高堆石坝土工格栅抗震加固效果分析

强震区高堆石坝坝顶堆石体常由于地震加速度放大效应处于不稳定状态,目前比较经济有效的抗震措施是在坝顶一定范围内加筋来提高堆石体的强度和自稳能力。土工格栅以其与土石体相互作用的优越性而被广泛运用于土石坝坝顶抗震加固工程。以 240 m 高长河坝心墙堆石坝为例,分析土工格栅对强震区坝顶堆石体的抗震加固效果。运用时程法对加筋坝体进行动力反应分析,利用动力响应应力结果并结合 Newmark 滑块法理论,采用滑面应力分析有限元法对加筋限制高堆石坝地震永久变形的工程效果进行研究和探讨。结果表明,动力作用下格栅所受最大拉力远小于其抗拉强度,且加筋基本不影响坝体动力反应结果。可一旦坝坡发生滑移,加筋能使地震永久位移减少 40% ～ 50% ,有效限制坝顶堆石体侧向滑移,提高了坝体抗震稳定性。抗震稳定性又对加筋长度与竖向加筋间距敏感,较适宜的加筋长度及间距分别为 40 ～ 60 m 和 1 ～ 4 m 。     

"土袋"在日本软土地基加固中的应用与分析

近年来,土工合成材料在加筋土工程中得到了广泛的应用,目前常规的设计方法是在土层中水平布设加筋材料,如土工织物、土工网、土工格栅等.介绍了目前在日本应用的一种新的结构形式,即采用加筋材料包裹土体--"土袋"加固软土地基的方法,并从试验和理论两个方面介绍了土袋的加固机理.列举了土袋在日本铁路基床加固、房屋软土地基处理、修筑挡土墙及导流堤坝的应用实例.     

Earthquake damage to and aseismic measures for earth-sheltered buildings in China

This paper discusses the behavior of earth buildings during the high level of seismic activity in China since the 1960s, aseismic measures for earth buildings, and proposed construction in the seismic region of China. The authors discuss damage characteristics and recommended aseismic measures for three basic types of structures: (1) those with adobe bearing walls; (2) structures with adobe arched roofs; and (3) cave dwellings. The paper concludes with a discussion of prospects for these types of earth architecture in China.     

工程结构可靠性基本理论的发展与应用(3)

自20世纪20年代以来,工程结构可靠性理论和应用的研究已取得了重大进展。本文根据大量的文献,从结构可靠性基本理论和方法、结构体系可靠度、结构可靠度的Monte-Carlo模拟方法、结构承载能力与正常使用极限状态可靠度、结构疲劳和抗震可靠度、钢筋混凝土结构施工期和老化期可靠度六个方面,分三部分对结构可靠性理论和应用国内外研究的现状进行了概括性总结,以期为我国在这方面研究的进一步发展提供一个参考。本篇是其中的第三部分,主要介绍了结构抗震可靠度,以及钢筋混凝土结构施工期和老化期可靠度研究和应用的发展。     

建筑结构震害预测方法研究评述

对现有的建筑结构进行具体分类,针对不同结构类型在地震作用下的受力特点和破坏机理,并结合现行规范的规定,系统详细地总结了相应的震害预测方法。所作的工作对于进行抗震防灾规划和震害预测工作具有较好的参考意义。     

Seismic Earth Pressure Exerted on Retaining Walls Under a Large Seismic Load

In recent years, serious damage has been done to retaining structures because of large earthquakes. In order to establish practical methods for evaluating the seismic earth pressure, which is one of the important external forces acting on retaining structures during large earthquakes, a series of shaking table tests was conducted on retaining wall (RW) models. The experiments revealed that the seismic active earth pressure was considerably smaller than that obtained by the Mononobe-Okabe theory, particularly under a large seismic load. Furthermore, it was demonstrated that the seismic earth pressure had an upper limit, which was determined by the force equilibrium of the soil wedge at the critical state when the RW lost its stability. On the basis of the test results, a new method to evaluate the seismic earth pressure for practical designs under a large seismic load has been suggested. This proposed method provides a reasonable earth pressure as well as an angle of failure plane, those of which depend on the seismic stability of the retaining wall. It has been confirmed that earth pressure obtained by the proposed method agrees well with the measured seismic earth pressure exerted on several retaining walls with different degrees of stability.     

