【作者】 张伟；

【导师】 刘健新；

【作者基本信息】 长安大学 ， 桥梁与隧道工程， 2007， 硕士

【摘要】 高墩大跨径连续刚构桥已成为西部地区公路线路穿越崇山峻岭和高原沟壑时首选桥型。由于高墩大跨径连续刚构桥的跨径及各墩高差较大,其结构特性相对一般的低墩桥梁更加复杂,由此导致其地震反应特点与一般桥梁也有所不同,尤其是高墩与低墩的地震反应特性有很大的差异、大震作用下桥梁结构非线性特性、桩—土相互作用、多点激励以及行波效应等问题,导致结构地震反应更加复杂,因此有必要研究高、低墩地震反应和非线性地震反应特点。由于现行的《公路工程抗震设计规范》仅适用于桥墩高度不超过30m的桥梁,而且高墩大跨径桥梁的震害资料严重匮乏,抗震设计经验还不丰富。所以研究高墩大跨径连续刚构桥,即研究其高低墩以及非线性等的地震反应特点,对于此类桥梁结构的合理的抗震设计和未来的抗震鉴定加固都有重要的意义。针对上述问题,本文以一座高墩大跨径连续刚构桥为例,分别建立了墩底固结模型、桩—土相互作用模型以及大质量模型,采用大型通用有限元程序ANSYS进行了线弹性与弹塑性地震反应分析,论文中主要考虑以下几点:1)考虑了竖向地震动的影响;2)利用改进Penzien模型建立桩—土相互作用弹簧、土层间剪切弹簧;3)采用大质量模型进行多点激励与行波效应的分析;4)根据《公路工程抗震设计规范》(JTJ004-89)计算塑性铰长度;5)采用Hognested模型建立混凝土非线性应力—应变关系;6)采用Mander模型建立塑性铰区约束混凝土的应力—应变关系。通过以上各模型间地震反应的对比分析,得出以下主要结论:1)竖向地震动对桥墩的轴力、主梁的顺桥向内力响应有一定影响;2)横桥向地震作用下结构反应相比顺桥向地震作用下复杂;3)顺桥向激励矮墩内力响应大,横桥向激励高墩内力响应大;4)结构顺桥向的可承载力相对薄弱,而顺桥向地震作用下低墩遭受大的内力,故低墩遭受破坏的概率要大于高墩;5)横系梁对桥墩轴力和顺桥向弯矩有影响,在横系梁处值出现突变;6)考虑桩—土相互作用,桥梁结构基频减小;7)考虑桩—土相互作用,高墩墩底截面的各项内力响应都减小,墩顶截面位移响应增大;主梁横桥向响应分量增大,轴力当横桥向激励时减小,顺桥向激励时则增大;8)考虑桩—土相互作用,采用无约束混凝土非线性应力—应变关系,在墩底及墩顶截面表现出了复杂的变化规律,无规律可循;桥墩横桥向位移峰值增大,高墩增幅大于矮墩;9)考虑桩—土相互作用,桥墩塑性铰区采用约束混凝土应力—应变关系,顺桥向激励时,各桥墩墩底及墩顶轴力、顺桥向响应值都有一定程度的增大,墩顶位移增大;横桥向激励时,各桥墩的内力响应分量及位移变化微小;表明,考虑箍筋约束作用后,顺桥向激励时,提高了桥墩的延性,而横桥向激励时,不能提高桥墩的延性;10)多点激励时,顺桥向的各项内力以及位移响应的峰值都有很大程度的增加,主梁的各项内力响应峰值增大很多;11)行波效应对高矮墩的影响不同;12)考虑行波效应,采用混凝土的非线性应力—应变关系,桥墩的轴力及顺桥向内力、位移响应增大,矮墩增大的比率大于高墩;主梁的轴力及顺桥向弯矩增大,在支承处的顺桥向剪力增大;13)考虑行波效应,桥墩塑性铰区采用约束混凝土的非线性应力—应变关系后,桥墩的轴力及顺桥向内力、位移响应增大,矮墩增大的比率大于高墩;主梁的轴力及顺桥向弯矩增大,在支承处的顺桥向剪力增大。更多还原

