as the whole depth increases of submerged water. Comparing the results with those calculated according to the Japanese and European criterion, it is found that the results calculated by the European criterion is much too conservative, such as the bridge whose whole depth of submerged water are relative fleet, and it is insecure while the results calculated by Japanese codes such as the bridges whose whole depth of submerged water are relative deep.更多还原