Alberto Carpinteri

Experimental Investigation on Crack Growth in Pre-Notched Concrete Beams

It is well-known that failure of unreinforced, pre-notched concrete beams in bending is mainly governed by the tensile strength (“ductile” behaviour) or by the fracture toughness (brittle behaviour) depending on the geometrical scale (beam size), and the value of the relative notch depth. In particular, relatively large beams made of high-strength concrete and with a small relative notch depth, show a brittle structural behaviour (unstable crack propagation); whereas relatively small beams made of low-strength concrete and with a large relative notch depth, show a relatively ductile structural behaviour (stable crack propagation). In this contribution, the damage progress, due to crack formation and propagation, in unreinforced, pre-notched concrete beam specimens, tested in three-point bending, is analysed by the Acoustic Emission (AE) and Digital Image Correlation (DIC) techniques. Beams with rectangular cross-section were considered. A relative notch depth (a/d) equal to 0.5 is assumed in all cases. The loading process was operated by controlling the vertical displacement. The specimens were instrumented by four transducers measuring the vertical displacements in correspondence to the supports and at mid-span, and the Crack Mouth Opening Displacement (CMOD). In addition, two AE transducers were located near the notch to acquire the AE signals originated by material damage. Moreover, the evolution of the deformation process was monitored around the notch by a DIC system, therefore obtaining the time evolution of strains. By analysing the acquired data, a correlation between the AE signals registered and the displacements/strains measured at several points was looked for. Furthermore, the fracture energy of each specimen was evaluated, according to RILEM recommendation, based on the measured load–deflection curves. Scale effects on fracture energy, bending strength, and AE energy per unit area were investigated.

Tectonic activity and climate change: Evolution of our planet from the primordial to the present situation

