Seismic Analysis of Masonry Gravity Dams Using the Discrete Element Method: Implementation and Application

Much research in recent years has focused on the seismic analysis of concrete and earthfill dams, and few works have addressed the case of masonry dams. The structural behavior of masonry dams is controlled essentially by its discontinuous nature, which may induce significant nonlinear response during an intense earthquake. In this article, a numerical tool based on the Discrete Element Method is presented, aimed at the static, dynamic, and hydromechanical analysis of masonry gravity dams. The use of discontinuous models is mandatory for the study of failure mechanisms involving the masonry discontinuities, the dam-rock interface or the rock mass joints. The Discrete Element Method is able to assemble continuous and discontinuous meshes simultaneously in the same model, providing a versatile tool to consider various assumptions and levels of analysis, ranging from simplified to detailed structural representations. A comprehensive study of the seismic behavior of Lagoa Comprida Dam, located in Portugal, is presented. Both continuous and discontinuous models were developed to assess the main failure mechanisms, including overstress, partial and global sliding, and overturning.     

Perceptual images of Conimbriga using High Dynamic Range

It is widely recognized that new technologies can play an important role in the interpretation of our cultural heritage legacy. This has become a powerful tool providing a better understanding of our past, and thereby, allowing us to attain a glimpse of the environments in which our ancestors lived. In this domain, the way we see such reconstructed environments is particularly important in order to establish an accurate interpretation of that historical setting. However, the desired visual accuracy in the representation of any archaeological scenario is strictly related to the technology used to visualize it. High Dynamic Range (HDR) technology encompasses the capacity to produce visual results similar to the visual acuity of the human eye, particularly in extreme lighting conditions, such as bright light or dim environments.     

Early Miocene bivalves from the Cape Melville Formation,King George Island,West Antarctica

Seven species of marine bivalves, including six new taxa, are described from the Cape early Miocene Melville Formation which crops out on the Melville Peninsula, King George Island, West Antarctica. The bivalve assemblage includes representatives of the families Nuculidae, Ennucula frigida sp. nov., E. musculosa sp. nov.; Malletidae, Neilo (Neilo) rongelii sp. nov.; Sareptidae, Yoldia peninsularis sp. nov.; Limopsidae, Limopsis psimolis sp. nov.; Hiatellidae, Panopea (Panopea) sp. cf. P. regularis; and Pholadomyoida (Periploma acuta sp. nov.). Species studied come from four sedimentary sections measured in the upper part of the unit. Detailed morphologic features of nucloid and arcoid species are exceptionally well preserved and allow for the first time reconstruction of muscle insertions as well as dentition patterns of Cenozoic taxa. Known geological distribution of the species is in agreement with the early Miocene age assigned to the Cape Melville Formation. The bivalve fauna from Cape Melville Formation is the best known from Antarctic Miocene rocks, a time of complex geologic, paleogeographic and paleoclimatic changes in the continent. The new fauna introduces new taxonomic and palaeogeographic data that bear on the question of opening of sea gateways and distribution of Cenozoic biota around Antarctica.     

Emergent Complexity,Changing Landscapes,and Spheres of Interaction in Southeastern South America During the Middle and Late Holocene

Newly created academic programs at Brazilian universities have provided the impetus for new archaeological projects in southeastern South America during the last two decades. The new data are changing our views on emergent social complexity, natural and human-induced transformation of the landscape, and transcontinental expansions and cultural interactions across the Río de la Plata basin during the Middle and Late Holocene. We concentrate on six major archaeological traditions/regions: the Sambaquis, the Pantanal, the Constructores de Cerritos, the Tupiguarani, the Southern Proto-Jê, and the middle and lower Paraná River. Diverse and autonomous complex developments exhibit distinct built landscapes in a region previously thought of as marginal compared with cultural developments in the Andes or Mesoamerica. The trajectories toward increased sociopolitical complexity flourished in very different and changing environmental conditions. While some groups were pushed to wetland areas during a drier mid-Holocene, others took advantage of the more humid Late Holocene climate to intensively manage Araucaria forests. The start of the second millennium AD was a critical period marked by an increased number of archaeological sites, the construction of ceremonial architecture, and the intensification of landscape transformation; it also was marked by the rapid expansion of influences from outside the La Plata basin. The Amazonian Tupiguarani and Arawak newcomers brought with them significant changes in technologies and social and political structures, as well as novel landscape management practices.     

