考虑SSI的减隔震简支桥梁（渡槽）建模及地震动力响应研究

发布时间：2018-04-10 07:30

本文选题：土-结构相互作用　切入点：减震　出处：《中国地质大学》2014年博士论文

【摘要】：对于建筑抗震体系,在理论分析和设计中通常忽略土-结构相互作用(SSI)。即采用刚性基础的假定,认为地震时基础的运动与邻近的自由场一致。也就是说,上部结构的惯性力传给地基,使之产生的变形,比地震波引起的地基变形应当小很多。否则假定不合理,基础会产生相对于地基的变形,从而导致上部结构的实际运动与按照刚性基础的假定得到的响应有较大的差别。因此,对柔性基础上的建筑物,在计算地震响应时有必要考虑土-结构的相互作用目前,隔震技术已经基本成熟,土-结构相互作用(SSI)研究正在深入,而二者的耦合研究则刚刚起步,研究文献不多,得出的结论有时还互相矛盾,因此关于隔震技术与SSI的耦合有待进一步研究。现今,关于考虑SSI影响的隔震研究还限于简单模型,结构简化为单质点或多质点剪切结构,地基假定为弹性半空间。研究主要集中在刚性浅基础对隔震的影响,对柔性基础对隔震的影响研究较少,但实际桥梁和渡槽很多采用具有一定柔性的桩基。本课题对柔性地基中简支桥梁(或渡槽)的减隔震进行研究,能够更真实地揭示土-结构相互作用对该类桥梁减隔震系统的影响。课题针对某试验隔震渡槽(即过水的桥梁)结构和常见的三跨桩基隔震桥梁结构,研究SSI对其减隔震效果的影响。研究内容如下：第一章绪论,综述了考虑土-结构动力相互作用问题的隔震结构研究与发展以及桥梁脆弱性曲线的研究与发展。第二章,论文对某简支渡槽进行了比较精细的有限元分析,桩采用梁单元建模,土和桩的相互作用采用弹簧单元,槽墩、槽身及槽中的水体,采用实体建模。这样可以得到工程上比较关注的上部结构不同部位的具体响应。通过该模型分析了实际的隔震支座对系统响应的的影响。第三章,对前面的模型桩基部分,采用了不同的建模方式,并进行了动力分析比较。即桩土之间的相互作用分别采用Mindlin方法和规范推荐的m法两种方法进行分析比较。改进的Penzien模型采用一组带阻尼的弹簧单元来模拟自由场土层在不同深度对桩的刚度效应和阻尼效应,弹簧的一端与桩连接,另一端和一足够大的质量单元连接,以模拟自由场地土对结构的质量效应；桩周土质量间增加了土的剪切弹簧和阻尼器；自由场地质量间也增加了土的剪切弹簧和阻尼器。第四章,采用Mindlin方法对某渡槽拟动力试验的结果进行了分析,说明该法有一定的可信性。实验位于大型土槽内,设计制作了缩尺的渡槽试验模型。模型由四根钢管桩支撑,上部槽体模拟单跨槽体和水体的作用,采用等效质量块代替,承台、槽墩及槽体均采用钢筋混凝土材料,槽墩与等效质量块之间布有四个抗震支座。实验主要了解桩土相互作用。本章采用三维有限元模型对实验进行了模拟。第五章,对不同场地土对智能隔震渡槽的影响进行了分析。智能隔震支座由隔震支座和磁流变阻尼器构成,位于渡槽墩顶,智能隔震系统的控制策略为半主动控制。对此智能隔震渡槽,分析了地震作用下,不同的场地土对结构体系的影响,智能隔震装置的有效性。第六章,对典型的三跨简支梁进行了隔震分析,特别考虑了桥面板之间、桥面板与桥台之间碰撞对隔震桥梁的的影响。前面的渡槽是简支结构,属于简支桥梁类型,与普通简支桥梁比,只是荷载不同罢了。前面的渡槽三维有限元模型比较复杂,自由度也较多。而第五章,考虑SSI的智能隔震渡槽的地震响应,其模型相对简单,自由度也较少。事实上,模型的复杂程度变化是很大的,可以从简单的,仅包括几个自由度的杆件模型(如第五章),到很精细的模型,即包括各个不同杆件的非线性行为的模型。合理的模型应该与桥梁的配置、桥梁的类型、期望的地震需求和地震响应相关。本章对典型的三跨简支桥梁进行了建模,比较全面地考虑了地震动力分析时的需要的一些重要因素,包括材料非线性、支座非线性、土-结构相互作用以及桥面板的碰撞等,对桥面板采用梁单元建模,对关键的桥墩柱采用纤维单元建模,对桥面板的碰撞采用碰撞单元建模。所建三维模型,既能较好反映该类桥梁的地震动力分析的响应特点,又不至于太复杂,导致后面脆弱性分析的计算成本过高。本章重点采用此模型,对桥面板的碰撞进行了研究,分析了碰撞对结构地震动力响应的影响,对隔震简支桥梁的减震效果的影响。第七章,对典型三跨简支梁进行了脆弱性分析,比较了隔震前后的桥梁构件和桥梁系统的脆弱性的变化。脆弱性是在给定地震动强度情况下,结构或结构达到或超过某个设定的损伤程度的条件概率。本章采用地震峰值加速度(PGA)作为地震动强度度量,挑选了五种地震类型中共10条地震波,每条地震以O.1g作为PGA增量来分析,共100个计算工况。通过对各个地震波的增量时程分析,共获得100个时程分析结果。从各时程分析中提取关注的响应变量,包括柱子曲率,固定支座位移,滑动支座位移等。这便是桥梁部件的地震需求。对这些量值进行回归分析,可以得到响应LN (Sd)和地震峰值LN (PGA)之间的关系。再根据桥梁损失极限状态比较,得出桥梁部件的脆弱性曲线,由此,进一步得到桥梁系统的脆弱性曲线。根据支座脆弱的特点,进行坚固处理时,优先考虑支座的替换。替换为隔震支座后,再按同样的方法进行各地震波的增量时程分析,得出隔震桥梁的需求响应。最后,可计算出隔震桥梁部件和桥梁系统的脆弱性曲线。