DSM for Web Crippling under Two-Flange Conditions

This paper summarizes recent investigations on the development of Direct Strength Method (DSM) for the design of cold-formed steel beams under two-flange (TF) loading against web crippling failure. Recently, the authors proposed a new approach to predict the web crippling failure load of cold-formed steel beams under External Two Flange (ETF) and Internal Two Flange (ITF) loadings using DSM. Firstly, existing experimental test data are summarized and then the accuracy of North-American Specification (AISI 2012) and Eurocode 3 (CEN 2006) provisions is briefly assessed. In order to obtain additional information on the web crippling behavior of each test specimen, non-linear numerical results are obtained. Since the calibration of the DSM-based formula involves the previous calculation of (i) elastic buckling load and (ii) plastic load, two procedures are presented. Buckling loads are determined using the GBTWEB software, intentionally developed for this purpose, while plastic loads are calculated using analytical expressions based on yield-line models. By adopting a non-linear regression, the coefficients of DSM-based formulae are determined using a set of 128 (ETF) and 130 (ITF) test results and the corresponding estimates of buckling and plastic loads. The DSM-based formulas for ETF and ITF web crippling design are successfully proposed and the resistance factors (LRFD) obtained are φ=0.81 (ETF) and φ=0.75 (ITF)

The effect of stress on egg quality in farmed Atlantic Cod (Gadus morhua L.)

Dissertação de mestrado, Aquacultura, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2011The Atlantic cod (Gadus morhua), is a prestigious species of fish that belongs to the Gadidae family, and is considered a promising species for future aquaculture in the northern hemisphere. Cod production has grown exponentially since the beginning of the millennium. The but development of cod farming has been hampered by bottlenecks in the production such as deformities, diseases as francisellosis, slow growth and early maturation, and in addition relatively low market prices compared to present production costs. Farming of cod relies on a stable supply of high quality eggs. Egg quality and production is dependent not only upon the female condition and hence broodstock diet, but can be negatively affected by stress. In addition, farmed females often fail to release their eggs, become eggbound and die. The project “Why do Atlantic cod females become eggbound? Studies on possible causes and mechanisms” (Research Council of Norway, grant no 190187/E40) investigates the physiological events during normal and abnormal (eggbound) spawning, with the aim to determine factors that may cause the problems. Two factors that may affect these are investigated in this project; The first is dietary lipid content as this correlates to gonadosomatic index (GSI, gonad weight as % of total weight). The fecundity of farmed cod is about 50% higher than wild cod, and one could suspect that abnormally large gonads would increase the problems with eggbound females. The second variable is stress, either directly due to distorted spawning behaviour or indirectly through the eicosanoid cascade. Eggs of poor quality can have a negative impact on production resulting in slow growth, high mortality rate and deformities. In this master it has been focused on the egg production from farmed cod fed either a high (20%) or a low (13%) fat diet, and either physically stressed or not. The stress treatment, imposed randomly once a week, consisted of reducing the water level to a height of 15 cm from the bottom, and for 1 minute the fish were chased with a landing’s nets. The low-stress treatment was nothing more than keeping fish in tanks. The amount of eggs spawned in the tanks was measured through the spawning season and used to calculate fecundity, and egg quality assessed by egg diameter, fertilization, deformities, and hatching rate. The dietary treatment affected final weight; cod fed the low fat diet, had a lower final weight after spawning compared with fish that were fed a high fat diet. The fecundity, expressed as total production of eggs spawned, was affected by diet. The fishes that were fed with the low fat diet had a lower fecundity than the fish fed with a high fat diet. The duration of the spawning season as like the fecundity was also influenced by the stress; the cod in the high stress treatment prolonged their spawning period compared to the low stress group. Egg diameter decreased during the spawning season in all treatments, The fertilisation rate was directly influenced by the type of treatment during the spawning season, but no significant differences were found when assessed 1 or 2 days after stress. Hatching rate was different between diets, but when combined with stress, only fish fed the low fat diet exhibited different rates of hatching. Finally, the rate of deformities did not differ between treatments. In a general assessment, good egg quality is obtained by finding a balance between diet and type of management. Furthermore, fish fed with high fat levels appear more tolerant to stressful activities. Consequently, egg quality, has to be defined by a combination of several parameters. It is also important not to set aside the inclusion of new parameters that may be decisive in order to minimize misclassification

Repulsive effect of stroboscopic light barriers on native salmonid (Salmo trutta) and cyprinid (Pseudochondrostoma duriense and Luciobarbus bocagei) species of iberia