高烈度地区高层建筑错层剪力墙结构抗震性能分析

错层结构对抗震不利。结合一幢高烈度区的钢筋混凝土剪力墙错层高层建筑,采用静力弹塑性推覆分析以及动力弹塑性时程分析方法,研究了结构在设计小震、中震以及大震作用下的变形特征、构件屈服机制及结构破坏模式,揭示出结构中可能存在的抗震薄弱部位,给出了结构在罕遇地震作用下抗震性能的评价,并提出了对同类工程结构设计有益的建议。     

浅谈学校抗震加固设计

针对抗震加固设计的重要性,分析了现有建筑物存在的问题,介绍了抗震结构整体性抗震加固方法,探讨了结构加固方案的优选,以积累技术人员的抗震加固设计经验,确保建筑物的安全。     

地铁车站的抗震分析研究

地铁结构抗震分析是地铁结构设计的重要组成内容.本文简要阐述三种抗震计算方法,将反应位移法理论应用于厦门市轨道交通1号线一期工程中山路西站车站结构的地震反应分析,计算结果表明：在中震作用下,车站的中柱轴压比未超过0.85的限值,结构最大层间位移比均小于1/550,可以认为结构处于弹性工作阶段,构件截面及配筋均满足抗震计算要求;在大震作用下,车站弹塑性层间位移未超过1/250的弹塑性层间位移限值,可以认为结构局部处于弹塑性工作阶段;最后提出抗震构造措施.本文研究方法和研究成果对地铁车站结构抗震设计具有指导意义.     

浅析校舍抗震加固技术现状及发展趋势

为贯彻执行《中华人民共和国防震减灾法》,特别是汶川、玉树大地震后,我国中小学校舍抗震设防标准随之大幅度提高.校舍抗震加固工程体量浩大、情况复杂、时间紧、要求高.文章针对校舍抗震加固工程的现状,存在问题及发展趋势,进行了分析并提出对策和建议.     

基于性能的既有建筑防屈曲支撑抗震加固设计

对于抗震能力低、抗震构造措施普遍不满足现行规范的原非抗震设防区既有建筑,采用消能减震技术加固结构,通过性能化设计方法实现抗震加固目标,可以解决传统加固方法效率低、难以实施等难题。以原非抗震设防区某既有框架结构教学楼加固项目为例,介绍了采用耗能防屈曲支撑提高抗震性能的具体方法和既有建筑基于性能的抗震加固设计流程。结果表明:加固前结构单体中最大的扭转周期比达到了0.96,最大位移比为1.38, 加固后扭转周期比控制为0.84,最大位移比为1.20; 加固前结构小震下构件承载力基本满足要求,但扭转周期比和抗震构造措施不满足现行规范要求,大震下结构会发生严重破坏甚至倒塌; 加固后结构构件承载力能满足7度小震(多遇地震提高1度)要求,小震下防屈曲支撑调整结构抗扭刚度,减小扭转效应,大震下防屈曲支撑屈服耗能,显著提高了结构的抗大震性能; 当结构的抗震性能明显提高时,抗震构造措施要求可适当降低。     