并对隔震前后的脆弱性进行比较。第八章,给出了主要的研究结果和结论。论文的主要成果如下： 1)渡槽结构采用减震支座后的动力响应安装减震支座后渡槽结构的最大动应力和内力得到了不同程度的抑制,支座在横槽向和顺槽向滞回曲线的滞回环明显、饱满,表明减震支座具有明显耗能效果。 2)不同桩土作用模型在三维渡槽地震动力响应分析中,采用m法和Mindlin方法分别建立桩。土相互作用模型,其余相同,Mindlin方法计算的桩顶剪力和弯矩比m法略小,而桩顶位移略大,这说明两种考虑桩-土作用的方法差别不大。而且,两种方法对上部结构,特别是槽体影响不大,渡槽的前三阶振型均为槽体的运动振型,且频率保持不变,槽身的位移也不变,这也说明对此类结构,桩-土作用的影响对上部结构影响较小。 3)计算分析与实验验证通过多种工况的计算,包括不同的地震波及不同地震波峰值,渡槽非线性有限元动力分析成果,无论是位移时程响应特征,在槽墩中部点位移响应的极值,还是桩体水平位响应值,与渡槽拟动力试验结果都比较接近,这在一定程度上验证了拟动力试验的合理性和正确性,也表明采用的计算模型在中、小震条件下,能够比较准确的模拟地震作用下的土-桩-结构-水体系统的地震响应。 4)对不同土体类型,SSI对减震效果的影响有隔震支座时,考虑SSI后,槽身和墩顶的水平横向位移略大。土越软,横向位移越大,但最大基底剪力,无论是软基还是刚基,差别不大有智能隔震系统时,考虑SSI后,槽身和墩顶的水平横向位移急剧减小。这种效果可以避免位移过大,损坏水封。有智能隔震系统时,考虑SSI后,最大基底剪力减小了。土越硬,基底剪力越小。考虑SSI后的减隔震控制系统,其控制效果不如不考虑SSI的情况。土越软,控制效果越差。硬土和刚性基础的控制效果相接近。故,对硬土上的基础,可以当作刚性基础处理,对中、软土上的基础,要考虑SSI效果,否者会高估减震的效果。小阻尼隔震支座,对横向漂移、横向速度和最大基底剪力的减小,均比大阻尼隔震支座要好。 5)考虑SSI的典型简支桥梁结构隔震 (1)碰撞对响应的影响：由于地震波的不同,碰撞可能导致柱子的响应或呈增加趋势,或者呈减小趋势。 (2)减震效果：从减震效果看,纵向减震效果良好,柱子的响应减小,减震支座的力-位移滞回曲线明显,但同时明显放大了支座以上梁的纵向瞬时加速度和梁的纵向位移。而横向减震,不仅没有效果,反而响应有所放大。 (3)碰撞对减震效果的影响：考虑碰撞,对隔震支座以下部位柱子的纵向隔震影响比不考虑碰撞更有效或接近。但都放大了支座以上梁的纵向位移和加速度。对横向,隔振支座不仅不能减震,反而增加了横向响应,考虑碰撞产生的放大作用更明显。 (4)隔震桥梁对基频更接近的地震波,减震效果更好。 (5)对同样的隔震支座,不同场地土情况下,土变硬后,隔震桥梁纵向地震力逐渐变大,而墩顶的位移以及中跨面板梁的位移变化不大。 6)通过对简支桥梁的脆弱性分析,明确了薄弱环节确实首先在于固定支座,其次是滑动支座和柱子。通过采用隔震支座,可以明显改善桥梁系统的脆弱性。论文的创新点：考虑土-结构相互作用对隔震桥梁的影响,以前的研究模型往往只考虑一个方向,并忽略碰撞的影响。本文采用合理的模型,可考虑两个方向的隔震效果,同时也考虑桥面板碰撞效果的影响。论文的章节安排如下：第一章,绪论。对考虑SSI的减隔震研究及桥梁结构脆弱性分析进行综述。第二章,简支渡槽动力数值模拟建模及减震模拟分析。包括建模及减震分析。第三章,考虑不同桩土作用模型的简支渡槽减震动力分析。包括两种桩土作用的模型建模,和对模型的动力时程分析和反应谱分析比较。第四章,对某渡槽拟动力试验的数值模拟分析。第五章,对不同场地土对智能隔震渡槽的影响进行了分析。第六章,考虑碰撞的简支桥梁在不同场地土中的隔震分析。对典型的三跨简支梁进行了隔震分析,特别考虑了桥面板之间、桥面板与桥台之间碰撞对桥梁隔震的影响。第七章,简支桥梁脆弱性分析,对典型三跨简支梁进行了脆弱性分析,比较了隔震前后的桥梁构件和桥梁系统的脆弱性的变化。第八章,结论与建议
[Abstract]:For the construction of seismic system, usually ignore the soil structure interaction in the process of analysis and design (SSI). The rigid foundation assumption, that the earthquake based motion and the adjacent free field. That is to say, the inertial force of upper structure to the foundation, so the deformation should be much smaller. The deformation caused by seismic waves than foundation. Otherwise the assumption is not reasonable, the foundation will have relative to the foundation deformation, resulting in the actual movement of the upper structure and the rigid foundation assumption according to the response obtained is different. Therefore, on the basis of flexible buildings, in the calculation of seismic response is necessary to consider the interaction of soil structure the
