Resilient performance of self-centering hybrid rocking walls with curved interface under pseudo-static loading

Frame and rocking wall(FRW)structures have excellent resilient performance during earthquakes.However,the concrete at interfacial corners of rocking walls(RWs)is easily crushed due to local extreme compression during the rocking process.An innovative RW with a curved interface is proposed to prevent interfacial corners from producing local damage,enhancing its earthquake resilient performance(ERP).The precast wall panel with a curved interface is assembled into an integral self-centering hybrid rocking wall(SCRW)by two post-tensioned unbonded prestressed tendons.Moreover,two ordinary energy dissipation steel rebars and two shear reinforcements are arranged to increase the energy dissipation capacity and lateral resistance.Two SCRW specimens and one monolithic reinforced concrete(RC)shear wall(SW)were tested under pseudo-static loading to compare the ERPs of the proposed SCRW and the SW,focusing on studying the effect of the curved interface on the SCRW.The key resilient performance of rocking effects,failure modes,and hysteretic properties of the SCRW were explored.The results show that nonlinear deformations of the SCRW are concentrated along the interface between the SCRW and the foundation,avoiding damage within the SCRW.The restoring force provided by the prestressed tendons can effectively realize self-centering capacity with small residual deformation,and the resilient performance of the SCRW is better than that of monolithic SW.In addition,the curved interface of the SCRW makes the rocking center change and move inward,partially relieving the stress concentration and crush of concrete.The rocking range of the rocking center is about 41.4%of the width of the SCRW.

Energy conversion and deposition behaviour in gravitational collapse of granular columns

The high-density gravitational collapse of granular columns is very similar to the movements of large collapsing columns in nature. Based on the development of dangerous columnar rock mass in fields, granular column collapse boundary condition in the physical experiments of this study is a new type of boundary conditions with a single free face and a three-dimensional deposit. Physical experiments have shown that the mobility of small particles during the collapse of granular columns was greater than that of large particles. For example, when particle size was increased from 5 to 15 mm, deposit runout was decreased by about 16.4%. When a column consisted of two particle types with different sizes, these particles could mix in the vicinity of layer interfaces and small particles might increase the mobility of large particles. In the process of collapse, potential and kinetic energy conversion rate is fluctuated. By increasing initial aspect ratio a, the ratio of the initial height of column to its length along flow direction,potential and kinetic energy conversion rate is decreased. For example, as a was increased from 0.5 to 4, the ratio of maximum kinetic energy obtained and total potential energy loss was decreased from47.6% to 7.4%. After movement stopped, an almost trapezoidal body remained in the column and a fanlike or fan-shaped accumulation was formed on the periphery of column. Using multiple exponential functions of the aspect ratio a, the planar morphology of the collapse deposit of granular columns could be quantitatively characterized. The movement of pillar dangerous rock masses with collapse failure mode could be evaluated using this granular column experimental results.

An Experimental and Analytical Study on Cross-Laminated Bamboo Rocking Walls with Friction Dampers

Cross-laminated bamboo(CLB)have a high strength to weight ratio and stable bidirectional mechanical properties.Inspired by the investigation on cross-laminated timber(CLT)rocking walls,CLB rocking walls with conventional friction dampers(CFDs)are studied in this paper.To investigate the mechanical properties of the CLB rocking wall,seven tests are conducted under a cyclic loading scheme,and different test parameters,including the existence of the CFDs,the moment ratio,and the loading times,are discussed.The test results show a bilinear behavior of the CLB rocking wall.The small residual displacements of the CLB rocking wall demonstrate an idealized self-centering capacity.The cumulative energy dissipation curves indicate that the energy dissipation capacity of the CLB rocking wall can be greatly improved with CFDs.The limit states of the CLB rocking wall under a lateral force are proposed based on the strains,stress,and damage level of the CLB material and posttensioned rebar.In addition,an analytical model of the CLB rocking wall is developed based on the proposed limit states of the CLB rocking wall to evaluate the hysteretic response of the CLB rocking wall,and the model is validated by the experimental data.The comparison results show the potential value of the analytical model for engineering design.

