Simple Seismic Assessment of Traditional Unreinforced Masonry Buildings

A framework for quick seismic assessment and retrofit of traditional unreinforced masonry (URM) structures is presented. The proposed methods build on simple principles of structural dynamics and are used as an alternative to detailed time-history analysis, in recognition of the prevailing need for simple and practical methods, compatible with the low-budget and the limited level of knowledge regarding materials, internal force paths, connectivity and condition of older URM structures. An objective is to identify areas in the building that are particularly susceptible to damage and for guiding the types of the required global interventions to improve seismic response. Demand and supply are expressed in terms of relative drift ratios that quantify the intensity of out-of-plane differential translation and in-plane shear distortion of masonry walls. A characteristic traditional building type of timber-laced masonry is used as a model structure for illustration of concepts. The morphology and geometry of the building correspond to a statistical sample of the actual traditional unreinforced masonry buildings (TURM) found in historical centers of many towns in the greater region of Northern Greece. The methodology is particularly useful for setting retrofit priorities and management of the collective seismic risk of historical entities.     

MODELLING OF RC MEMBERS UNDER CYCLIC BIAXIAL FLEXURE AND AXIAL FORCE

A model is proposed for the incremental force-deformation behaviour of reinforced concrete sections and members, under generalised load or deformation histories in 3D, including cyclic loading, up to ultimate deformation. At the section level the model is of the Bounding Surface type and accounts for the coupling between the two directions of bending and between them and the axial direction. For the construction of the member tangent flexibility matrix on the basis of the section tangent flexibility matrix, a piecewise-linear variation along the member is assumed for the nine terms of the tangent section flexibility matrix. Model parameters are derived on the basis of available test results for: (a) the force-deformation response under cyclic biaxial bending with normal force; (b) the hysteretic energy dissipation; (c) the secant-to-yield member stiffness, and (d) the ultimate deformation of the member under cyclic biaxial load paths.     

基于古建木构文物修缮的木材抗弯性能实验研究

受自然作用、人为因素及材性退化的影响,已有数百年甚至千年历史的古建筑木结构构件及斗栱节点存在不同程度的损伤,需进行合理修缮加固。而在木结构修缮选材中,抗弯弹性模量是需要考虑的一项重要指标。为了找到更合适的古建筑修缮加固用材,本研究选用五种木材进行横纹径向、弦向和斜向抗弯测试,采用力学试验机以及自制的力传感器通过电阻应变采集仪分别记录了五种木材所受力和位移的关系,然后按荷载与位移的关系分别计算出各自的抗弯弹性模量。通过对五种木材抗弯弹性模量的测量与分析,比较了相同含水率的木材抗弯弹性模量随密度的变化情况。试验表明:同种木材不同受弯方向抗弯弹性模量差异较大;与其他木材相比,落叶松不同受弯方向的平均抗弯弹性模量高于其他木材;木材的抗弯弹性模量有随密度增加而增加的趋势。此试验结果可为今后古建木结构的维修与加固以及构件替换提供参考。     

In the Shadow of the 1919 Total Solar Eclipse: The Two British Expeditions and the Politics of Invisibility**

This paper addresses the legendary total solar eclipse of 29 May 1919. Two British teams confirmed the light bending prediction by Albert Einstein: Charles R. Davidson and Andrew C. C. Crommelin in Sobral, Brazil and Arthur S. Eddington and Edwin T. Cottingham on the African island of Príncipe, then part of the Portuguese empire. By jointly analyzing the two astronomical expeditions supported by written and visual sources, I show how, despite extensive scholarship on this famous historical episode and the historiographical emphasis on the plural dimensions of knowledge construction, many human and non-human actors have been kept in the shadow of the eclipse. I do so by focusing on what I call knowledge from the periphery together with knowledge from below, grounded literally on how localities (sites) affect choices and events, and growing outward to encompass a wide range of participants. I show how the geopolitical status of the two nations where the observational sites were located, and specifically Portugal's condition of colonial power, affected main decisions and events, while highlighting the active role of participants, ranging from experts from the peripheries and those involved in the travels to local elites and anonymous peoples, some of whom contributed to the observation of totality.