Assessment of Effects of Reductions of Lateral Stiffness along Height on Buildings Modeled as Elastic Cantilever Shear Beams

A simplified model useful for assessing economic losses due to moderate seismicity events in urban areas has been developed by studying the behavior of buildings before yielding their structural system, allowing for nonuniform stiffness along their height. In particular, buildings are modeled as cantilever shear beams with uniform mass and parabolic reduction of lateral stiffness. This particular stiffness distribution is relevant, as it could be expected to occur in buildings where earthquake action is a critical structural design criterion. The equation of motion governing the dynamic behavior of the proposed model is solved analytically, finding mode shapes in terms of first and second zero-order Legendre functions. The solution is verified by comparing it with results obtained from fine mesh finite element models. The effect of reducing the lateral stiffness is then studied in the first five modes of vibration. Results include modal periods, mode shapes, modal participation factors, and derivatives of mode shapes. In general, it is found that effects of reduction of lateral stiffness in mode shapes are moderate when the lateral stiffness in the free end is smaller than about seventy percent of the lateral stiffness at the fixed end, but become significant for larger reductions. Effects are particularly important for the derivative of the mode shapes, which could play a significant role in estimating interstory drift demands in buildings. Model usefulness is showcased by analyzing a test case where both acceleration and drift demands are assessed by considering uniform beams and beams with parabolic stiffness variation, finding notable improvements by considering the latter.     

Controlled Rocking CLT Walls for Buildings in Regions of Moderate Seismicity: Design Procedure and Numerical Collapse Assessment

Controlled rocking heavy timber walls are designed to rock on their foundations in response to earthquakes. For regions of moderate seismicity, it is proposed that this rocking behaviour can be adequately controlled using only post-tensioning, even with a large force-reduction factor and no supplemental energy dissipation. This article presents a force-based design procedure for controlled rocking cross-laminated timber walls without supplemental energy dissipation, including a method for estimating higher mode effects. Fragility analyses of three prototype walls demonstrate that the procedure can limit the probability of collapse to <10% during a maximum considered earthquake in a region of moderate seismicity.     

宋代官员墓葬相关问题刍议

从现有考古材料来看,与前代相比,宋代墓葬体现的等级制度并不明显,而官员墓葬似恰是造成这一状况的原因.原本应当尊奉制度、为民表率的官员群体中,有很大一部分官员并未向下传递上层的丧葬文化,反而被出身之地或归葬之所的富裕平民阶层同化.由此使其地下墓葬部分呈现出“地方化”的特征.而这一情形,所反映的可能是两宋时期,民间经济力量...     

把创先争优与学习型党组织建设结合起来

当前,学习型党组织建设和创先争优活动正在全党深入开展,正确认识和把握两者结合的根据、内容和实现,对于在实践中促进和实现两者的结合,使之相互促进、相得益彰,具有重要意义。创先争优与学习型党组织建设结合的根据在于两者本质属性相同、根本目标一致、活动内容交叉和活动功能互动;结合的内容包括总体要求、主要内容、方式方法、组织领导等方面;结合的实现最重要的是要落实到争当优秀共产党员上来。     

Comparison of Numerical and Experimental Seismic Responses of FREI-Supported Un-reinforced Brick Masonry Model Building

Comparative study of numerically and experimentally obtained seismic responses of un-reinforced masonry building supported on in-house designed un-bonded fibre reinforced elastomeric isolator (U-FREI) are presented in this article. The effectiveness of U-FREI is established very clearly in terms of controlled dynamic response of the model building. Experimental studies are carried out on a shake table with elaborate instrumentations for measurement of acceleration and displacements at different floor levels. Numerical study of the model building supported on U-FREI is carried out to compare the results with experimental investigation. Multi-linear pivot hysteretic plasticity model is used to simulate the behavior of FREI, while plate elements are used for brick-masonry walls. Experimentally obtained force-displacement curves of FREI are used for defining the properties of multi-linear model representing FREI. The dynamic responses obtained from the numerical studies are compared with those from experimental investigations. This study indicates that the seismic responses of building supported on U-FREI can be numerically evaluated with quite reasonable accuracy. A good numerical model can be judiciously used at the preliminary design stage, followed by actual testing and construction of the base isolated building.     