Seismic response of rocking isolated railway bridge piers with sacrificial components

In this study, sacrificial components were incorporated into self-centering railway bridge piers to improve the lateral stiffness. The seismic response of this new detail was investigated. First, the method to compute the initial uplift moment of the self-centering pier is given. In addition, shaking table tests were conducted on a free-rocking pier without sacrificial components, which was used to validate a two-spring numerical model. Good agreement was obtained between the numerical results and experimental data. Furthermore, the validated model was employed to investigate the influence of sacrificial components on the seismic response of rocking piers. For this purpose, two models were developed, with and without sacrificial components. Nonlinear response history analysis was then performed on both models under three historical motions. The results showed that compared to the one without sacrificial components, the rocking pier with sacrificial components has comparable displacement at the top of the pier, and maximum uplift moment at high amplitude motion. Therefore, incorporating sacrificial components into the rocking pier can increase the lateral stiffness at service load and low amplitude frequent earthquakes but can produce comparable response at high seismic excitation. These results provide support for performance-based seismic design of self-centering rocking piers.

Optimization of design parameters for controlled rocking steel braced dual-frames

A controlled rocking concentrically steel braced frame(CR-CSBF)is introduced as an alternative to conventional methods to prevent major structural damage during large earthquakes.It is equipped with elastic post-tensioned(PT)cables and replaceable devices or fuses to provide overturning resistance and dissipate energy,respectively.Although CR-CSBFs are not officially legalized in globally valid codes for new buildings,it is expected to be presented in them in the near future.The main goal of this study is to determine the optimal design parameters consist of the yield strength and modulus of elasticity of the fuse,the initial force of the PT cable,and the gravity load on the rocking column,considering different heights of the frame,spanning ratios and ground motion types for dual-configuration CR-CSBF.Nonlinear time-history analyses are performed in OpenSees.This study aims to define the optimal input variables as effective design parameters of CR-CSBFs by comparing four seismic responses consisting of story drift,roof displacement,roof acceleration and base shear,and also using the Euclidean metric optimization method.Despite the previous research,this study is innovative and first of its kind.The results demonstrate that the optimal design parameters are variable for various conditions.

Investigation of long-wavelength elastic wave propagation through wet bentonite-filled rock joints

The saturation of the compacted bentonite buffer in the deep geological repository can cause bentonite swelling,intrusion into rock fractures,and erosion.Inevitably,erosion and subsequent bentonite mass loss due to groundwater inflow can aggravate the overall integrity of the engineered barrier system.Therefore,the coupled hydro-mechanical interaction between the buffer and rock during groundwater inflow and bentonite intrusion should be evaluated to guarantee the long-term safety of deep geological disposal.This study investigated the effect of bentonite erosion and intrusion on the elastic wave propagation characteristics in jointed rocks using a quasi-static resonant column test.Jointed rock specimens with different joint conditions(i.e.joint surface saturation and bentonite filling)were prepared using granite rock discs sampled from the Korea Underground Research Tunnel(KURT)and Gyeongju bentonite.The long-wavelength longitudinal and shear wave velocities were measured under different normal stress levels.A Hertzian-type power model was used to fit the wave velocities,and the relationship between the two fitted parameters provided the trend of joint conditions.Numerical simulations using three-dimensional distinct element code(3DEC)were conducted to better understand how the long-wavelength wave propagates through wet bentonite-filled rock joints.

近场脉冲型地震作用下附加支撑双柱式摇摆桥墩的抗震性能研究

为了解决摇摆桥墩承载力和耗能能力不足的问题,该文提出一种附加人字形支撑的双柱式摇摆桥墩结构,支撑为纯耗能支撑或自复位耗能支撑,支撑通过连接装置安装在双柱式摇摆桥墩的盖梁和承台之间。为了研究新型附加人字形支撑双柱式摇摆桥墩的抗震性能,对其进行拟静力分析,将双柱式现浇桥墩和双柱式纯摇摆桥墩作为对比模型,研究附加纯耗能支撑和自复位耗能支撑双柱式摇摆桥墩的滞回性能;分别对这四种桥墩结构进行动力时程分析,探究这四种桥墩在近场对称脉冲、近场非对称脉冲和远场无脉冲地震动作用下的动力响应。研究结果表明:附加支撑的双柱式摇摆桥墩中的墩柱仍具有摇摆机制,可有效避免墩身出现塑性铰发生严重的损伤破坏,同时附加的支撑可以显著提高桥墩的承载能力和耗能能力,有效降低桥墩结构的位移响应,特别是自复位耗能支撑还可额外为桥墩提供自恢复力,有效提高结构的抗震性能。

