An Enhanced Finite Element Macro-Model for the Realistic Simulation of Localized Cracks in Masonry Structures: A Large-Scale Application

ABSTRACT

Finite element macro-modeling approaches are widely used for the analysis of large-scale masonry structures. Despite their efficiency, they still face two important challenges: the realistic representation of damage and a reasonable independency of the numerical results to the used discretization. In this work, the classical smeared crack approach is enhanced with a crack-tracking algorithm, originating from the analysis of localized cracking in quasi-brittle materials. The proposed algorithm is for the first time applied to a large-scale wall exhibiting multiple shear and flexural cracking. Discussion covers structural aspects, as the response of the structure under different assumptions regarding the floor rigidity, but also numerical issues, commonly overlooked in the simulation of large structures, such the mesh-dependency of the numerical results.     

Eratosthenes’ Contribution to Ptolemy’s Map of the World

This article attempts to shed some light on the origins of Ptolemy’s map of the world, which remains a mystery. The premise is that Ptolemy and other ancient geographers largely drew on the same or a similar pool of sources and common beliefs. Similarities between them can, therefore, give us a key to understanding the prehistory of Ptolemy’s map. Comparison of distances on his map with those given by other sources leads to the conclusion that a large area of the map, approximately from the Bosporus to the Indus, reproduced Eratosthenes’ geographical system, with linear distances converted to angular degrees according to Eratosthenes’ own scale. It is argued that this area represents a remnant of an earlier version of Ptolemy’s map. Analysis of latitude and longitude reveals notable differences between Ptolemy’s map and Eratosthenes’ ideas concerning the latitude of Babylon and the Alexandrian prime meridian, and the impact this seems to have had on the shape of neighbouring regions is noted.     

何郢遗址出土青铜器铜矿料来源的初步研究

本文利用地球化学示踪的方法对何郢遗址出土青铜器的铜矿料来源进行了初步研究.采用ICP-AES测试了样品的微量元素,根据元素的地球化学亲和性,探索其在冶炼过程中的化学行为和再分配规律,从而选出对铜绿山和皖南的铜陵、南陵铜矿具有指示意义的特征元素,作为判断其铜料输出路线的综合判别标志.结合文献和地质资料,可初步认为何郢遗址青铜器的铜矿料来自滁县.     

Enhancing Understanding of the Emergence of Global Trade: Analysis of 17th‐ to 19th‐Century Spanish Coins Recovered from Western Australian Shipwrecks Using Laser Ablation – Inductively Coupled Plasma – Mass Spectrometry (LA–ICP–MS)

This research uses legacy data from shipwrecks to further our understanding of global silver movement in the 17th to 19th centuries by analysing a collection of silver coins held by the Western Australian Museum. Three hundred and eighty‐nine silver coins were analysed for their trace element fingerprint in order to identify provenance. The coins are a selection from the ships Batavia, Vergulde Draeck, Zuytdorp, Rapid and Correio da Azia, all wrecked off the coast of Western Australia between 1629 and 1816. Analysis was undertaken using laser ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS), a relatively non‐destructive technique with a sensitivity of parts per million to parts per billion. Data were interpreted using linear discriminant analysis (LDA), which allowed the coins of known provenance to be sorted into identifiable subgroups on the basis of their trace and minor elemental fingerprints, while 27 unidentified coins were compared with this database and their mint of origin predicted. These results have implications for the provenance determination of archaeological artefacts of many materials.     

Modelling the Lost City hydrothermal field: influence of topography and permeability structure

The Lost City hydrothermal field (LCHF) is hosted in serpentinite at the crest of the Atlantis Massif, an oceanic core complex close to the mid‐Atlantic Ridge. It is remarkable for its longevity and for venting low‐temperature (40–91°C) alkaline fluids rich in hydrogen and methane. IODP Hole U1309D, 5 km north of the LCHF, penetrated 1415 m of gabbroic rocks and contains a near‐conductive thermal gradient close to 100°C km^?1. This is remarkable so close to an active hydrothermal field. We present hydrothermal modelling using a topographic profile through the vent field and IODP site U1309. Long‐lived circulation with vent temperatures similar to the LCHF can be sustained at moderate permeabilities of 10^?14 to 10^?15 m² with a basal heatflow of 0.22 W m^?2. Seafloor topography is an important control, with vents tending to form and remain in higher topography. Models with a uniform permeability throughout the Massif cannot simultaneously maintain circulation at the LCHF and the near‐conductive gradient in the borehole, where permeabilities <10^?16 m² are required. A steeply dipping permeability discontinuity between the LCHF and the drill hole is required to stabilize venting at the summit of the massif by creating a lateral conductive boundary layer. The discontinuity needs to be close to the vent site, supporting previous inferences that high permeability is most likely produced by faulting related to the transform fault. Rapid increases in modelled fluid temperatures with depth beneath the vent agree with previous estimates of reaction temperature based on geochemical modelling.     

