Influence of Vertical Irregularity on the Seismic Behavior of Base Isolated RC Structures with Lead Rubber Bearings under Pulse-Like Earthquakes

Nowadays,an extensive number of studies related to the performance of base isolation systems implemented in regular reinforced concrete structures subjected to various types of earthquakes can be found in the literature.On the other hand,investigations regarding the irregular base-isolated reinforced concrete structures’performance when subjected to pulse-like earthquakes are very scarce.The severity of pulse-like earthquakes emerges from their ability to destabilize the base-isolated structure by remarkably increasing the displacement demands.Thus,this study is intended to investigate the effects of pulse-like earthquake characteristics on the behavior of low-rise irregular base-isolated reinforced concrete structures.Within the study scope,investigations related to the impact of the pulse-like earthquake characteristics,irregularity type,and isolator properties will be conducted.To do so,different values of damping ratios of the base isolation system were selected to investigate the efficiency of the lead rubber-bearing isolator.In general,the outcomes of the study have shown the significance of vertical irregularity on the performance of base-isolated structures and the considerable effect of pulse-like ground motions on the buildings’behavior.

A Study on the Seismic Isolation Systems of Bridges with Lead Rubber Bearings

This study consists of the development and presentation of example of seismic isolation system analysis and design for a continuous, 3-span, cast-in-place concrete box girder bridge. It is expected that example is developed for all Lead-Rubber Bearing (LRB) seismic isolation system on piers and abutments which placed in between super-structure and sub-structure. Design forces, displacements, and drifts are given distinctive consideration in accordance with Caltrans Seismic Design Criteria (2004). Most of all, total displacement on design for all LRBs case is reduced comparing with combined lead-rubber and elastomeric bearing system . Therefore, this represents substantial reduction in cost because of reduction of expansion joint. This presents a summary of analysis and design of seismic isolation system by energy mitigation with LRB on bridges.

Development of a modified Mooney-Rivlin constitutive model for rubber to investigate the effects of aging and marine corrosion on seismic isolated bearings

In this study, aging and marine corrosion tests of a large number of rubber material and rubber bearings have been carried out. The constitutive Mooney-Rivlin model parameters for a rubber isolated bearing have been determined. By applying the least-square method to the experimental data, the relationships between the aging time and the marine corrosion time with the constants in the constitutive model for a rubber beating have been derived. Next, the Mooney-Rivlin model has been modified accordingly. Further, using the modified Mooney-Rivlin model and the Abaqus software, the performance of the rubber isolated bearings has been simulated. The simulation results have been compared to the experimental results so as to verify the accuracy of the modified model. The comparison shows that the maximum errors for the vertical and horizontal stiffnesses are 16.8% and 0.49%, respectively. Since these errors are considered acceptable, the accuracy of the modified constitutive model can be considered verified. The results of this study can provide theoretical support for the performance study on rubber isolated bearings under the complex ocean environment and the life-cycle performance evaluation of bridges and other offshore structures.

Numerical Analysis of Seismic Elastomeric Isolation Bearing in the Base-Isolated Buildings

Base isolation concept is currently accepted as a new strategy for earthquake resistance structures. According to different types of base isolation devices, laminated rubber bearing which is made by thin layers of steel shims bonded by rubber is one of the most popular devices to reduce the effects of earthquake in the buildings. Laminated rubber bearings should be protected against failure or instability because failure of isolation devices may cause serious damage on the structures. Hence, the prediction of the behaviour of the laminated rubber bearing with different properties is essential in the design of a seismic bearing. In this paper, a finite element modeling of the laminated rubber bearing is presented. The procedures of modeling the rubber bearing with finite element are described. By the comparison of the numerical and the experimental, the validities of modelling and results have been determined. The results of this study perform that there is a good agreement between finite element analysis and experimental results.

Experimental and Finite Element Analysis for Multi-lead Rubber Bearings:A Comparative Study

The mechanical properties of multi-lead rubber bearings （MLRBs） were investigated by experiment and finite element analysis. First, the vertical stiffness, horizontal stiffness and yielded shear force were tested for four MLRB specimens and two specimens of the single-lead rubber bearings （ SLRBs）. Then, the MLRBs were modeled by the explicit finite element analysis software ANSYS/ LS-DYNA, in order to evaluate the horizontal force-displacement hysteretic curves under static vertical and dynamical horizontal loadings. The disagreement between the tested and theoretical values was less than 11.4%, and MLRBs and SLRBs were similar in vertical stiffness, pre-yield stiffness and yield stiffness.

