Seismic Assessment of Non-conforming Infilled RC Buildings Using IDA Procedures

The seismic performance of existing non-conforming reinforced concrete (RC) buildings is numerically investigated, taking into account the presence of clay brick masonry infill walls. The effect of infill walls on the seismic response of RC frames is widely recognised and has been a subject of numerous analytical and experimental investigations. In this context, Static Pushover analyses of typical existing RC infilled frames have established these structures' inelastic characteristics, focusing on the significant contribution of infill walls to their dynamic characteristics, overstrength, form irregularity and damage. Furthermore, more comprehensive studies of inelastic static response considered the typical variability among different generations of constructed buildings in Greece since the 60s in the form, the seismic design and detailing practice and the structural materials, with different masonry infill configurations and properties. In the present study, the results from such Static Pushover analyses are extended with Incremental Dynamic Analysis predictions using a large number of recorded base excitation from recent destructive earthquakes in Greece and abroad. Evaluation of the time history predictions and comparisons with the Static Pushover analysis findings corroborate that the presence of regular arrangements of perimeter infill walls increase considerably the stiffness and resistance to lateral loads of the infilled RC structures, while at the same time, reducing their global ductility and deformability. Fully or partially infilled RC frames can perform well, while frames with an open floor usually have the worst performance due to the formation of an unintentional soft storey. The analyses further prove that lower strength masonry provides the building with lower overstrength but higher ductility

The evolution of synoptic ozone anomalies during the European Arctic Stratospheric Ozone Experiment in winter 1991/1992

The evolution of ozone anomalies over the middle and high latitudes of the Northern Hemisphere during the winter 1991-1992 is studied in this work. The largest monthly mean negative deviations in the middle latitudes of the Northern Hemisphere were about 10 percent in November and December, and up to 20 percent in January, February, and March over Eurasian territories, and much smaller over the Canadian sector. At the end of January, on individual days, total ozone values of 190-210 D.U. were observed over Eastern Europe and European part of Russia, that is 40-45 percent below normal. On the whole, the 1991-1992 winter was one of the most anomalous over all the period of ozone observations. Finally, an attempt is made to quantify the contribution of transport in the ozone layer changes over Europe during this period

Detecting volcanic sulfur dioxide plumes in the Northern Hemisphere using the Brewer spectrophotometer, other networks, and satellite observations

This paper demonstrates that SO 2 columnar amounts have significantly increased following the five largest volcanic eruptions of the past decade in the Northern Hemisphere. A strong positive signal was detected by all the existing networks either ground based (Brewer, EARLINET, AirBase) or from satellites (OMI, GOME-2). The study particularly examines the adequacy of the existing Brewer network to detect SO 2 plumes of volcanic origin in comparison to other networks and satellite platforms. The comparison with OMI and 45 GOME-2 SO 2 space-borne retrievals shows statistically significant agreement between the Brewer network data and the collocated satellite overpasses. It is shown that the Brewer instrument is capable of detecting significant columnar SO 2 increases following large volcanic eruptions, when SO 2 levels rise well above the instrumental noise of daily observations, estimated to be of the order of 2 DU. A model exercise from the MACC project shows that the large increases of SO 2 over Europe following the Bárðarbunga eruption in Iceland were not caused by local sources or ship emissions but are clearly linked to the eruption. We propose that by combining Brewer data with that from other networks and satellites, a useful tool aided by trajectory analyses and modeling could be created which can be used to forecast high SO 2 values both at ground level and in air flight corridors following future eruptions

The geographical distribution of meteorological parameters associated with high and low summer ozone levels in the lower troposphere and the boundary layer over the eastern Mediterranean (Cairo case)

In continuation of previous research for evaluation of the high ozone levels observed during summer time over the eastern Mediterranean, MOZAIC profiles collected at the airport of Cairo from 1994 to 2008 are analysed. Average profiles corresponding, respectively, to the highest and the lowest ozone mixing ratios for the 0–1.5 km layer over Cairo in summer (JJA) (94 profiles) are examined along with their corresponding composite maps of geopotential height (and anomalies), vertical velocity (and anomalies), specific humidity anomalies, precipitable water anomalies, air temperature anomalies and wind speed at 850 hPa. In addition, backward trajectories arriving in the boundary layer over Cairo during the days with highest or lowest ozone mixing ratios are examined. During the 7% highest ozone days at the 0–1500 m layer over Cairo, very high ozone concentrations of about 80 ppb on average are observed from the surface up to 4–5 km altitude. The difference in ozone concentrations between the 7% highest and the 7% lowest ozone days reaches maximum values around 60 ppb close to the ground. During the highest ozone days for both 1.5–5 and 0–1.5 km layer, there are extended regions of strong subsidence in the eastern Mediterranean but also in eastern and northern Europe and over these regions the atmosphere is dryer than average. In addition, characteristic profiles with the highest ozone concentrations in the 0–1500 m layer are examined in order to assess the influence of atmospheric transport and photochemistry on the ozone concentrations over the area