花凉亭水库砂壳坝的抗震性能分析与加固研究

经过对花凉亭水库黏土心墙砂壳坝进行地质勘察取样试验和液化分析,由于其上游坝坡砂土密实度不够,在7度地震时,水下部分可能发生液化并产生滑坡,需要进行抗震加固处理。我国目前已进行过抗震加固的土石坝不多,工程经验较少,还没有成熟的加固设计方法和技术规范。本工程应用砂土动强度试验成果,采用动力有限元分析对大坝抗震加固方案进行技术论证,并提出了帮坡压重的抗震加固方案,即在上游坝坡的水下部分抛块石帮坡压重和水上部分填筑石渣料帮坡压重,有效解决了水库蓄水条件下的大坝上游坝坡的抗震加固问题,其经验可供类似工程借鉴。     

Implementation of an Active Mass Driver Using Acceleration Feedback Control

Abstract: Most of the current research on active structural control for aseismic protection has focused on either full-state feedback strategies or velocity-feedback strategies. However, accurate measurement of the necessary displacements and velocities of the structure is difficult to achieve directly, particularly during seismic activity. Because accelerometers are inexpensive and can readily provide reliable measurement of the structural accelerations at strategic points on the structure, development of control methods based on acceleration feedback is an ideal solution to this problem. Recent studies of active bracing and active tendon systems have shown that H₂/LQG frequency domain control methods employing acceleration feedback can be used effectively for aseismic protection of structures. This paper demonstrates experimentally the efficacy of acceleration-feedback–based active mass driver (AMD) systems in reducing the response of seismically excited structures.     

Geosynthetics reinforcement application for tsunami reconstruction: Evaluation of interface parameters with silty sand and weathered clay

Great attention is directed to rebuild livelihoods and rehabilitate coastal communities affected by the Tsunami in the Indian Ocean in South Asia. It takes years of effort of different engineering disciplines to recover from recent devastations caused by the Tsunami. Geosynthetics can play important and vital roles in the protection, mitigation and rehabilitation efforts in affected coastal areas. Geosynthetics can be applied for reinforcement, filtration, drainage, protection, lining, and containment. Particularly, geotextiles can be used effectively for erosion protection and for reinforcement of earth embankments to resist failure during the occurrence of earthquakes associated with tsunami. Presented in this paper is the interaction behavior at pullout interfaces of high strength geotextile confined in weathered clay and silty sand. The interface parameters which are needed for both finite element and conventional analyses of geotextile-reinforced earth structures such as the local shear stress/shear displacement, the interface interaction coefficient and the in-soil stress/strain of the reinforcement have been successfully interpreted by the newly proposed method considering the softening behavior and non-uniform distribution of shear stress along the extensible reinforcement. Results from this study indicate that the interpretation of pullout tests using conventional methods underestimated both the shear stiffness and the peak shear strength at the pullout interface of extensible reinforcement.     

彭山体育馆的抗震加固

近年来地震频发,2010年国家颁布了新的抗震规范,根据《防震减灾法》的有关要求需对新规范颁布之前修建的既有体育馆进行抗震分析与鉴定加固。同时,体育馆由于空间大、可容纳人数多等优点已渐渐成为重要的避难场所。为此,开展对既有大跨度体育馆进行动力时程分析与抗震加固的研究,对其能否作为抗震区域紧急避难场所的建筑物有着重要意义。汶川地震之后的鉴定过程中,一些既有大跨度钢结构体育馆建筑在设计上暴露了一些问题,如抗震性能差、钢柱倾斜过大、结构锈蚀严重等问题。通过对20世纪80年代建设的彭山体育馆抗震加固前后的动力时程分析,探讨柱间侧向支撑对柱端位移和柱底剪力的影响,指出侧向支撑在大跨度体育馆钢结构中的重要性。     

