A study on the effects of the foundation compliance on the response of yielding structures using dimensional analysis

The effects of the foundation compliance on the dynamic response of yielding systems are evaluated using rigorous dimensional analysis. To this end, a soil-foundation-structure system is subjected to strong ground motion and its seismic response is determined in terms of dimensionless parameters. The seismic demand of the system is calculated as a function of meaningful engineering parameters, such as the yielding acceleration and yielding displacement of the structure, the system mass and damping, as well as the dynamic characteristics of the foundation. It is proved that the seismic demand is strongly dependent on the foundation to excitation pulse predominant frequency ratio. For large values of yielding acceleration, the demand depends strongly on the yielding displacement and the mass. Moreover, there is a strength range where an increase in strength results in an increase in displacements—a counter intuitive situation. The larger the yielding displacement, the larger the seismic demand. Furthermore, the larger the foundation soil mass, the larger the seismic demand. Finally, an application of the procedure on an actual structure proves that soil-foundation-structure interaction (SFSI) is not always beneficial for the structure.     

Turbulence in vegetated flows: Volume-average analysis and modelling aspects

Two approaches for the modelling of turbulence in vegetated flows have been developed in the past. The “microscopic” approach which is straightforward but limited to simple cases and the “macroscopic” approach which is based on Volume Average Theory (VAT). In this study, aspects of Volume-Average (VA) analysis and modelling are investigated for turbulent vegetated flow using computed three-dimensional results from the solution of the Reynolds-Averaged Navier-Stokes (RANS) equations around a representative vegetal element. In particular (a) the VA transport equations for k and ε, based on VAT, are properly derived, (b) the Boussinesq hypothesis for the VA quantities, employed in 〈k〉-〈ε〉 turbulence models is tested, and (c) the values of the coefficients used in such turbulence models are assessed in comparison with those used in the classical turbulence models.     

Microseismicity and focal mechanisms at the western termination of the North Anatolian Fault and their implications for continental tectonics

For seven weeks, a temporary network of 68 seismological stations was operated in Central Greece, in the region of Thessaly and Evia, located at the western termination of the North Anatolian Fault system. We recorded 510 earthquakes and computed 80 focal mechanisms. Seismic activity is associated with the NE–SW dextral North Aegean Fault, or with very young E–W-striking normal faults that are located around the Gulf of Volos and the Gulf of Lamia. The important NW–SE-striking faults bounding the Pilion, or the basins of Larissa and Karditsa, are not seismically active, suggesting that it is easier to break continental crust, creating new faults perpendicular to the principal stresses, than to reactivate faults that strike obliquely to the principal stress axes     

Study of the air-earth electrical current density in Athens

In the present study, we examine the daily and annual variation of the air-earth current density in Athens for all weather as well as for fair weather for a 16-year period 1965–1980.The daily variation of the air-earth current density has a definite bimodal form while the annual variation has no definitive form but simply reaches its larger values during the summer months. There has also been a Fourier analysis of the daily variation.Furthermore, and for a 3-year period 1968–70, we present the mean daily and annual variation of the electric field, air-earth current density and total conductivity of the air. Based on these parameters we have estimated the conduction and the convection current and we have correlated them to the total (measured) current. In addition, we have estimated the values of the parameter, in order to test the fulfillment of Ohm's law in atmosphere.     

Protection of architectural heritage: attitudes of local residents and visitors in Sirako,Greece

Architectural heritage comprises one of the most important elements of mountain settlements in Greece. It holds high cultural value, represents the tangible continuation of the past and forms the unique character and identity of each mountain region. Yet, controversy regarding funding for its preservation often arises. In this paper, we used two Contingent Valuation surveys to estimate the social benefit deriving from protecting the traditional architecture in the mountainous village of Sirako and, through it, to examine perceptions and attitudes of local residents and visitors. Research findings revealed a strong social will in favor of the good’s protection followed by high percentages of positive willingness to pay (WTP). However, WTP is significantly higher among residents. Cultural heritage value, of the good, appears to prevail, along with the environmental one. However, both residents and visitors pointed out that local heritage, if well-preserved, will boost tourism development. Residents appeared to better recognize the true level of architectural decay, expressed higher apprehension for its protection and were willing to pay higher amount of money. Tourists, on the other side, expressed high satisfaction for their visit, appreciated the beauty and serenity emerging from local built and natural environment and spent several days visiting the surrounding area. The longer they stayed and got familiar with the village, the more willing they were to contribute to local heritage’s protection. Percentages reflecting indifference for protecting architecture were extremely low. Yet, they were higher among tourists. Traditional architecture is considered as public good; an opinion resulting in an important percentage of visitors stating that national government should provide the necessary funding. In addition, the architecture appears to hold a high level of topicality. Those descending from Sirako or emotionally connected to it, of both social groups, turned out to be more concerned about the good and with a stronger sense of responsibility for it. Use-value of the good holds high economic value, as well, while higher percentages of zero WTP appeared among non-users. Research findings revealed social attitudes and perceptions on what constitutes architectural heritage, in its cultural and economic frame. If taken under consideration, they may form useful drivers for local, heritage-based, sustainable development.     

Modeling plant density and ponding water effects on flooded rice evapotranspiration and crop coefficients: critical discussion about the concepts used in current methods

Theoretical and Applied Climatology - The aim of the study is to propose new modeling approaches for daily estimations of crop coefficient K c for flooded rice (Oryza sativa L., ssp. indica) under...     

Surface tension effects on energy dissipation by small scale,experimental breaking waves

Much of the existing knowledge about breaking waves comes from physical model experiments scaled using Froude's law. A widely held assumption is that surface tension effects are not significant at typical laboratory scales and specifically for waves longer than 2 m. Since, however, smaller wavelengths are not untypical in small to medium scale laboratory facilities, a consideration of surface tension effects is indeed important. Although some emphasis has been given in the past, little is known regarding the importance of surface tension following impingement of the breaking-wave crest and especially on the overall energy dissipation by laboratory breaking waves.