Soluble Salts Amplify the Effect of Small Heterogeneities in the Structure of Porous Building Materials During Drying

Salt crystallization is a major cause of degradation in old buildings. One of the issues that stills need clarification is regarding the influence of the salts on the capillary absorption and subsequent drying of porous building materials. This article presents an experimental study that included capillary absorption and evaporative drying tests on two types of material (lime mortar and ceramic brick) using pure water or saturated solutions of six salts (sodium chloride, sodium sulfate, sodium nitrate, sodium carbonate, potassium nitrate, or potassium carbonate). The results of capillary absorption agree only roughly with the linear relationship, predicted by theory, between sorptivity and the square root of the ratio between viscosity η and surface tension σ of the solution (σ/η)^1/2. This poor agreement is probably due to material heterogeneity. The drying dynamics was regular and showed little dispersion between specimens, but only for the uncontaminated materials. Indeed, the drying dynamics of the salt contaminated materials was often irregular or diverged among similar specimens, and the same happened with their salt decay patterns. The main conclusion is that soluble salts can amplify the effects on drying of the small structural heterogeneities that porous building materials normally depict.     

Design and Analysis of Cross Vaults Along History

The history of cross vaults began almost 2,000 years ago with a widespread use during the Middle Ages and Renaissance, becoming nowadays one of the most diffused and fascinating structural typologies of the European building cultural heritage. However, conversely to the undeniable excellence achieved by the ancient masons, the structural behavior of these elements is still at the center of the scientific debate. In this regard, with the aim of reviewing the knowledge on this subject as a concise and valuable support for researchers involved in conservation of historical buildings, with a focus on design rules and structural analysis, the present study firstly introduces the cross vaults from a historical perspective, by describing the evolution of the main geometrical shapes together with basic practical rules used to size them. Then, the article deals with the subsequent advancements in structural analysis methods of vaults, until the development of modern limit analysis.     

The Holy War in Syria: Cemal Pasha and the Ottoman Plan to conquer Egypt in the First World War

This article aims to analyse the importance of the Egyptian campaign to Ottoman policy in the First World War. It seeks to add to our knowledge of the Ottoman war experience by putting the focus on the empire’s preparations for conquering Egypt and by giving priority to understand the aims of the expedition. The expedition itself is placed within the context of the jihad policy adopted at the beginning of the war and which sought to put an end to the Entente’s colonial domination of Muslim countries. The Ottomans’ propaganda initiatives in support of the measures were meant to motivate support among the Syrian population through the idea of holy war.     

Dacura: A new solution to data harvesting and knowledge extraction for the historical sciences

New advances in computer science address problems historical scientists face in gathering and evaluating the now vast data sources available through the Internet. As an example we introduce Dacura, a dataset curation platform designed to assist historical researchers in harvesting, evaluating, and curating high-quality information sets from the Internet and other sources. Dacura uses semantic knowledge graph technology to represent data as complex, inter-related knowledge allowing rapid search and retrieval of highly specific data without the need of a lookup table. Dacura automates the generation of tools to help non-experts curate high quality knowledge bases over time and to integrate data from multiple sources into its curated knowledge model. Together these features allow rapid harvesting and automated evaluation of Internet resources. We provide an example of Dacura in practice as the software employed to populate and manage the Seshat databank.     

Task-Specific Sites and Paleoindian Landscape Use in the Shaw Creek Flats,Alaska

The Shaw Creek Flats and nearby middle Tanana river, in central Alaska, constitute one of the areas in the Americas with the densest known distribution of Late Glacial (about 14,500–11,700 cal. B.P.) archaeological sites. Local high rates of sediment deposition and low post-depositional disturbance allow for the interpretation of the function of archaeological occupations within larger economic and mobility strategies. Residential sites used over the long term seem to be located near critical but immovable resources such as clear water and vegetation. The spatial association of artifacts and faunal remains at other sites in the Flats suggest that they were specialized, short-lived locations dedicated to a single or few activities. For instance, the site of Swan Point Cultural Zone 4b is interpreted as a workshop related to the production of composite tools, particularly on mammoth ivory, and the site of Keystone Dune is interpreted as a camp related to wapiti (Cervus elaphus) hunting. These task-specific sites and others were probably used as part of a predominantly logistical mobility and economy strategy, which maximized efficiency in harvesting and processing resources that were distributed heterogeneously on the landscape.     

A Fully Graphical Approach for Limit State Analysis of Existing Structures: Application to Plane Elastic-Plastic Bended Structures and to Plane Masonry Arches

ABSTRACT

When classical elastic analysis fails to model correctly the structural behavior of historical masonry structures because of the brittle, rigid, anisotropic, and inhomogeneous characteristics of their building material, equilibrium-based limit state analysis constitutes an efficient alternative for their structural assessment. The lack of knowledge about the history of loading makes the actual state of stresses impossible to determine for these statically indeterminate structures. However, Plastic Theory provides a powerful theoretical framework that defines in a rather simple way the structural safety level. The lower-bound theorem of plasticity can be applied using graphic statics because it ensures that equilibrium and yield conditions are respected when applying specific constraints to the nodes of the reciprocal diagrams.

This article focuses on limit stat analysis of statically indeterminate structures by means of geometrical considerations using graphic statics reciprocal diagrams. For linear-bended structures, we show that: (1) the conditions of stability can be defined graphically by constructing safety domains; (2) collapse modes can be identified and related to specific reciprocal polygons; and (3) the exact value of the collapse load factor can be deduced graphically from the diagrams. Finally, we extend these results to plane masonry arches in relation with the classical thrust line approach.