Strengthening of moment‐resisting frame structures against near‐fault ground motion effects

Near‐fault ground motions with forward directivity are characterized by a large pulse. This pulse‐like motion may cause a highly non‐uniform distribution of story ductility demands for code‐compliant frame structures, with maximum demands that may considerably exceed the level of code expectations. Strengthening techniques for multi‐story frame structures are explored with the objective of reducing maximum drift demands. One option is to modify the code‐based SRSS distribution of story shear strength over the height by strengthening of the lower stories of the frame. The modified distribution reduces the maximum story ductility demand, particularly for weak and flexible structures. However, this strengthening technique is less effective for stiff structures, and is almost ineffective in cases in which the maximum demand occurs in the upper stories, i.e. strong and flexible structures. As an alternative, the benefits of strengthening frames with elastic and inelastic walls are evaluated. The effects of adding walls that are either fixed or hinged at the base are investigated. It is demonstrated that strengthening with hinged walls is very effective in reducing drift demands for structures with a wide range of periods and at various performance levels. Wall inelastic behavior only slightly reduces the benefits of strengthening with hinged walls.Copyright © 2004 John Wiley & Sons, Ltd.     

Developmental,Reproductive, and Demographic Alterations in Aquatic Wildlife: Establishing Causality between Exposure to Endocrine‐active Compounds (EACs) and Effects

This brief overview discusses the difficulty of demonstrating causal associations between exposure to endocrine active compounds (EACs) and the occurrence of developmental, reproductive, or demographic disturbances in aquatic wildlife. While for biological responses at the suborganism level correlational or causal evidence of an EAC etiology has been established in a number of cases, well proven examples of ecological consequences of endocrine disruption are rather few in number. The attribution of causality is complicated due to (i) lack of data on EAC exposure and bioaccumulation, (ii) lack of specific biomarkers and endpoints, together with insufficient knowledge on the mechanisms and conditions by which EAC‐induced disruption of endocrine functions translates into impaired organism development and reproduction, and (iii) insufficient understanding of the importance of species diversity in endocrine physiology and life histories for the consequences of endocrine disruption. Future research should address these gaps in our understanding of EAC exposure and effects, but additionally needs to pay more attention (i) to ecological determinants influencing the population‐level consequences of the endocrine disruption of developÍmental and reproductive functions, and (ii) to the use of epidemiological principles and approaches.     

People of German descent in CIS States — areas of settlement,territorial autonomy and emigration

Until 1989 the ethnic Germans tended to live in Kazakhstan, Central Asia and South-West Siberia. Not only German but also Russian and Ukrainian residents in Kazakhstan and Central Asia have been induced to leave. In South-West Siberia attempts are beeing made to keep the ethnic Germans there. Two autonomous German districts have been established. The mass scale emigration to Germany has, however, affected these areas, too. That means that not only push factors are effective but also pull factors play a role. They concern the privileged immigrant status of Aussiedler in Germany. The economic damage suffered by Siberia on account of this kind of undifferentiated drain of workers and specialists puts whole economic regions in jeopardy. The German Home Office tried to support the re-establishment of the German Volga Republic which was dissolved by Stalin in 1941. Some German unprofessionally organised economic projects and severe diplomatic mistakes actually strengthened the nationalistic Russian opposition so that the reestablishment failed. An improvement of the ethnic Germans' perspectives in the CIS is only possible if Germany makes use of the tried and tested instruments of development aid and regional planning. German consulates and trade agencies should be opened in the Volga region, and in Siberia. It is necessary to establish a Siberian-German bank and Russian-German universities. A special programme should provide support for well-qualified people whose knowledge and skills are vital for a continuation of the ethnic Germans' economy and culture.     

Zur Frage der Vergenzen in den Katalonischen Küstenketten

The problem of simultaneously created but antagonistically verging structures is treated. Starting-point are the Catalan Coast Ranges (Ne-Spain), especially their southern part which comprises the Maestrazgo an the Lower Aragon Ranges. That region is bounded, which, what concerns the tertiary tectonics, acted as a unit. In the so bounded area the inland verging structures are attributed to gravity tectonics. The reasons are:

1. the perpendicular to the tectonical direction convex arcform of the axis, parallel to the lines of force of a pressing unit.
2. the transition against the verging structure from strongest pressure to strain across a region of normal layering.
3. the stratigraphical sequence: it exists an alternation of competent (lime-, sand-stones) and incompetent (sands, clays, marls) sediments.

What we have in the Maestrazgo is not a single gliding unit, but an in itself glided mass. Everywhere where the competent layers lie upon incompetent strata happened a horizontal equalization of the concerned forces (Faziestektonik, selektive Tektonik). And this alernation is the very typical of the stratigraphy in the Maestrazgo. In some final remarks the position of the Catalan Coast Ranges in the Mediterranean Orogeny is discussed.     

GRAVEL SLUICING IN ALPINE RUN-OF-RIVER HYDROPOWER PLANTS

1 INTRODUCTIONNdsral rivers entering reservoirs carry also sediment, partly as bedload and patly in suspension. At theentrance of the reservoir flow velocity is considerably reduced and the capability of sediment transport isdrashcally fading. Bedload maerial is deposited totally at the reservoir entrance fondng a delta, material...in suspension is cAned further intO the reservoir ulh.. it is partly deposited and partly dischargedthrough the dam towards downstreaxn (depending on the trapp…     

Contraction,fragmentation and expansion dynamics determine nutrient availability in a Mediterranean forest stream

Temporary streams are a dominant surface water type in the Mediterranean region. As a consequence of their hydrologic regime, these ecosystems contract and fragment as they dry, and expand after rewetting. Global change leads to a rapid increase in the extent of temporary streams, and more and more permanent streams are turning temporary. Consequently, there is an urgent need to better understand the effects of flow intermittency on the biogeochemistry and ecology of stream ecosystems. Our aim was to investigate how stream nutrient availability varied in relation to ecosystem contraction, fragmentation and expansion due to hydrologic drying and rewetting. We quantified the temporal and spatial changes in dissolved nitrogen (N) and phosphorus (P) concentrations along a reach of a temporary Mediterranean forest stream during an entire contraction–fragmentation–expansion hydrologic cycle. We observed marked temporal changes in N and P concentrations, in the proportion of organic and inorganic forms as well as in stoichiometric ratios, reflecting shifts in the relative importance of in-stream nutrient processing and external nutrient sources. In addition, the spatial heterogeneity of N and P concentrations and their ratios increased substantially with ecosystem fragmentation, reflecting the high relevance of in-stream processes when advective transport was lost. Overall, changes were more pronounced for N than for P. This study emphasizes the significance of flow intermittency in regulating stream nutrient availability and its implications for temporary stream management. Moreover, our results point to potential biogeochemical responses of these ecosystems in more temperate regions under future water scarcity scenarios.