At present, the isolation technology has been basically mature, and the research on soil structure interaction (SSI) is deepening. The coupling research between the two has just started. There are not many studies and the conclusions sometimes are contradictory. Therefore, the coupling between the isolation technology and SSI needs further research.
Today, the research on seismic isolation to consider the impact of SSI are limited to simple model structure is simplified as single or multi particle shear structure, the foundation is assumed to be elastic half space. The research mainly focused on the rigid shallow foundation influence on isolation, less studies on the influence of flexible foundation on isolation, but the actual bridge and aqueduct with many flexible the pile foundation. The flexible foundation bridges (or aqueduct) seismic isolation research, can more accurately reveal the effect of soil structure interaction on the seismic reduction and isolation system.
Aiming at the structure of a test isolated aqueduct (the bridge over water) and the common three span pile foundation isolated bridge structure, the effect of SSI on its seismic isolation effect is studied.
The contents of the study are as follows:
In the first chapter, the research and development of the seismic isolation structure considering the soil structure dynamic interaction and the research and development of the bridge vulnerability curve are summarized.
The second chapter, the thesis carries out finite element fine analysis of a simply supported aqueduct, piles are modeled by beam elements, the interaction between soil and pile by spring elements, the pier, and the water in the tank body, by solid modeling. The specific response so that we can obtain the different parts of the upper structure concerned in the engineering of through the model analysis. The actual bearing effect on the response of the system.