远距离下保护层开采遗留煤柱对被保护层回采的影响研究

为探究远距离下保护层开采遗留煤柱对被保护层回采效果的影响,以平顶山六矿戊_(8)煤层的戊_(8)-22310机巷和戊_(8)-32010风巷之间遗留宽度为4 m的区段煤柱和丁_(5-6)-22190工作面为研究对象,采用理论分析、数值模拟和现场实测结合的方法,研究了煤柱影响范围、煤柱区域垂直应力分布及影响区相关参数变化规律。结果表明:宽4 m遗留煤柱的影响范围为27.3 m,极限强度为25.9 MPa,塑性区宽度为2.26 m,弹性区宽度为2.68 m;煤柱两侧工作面均回采后,其承载的最大垂直应力87.9 MPa,远超煤柱本身的承载极限;在煤柱影响范围内测得的残余瓦斯含量、压力与卸压保护区无明显差异,并均小于突出危险临界值,煤柱影响区内瓦斯得到较好释放;煤柱影响范围内未产生明显应力集中现象,遗留小煤柱对被保护效果影响较小,保护效果在倾向上有连续性,对被保护层工作面回采影响小。

胶西北海岸带海底基岩矿床开采海水入浸防治

海底基岩矿床顶部分布着大面积的海水,开采过程中存在海水突入矿坑问题。以胶西北海岸带区域为研究背景,对矿坑涌突水的影响因素及涌水量进行分析,并提出防治措施。结果表明,自然灾害、开采活动、孔隙含水层是导致矿坑涌突水主要原因;提出了留设保安护顶矿(岩)柱,钻孔注浆,加强地表防海水入浸配套设施建设,提高井下排水系统能力,构筑防水闸门等措施。胶西北海岸带海底金矿开采时-165m标高以上设为保安护顶矿柱是安全的,北皂煤矿-200m以上设为保安护顶矿柱是安全的;海底金矿极限开采高度为-65~-87.2m,北皂煤矿极限高度为-120~-160m,可以作为整个海底矿床开采完毕后回采保安护顶矿柱时的参考依据。

基于沿空留巷技术的工作面过陷落柱工程实践

矿井采掘工作揭露陷落柱等地质构造时,往往会带来较多潜在隐患,可能导通含水层、造成瓦斯超限和形成支护难题等。针对6102工作面揭露大型陷落柱影响区的技术难题,矿方根据陷落柱产状及潜在的隐患情况,结合矿井较成熟的沿空留巷理论及经验,成功实施了基于沿空留巷技术的过陷落柱工程实践,在损失一定保护煤柱的代价下,确保了工作面安全快速跳过陷落柱影响区域,沿空留巷技术优势得到验证。

Numerical analysis of seepage flow characteristic of collapse column under the influence of mining

Based on the importance of fractured rock mass seepage research, in order to analyze seepage flow characteristics of collapse column under the influence of mining, a method by embedding fractured rock mass flow solid coupling relationship into FLAC3D internal flow models is presented according to fluid-solid coupling theory and strength criterion. A calculation model of numerical analysis was established, and the influences of mining pressure and plastic damage to pore water pressure and seepage vector change rule were studied. The results show that collapse column is the main channel of confined water seepage upward. The impact is not big when the workface is away from the collapse column. But when the workface is nearing a collapse column, there will be a seepage channel on a side near the workface, in which seepage vector and head are comparatively large. With workface pushing through collapse column, the seepage channel transfers to the other side of the column. In addition, when the plastic damage area within the collapse column breaks through, a "pipeline flow" will be formed within the column, and seepage field will change remarkably and the possibility of water bursting will be greater.