I the Eastern Desert of Egypt, some banded iron and volcanogenic massive sulfide ores have been considered auriferous based on their assay results, though all available information indicate that gold, if presents, is epigenetic in these deposits. Au anomalies in fresh BIF samples are completely absent (assaying tens of BIF samples from different locations in the Egyptian Eastern Desert gave no gold concentrations). Even where subjected to pervasive metasomatism, gold values in the Neoporterozoic BIF deposits are consistently nil. If reported in the BIF, gold is confined to auriferous quartz veins along prominent fault/shear structures (e.g., Abu Marawat BIF). The banded iron ores are associated with Au-quartz veins only where sheared and tectonized. A single evidence for the syn-genetic origin of occasional Au in the Egyptian BIFs is completely missing. Stratabound gold deposits in the Egyptian basement are suggested on basis of assaying results of some samples while no comprehensive genetic studies were done. This will remain a big problem of scientific credibility of the classification suggested by Botros (OGR 2004). Accidental gold traces in some Egyptian massive sulfide ores can be related to post-formation circulating metamorphic/hydrothermal fluids. On the other side, the majority of the discrete gold occurrences in the Eastern Desert are of mesothermal vein-type, either related to fault/shear zones, or confined to peripheries of small granitoid massifs in regional transpression/transcurrent systems. Gold could have been leached from various lithologic units (i.e. volcanic/volcaniclastic or mafic/ultrmafic rocks in depth) or derived from late-orogenic granitoid magamas. Alternatively, hot magmatic intrusions could have aided convection of metamorphic±meteoric, low salinity aqueous-carbonic fluids and thus effectively dissolved, transported, and deposited gold in zones of dilation.The present study deals with detailed geochemical and mineralogical studies of the coastal plain sediments formed along the shoreline of the Arabian Gulf area, Kuwait. These deposits are mainly fluviomarine and beach sands. The coastal plain deposits of the central Kuwait shoreline zone were found to consist of average medium-grained sand. The sand composed, on average of about 90% sand, and about 10% or less is mud, and has a unimodal distribution with a mode of medium sand (1-2 ф). The sediments consists mainly quartz, Feldspar, clay minerals with carbonate minerals (detritus calcite and dolomite) and rock fragments (chart). The mineralogy of the clay fractions of the sediments is dominated by illite, palygorskite, mixed layer illite-montmorillonite with minor amounts of chlorite and Kaolinite. Heavy minerals are concentrated in the very fine sand fraction and are dominated by opaque minerals, and non opaque minerals which represented by amphiboles, pyroxenes, epidotes, dolomite, zircon, tourmaline, rutile, garnet and other which represented by Staurolite, Kyanite, Andalusite and Sillimenite as a trace amounts. The chemical analysis for the detrital amphibole grains from sandstone of coastal plain sediments shows the following features; the grains which have (Na + K) 0.50 its composition have wide variation and on the (Na + K) -Al IV diagram can be characterized two association: Association 1 which characterized by low amount of AlIV and low amount of (Na + K), by comparing the chemical composition of this association and the chemical composition of amphibole grains from older basement rock, can, these association may be derived from metamorphic source rocks and association 2 which characterized by high amount of Al IV and low amount of (Na + K), which may be derived from volcanic source rocks.T effect of long period ground motions on structure seismic responses has become an important consideration because of the increasing number of long-period buildings such as base-isolated structures and high-rise buildings. As a reliable anti-seismic technology, base isolation is used in many research programs to minimize seismic response of nuclear power plants (NPPs), which are a kind of critical constructions and any damage of them could lead to severe disasters. However, long period ground motion effects on isolated structures are not considered in these researches. In this paper, a representative multi-particle model of NPPs is built and lead-rubber bearing is considered as isolation system. Several classic long period and ordinary ground motions are chosen to investigate their characteristics of time domain and frequency domain, and the comparison analysis well explain the response differences of isolated NPPs under long period ground motions and ordinary ground motions. According to the comparison of acceleration responses, displacement responses and shear force responses of these two kinds earthquake, time-domain analysis is carried out using the NPPs model with and without isolation system. It is observed that seismic responses of superstructures could be reduced more effectively under ordinary ground motions than with long period motions input, and isolation layer displacements are larger with long period ground motions action. Seismic safety of nuclear power plants could be enhanced effectively by isolation system, and influences of long period ground motions on it should be considered carefully in further isolation design.S pollution and water pollution are posing a big threat today. With the multiplying population and progress of urban civilization, pollution caused by petroleum products and their wastes is increasing in logarithmic manner. In bioremediation of petroleum compound process in the environment, bacteria have been shown to be relatively more successful in breaking down the higher molecular weight compounds. The n-alkanes are generally considered the most readily degrading components in petroleum mixture. The hydrocarbons are broken by a series of enzyme mediated reactions. First it is mono terminal attack and oxygen serves as an external electron acceptor, while an organic component of the contaminating substance functions as the electron donor or energy source. The general pathway involves sequential formation of an alcohol, an aldehyde and a fatty acid. These organisms carry out their normal life processes using these contaminants as their source of nutrients. Metabolic processes of these organisms are capable of using chemical contaminants as energy source, rendering the contaminants harmless or less toxic in most cases. This review provides an outline of the occurrence of PAHs in the environment and the ability of bacteria to degrade the compound, including pathways for PAHs degradation by these organisms.The effects of emerging environmental problems associated with climate change and human-induced land cover change often directly impede livelihoods of the rural population in Africa. Erratic rainfalls, flooding, forest cover loss, and land degradation are causing unstable agricultural yields and incomes. Earth Observation (EO) has the potential to monitor landscape dynamics in relation to climate or human-induced environmental effects. Moreover, EO can provide seamless and integrative, that is multi-data and multi-scale, geospatial monitoring solutions that are of particular use within data scarce environments. This paper illustrates examples, possibilities and future perspectives from current EO research to address emerging environmental issues in Africa. Two experimental EO examples from eastern Africa are presented; (1) a multi-sensor approach to map vegetation productivity decline over eastern Africa, and (2) an integrative (multi-data) approach to map the spatial distribution of flowering plants at a local to landscape scale. In the first example, vegetation productivity decline, mapped at a regional scale using time-series of 250-meter MODIS NDVI imagery (from 2001 to 2012), is related to very high resolution (VHR) imagery in Google Earth. The MODIS-based productivity data could be effectively linked to land transformation processes (i.e. “deforestation”) using the multi-date VHR imagery. Climate-induced change could be largely disentangled from the human-induced change using rainfall trends derived from passive radar satellite observations. In the second example, the spatial distribution and abundance of flowering plants are mapped for a local site in Kenya using 0.6-meter hyperspectral data. The locations of flowering plants were verified in the field using a Smartphone geo-tagging. The up-scaling potential of the hyperspectral derived flowering map to a multi-spectral Worldview-2 image was probed. The results are instigated for the quantification of pollination effects in Africa and to sustain healthy honey bee colonies. Multi-sensor and multi-scale monitoring of environmental effects in Africa is effectively possible given that adaptable and ‘intelligent’ data integration models or techniques are used.