The third chapter, the model of pile foundation on the front, using different modeling methods, and analyzed and compared. The two methods was that the interaction between pile and soil were determined by Mindlin method and the standard recommended m method are analyzed and compared. The improved Penzien model by a group with damping spring element to simulate the free field the soil in different depth of pile stiffness effect and damping effect, the end of the spring is connected with the other end of the pile, and a large enough quality unit connection, to simulate the free soil on the quality of the structure effect; soil quality increased between soil shear spring and damper; free field quality also increased soil shear spring and damper.
The fourth chapter, using the Mindlin method of pseudo dynamic test on an aqueduct are analyzed, the results show that the method has a certain credibility. The experiment is located in a large soil tank model was designed. The test scale aqueduct model consists of four pieces of steel pile support, the upper tank and water tank simulation of single span, equivalent mass block instead, pile caps, pier and tank adopts reinforced concrete materials, between pier and equivalent quality cloth four seismic bearing. The experiment mainly to understand the interaction between pile and soil. This chapter of the experiment was simulated using a three-dimensional finite element model.
In the fifth chapter, the influence of different site soil on the intelligent isolation aqueduct is analyzed.
Intelligent bearings by bearings and magnetic damper which is located in the aqueduct pier, the control strategy of intelligent isolation system for semi-active control. This intelligent isolation aqueduct, the effects of the earthquake under the influence of site soil of different structure system, the effectiveness of intelligent isolation device.
In the sixth chapter, the seismic isolation analysis of typical three span simple beam is carried out, especially the impact of the collision between the bridge panel and the bridge deck on the isolated bridge.
In front of the aqueduct is simple structure, which belongs to the simple bridge type, and ordinary bridges than just load is different. The three-dimensional finite element model of the aqueduct in front of the more complex, more degrees of freedom. And the fifth chapter, considering the intelligent isolation SSI seismic response of aqueduct, the model is relatively simple, less degree of freedom in fact, the complexity of the model change is very big, can from the simple, only including bar model with several degrees of freedom (such as fifth), to a fine model of nonlinear behavior which includes different bar model. The model should be reasonable and bridge configuration, the bridge type. Seismic demand and seismic response of expectations.
This chapter of the three span simply supported bridge of typical modeling, comprehensively considered the earthquake dynamic analysis to some important factors, including material nonlinear, nonlinear bearing, soil structure interaction and collision of the bridge deck, bridge deck beam element modeling, the key bridge pier by fiber unit modeling, collision of bridge deck by using collision element modeling. The three-dimensional model of seismic dynamic analysis can reflect the response characteristics of this kind of bridge, and not too complicated, leading to computational cost analysis behind the vulnerability is too high.
This chapter mainly applies this model to study the impact of bridge deck, and analyzes the impact of collision on the seismic response of structure, and the influence of isolation on simply supported bridges.
In the seventh chapter, the fragility of the typical three span simple beam is analyzed, and the changes of the vulnerability of the bridge components and the bridge system are compared before and after the shock isolation.
The vulnerability is given in the case of earthquake intensity, structure or structure to meet or exceed a certain degree of injury. This chapter uses the conditional probability of earthquake peak acceleration (PGA) as the ground motion intensity measurement, selection of the five type earthquake the 10 seismic waves, each earthquake with O.1g as PGA increment analysis. A total of 100 calculation conditions.
Based on the increment of every seismic wave time history analysis, history analysis results were obtained from 100. When the response variable in the analysis of the extraction of attention, including column curvature, fixed displacement, displacement of sliding bearings. This is part of the bridge seismic demand. These values can be obtained by regression analysis. The response of LN (Sd) and the peak LN (PGA). The relationship between the loss of bridge according to limit state, the vulnerability curve of bridge components thus obtained fragility curves of bridge system.
According to the characteristics of bearing fragile, sturdy handle, preferred bearing replacement. Replace bearings, incremental following the same method around the shock time history analysis, the response of isolated bridge demand. Finally, calculate the fragility curves of isolated bridge components and bridge system and vulnerability to. Before and after isolation were compared.
In the eighth chapter, the main research results and conclusions are given.
The main achievements of the paper are as follows:
1) the dynamic response of the aqueduct structure with the shock absorber support
After installing the damping support, the maximum dynamic stress and internal force of the aqueduct structure are restrained to varying degrees. The hysteresis loops of the bearing in the transverse groove direction and the groove loop are obvious and full, indicating that the damping bearing has obvious energy dissipation effect.