Modeling and cyclic behavior of segmental bridge column connected with shape memory alloy bars

This paper examines the quasi-static cyclic behavior,lateral strength and equivalent damping capacities of a system of post-tensioned segmental bridge columns tied with large diameter martensitic Shape Memory Alloy(SMA) link-bars.Moment-curvature constitutive relationships are formulated and analysis tools are developed for the PT column,including a modified four-spring model prepared for the SMA bars.The suggested system is exemplified using a column with an aspect ratio of 7.5 and twelve 36.5 mm diameter NiTi martensitic SMA bars.A post-tensioning force of 40% to 60% of the tendon yield strength is applied in order to obtain a self re-centering system,considering the residual stress of the martensitic SMA bars.The cyclic response results show that the lateral strength remains consistently around 10% of the total vertical load and the equivalent viscous damping ratios reach 10%-12% of critical.When large diameter NiTi superelastic SMA bars are incorporated into the column system,the cyclic response varies substantially.The creep behavior of the superelastic SMA bar is accounted for since it affects the re-centering capability of the column.Two examples are presented to emphasize the modeling sensitivities for these special bars and quantify their cyclic behavior effects within the column assembly.

不同级配陷落柱充填体力学特征实验研究

为研究不同颗粒级配陷落柱充填物在不同固结荷载下的力学特性,基于土工固结试验制备不同状态下的相似模拟充填体试样,通过充填体在不同状态下的三轴加载实验、压汞及扫描电镜实验,研究了陷落柱充填体三轴应力状态下的力学特征及微观结构演化机制。结果表明:充填体具有明显的塑形特征,其应力−应变曲线可以划分为4个阶段:孔隙压密段、稳定变形段、变形破坏段和类蠕变阶段。充填体偏应力随Talbol指数n呈先增加后减小的趋势,充填体三轴抗压强度与Talbol指数之间符合二次多项式关系,均满足较高的拟合度并且偏应力强度达到最优的Talbol指数分别为0.71、0.65和0.64;偏应力随着固结荷载的增加而线性增加,增长率随着固结荷载和Talbol指数的增加呈逐渐减小的趋势。结合压汞和扫描电镜测试结果,固结荷载和Talbol指数的变化改变了颗粒间的接触状态,影响着岩土体试样的偏应力强度;随着Talbol指数的增加,充填体内颗粒间的相互作用增强,初始承受的外荷载比例增大,骨架结构效应更加显著,偏应力则主要来自岩土颗粒的接触应力集中。通过力学强度和微观结构特征研究在宏观和微观尺度上解释了充填体的颗粒级配效应提供参考。

基于抗损性的钢筋混凝土摇摆柱力学性能研究

抗震韧性将震后建筑的功能维持或快速恢复作为最终目标。构件层次的摇摆机制是实现主体结构功能可恢复的有效途径,但应以构件的抗损性为前提。以钢筋混凝土摇摆柱为对象,比拟弹性半空间局部受载经典拉芒(Flamant)理论,推导摇摆柱轴向应力分布弹性力学解答,以此为基础,假定摇摆柱侧移由柱端接触面转角和柱身弯剪变形引起,建立钢筋混凝土摇摆柱荷载-侧移力学模型,与有限元模拟结果对比验证合理性。开展轴压比和柱端强度分析,结果表明,在柱体抗损的前提下,单纯提高轴压比可提高柱体承载能力,但对侧移能力提升不显著;随着柱端材料强度提升,柱体承载力和侧移能力均显著改善,因此,采用柱端局部增强的方法改善钢筋混凝土摇摆柱工作性能具有可行性。

基于韧性的摇摆桥墩桥梁抗震研究综述

实现地震后桥梁使用功能的快速恢复即基于韧性的桥梁抗震设计方法是当前研究的热点方向.首先,总结基于韧性的抗震设计理论,从摇摆体系、自复位体系、可更换构件体系3个方面展开详细探讨,介绍易损性分析曲线研究的发展阶段.然后,回顾国内外摇摆桥墩可恢复性设计理论与试验研究现状,分析摇摆桥墩在震后恢复上的优势及不同摇摆桥墩体系的特点.最后,归纳现有的计算分析方法,讨论当前基于韧性的桥梁抗震设计研究中的不足和发展趋势.研究结果表明:基于韧性的抗震设计理念及摇摆桥墩在桥梁震后恢复上的优势已得到普遍认可,但仍存在一些问题需进一步研究;基于韧性抗震设计亟待实现韧性指标量化及多道设防指标的梯度控制;摇摆桥墩的关键构造问题有待解决,应注重新材料、新构造形式的开发;现有分析模型忽略了增加耗能装置后的体系阻尼的变化,需进一步研究桥梁抗震性能与韧性耗能复位装置的交互作用.