Out-of-Plane Seismic Response of Unreinforced Masonry Walls: Conceptual Discussion,Research Needs,and Modeling Issues

ABSTRACT

Modeling unreinforced masonry walls, subjected to seismic loads applied normal to their plane, has received much attention in the past. Yet, there is a general lack of conformance with regard to what aspects of seismic response a computational model should reflect. Boundary conditions are certainly an important aspect, as the response can involve two-way bending or just one-way bending and, in the second case, along vertical or horizontal directions. In this respect, flexural restraint of wall intersections can be significant in addition to size and placement of openings. Moreover, in-plane damage can modify the boundary conditions and the overall out-of-plane performance. Proper modeling of actions is also relevant, as they can be a result of distortions imposed upon wall elements and/or inertial forces along the span of a wall. Axial forces can markedly affect the out-of-plane response of the wall, particularly vertical compressive forces, which can enhance out-of-plane strength. The outcome of static verifications can be more conservative than that of dynamic analyses, but the latter are much more complex to carry out. These topics are discussed with reference to previous research, observations in the field and in the laboratory, as well as numerical analyses on three-dimensional models.     

Simulation of Shake Table Tests on Out-of-Plane Masonry Buildings. Part (IV): Macro and Micro FEM Based Approaches

ABSTRACT

This article presents a study on the out-of-plane response of two masonry structures without box behavior tested in a shaking table. Two numerical approaches were defined for the evaluation, namely macro-modeling and simplified micro-modeling. As a first step of this study, static nonlinear analyses were performed for the macro models in order to assess the out-of-plane response of masonry structures due to incremental loading. For these analyses, mesh size and material model dependency was discussed. Subsequently, dynamic nonlinear analyses with time integration were carried out, aiming at evaluating the collapse mechanism and at comparing it to the experimental response. Finally, nonlinear static and dynamic analyses were also performed for the simplified micro models. It was observed that these numerical techniques correctly simulate the in-plane response. The collapse mechanism of the stone masonry model is in good agreement with the experimental response. However, there are some inconsistencies regarding the out-of-plane behavior of the brick masonry model, which required further validation.     

The world archaeological congress from a critical and personal perspective

Este trabajo trata sobre el contexto epistemológico y político que regula la organización del congreso arqueológico mundial y su historia. WAC introdujó una serie de puntos políticos renovadores, como por ejemplo el código de ética, la participación de los representantes indígenas y regionales, llevando a la arqueología a un nuevo contexto mundial. Como un ex secretario WAC, el autor argumenta por una democracia más profunda en la organización.

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Résumé Cet article aborde le contexte épistémologique et politique qui a mené à l'organisation du Congrès mondiale de l'archéologie et l'histoire de la discipline subséquente. Le CMA a introduit une série de positions politiques, comme un code d'étiques, une représentation régionale et autochtone, ainsi que l'aboutissement de l'archéologie dans une nouvelle étape mondiale. Comme ancien secrétaire du CMA, l'auteur plaide en faveur de l'approfondissement des aspects démocratiques de l'organisation.

     

ROAD INVESTMENTS,SPATIAL SPILLOVERS,AND DEFORESTATION IN THE BRAZILIAN AMAZON*

ABSTRACT Understanding the impact of road investments on deforestation is part of a complete evaluation of the expansion of infrastructure for development. We find evidence of spatial spillovers from roads in the Brazilian Amazon: deforestation rises in the census tracts that lack roads but are in the same county as and within 100 km of a tract with a new paved or unpaved road. At greater distances from the new roads the evidence is mixed, including negative coefficients of inconsistent significance between 100 and 300 km, and if anything, higher neighbor deforestation at distances over 300 km.