汶川地震中道路边坡工程震害分析

 发生在山区的地震对边坡工程所造成的危害,在致灾机制和破坏形式方面具有鲜明的特征。结合汶川地震灾区道路边坡工程震害实例,分析路堑、路堤以及与桥隧相连的各类边坡及相应支挡结构的震害机制和破坏形式。锚索(杆)地梁或预应力锚索抗滑桩加固的边坡具有较好的抗震性能,其原因是这些结构已与坡体联接在一起而形成一个整体,在地震波作用下结构与坡体的位移和变形能够很好地协调一致。铺设土工格栅或施加加筋材料的路堤边坡工程具有较好的抗震性能,一般填筑路堤特别是高路堤,其抗震性能较差。根据沙土液化和软弱黏性土层震陷造成的震害实例,提出含水沙质地层路堤边坡应注意坡脚沙土液化造成的震害,应采取措施防止软弱黏性土层地基震陷造成路面破坏以及坡脚震陷造成的边坡失稳。山区隧道洞口边、仰坡的抗震设计应重视支挡结构的耐震性。建于坡体上的桥台、桥基和桥路过渡段的安全性与坡体稳定性直接相关,应切实加强这些结构所在边坡的抗震设计。对于依山傍水而建的顺河桥,相关边坡的失稳危害桥梁时,应对其采取抗震措施。目前公路、铁路工程抗震规范涉及边坡工程及支挡结构的内容极少,研究成果可为规范的修改和补充提供有益的参考。     

工程结构可靠性基本理论的发展与应用(2)

自20世纪20年代以来,工程结构可靠性理论和应用的研究已取得了重大进展。本文根据大量的文献,从结构可靠性基本理论和方法、结构体系可靠度、结构可靠度的Monte-Carlo模拟方法、结构承载能力与正常使用极限状态可靠度、结构疲劳和抗震可靠度、钢筋混凝土结构施工期和老化期可靠度六个方面,分三部分对结构可靠性理论和应用国内外研究的现状进行了概括性总结,以期为我国在这方面研究的进一步发展提供一个参考。本篇是其中的第二部分,主要介绍了结构承载能力和正常使用极限状态可靠度,以及结构疲劳可靠度研究和应用方面的发展。     

地基条件对挡土墙地震土压力影响的振动台试验研究

地震土压力研究是挡土墙抗震设计的核心内容。汶川地震震害调查发现建于土质地基上的挡土墙较建于岩质上的更易发生震害,因此,研究地基条件对挡土墙地震土压力的影响是十分必要的,然而目前许多国家的铁路或公路抗震设计规范中未包含地基条件对挡土墙地震土压力的影响。鉴于此,为了深入了解地基条件对挡土墙地震土压力的影响,利用大型振动台试验这一最能直接反映地震响应特征的动力研究手段,就地基条件对挡土墙地震土压力的分布形式、合力大小、合力作用点位置的影响开展研究,并把实测结果与几个国家的抗震设计规范进行了对比,提出了挡土墙的抗震设计建议。     

Bruchmechanik als Komplementärmethode zur Bestimmung der Restnutzungsdauer alter genieteter Stahlbrücken in Rumänien

Fracture Mechanics as a complementary method for determination of service life of old riveted steel bridges in Romania. A majority of existing railway steel bridges that has been built at the beginning of 20^th century are riveted structures. Many of the bridges are still in operation after several phases of repair and strengthening. The problem of the structures is the assessment of the present safety for traffic loads and the remaining service life. Replacement with new structures raises financial, technical and political problems. Along with the classical method of damage accumulation, a new approach based on the fracture mechanics principles is proposed. The paper includes a general presentation of the verification methods and a case study. In the following investigations of the old riveted railway steel bridge over the Mures River in Arad are presented. This structure has been dismantled in 2000, after 88 years in operation. Therefore a detailed analysis on main structural elements could be made. Many similar structures with the same age are still in operation. The conclusions can be extended to other countries from Middle and Southeast Europe, where the situation of the existing bridges is comparable.     

防落梁装置及其在宿新高速工程中的应用

如何提高桥梁在地震中的抗震、安全性一直以来是个研究重点,本文介绍了防落梁装置的作用原理及特点,以及通过其在某工程中的应用说明了其应用性,作为桥梁的二次防护系统,加大其应用对国内桥梁的安全性提高具有重要的意义。