淮南煤田逆冲叠瓦扇构造系统

淮南煤田推覆构造发育于淮南复向斜南、北两翼。南缘推覆构造更为强烈,规模亦大,系由一系列走向近EW,向S倾斜的逆冲断裂组成。剖面上各断裂上陡下缓,向下逐渐归并于统一的滑脱面,从而构成上叠式逆冲叠瓦扇构造。滑脱面在倾向上及走向上均呈波状变化。北缘的反向逆冲叠瓦扇可能是在南缘逆冲推覆的构造作用下被动产生的。这在宏观、微观及超微观分析中都清晰地得到显示。然而,它们是近于同时形成的。这样就构成了淮南煤田的前缘止于反向断层的逆冲叠瓦构造系统。      

藏北唐古拉山木乃中生代末花岗岩地球化学特征及其构造环境意义

根据花岗岩同源岩浆演化序列,将唐古拉山北坡木乃复式花岗岩体划分为5个单元,归并为木乃超单元。岩石类型依次为紫苏辉石石英二长岩、石英二长岩、二长花岗岩和石英二长斑岩,精确的锆石U—Pb法测年及磷灰石裂变径迹定年表明,它们侵位于晚白垩世晚期,冷却于古新世末。岩石地球化学以贫硅、富钾、贫铝、轻稀土强烈富集、δEu负异常较明显为特征,初始锶同位素比值(^87Sr／^86Sr)为0．706039～0．711251,上述岩石及岩石地球化学和同位素组成揭示了一个壳幔混熔的物源区。研究表明,中生代末花岗岩浆起源于壳幔混熔,为印-亚早期碰撞的产物,属同碰撞-晚造山期壳幔型花岗岩。     

尼泊尔地震中樟木镇自建框架地震灾变机理研究

2015年尼泊尔遭受了4次7级以上大地震灾害,对我国西藏局部地区产生了重大影响。由于我国樟木镇是中尼两国的重要通商口岸,在此区域建造了大量尼泊尔式自建RC框架结构。通过对这些自建框架结构的震害调查,结合其独特的建造方式和结构特点,分析其抗震受灾能力,研究在地震作用下该类框架结构的地震破坏规律和致灾机理。研究结果表明:该类自建框架结构的构件承载能力利用率高,经济效益好,但安全储备小;地震破坏模式主要以框架柱失效和填充墙开裂为主;房屋建造层数对其地震致灾影响较大,该类房屋宜为1~7层;该类建筑结构抗震性能优越,适合在我国低烈度地区推广应用。研究成果对指导我国乡镇自建房屋的抗震规划及建设具有重要意义。     

An enhanced base isolation system equipped with optimal tuned mass damper inerter (TMDI)

In seismic base isolation, most of the earthquake‐induced displacement demand is concentrated at the isolation level, thereby the base‐isolation system undergoes large displacements. In an attempt to reduce such displacement demand, this paper proposes an enhanced base‐isolation system incorporating the inerter, a 2‐terminal flywheel device whose generated force is proportional to the relative acceleration between its terminals. The inerter acts as an additional, apparent mass that can be even 200 times higher than its physical mass. When the inerter is installed in series with spring and damper elements, a lower‐mass and more effective alternative to the traditional tuned mass damper (TMD) is obtained, ie, the TMD inerter (TMDI), wherein the device inertance plays the role of the TMD mass. By attaching a TMDI to the isolation floor, it is demonstrated that the displacement demand of base‐isolated structures can be significantly reduced. Due to the stochastic nature of earthquake ground motions, optimal parameters of the TMDI are found based on a probabilistic framework. Different optimization procedures are scrutinized. The effectiveness of the optimal TMDI parameters is assessed via time history analyses of base‐isolated multistory buildings under several earthquake excitations; a sensitivity analysis is also performed. The enhanced base‐isolation system equipped with optimal TMDI attains an excellent level of vibration reduction as compared to the conventional base‐isolation scheme, in terms not only of displacement demand of the base‐isolation system but also of response of the isolated superstructure (eg, base shear and interstory drifts); moreover, the proposed vibration control strategy does not imply excessive stroke of the TMDI.     

Estimation of element‐by‐element demand‐to‐capacity ratios in instrumented SMRF buildings using measured seismic response

This paper presents a methodology to estimate element‐by‐element demand‐to‐capacity ratios in instrumented steel moment‐resisting frames subject to earthquakes. The methodology combines a finite element model and acceleration measurements at various points throughout the building to estimate time history of displacements and internal force demands in all members. The estimated demands and their uncertainty are compared with code‐based capacity from which probabilistic bounds of demand‐to‐capacity ratios are obtained. The proposed methodology is verified using a simulated six‐story building and validated using acceleration data from California Strong Motion Instrumentation Programstation 24370 during the Northridge and Sierra Madre earthquakes.     