Numerical investigation on seismic performance of a shallow buried underground structure with isolation devices

A design procedure for improving the seismic performance of unequal-span underground structures by installing isolation devices at the top end of columns is proposed based on the seismic failure mode of frame-type underground structures and the design concept of critical support columns.A two-dimensional finite element model(FEM)for a soil-underground structure with an unequal-span interaction system was established to shed light on the effects of a complex subway station with elastic sliding bearings(ESB)and lead rubber bearings(LRB)on seismic mitigation.It was found that the stiffness and internal force distribution of the underground structure changed remarkably with the installation of isolation devices at the top end of the columns.The constraints of the beam-column joints were significantly weakened,resulting in a decrease in the overall lateral stiffness and an increase in the structural lateral displacement.The introduction of the isolation device effectively reduces the internal force and seismic damage of the frame column;however,the tensile damage to the isolation structure,such as the roof,bottom plate,and sidewall,significantly increased compared to those of the non-isolation structure.Although the relative slip of the ESB remains within a controllable range under strong earthquake excitation as well as frame columns with stable vertical support and self-restoration functions,the LRB shows a better performance during seismic failure and better lateral displacement response of the unequal-span underground structure.The analysis results provide new ideas and references for promoting the application of seismic isolation technology in underground structures.

钢板削弱型叠层橡胶支座力学性能试验研究

结合厚层橡胶支座和普通叠层橡胶支座的优点设计新型钢板削弱型叠层橡胶支座,通过调节环形钢板的总数和位置进行支座水平和竖向刚度的有效控制.选择3种中心橡胶层厚度的钢板削弱型叠层橡胶支座,分析所设计支座的滞回特性、刚度特性和耗能特性.基于串-并联模型,构建水平和竖向刚度的计算模型.试验结果表明,相比普通叠层橡胶支座,钢板削弱型叠层橡胶支座的水平和竖向刚度更低,水平和竖向耗能比更高,滞回曲线更光滑饱满.所建模型的计算结果与试验结果的一致性较好,误差绝对值不超过10%.所建模型在评估钢板削弱型叠层橡胶支座的水平和竖向刚度方面具有较高的精度和适用性.

铅芯隔震橡胶支座关键抗震性能参数极低温效应试验研究

中国北方部分地区冬季易受到极寒气候的影响,研究铅芯隔震橡胶支座在此环境下的性能变化规律和规范适用性,对结构抗震安全性具有非常重要的意义。对3种不同形状的铅芯隔震橡胶支座,分别进行了不同温度(-60~40℃)和不同低温暴露时间(1、2、7 d)下的剪切性能试验,得出了支座的关键抗震性能参数(特征强度、水平等效刚度、屈服后刚度和等效阻尼比)随温度和低温暴露时间的变化规律。研究表明:支座形状对铅芯隔震橡胶支座的低温隔震性能影响较小;而橡胶配比在极低温时的影响至关重要;在满足各项性能需求的前提下,低温减隔震支座宜优先选择剪切模量较小的支座;支座的关键抗震性能参数在低温暴露时间约为2 d时达到一个相对稳定的状态。

高速公路多联连续梁桥隔震研究

针对高速公路多联连续梁桥的抗震问题,本文对铅芯橡胶支座和摩擦摆支座进行了隔震效应分析与设计优化。本文基于多联有限元模型和非线性时程分析方法,分析了多联体系下各墩地震响应的差异,及铅芯橡胶支座和摩擦摆支座的隔震和耗能效果,并对隔震支座的参数布置进行了优化。结果表明:多联桥梁交界墩的地震响应较联内墩一般增大20%以上,交界墩上部结构跨径差异较大时甚至可达75%。铅芯橡胶支座位移限制能力和大震耗能更好,且屈服前刚度越大、屈服强度和屈服后刚度越小,滞回耗能能力越强;摩擦摆支座小震时即可发挥其隔震效果,且滑动摩擦系数越小、曲率半径越大,隔震效果越好。通过在交界墩布置更多隔震支座可在保证一定隔震率的同时改善桥墩受力不均匀的问题,具有一定的工程参考价值。