领略贵州古村落风韵

引言：最近,受清华大学陈志华、李秋香两教授的邀请,我参与《中华古村落》大系的编撰工作。每省一卷,我承担贵州卷。每卷收录20个古村落,每个村落3000字,20幅照片。另外,写一篇一万字的《分卷序》。在此基础上,我撰写了《领略贵州古村落风韵》一文,主要介绍贵州古村落的自然环境、历史流年、地域特点、民族特色、美丽外观、鲜明个性、丰富的内涵等等。     

The Politics of Sources Meets the Practices of the Librarian: An Interview with Esther Chen**

[I] want to single out one phenomenon that could be called the ‘politics of sources’. It points to the extent to which the histories that both scientists and historians can write are artifacts of the available sources. The Rockefeller Foundation not only opened its archives very early on for historical work but also invested a lot in making the archives readily available for historical exploration. During the 1980s, many young historians took advantage of this opportunity. Thus, in a relatively early phase of the professional historiography of molecular biology, one could have gained the impression that the development of the new biology as a whole was a bio-politically directed enterprise of the Rockefeller Foundation sustained by the vision that social processes could ultimately be controlled by biological processes.     

Evaluating effects of chemical weathering and surface contamination on the in situ provenance analysis of building stones in the Cuzco region of Peru with portable XRF

As the only type of instrument capable of determining artifact geochemistry in a wide variety of settings, portable X-Ray Fluorescence (PXRF) may be frequently utilized as probably the best option for collecting data when removal of objects in part or in whole is unfeasible. However, using PXRF in circumstances where sample selection and preparation diverge from standards developed for lab-based instrumentation requires assessing the impact of new and potentially limiting factors to establish the validity of the method in these new contexts. Here we examine the effects of surface contamination and chemical weathering on the ability to assess provenance of igneous building stones used in the Cuzco region of Peru. Surface contamination was assessed through comparing low-impact cleaning methods on diorite and andesite blocks, and weathering was examined by comparing weathered vs. fresh surfaces of samples from two andesite quarries. In general, the lightest elements were most impacted by contamination and weathering while measurements of many of the heavier elements commonly used in provenance studies were relatively unaffected. Concentrations of Pb and Zn were problematic in the urban context of Cuzco because of pollution. Ability to determine provenance of building stones within those limitations (i.e., the validity of this application of PXRF) was demonstrated in a preliminary study by comparing measurements from uncleaned, exposed building stones in the region to fresh quarry samples.     

浅谈新闻媒体在构建和谐社会中的作用

构建和谐社会,新闻媒体肩负着重要的职责。做好构建和谐社会的舆论宣传工作,新闻媒体必须进一步挖掘潜能,提高宣传质量和舆论引导水平,更好地为构建和谐社会提供强大的舆论支持。     

Muslims' nation‐building process in socialist Bosnia and Herzegovina in the 1960s

During the 1960s, the Yugoslav Socialist authorities gradually recognised Bosnia and Herzegovina's Muslims as a nation. Interestingly, in the 1940s, the Yugoslav Communist leaders refused to consider Muslims even as an ethnic group and saw them only as a religious community whose members had to designate themselves as Serbs or Croats. Why did the regime decide to recognise Muslims as a nation in the 1960s, whereas 20 years earlier they supported the opposite position? To understand the shift, this nation‐building process must be understood as the result of a dual dynamic on the federal and the republican level, where important changes occurred. At the federal one, the Communist authorities initiated a decentralisation process within the context of Yugoslav self‐management in the 1950s, which significantly reinforced the republic elites. This coincided with the resurgence of the national question in the whole of Yugoslavia. Simultaneously, in Bosnia and Herzegovina, a new elite progressively rose to power in the 1960s and put the ‘Muslim question’ on the political agenda. This led to the gradual increase in status of the Muslims from a religious community to an ethnic group at the beginning of the 1960s and then to a nation at the end of the decade.