浮式两级缓冲防撞系统及浮体结构构型研究

以浮式两级缓冲防撞系统为研究对象,介绍其工作原理,利用动力学分析软件LS-DYNA构建了碰撞模型并进行了仿真计算,依据仿真结果完成了以阻尼索组与浮体结构构型为主要内容的防撞系统设计。研究确定了阻尼索组的布置位置、材料及数量,为浮体内部结构构型设计了7种比选方案,分别对5 000 t船舶撞击浮体前梁和侧梁的动态过程进行了仿真分析,对比了不同方案及不同板梁厚度下的接触力。研究结果表明:浮体内部构造若选用板梁厚度12 mm的方案6设计,则碰撞发生时浮体前梁和侧梁分别可以稳定地提供10.4 MN和7.9 MN的均值力,以及11.5 MN和8.9 MN的峰值力,设计浮体能够满足整体刚度要求,防撞系统符合双保护原则。防撞系统及浮体结构构型设计为下一步全面开展船舶撞击防撞系统后的动力学响应分析奠定了基础。     

多层空心砌块房屋混凝土结构抗震性测试研究

为了研究多层空心砌块房屋混凝土结构抗震性测试,按照1∶5缩尺比例建造空心砌块房屋混凝土结构模型进行抗震性测试实验。根据实际原型参数遵从相似理论的要求选择模型参数,通过电液伺服加载装置和液压千斤顶加载水平、垂直方向荷载,对所建造模型进行动力特性测试、地震反应分析、结构最大地震反应以及位移响应进行了实例分析。结果表明,随着破坏程度加大,模型结构自振频率随之减小,阻尼比随之增大;有芯柱多层空心砌块房屋模型的抗震效果较强;强震状态下,结构动力特性变化较大,破坏层聚集了房屋结构的最大反应;当加速度为125 cm/s时,结构最大位移为2.73 mm,低于规范值,模型结构具备一定延性。     

Earthquake‐induced structural response output‐only identification by two different Operational Modal Analysis techniques

Output‐only system identification is developed here towards assessing current modal dynamic properties of buildings under seismic excitation. Earthquake‐induced structural response signals are adopted as input channels for two different Operational Modal Analysis (OMA) techniques, namely, a refined Frequency Domain Decomposition (rFDD) algorithm and an improved Data‐Driven Stochastic Subspace Identification (SSI‐DATA) procedure. Despite that short‐duration, non‐stationary, earthquake‐induced structural response signals shall not fulfil traditional OMA assumptions, these implementations are specifically formulated to operate with seismic responses and simultaneous heavy damping (in terms of identification challenge), for a consistent estimation of natural frequencies, mode shapes, and modal damping ratios. A linear ten‐storey frame structure under a set of ten selected earthquake base‐excitation instances is numerically simulated, by comparing the results from the two identification methods. According to this study, best up‐to‐date, reinterpreted OMA techniques may effectively be used to characterize the current dynamic behaviour of buildings, thus allowing for potential Structural Health Monitoring approaches in the Earthquake Engineering range.     

供给侧改革与科技创新耦合助推西藏渔业资源养护

由于西藏生态环境脆弱、生态系统结构简单、生产力低下以及高原鱼类生长缓慢、资源补充周期长、对生境高度适应和依赖等特点,高原水域水生生态更容易受到外界的影响.尤其近几十年以来,外来鱼类入侵、水电水利设施的兴建、过度捕捞、水质环境恶化,导致162种青藏高原鱼类中,处于极危、濒危、易危或野外绝灭鱼类就有35种,超过了20%,在雅鲁藏布江中游,常见的6种裂腹鱼类中,有3种鱼类处于濒危状态,因此推动西藏渔业资源养护刻不容缓.供给侧改革和科技创新,将为西藏渔业资源养护注入新的活力.通过科学引导放生行为,规范和加强增殖放流行为,积累和推广本土鱼类繁育技术,密切关注西藏水生态系统,将会推动西藏渔业资源养护工作迈上一个新台阶,也会助推西藏"精准扶贫"进程.     

Dynamics of rocking podium structures

A rocking podium structure is a class of structures consisting of a superstructure placed on top of a rigid slab supported by free‐standing columns. The free‐standing columns respond to sufficiently strong ground motion excitation by uplifting and rocking. Uplift works as a mechanical fuse that limits the forces transmitted to the superstructure, while rocking enables large lateral displacements. Such ‘soft‐story’ system runs counter to the modern seismic design philosophy but has been used to construct several hundred buildings in countries of the former USSR following Polyakov's rule‐of‐thumb guidelines: (i) that the superstructure behave as a rigid body and (ii) that the maximum lateral displacement of the rocking podium frame be estimated using elastic earthquake displacement response spectra. The objectives of this paper are to present a dynamic model for analysis of the in‐plane seismic response of rocking podium structures and to investigate if Polyakov's rule‐of‐thumb guidelines are adequate for the design of such structures. Examination of the rocking podium structure response to analytical pulse and recorded ground motion excitations shows that the rocking podium structures are stable and that Polyakov's rule‐of‐thumb guidelines produce generally conservative designs. Copyright © 2017 John Wiley & Sons, Ltd.