外置耗能器与复位器的自复位桥墩抗震性能研究

为发展易于实现损伤控制的摇摆自复位(rocking self-centering,RSC)桥墩,选取防屈曲支撑(buckling restrained brace,BRB)作为外置耗能器,弹簧作为外置复位器,设计外置防屈曲支撑与弹簧的自复位(BS-RSC)桥墩。利用Opensees有限元软件建立BS-RSC桥墩的数值分析模型,并验证模型正确性,分析BRB屈服强度、弹簧刚度及轴压比对BS-RSC桥墩滞回性能的影响;进行动力时程分析,研究不同参数对最大墩顶位移角、残余位移角的影响。研究结果表明:BS-RSC桥墩滞回曲线饱满,BRB可显著提升BS-RSC桥墩的耗能能力,控制弹簧刚度可在不影响整体耗能下控制残余位移;进行动力时程分析,在罕遇地震下,桥墩残余位移角处于低值,最大墩顶位移角随着BRB屈服强度的提高而显著降低,说明BS-RSC桥墩是各构件协调工作、功能明确且具有优秀耗能能力与自复位能力的新型桥墩。

基于MC-ICP-MS的地质样品的高精度钾同位素分析方法

近年来,得益于多接收电感耦合等离子体质谱(MC-ICP-MS)的快速发展,钾(K)同位素的分析精度得到显著提升,极大地促进了K同位素地球化学的发展,在示踪大陆风化、壳幔物质循环等方面已经展现出良好的应用前景。目前,样品分离提纯过程繁琐,耗时长,以及ArH^(+)对K的直接干扰导致的分析精度不足依旧是K同位素得到更广泛应用的最大阻碍。在使用盐酸、硝酸以及氢氟酸将样品彻底溶解后,利用装有约2.7 mL AG50W-X8(BioRadTM,200~400目)阳离子交换树脂的定制石英离子交换柱,以及0.5 mol/L硝酸作为淋洗液可以有效地将地质样品中的K与Na、Ti、Mg、Mn、Al、Ca等主要基体元素一次性分离开来,从而有效分离提纯常见地质样品中的K(高Cr样品除外)。在仪器分析方面,为达到最大程度降低测试过程中的ArH^(+)产率以及提高仪器测试的稳定状态,分别采用了高分辨模式、高分辨加连续采集模式以及低分辨下扣除ArH^(+)干扰模式进行测试,结果表明低分辨模式下测试成本较低,测试稳定时间最长且能达到与高分辨率测试相比拟的分析精度(实验室长期精度~0.08‰)。在此基础上测定了一套中国国家岩石标准物质的K同位素组成,得出的K同位素测量值可以为今后不同实验室间的数据对比给出参考。

强采动影响复用巷道墩柱支护技术研究与应用

针对复用巷道服务期间受多次采动影响、围岩变形破坏严重的问题,分析了侧向采动应力对于复用巷道的影响,揭示了复用巷道围岩运移的变形规律以及破坏机理。提出了利用强力墩柱进行巷内补充支护的支护策略,通过建立复用巷道板破断与墩柱支护的力学模型,分析了“煤柱-巷内支护”联合支护体的支护强度,理论计算了墩柱所需满足的支护力载荷要求。以王坡煤矿3306运输平巷为实际背景,分别从支护环境、充填体材料、支护体结构设计以及施工工艺进行了柔模墩柱的设计与应用。现场监测结果表明:复用巷道超前工作面范围内巷道围岩变形量小,影响范围为超前工作面200 m;滞后工作面50 m范围内为变形量快速增长区域,应重点进行维护。强力柔模墩柱巷内支护的方式能够有效缓解复用巷道变形严重问题,维护围岩的稳定性,提高支护效果的同时大大节省支护成本。

石柱木梁架古建筑抗震性能临界状态理论分析

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