Identification Technique for Soil-Structure Analysis of the Ghirlandina Tower

Historical towers, in particular medieval towers, are an important part of cultural heritage, and their preservation mandates monitoring and detailed analyses of vulnerability under seismic actions as well as of their long-term performance. Certain aspects of structural nature are linked to the masonry behavior as a unilateral material, and other are aspects related to the interaction with soft soil conditions. This study aims to contribute to the aspects of preservation by exploring the role of the soil-structure interaction in predicting the behavior of the structures, with specific reference to the well-documented case history of the medieval Ghirlandina Tower (Modena, Italy). A significant contribution comes from an experimental identification analysis, performed in the presence of ambient vibration. A novel finding is that the soil structure interaction cannot be neglected, in contrast to most published identification analyses that usually assume the structure to have rigid constraint at base.     

毕仲衍《中书备对》目录的发现及其意义

北宋毕仲衍所修的《中书备对》今已散佚,传世的一些文献尚存其中少数内容。《四库全书》文津阁本《西台集》中收有一篇题名为《毕仲衍〈上编次官制卷目稿札子〉》的奏议。据考证,它是毕仲衍进呈《中书备对》时所上的奏议,与元丰新官制无关。其中的“卷目”,正是《中书备对》的目录。这个目录的发现,对考证此书的卷数、了解该书的内容和辑佚这部残存文献有重要价值。     

Aboriginal Performance on Standardized Tests: Evidence and Analysis from Provincial Schools in British Columbia

Many indigenous populations are experiencing rural-to-urban migration. In making this transition, indigenous peoples are entering industrial societies where most income derives from wages or salaries, and formal educational achievement is crucial in determining economic prospects. This research analyzes the gap in test score results between Aboriginal and non-Aboriginal students in public schools in the Canadian province of British Columbia. It finds a strong effect of school quality, as measured by non-Aboriginal achievement, on Aboriginal achievement. It also finds a nonlinear negative relationship between Aboriginal achievement and the number of Aboriginal students in a school over the empirically observed range. It thus suggests a possible trade-off and dilemma between, on the one hand, policies that enable Aboriginal students to concentrate in a few schools able to provide a culturally sensitive curriculum and, on the other, policies to maximize Aboriginal academic achievement.     

On the frontiers of Europe,not all musket balls were round; accuracy and penetration of various types of military small arms munitions from the mid seventeenth century to the early eighteenth century

While many armies began to adopt large calibre weapons in the seventeenth and eighteenth century, frontier conflicts in the outer reaches of Europe and in North America have provided evidence for the retention of smaller calibres, particularly evidenced through the archaeological recovery of ammunition. Present within these assemblages are various forms of non-standard ammunition — i.e. not round — including bullets with casting sprues still attached at the time of firing. This paper provides an assessment of the combat effectiveness of these various types of ammunition through a series of firing tests using replicated ammunition.     

SHAKING TABLE DYNAMICS: RESULTS FROM A TEST-ANALYSIS COMPARISON STUDY

This paper presents the results of a comprehensive comparison study between the analytically predicted and experimentally identified dynamics of the shaking table system built recently in the Structural Engineering Laboratory at Rice University in Houston, Texas. The primary objectives of the research presented here are two-fold: (1) to shed light into the dynamic performance of asmall-tc-medium size, uni-axial, servo-hydraulic, displacement-controlled shaking table system, and (2) to validate a linearised dynamic model of the system (in the form of the total shaking table transfer function) developed earlier by the authors from basic principles. The analytical model incorporates the inherent dynamic characteristics of the various components of the shaking table system (i.e. controller, servovalve, actuator, test specimen, and reaction mass) and their dynamic interaction.

The test-analysis correlation study performed over a wide range of operating and payload conditions provides useful information on the sensitivity of the shaking table transfer function to control gain parameters and how it can be used to tune the shaking table controller for optimum performance under various payload conditions. The good test-analysis correlation results obtained validate the analytical shaking table model, show its robustness, and provide keen insight into the underlying coupled dynamics of a shaking table system. In order to achieve this good test-analysis correlation, it was crucial to include a time delay in the analytical model of the shaking table system (innovative feature of the model to account for the time lag in the response of the servovalve-actuator system). The expected significant dynamic interaction between payload and shaking table is also confirmed by this study.     