The functional dimensions of earth oven cooking: An analysis of an accidently burned maize roast at the C. W. Cooper site in West-central Illinois

Abstract

Despite the prevalence of earth ovens, a subclass of pit features used for cooking, there is little consensus regarding how these cooking features were used or about the foodstuffs that were prepared in them. To provide a more detailed understanding of earth oven cooking in the archaeological record, we analyze the archaeobotanical contents, stratigraphy, and morphology of a cooking pit recently excavated at C. W. Cooper, an early Mississippian (a.d. 1150–1200) site in west-central Illinois in order to contribute to research on late Prehistoric foodways. Filled with nearly 100 ears of maize, this earth oven presents the opportunity to document the process of undertaking a maize roast. The volume of maize and its presence within a dense concentration of cooking, processing, and storage facilities allows us to consider the communal nature of outdoor earth oven cooking in the 12th century Central Illinois Valley and the socioeconomic dimensions of commensal politics more broadly during the Precolumbian era.     

A combined visual-geochemical approach to establishing provenance for pegmatite quartz artifacts

A technique for establishing source provenance for pegmatite quartz artifacts was developed using a quarry sample from the Churchill River basin of northern Manitoba and Saskatchewan. Secondary ion mass spectrometry (SIMS) was used to quantify Ti, Ge, Th, and U trace element concentrations and Pb isotope ratios, coupled with qualitative visual characteristics to distinguish between pegmatite quartz from different archaeologically exploited sources in the Churchill River basin region. The technique was also applied to a small sample of quartz artifacts recovered from sites in and around the study area in a preliminary attempt to assign or rule out raw material provenance to characterized sources.     

Inquiry in the Physical Geology Classroom: Supporting Students' Conceptual Model Development

This study characterizes the impact of an inquiry-based learning (IBL) module versus a traditionally structured laboratory exercise. Laboratory sections were randomized into experimental and control groups. The experimental group was taught using IBL pedagogical techniques and included manipulation of large-scale data-sets, use of multiple representations and a physical model and exposure to ill-constrained problems common to the Texas Gulf Coast. The control groups were taught using traditional laboratory activities. The groups were not significantly different prior to exposure. Pre/post-expressed conceptual models and final written reports indicate that the experimental group had greater increases in their conceptual model development of sand-sediment transport.     

OUT-OF-PLANE SEISMIC RESISTANCE OF MASONRY WALLS

Seismic vulnerability of unreinforced masonry buildings is studied by means of simplified out-of-plane collapse mechanisms that take into account connections with transversal walls. According to experimental evidence, the analysis assumes that failure is reached with a rigid body motion of a part of the facade that falls down. Two classes of mechanism are examined: the overturning of the facade due either to a vertical crack at the connection or a diagonal crack on the transversal wall, both defined resorting to a simple model of masonry fabric, viewed as a regular assembly of rigid blocks and elastic plastic joints with friction but no cohesion. The use of simplified mechanisms give rise to an explicit evaluation of the seismic resistance to changes in the geometry and in the masonry fabrics, that could be used by practising engineers. This formulation is developed for both static horizontal actions and ground velocity peak, in the belief that the latter probably gives a better approximation of seismic action, while also providing, by comparison with the results of static forces, an estimate of the behaviour factor for unreinforced masonry. Eventually, the analytical forecasts are compared with numerical results obtained by means of the distinct element method.     

COUPLED P-Y T-Z ANALYSIS OF SINGLE PILES IN COHESIONLESS SOIL UNDER VERTICAL AND/OR HORIZONTAL GROUND MOTION

Various approaches are currently used for the analysis of piles under vertical and lateral loading. Among these, the beam-on-a-nonlinear Winkler foundation (BNWF) approach using published P-y, T-z and Q-z curves is widely used in practice. In this approach, the P-y and T-z responses are generally uncoupled from each other. The objective of this paper is to investigate the influence that the coupling of the P-y and T-z responses has.on the cyclic and dynamic response of piles in cohesionless soil. A cyclic model is first developed and a parametric study is conducted to investigate the effect the initial confining pressure, angle of wall friction and effective vertical stiffness have on the lateral cyclic hysteretic response. A dynamic model is then developed, and used to study the response of a single pile in cohesionless soil under horizontal and/or vertical ground motion. Results from the parametric study showed that the three parameters did not have a significant influence on the lateral cyclic hysteretic response. Under horizontal and/or vertical ground motion, the horizontal ground motion was observed to dominate the inertial interaction response, and significantly affected both the horizontal and vertical displacement response, mainly due to second-order P-Δ and gapping effects.