【Abstract】 High pier and long span continuous rigid frame bridges have became to be the first choice for crossing mountain valley and gully. Influenced by the long span and big height difference of piers, their structure characteristics are more complex than the low pier bridges, and seismic response are also different from the usual bridges. Especially when the big difference of high pier and low pier’s seismic response characteristics, nonlinear characteristics of bridge structures under large earthquake, interaction between pile and soil, multi-support excitations and travelling effect being consideration, the seismic response of the structures become more complex. So, it is necessary to do some research on high pier and low pier’s seismic response characteristics and nonlinear seismic response characteristics. The current Specifications of Earthquake Resistant Design for Highway Engineering is only suitable for the bridges whose piers are lower than 30 meters, further more, the lack of earthquake damage material and the experience of seismic design about long span and high pier bridges, all of them make the research on high pier and low pier’s seismic response characteristics and nonlinear seismic response characteristics being important to reasonable seismic design and seismic evaluation and reinforce.Aiming at these problems, in this paper, take a high pier and long span continuous rigid frame bridge as example. Bottom fixed piers model, interaction between pile and soil model and massive quality model are built separately by general FEA program ANSYS. In order to do analysis on linear elasticity and elastic plastic of seismic response characteristics, following are the points taken into considerasion.1) Taking the influence of vertical component of earthquake into consideration;2) Modified Penzien model was used to build the springs which are used for simulating the interaction between pile and soil and interlaminar shear between earth layers;3) Massive quality model was used to do analysis on multi-support excitations and travelling effect;4) Calculating the length of the plastic hinge according to Specifications of Earthquake Resistant Design for Highway Engineering;5 ) Hognested model was used to establish nonlinear stress strain relation of concrete; 6) Mander model was used to establish nonlinear stress strain relation of concreate in the region of plastic hinge.By contrast the seismic response of different model, this study get to the conclusion thereinafter:1) Vertical component of earthquake have some influence on the axial force in pier and the inner force in main girder along the longitudinal direction;2) The response of structure along the cross direction is more complex than the longitudinal direction;3) Excitations along the longitudinal direction do more influences on low piers, and excitations along the cross direction do more influences on high piers;4) The low piers’ inner force caused by the longitudinal direction earthquake are higher, at the mean time, the longitudinal direction bearing capacity are lower, so, low piers have a higher broken probability than the high piers;5) Diaphragms have some influences on the piers’ axis force and bent moment along longitudinal direction in girder, they both abrupt changed at where the diaphragms existing;6) Base frequency of bridge structure decreases for taking interaction between pile and soil into consideration;7) Taking interaction between pile and soil into consideration, the inner force of the piers’ bottom sections all decrease and at the mean time the displacement of the piers’ top sections increase; the displacement along cross direction of the main girder increase; the axis force decrease under the excitations along the cross direction and increase under the excitations along the longitudinal direction;8) Taking interaction between pile and soil into consideration and establishing stress strain relation of nonresistant concreate in the region of piers’ plastic hinge, no disciplinarian can be established for the stress strain relation complexity of the piers’ bottom sections and top sections; the displacement along cross direction increase,and the increase range of high piers is higher than low piers;9) Taking interaction between pile and soil into consideration and establishing stress strain relation of resistant concreate in the region of piers’ plastic hinge,the axis force in the whole pile, the response along longitudinal direction and the displance of the piers’ top all increase under the excitations along the longitudinal direction;all of the them decrease under the excitations along the cross direction. The response difference demonstrates that taking stirrups confinement into consideration, ductility along longitunal direction increase and ductility along cross direction have any increasement;10) The peak value of inner force and displacement along longitunal direction all increase greatly; the peak value of the main girder’s inner force also increase greatly; 11) Travelling effect has different influence on high piers and low piers;12) Taking travelling effect into consideration and establishing nonlinear stress strain relation of concreate, the low piers’ axis force, inner force along longitunal direction and displacement increase higher than the high piers; the axis force and the bent monment along longitunal direction in the main girder increase too; the shear in the bearing along longitunal direction increase;13) Taking travelling effect into consideration and establishing stress strain relation of resistant concreate in the region of piers’ plastic hinge, the low piers’ axis force, inner force along longitunal direction and displacement increase higher than the high piers; the axis force and the bent monment along longitunal direction in the main girder increase too; the shear in the bearing along longitunal direction increase.更多还原