A practical method for optimum seismic design of friction wall dampers

Friction control systems have been widely used as one of the efficient and cost effective solutions to control structural damage during strong earthquakes. However, the height-wise distribution of slip loads can significantly affect the seismic performance of the strengthened frames. In this study, a practical design methodology is developed for more efficient design of friction wall dampers by performing extensive nonlinear dynamic analyses on 3, 5, 10, 15, and 20-story RC frames subjected to seven spectrum-compatible design earthquakes and five different slip load distribution patterns. The results show that a uniform cumulative distribution can provide considerably higher energy dissipation capacity than the commonly used uniform slip load pattern. It is also proved that for a set of design earthquakes, there is an optimum range for slip loads that is a function of number of stories. Based on the results of this study, an empirical equation is proposed to calculate a more efficient slip load distribution of friction wall dampers for practical applications. The efficiency of the proposed method is demonstrated through several design examples

Environmental constraint of intraguild predation: Inorganic turbidity modulates omnivory in fairy shrimps

Omnivory is widespread in food webs, with an important stabilising effect. The strength of omnivorous trophic interactions may change considerably with changes in the local environment. Shallow temporary waters are often characterised by high levels of inorganic turbidity that may directly limit the food uptake of filter-feeding organisms, but there is little evidence on how it might affect omnivorous species. Anostracans are key species of temporary waters and recent evidence suggests that these organisms are omnivorous consumers of both phyto- and zooplankton. Using Branchinecta orientalis as a model species, our aim was to test how turbidity affects the feeding of an omnivorous anostracan. To do this, we used short-term feeding experiments and stable isotope analyses, with animals collected from soda pans in eastern Austria. In the feeding experiments, algae and zooplankton were offered as food either separately or in combination. The prey type treatments were crossed with turbidity levels in a factorial design. There was a pronounced decrease in the ingested algal biomass with increasing turbidity. Conversely, ingestion rates on zooplankton were less affected by turbidity. Stable isotope analyses from field material supported our experimental results by showing a positive relationship of the trophic position of anostracans and the trophic niche of the communities with turbidity. Our results show that turbidity modulates the intraguild trophic relationship between anostracans and their prey by shifting the diet of anostracans from more herbivorous in transparent to more carnivorous in turbid waters. Thus, inorganic turbidity might also have a community-shaping role in plankton communities of temporary waters through altering trophic relationships

Moina weismanni Ishikawa, 1896, a rare East Palearctic faunistic element from S. W. Yugoslavia (Crustacea, Cladocera)

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Two new copepod species (Crustacea : Copepoda) from the Ohrid Lake

Two new copepod species are described from Lake Ohrid (Balkan peninsula). Diacyclops ichnusoides n.sp. (Cyclopoida, Cyclopidae) collected from interstitial waters on the lake coast, and it belongs to the “languidoides”-group. Bryocamptus (R.) mirus n.sp. (Harpacticoida, Canthocamptidae) lives in deep water and belongs to the “zschokkei”-group. With this investigation, the copepod list in Lake Ohrid increases to 36 species, of which 6 are endemic

Two interesting ostracod species from Montenegro (SE Europe)

Two species of superfamily Cytheracea from Skadar Valley (Montenegro), are presented in this paper. Leptocythere pseudoproboscidea n.sp., collected in a spring is very close to Leptocythere proboscidea Klie, 1939, an endemic species of the Ohrid Lake. Paralimnocythere karamani (Petkovski, 1960) occurred in two localities : river and spring. Until now, this species was considered endemic in the Ohrid-Prespa region. Its known distribution is non extended westwards and its presence in Skadar Valley confirms exchanges between faunas of Ohrid and Skadar drainage areas