Partitioning chi-square for the analysis of frequency table data: an archaeological application

Archaeologists often wish to compare observed frequency distributions with expectations generated by a model. We describe a technique of partitioning chisquare which yields information about goodness of fit to a model and about homogeneity among populations simultaneously, and which is often superior to other commonly used methods of evaluating frequency data. The technique is demonstrated with data from the Upper Paleolithic rockshelter Le Flageolet I. The results suggest selective raw material use by the Aurignacian occupants.     

Analysis of the Out-Of-Plane Seismic Behavior of Unreinforced Masonry: A Literature Review

Although the issue of the out-of-plane response of unreinforced masonry structures under earthquake excitation is well known with consensus among the research community, this issue is simultaneously one of the more complex and most neglected areas on the seismic assessment of existing buildings. Nonetheless, its characterization should be found on the solid knowledge of the phenomenon and on the complete understanding of methodologies currently used to describe it. Based on this assumption, this article presents a general framework on the issue of the out-of-plane performance of unreinforced masonry structures, beginning with a brief introduction to the topic, followed by a compact state of art in which the principal methodologies proposed to assess the out-of-plane behavior of unreinforced masonry structures are presented. Different analytical approaches are presented, namely force and displacement-based, complemented with the presentation of existing numerical tools for the purpose presented above. Moreover, the most relevant experimental campaigns carried out in order to reproduce the phenomenon are reviewed and briefly discussed.     

传统方法加固馆藏浮放文物抗震性能试验

为探索馆藏浮放文物的有效抗震加固方法,采用振动台试验手段,研究了传统方法加固浮放文物的抗震性能。基于故宫博物院某展柜原型尺寸,制作了1:1比例陈列柜模型。在陈列柜内浮放一轻质陶瓷文物,分别考虑采用砂子、塑料卡、鱼线、橡皮泥及磁铁加固文物,进行了振动台试验。通过白噪声激励,获得了陈列柜基频分布;通过输入不同强度、不同类型的地震波,获得了不同方法加固条件下陈列柜和文物的位移响应、加速度响应和和动力放大系数,评价了不同方法的加固效果。结果表明:陈列柜的基频与输入地震波相差较大,这是陈列柜震害不明显的主要原因之一;传统方法加固文物后,输入地震波的加速度仍有一定放大,但是与加固前文物相比,文物的位移和加速度响应均有所减小,且文物因摇晃幅度而产生倾覆的可能性减小。此外,从减小文物加速度响应峰值角度考虑,橡皮泥和鱼线加固文物效果优于其它方法。试验结果可为文物防震保护研究提供较全面的参考。     

Simulation of Shake Table Tests on Out-of-Plane Masonry Buildings. Part (VI): Discrete Element Approach

ABSTRACT

Although many experimental tests and numerical models are available in the literature, the numerical simulation of the seismic response of existing masonry buildings is still a challenging problem. While the nonlinear behavior of masonry structures is reasonably predictable when the out-of-plane behavior can be considered inhibited, when the in-plane and out-of-plane responses coexist and interact, simplified models seem unable to provide reliable numerical predictions. In this article, taking advantage of the experimental tests carried out in a shaking table on two masonry prototypes at LNEC, a macro-element approach is applied for the numerical simulations of their nonlinear response. The adopted approach allows simulating the nonlinear behavior of masonry structures considering the in-plane and out-of-plane responses. Since it is based on a simple mechanical scheme, explicitly oriented to representing the main failure mechanisms of masonry, its computational cost is greatly reduced with respect to rigorous solutions, namely nonlinear FEM approaches. Two modeling strategies are adopted, namely a regular mesh independent from the real texture of the prototypes and a detailed one coherent with the units disposal. The numerical results are discussed and the correlation between the nonlinear static analyses and the dynamic response is provided.