The role of virtual turning points in the deformation of higher order linear equations (Microlocal Analysis and Related Topics)

The problem of axial dynamic pile-soil interaction and its analytical representation using the concept of a dynamic Winkler support are revisited. It is shown that depth- and frequency-dependent Winkler springs and dashpots, obtained by dividing the complex-valued side friction and the corresponding displacements along the pile, may faithfully describe the interaction effect, contrary to the common perception that the Winkler concept is always approximate. An axisymmetric wave solution, based on linear elastodynamic theory, is then derived for the harmonic steady-state response of finite and infinitely long piles in a homogeneous viscoelastic soil stratum, with the former type of pile resting on rigid rock. The pile is modelled as a continuum, without the restrictions associated with strength-of-materials approximations. Closed-form solutions are obtained for: (a) the displacement field in the soil and the pile; (b) the stiffness and damping ('impedance') coefficients at the pile head; (c) the actual, depth-dependent, dynamic Winkler moduli; and (d) a set of fictitious, depth-independent Winkler moduli to match the dynamic response at the pile head. Results are presented in terms of dimensionless graphs, tables and simple equations that provide insight into the complex physics of the problem. The predictions of the model compare favourably with existing solutions, while new results and simple design-oriented formulae are presented

Controversies and lessons from the history of smallpox: The case of massive vaccination in british corfu (1852)

The study presents an anti-vaccination action in the 19th century involving both scientific and political motiva-tion. The research is based on an unpublished archive, namely the registries of the British Executive Police during the massive vaccination campaign in Corfu, the cap-ital of the British possession in the Ionian Islands-Greece (1815-1864), after the smallpox outbreak of 1852. The archival material provides information about the num-ber of vaccinated people, namely their sex, age, nation-ality, the year of the previous vaccination, along with the last year when a citizen “had smallpox”. The records in-dicated 40,858 citizens and of these, a total 21,845 (53.46%) were vaccinated. Despite the impressive or-ganization, the vaccination project caused a great con-troversy at both the scientific and political level between the British authorities and the Greek Ionian Assembly. The archival material gives a diachronic message in the fields of public health, infectious disease control, and health crisis management. The lack of control by a State or local authority, combined with political instability and the public’s ignorance or distrust of scientific mat-ters, are the main factors behind the failure to prevent, restrict or eradicate infectious diseases even nowadays. © 2021, EDIMES Edizioni Medico Scientifiche. All rights reserved

Infectious diseases in Athens during the German Occupation (1941-1944)

<p>The aim of the study is to present the second most frequent cause of death in Athens, during the German Occupation (1941-1944), which was the infectious diseases. Until now the majority of studies have focused to the great famine of 1941-42 with thousands of victims. Although the famine was the main cause of death, a significant number of cases were due to infection diseases or noncommunicable diseases. The study was based on the archives, such as the books of admissions of the hospitals located in Athens, but also to the official public records of the Prefecture of Athens. From the study of the archival material it is evident that tuberculosis, malaria, epidemic typhus, typhoid fever and meningitis, were the most important causes of morbidity and mortality. During the German Occupation, tuberculosis and malaria significantly increased. While epidemic outbreaks reported of epidemic typhus (1941), malaria (1942) and food-born poisoning of bacterial etiology (1941, 1942 and 1943). It is worth mentioning that there was an increase of syphilis, genital warts, pediculosis and scabies.</p><p>The topographic study indicated that the southwest and southeast areas of the Municipality of Athens, and the bordering Municipalities, were areas with higher morbidity and mortality. These areas were the residence of the working social class and the refugees from the Asia Minor (1922). The increase of morbidity and mortality in these areas can be explained by the low social-economic living conditions, since the Interwar period, the deterioration due to the Occupation, and the population density. The spectrum of the infectious diseases in Athens was not significantly different from that of Interwar. The difference was the increase of the cases due to the miserable living conditions and the collapse of the public services for the surveillance and control of the infectious diseases.</p&gt

Experimental Investigation of Soil-Pile-Structure Seismic Interaction

The cyclic and seismic response of soil-pile-structure systems is assessed through comprehensive experimental tests performed on the 3mx3m shaking table of the Bristol Laboratory for Advanced Dynamics Engineering (BLADE), University of Bristol (UK). Such tests were carried out in the framework of the Seismic Engineering Research Infrastructures for European Synergies (SERIES). The present work discusses preliminary results of the cyclic response of a pile group in a bi-layered soil profile. The outcomes of the test results discussed hereafter emphasize that kinematic effects are of paramount importance for the seismic analysis and design of structural systems with piled foundations. Appropriate combination rules to account for both inertial and kinematic effects are deemed necessary. The experimental results derived with the shaking table tests will be employed to calibrate numerical models, which, in turn, will be utilized to perform comprehensive parametric analysis aimed at providing sound design rules to be implemented in next generation performance-based seismic codes of practice

Experimental Assessment of Seismic Pile-Soil Interaction

Physical modeling has long been established as a powerful tool for studying seismic pile-soil-superstructure interaction. This chapter presents a series of 1-g shaking table tests aiming at clarifying fundamental aspects of kinematic and inertial interaction effects on pile-supported systems. Pile models in layered sand deposits were built in the laboratory and subjected to a wide set of earthquake motions. The piles were densely instrumented with accelerometers and strain gauges; therefore, earthquake response, including bending strains along their length, could be measured directly. Certain broad conclusions on kinematic and inertial SSI effects on this type of systems are drawn

Chapter 27 - Experimental Assessment of Seismic Pile-Soil Interaction

© Springer International Publishing Switzerland 2014. Physical modeling has long been established as a powerful tool for studying seismic pile-soil-superstructure interaction. This chapter presents a series of 1-g shaking table tests aiming at clarifying fundamental aspects of kinematic and inertial interaction effects on pile-supported systems. Pile models in layered sand deposits were built in the laboratory and subjected to a wide set of earthquake motions. The piles were densely instrumented with accelerometers and strain gauges; therefore, earthquake response, including bending strains along their length, could be measured directly. Certain broad conclusions on kinematic and inertial SSI effects on this type of systems are drawn.status: publishe