工程结构中新型减隔震支座的研究综述

多次震害经验表明,通过在上部结构和地基之间设置减隔震支座,利用橡胶垫的变形使上部结构的振动周期延长,利用钢构件的屈服或者滑动摩擦耗能来达到消能减震的目的,是一项有效的防震减灾措施。论文从减震机理、性质及应用等方面系统阐述和总结了拉索减震支座、叠层橡胶支座、球形抗震支座以及若干新型减震支座的研究成果,对未来新型减隔震支座的研究方向进行了展望。

基于刚度矩阵分析法的变刚度橡胶支座力学性能研究

在橡胶支座力学行为基础上提出了一种适合隔离三维地震或竖向振动的新型变刚度橡胶支座,并阐述了能解决变刚度支座非均质体力学问题的刚度矩阵分析法。首先,基于常用橡胶支座解析解和压剪试验的非线性响应分析,采用刚度矩阵分析法对该支座进行计算,其结果和试验值高度一致验证了该方法计算精度较高。接着,对比三种支座结果:在相同外部荷载和材料参数下,厚层支座力和变形最大,变刚度支座和普通支座力和变形显著低于厚层支座;不同轴压下,P-Δ效应表现为厚层支座力和变形及水平刚度受轴压影响最为显著,而变刚度支座与普通支座受轴压影响较小。通过算例表明,可通过调整变刚度支座实现竖向刚度的优化。综合而言,变刚度支座对力和变形的承载能力较好,为三维隔震(振)提供了一种简单实用的解决方案。

隔震橡胶支座力学性能的损伤评估

在遭遇罕遇和极罕遇地震时,采用螺栓连接的隔震橡胶支座可能会因为局部橡胶损伤而导致整体屈曲或失稳。这种支座的力学性能深受其构成材料-钢和橡胶的物理属性的影响。橡胶的特点包括低模量、高延展性、超弹性以及弱压缩性。通过解析解和试验非线性响应结果表明:当水平力较小时,支座纯压下的最大和平均剪应变较大,随水平力增加,其纯剪下的最大和平均剪应变以及弯曲平均剪应变增加显著,因此,在评估支座最大和平均剪应变时,必须同时考虑压缩、剪切和弯曲效应的综合影响。此外,美国规范中最大剪应变限值可作参考,英国规范的名义压应变偏大。支座中橡胶的体积膨胀可能引起内部破裂,因此,在大应变和高轴压下,准确确定隔震支座的剪切模量和剪应变对于描述其力学行为和局部拉、压应力,以及预测内部损伤和破坏程度具有重要意义。

济南某复杂综合体结构设计难点研究

济南某复杂综合体项目由两座约90m高塔楼+大底盘商业裙房+低区U形幕墙+高区拱形连桥组成,高区连体建筑采用铅芯橡胶隔震支座与塔楼相连,低区采用两端固定铰支座与塔楼相连,为大底盘多塔复杂连体结构。塔楼采用钢筋混凝土框架-核心筒结构体系,高区拱形连桥采用钢结构空腹桁架结构体系,低区U形幕墙采用劲性索体系。针对工程特点,着重阐述了大底盘裙房不分缝可行性及低、高区弱连体的合理支座形式,提出了采用两端固定铰U形劲性索的弱连体新形式。结果表明:低区U形幕墙采用两端固定铰连接形式,高区连桥采用铅芯橡胶隔震支座连接形式均能较好地实现弱连接,保证塔楼和连桥的抗震性能。

楼梯设置橡胶支座框架结构抗震性能研究

为减轻楼梯在地震作用下的破坏,本研究拟在框架结构楼梯间梯段板下端设置橡胶隔震支座并对其抗震性能进行研究。首先,利用ETABS分析软件,分别建立了不设置楼梯、设置现浇楼梯和在楼梯梯段板下端设置橡胶隔震支座的钢筋混凝土框架结构模型;然后,采用反应谱和非线性时程分析法,对比研究了地震作用下楼梯和橡胶隔震支座对框架结构受力性能的影响。研究结果表明,楼梯的存在会显著改变结构的自振周期、楼层刚度、层间位移角等参数,而在楼梯梯段板下端设置橡胶隔震支座后,楼梯梯柱、梯梁内力明显减小,结构的抗震性能得到明显改善。

