A new method for formulating crack spacing models of RC ties

Cracking of concrete is one of the most complicated phenomena in reinforced concrete analysis and is one of the key aspects governing serviceability analysis of RC structures. Current methods for investigating cracking rely on empirical approaches that give unreliable results with errors of multiple times the real value. A new non-empirical method based on the combination of the stress-transfer and the smeared approaches is proposed for deriving crack spacing models. The stress-transfer approach governs the strain distribution of the reinforcement between the consecutive cracks whereas the smeared approach allows for the estimation of the mean strain of the element. The suggested method introduces the concept of damage zones: the bond in the area adjacent to the normal cracks is considered to be fully damaged, thus bond behaviour is non-uniform in the segment between cracks. Crack spacing models were derived using the load-strain analysis method presented in the Eurocode 2 and were shown to give results that are in good agreement with the crack spacing values taken from available experimental data

Alteration of the phenology of leaf senescence and fall in winter deciduous species by climate change: effects on nutrient proficiency

Leaf senescence in winter deciduous species signals the transition from the active to the dormant stage. The purpose of leaf senescence is the recovery of nutrients before the leaves fall. Photoperiod and temperature are the main cues controlling leaf senescence in winter deciduous species, with water stress imposing an additional influence. Photoperiod exerts a strict control on leaf senescence at latitudes where winters are severe and temperature gains importance in the regulation as winters become less severe. On average, climatic warming will delay and drought will advance leaf senescence, but at varying degrees depending on the species. Warming and drought thus have opposite effects on the phenology of leaf senescence, and the impact of climate change will therefore depend on the relative importance of each factor in specific regions. Warming is not expected to have a strong impact on nutrient proficiency although a slower speed of leaf senescence induced by warming could facilitate a more efficient nutrient resorption. Nutrient resorption is less efficient when the leaves senesce prematurely as a consequence of water stress. The overall effects of climate change on nutrient resorption will depend on the contrasting effects of warming and drought. Changes in nutrient resorption and proficiency will impact production in the following year, at least in early spring, because the construction of new foliage relies almost exclusively on nutrients resorbed from foliage during the preceding leaf fall. Changes in the phenology of leaf senescence will thus impact carbon uptake, but also ecosystem nutrient cycling, especially if the changes are consequence of water stress

Epifitinių makrokerpių rūšinė įvairovė ir gausumas Lietuvos miškuose

Vytauto Didžiojo universitetasŽemės ūkio akademij

Epifitinių makrokerpių rūšinė įvairovė ir gausumas Lietuvos miškuose

Vytauto Didžiojo universitetasŽemės ūkio akademij

Implementation of the test-battery approach into routine effluent control in Lithuania

Recently, HELCOM, expressing a concern on the status of the Baltic Sea, has initiated several international programmes such as Cohiba, BaltHaz, etc., particularly targeted to promote the usage of Whole Effluent Assessment (WEA) methods in routine regulation. Contrary to the control of individual substances, which is based on knowledge of a single concentration, mn unicipal and industrial effluents can be regulated directly on basis of harmful effects that occur in testing organisms. Various countries use laboratory toxicity tests to monitor effluent discharges into surface waters in various degrees. For example, acute and chronic toxicity tests are used in the USAand Sweden, whereas acute tests are used in Canadaand several European countries. Up to date, the majority of countries provide chemical-based effluent controls, however, the progressive increase of chemicals under control and difficulties in measuring them make individual-substance approach problematic. In some countries, toxicity data are included for taxation purposes, in parallel to chemical-based taxation. For example, toxicity data obtained from D. magna acute and fish embryos tests used inFrance andGermany, respectively. In 2011, the Ministry of Environment of Lithuania put forward a national programme with the aim to elaborate a system of effluent control by implementing toxicity tests. The outcome of this programme includes appearance of necessary environmental juristic documents and/or their updates, selection of test-batteries, selection of the cumulative index for toxicity evaluation and performance of initial stage of effluent inventory monitoring. The evaluation of potential harm for aquatic environment is limited to the application of end-of-pipe principle, the assessment of effluent by acute and/or chronic toxicity test-batteries as well as effluent-and stream-flow rates. [...]Aplinkotyros katedraBotanikos institutasVitkus, RVytauto Didžiojo universitetasŠvietimo akademij