2) different pile soil interaction model
In the analysis of 3D aqueduct seismic response, using m method and Mindlin method were established. The pile soil interaction model, the same Mindlin method to calculate the pile top shear and bending moment than m slightly smaller, and the displacement of pile top is slightly larger, indicating that the two little difference method considering the pile-soil interaction and. On the upper structure, two kinds of methods, especially the impact of the aqueduct with three modes of vibration are motion type trough, and the frequency remains unchanged, displacement of aqueduct body is also unchanged, it also shows that in such structure, the interaction of soil pile superstructure of little influence.
3) calculation analysis and experimental verification
Through the calculation of various conditions, including different seismic waves and different seismic wave peak, nonlinear finite element dynamic analysis results of aqueduct, both the characteristics of response displacement, in the extreme value of displacement response of central pier, level or pile response value and aqueduct pseudo dynamic test results are relatively close, which verifies the rationality and the correctness of the pseudo dynamic test to a certain extent, also shows that the calculation model in small earthquake conditions, can simulate the earthquake accurately under the soil pile structure water system seismic response.
4) the effect of SSI on the damping effect of different soil types
There are bearings when considering SSI, transverse displacement of aqueduct and the pier top is slightly larger. In soft soil, the lateral displacement is greater, but the maximum base shear, whether it is soft or Ganj little difference.
In an intelligent isolation system, the horizontal lateral displacement of the body and the top of the pier sharply decreases after the SSI is considered. This effect can avoid excessive displacement and damage to water seal.
When the SSI is considered, the maximum base shear force decreases when the intelligent isolation system is considered. The harder the soil is, the smaller the base shear is.
Consider isolation control system after SSI, the control effect is not considered in the case of SSI. The soil is soft, the control effect is worse. The control effect of the hard soil and rigid foundation are close. Therefore, based on the hard soil, can be used as a rigid foundation, the foundation, the soft soil, to considering the SSI effect, it will overestimate the damping effect.
The decrease of the lateral drift, the lateral velocity and the maximum base shear is better than the large damping isolation bearing.
5) seismic isolation of typical simple supported bridge structures considering SSI
(1) the impact of the collision on the response:
Due to the difference of seismic waves, collisions may lead to an increase in the response of the column, or a decreasing trend.
(2) the effect of shock absorption:
From the damping effect, longitudinal good cushioning effect, reduce post response, bearing force displacement hysteresis curve is obvious, but also significantly enlarge the vertical displacement of the longitudinal beam above and the instantaneous acceleration of bearing beam. And the transverse vibration, not only has no effect, but the response has been enlarged.
(3) impact on the effect of shock absorption:
Consider the collision, vertical isolation influence on the bearings below the column is more effective than that without considering the collision or close. But the longitudinal displacement and acceleration amplification support above beam. On the transverse vibration isolator, not only shock, but increased the transverse response, considering the collision produced by the amplification effect is more obvious.
(4) the seismic waves which are closer to the base frequency of the isolated bridge are better in shock absorption.
(5) for the same isolation bearings and soil under different soil conditions, the longitudinal seismic force of the isolated bridge gradually increases, while the displacement of the pier top and the displacement of the mid span face slab change little.
6) through the analysis of the vulnerability of simply supported bridges, it is clear that the weak links do first lie in the fixed bearings, followed by the sliding bearings and columns. By adopting the isolation bearings, the vulnerability of the bridge system can be obviously improved.
The innovation of the thesis:
Considering the influence of soil structure interaction on isolated bridges, the previous research models usually only consider one direction and ignore the impact of collision. In this paper, a reasonable model can be used to consider the isolation effect in two directions, and the impact of bridge deck impact is also considered.
The chapters of the paper are arranged as follows:
In the first chapter, the introduction. A review of the research on the isolation of SSI and the analysis of the structural vulnerability of the bridge is made.
The second chapter, the dynamic numerical simulation modeling and the shock absorption simulation analysis of the simply supported aqueduct, including the modeling and the shock absorption analysis.
In the third chapter, we consider the dynamic analysis of simply supported aqueducts with different pile-soil interaction models, including two kinds of pile soil interaction model modeling, and the dynamic time history analysis and response spectrum analysis of the model.
In the fourth chapter, the pseudo dynamic test of a aqueduct

【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U442.55;P315.9

【参考文献】