高速铁路高低塔斜拉桥减隔震装置研究

通过分析各类减隔震装置对高速铁路高低塔混合梁斜拉桥的减隔震作用,从而选取合理减隔震装置。以阜淮(阜阳—淮北)新建高速铁路跨颍河主跨230 m的高低塔混合梁斜拉桥为研究对象,建立铅芯橡胶支座、摩擦摆式减隔震支座、黏滞阻尼器有限元模型,采用非线性时程分析法对塔底弯矩、梁端水平位移等目标函数进行地震响应分析。结果表明:采用铅芯橡胶支座,塔底弯矩降幅达到49.9%;采用摩擦摆减隔震支座,塔底弯矩降幅达到54.3%;采用黏滞阻尼器,塔底弯矩降幅达到62.0%。对于高速铁路高低塔混合梁斜拉桥而言,黏滞阻尼器减隔震装置更合理,并给出合适设计参数。

隔震橡胶支座在砌体结构抗震加固中的应用

砌体结构的加固改造,经常遇到抗震设防类别的提高,导致上部结构的构造措施难以满足规范要求,给加固设计带来一定的困扰。橡胶隔震支座在加固设计的运用,可以有效减小上部结构的地震作用,从而减少上部结构的加固设计难度。以五层砌体结构的改造加固为例,探讨隔震橡胶支座在砌体结构抗震加固中的应用。该建筑使用功能由办公楼改为幼儿园,抗震设防类别由丙类提高为乙类。通过在底层设置隔震橡胶支座,对比加固前后底部剪力、弯矩的变化,可以看出橡胶支座显著降低了砌体结构底部的地震力,减少了上部结构的加固量。

考虑橡胶隔震支座速度相关性的隔震桥梁地震响应研究

研究了橡胶支座在桥梁工程隔震结构中的速度相关性,以及在两种不同级别地震作用下的橡胶支座响应变化.通过即时子结构试验,对隔震桥梁工程中采用三种不同阻尼的橡胶支座,在小震和大震环境中的地震反应进行了速度相关性分析.发现在大震情况下,结构响应受到了速度相关性强烈影响,高阻尼比的支座影响更加明显;不同阻尼的橡胶支座的速度相关性对整体抗震结构的地震响应起到关键作用.通过三种支座模型比较分析,发现速度无关的模型与本文研究的速度相关性模型相比,后者结果更接近试验值.

铅芯橡胶隔震支座与黏滞阻尼器在某高位连体结构中的应用研究

一项目两栋塔楼通过高位钢连廊连接为双塔连体结构,该项目采用了铅芯橡胶隔震支座与黏滞阻尼器的柔性支座连接方案。详细介绍了柔性支座连接方案的设计要点,并建立了考虑钢连廊与塔楼相互作用的高位连体结构整体计算模型。采用YJK软件对高位连体结构进行了风荷载和小震作用下的计算分析,并采用SAUSAGE分析软件进行了罕遇地震作用下的弹塑性时程分析,分析了铅芯橡胶隔震支座和黏滞阻尼器的非线性地震响应。分析结果表明,在风荷载和小震作用下,铅芯橡胶隔震支座均处于弹性工作状态;在罕遇地震作用下,铅芯橡胶隔震支座产生屈服变形并耗能,最大剪切变形值在规范允许范围内,黏滞阻尼器滞回曲线饱满,出力明显;此外柔性支座连接方案减弱了高位钢连廊对主体结构的影响,按各塔楼进行独立设计并局部采取加强措施能够满足实际工程要求,而且能够降低主体结构设计难度。

建筑隔震橡胶支座四立柱平板硫化机加热方式优选

根据建筑隔震橡胶支座生产工艺的特殊性,对其硫化所用四立柱平板硫化机(简称平板硫化机)加热方式进行优选。从平板温升情况和温度极差以及平板硫化机制程稳定性和联程统一性4个方面分析,确定建筑隔震橡胶支座平板硫化机最佳的加热方式是导热油载体加热,以实现多台平板硫化机集中加热、联机运行。

橡胶支座隔震与摩擦摆支座隔震效果的对比研究

为了对比研究摩擦摆支座、橡胶支座对建筑结构的隔震效果,采用通用有限元软件ETABS建立一栋5层框架结构作为计算模型,基于非线性动力时程分析方法,考虑摩擦摆支座滑动摩擦系数和曲率半径的不同组合,从隔震结构自振周期,隔震支座位移、减震系数和层间位移角方面评估了两种不同产品类型的隔震效果;最后对比了支座隔震性能与外形尺寸。数值模拟结果表明:通过调整摩擦摆支座设计参数,能实现与橡胶支座相当甚至更优的隔震效果,且摩擦摆支座外形尺寸较小,为支座安装提供了充足的空间。