A repulsive effect, that some induced primary stimuli, like sound and light, is known to be provoked in fish behavior. In the present study, two strobe light frequencies, 350 flashes/minute and 600 flashes/minute, were tested in laboratorial conditions, using three native freshwater fish species of northern Portugal: Brown trout (Salmo trutta), Northern straight-mouth nase (Pseudochondrostoma duriense) and Iberian barbel (Luciobarbus bocagei). The results showed a differential repulsive behavior of the fish species to light stimulus, and particularly to a frequency of 600 flashes/minute. S. trutta presented the most repulsive behavior, whereas the L. bocagei showed less repulsion to the light stimulus. No relevant differences were found between pre-test and post-assessments, confirming a rapid recovery of natural fish behavior after the deterrent effect. The results highlighted the potential of behavioral barriers, particularly in salmonid streams, based on strobe light stimulus.The project n 13737: Original Solutions—ENI and CITAB-UTAD was funded project: ANI/QREN/FEDER. European Investment Funds by FEDER/COMPETE/POCI—Operational Competitiveness and Internationalization Programme, under Project POCI-01-0145- FEDER-006958 and National Funds by FCT— Portuguese Foundation for Science and Technology, under the project UID/AGR/04033/2013. Acknowledgments: The present study was technically supported by Instituto da Conservação da Natureza e Florestas (ICNF—Departamento Norte), namely the facilities at the fish farm “Posto Aquicola de Castrelos”, for the execution of the experimental design.info:eu-repo/semantics/publishedVersio

Acoustic barriers as an acoustic deterrent for native potamodromous migratory fish species

This study focused on the use of sound playbacks as acoustic deterrents to direct native potamodromous migratory species away from all kind of traps. The effects of two acoustic treatments, a repeated sine sweep up to 2 kHz (sweep-up stimulus) and an intermittent 140 Hz tone, were tested in three fish species native to Iberia: Salmo trutta, Pseudochondrostoma duriense and Luciobarbus bocagei. In contrast with S. trutta, the endemic cyprinids P. duriense and L. bocagei exhibited a strong repulse reaction to the frequency sweep-up sound. The 140 Hz stimulus did not seem to alter significantly the behaviour of any of the studied species. These results highlight the potential of acoustic stimuli as fish behavioural barriers and their application to in situ conservation measures of native Iberian fish populations, to protect them from hydropower dams. In addition, this study shows that acoustic deterrents can be used selectively on target species.The project n 13737: Original Solutions - ENI and CITAB-UTAD was funded project: ANI/QREN/FEDER. The Science and Technology Foundation, Portugal funded M.C.P.A. (strategic projects UID/MAR/04292/2013 granted to MARE) and P.J.F. (UID/BIA/00329/2013 granted to cE3c). The scientific plan was achieved under European Investment Funds by FEDER/ COMPETE/POCI– Operational Competitiveness and Internationalization Programme, under Project POCI- 01-0145-FEDER-006958 and National Funds by FCT - Portuguese Foundation for Science and Technology, under the project UID/AGR/04033.info:eu-repo/semantics/publishedVersio

Efeitos de barreira comportamental seletiva com estímulos acústicos, luz e bolhas, no salmonídeo: S. trutta e ciprinídeos: P. duriense e L. bocagei

O desenvolvimento de barreiras comportamentais seletivas e adaptadas às espécies piscícolas autóctones dulçaquícolas constitui uma importante ferramenta na salvaguarda dos fluxos migratórios das espécies potamódromas ameaçadas pela regularização dos cursos de água. Estes sistemas comportamentais podem fornecer condições específicas de orientação dos peixes para zonas de desova ou habitats de substituição, ou exercer efeito repulsivo no seu afastamento das armadilhas hidráulicas impostas por aproveitamentos hidroelétricos. A resposta das espécies dulçaquícolas selecionadas ao estímulo acústico (Sweep-up 2000Hz), estímulos luminosos (Strobe Light – 600 flashes/minuto) e cortina de bolhas, foram testadas em condições de laboratório, quer de forma isolada, quer de forma combinada: acústica/luz/bolhas. Apesar da diferenciação de sensibilidades registadas entre a espécie salmonícola testada: Salmo trutta e as espécies ciprinícolas testadas: Pseudochondrostoma duriense e Luciobarbus bocagei, em relação aos ensaios isolados com estímulos acústicos (maior sensibilidade repulsiva nas espécies ciprinícolas), assim como em relação aos ensaios isolados com estímulos luminosos (maior sensibilidade repulsiva na espécie salmonícola), quando utilizados de forma combinada apresentam sensibilidades repulsivas semelhantes e elevadas. A cortina de bolhas de forma isolada evidenciou sensibilidade repulsiva muito baixa para todas as espécies testadas. Os resultados demonstram o elevado potencial das barreiras comportamentais seletivas para peixes com base em sistemas combinados acústica/luz/bolhas, principalmente em cursos de água Salmo–ciprinícolas.info:eu-repo/semantics/publishedVersio