How Effective and Prerequisite Are Electromagnetic Extremely Low Frequency (ELF) Recordings in the Schumann Resonances Band to Function as Seismic Activity Precursors

ELF recordings, especially in the 0–50 Hz range (Schumann Resonances), have gained great interest during the last twenty years because of their possible relation to many geophysical, climatological, solar, and even biological phenomena, which several well-known scientists have reported. A very important question that still has not been answered is whether some particular variations in the Schumann Resonances (SR) band operate as precursors of forthcoming seismic activity. Greece and the wider Mediterranean area are a very seismic territory where medium size earthquakes (4–6.5 Richter) occur very often, contributing to a high percentage of the natural hazards of the area. In our effort to make evident how effective and prerequisite SR recordings are in the detection of forthcoming earthquakes, we analyze data collected for almost five years by two SR stations located in the north and the south edge of the Greek territory, respectively. We have come to the conclusion that particular SR modulations are very useful in the predictability of forthcoming seismic activity, but they need to be completed with additional observations of adjoining effects which can contribute to the final decision

How Effective and Prerequisite Are Electromagnetic Extremely Low Frequency (ELF) Recordings in the Schumann Resonances Band to Function as Seismic Activity Precursors

ELF recordings, especially in the 0–50 Hz range (Schumann Resonances), have gained great interest during the last twenty years because of their possible relation to many geophysical, climatological, solar, and even biological phenomena, which several well-known scientists have reported. A very important question that still has not been answered is whether some particular variations in the Schumann Resonances (SR) band operate as precursors of forthcoming seismic activity. Greece and the wider Mediterranean area are a very seismic territory where medium size earthquakes (4–6.5 Richter) occur very often, contributing to a high percentage of the natural hazards of the area. In our effort to make evident how effective and prerequisite SR recordings are in the detection of forthcoming earthquakes, we analyze data collected for almost five years by two SR stations located in the north and the south edge of the Greek territory, respectively. We have come to the conclusion that particular SR modulations are very useful in the predictability of forthcoming seismic activity, but they need to be completed with additional observations of adjoining effects which can contribute to the final decision

Palaeo-Tsunami Events on the Coasts of Cyprus

Cyprus has a long history of tsunami activity, as described in archaeological and geological records. Although the study area has experienced tsunamis in the past and constitutes an area threatened by this hazard both from the Cyprean arc and from the neighboring Hellenic arc, field research on tsunami evidence on the coastal zone of Cyprus still remains scarce. It is clear from the literature that large boulder accumulations are an important feature along the coasts of Cyprus, testifying to extreme events. A detailed field survey revealed that at various locations cited in the literature as hosting geomorphological evidence of past tsunamis, no such evidence was identified. It is likely that the high touristic activity that has been occurring on the coasts of Cyprus during the last 20 years may have affected tsunami indicators such as boulder accumulations. Tsunamis are unpredictable and infrequent but potentially large-impact natural disasters. The latest strong tsunami that caused damage to the Cypriot coast was centuries ago, when the population and economic growth and development at the Cypriot shoreline did not exist. Today, the coastal zone hosts a higher population as well as increasing touristic activity, highlighting the need for better preparedness, awareness raising and for tsunami-related risk reduction

Anthropogenic sources of electromagnetic interference in the lowest ELF band recordings (Schumann resonances)

Recording systems that deal with Extra Low Frequency (ELF) data in the Schumann resonance (SR) range exhibit high sensitivity to external noise. In our effort to refine a time series by identifying and removing external disturbances from real data, we analyzed the effect of induced deliberate anthropogenic disturbances. The signals were recorded at the same time and same place by two separate systems with different designs and implementations. The main purpose of this experiment was to confirm that different systems in various observational sites could identify parasitic noises in the same way. The outcomes of this study may help ELF observers to discern intrinsic signals from artificial nois