Elastic analysis of plated grillages in ships’ structures using finite element method

Grillages consisting of intersecting beams are supporting shell structures of the ships in different places such as bottom, deck and sides. Different methods available for strength analysis of plated grillages are studied from the viewpoints of characteristics and limitations. Finally, the way to assess the strength of such structural elements is investigated. This study is based on preparation of a software for analyzing the grillages. Using the software, it is possible to analyze grillages used in the ships’ structures for any type of boundary and loading conditions that are simply selectable by users. Getting the required input data from the user, elastic deflections and stresses induced as a result of applying concentrated or distributed loads are calculated at the intersections of the longitudinal and transverse members, relieving the need to complicated numerical calculations. To corroborate the accuracy of prepared software results, two models of plated grillages are analyzed and comparing the results confirms that

Numerical investigation on novel method for adhesively bonded t-joint between aluminum and sandwich panel

A common way to join dissimilar materials in industrial applications is to use adhesives. Marine industries use this kind of joints for attaching main hull to superstructure of the ships. Most previous researches have focused on composite-composite joints, while a few of them are devoted to aluminum- sandwich panel joints. This study focuses on the numerical static strength analysis of a typical aluminum-sandwich panel T-joints and improving its strength through a novel design. The results of numerical analyses are in a good agreement with those of the experimental tests and confirm the accuracy of numerical analyses. In analyzing the adhesive between joint elements, contact elements and cohesive zone model (CZM) in ANSYS as well as nonlinear analysis is used. Results show that change in joint geometry considered in this paper, caused a 7.25% increase in vertical failure load of the joint. This increase in strength of joint attained in a situation that because of the merging of the joined parts, the process of construction became easier

Analyzing the effects of aquaculture and rebuild aquatics stocks on fisheries development in the Caspian Sea

Using SWOT analysis with traditional matrix and quantitative matrix methods, the strategies to benefit from strengths and opportunities to vanishing weaknesses and decrease of threats for strategic management of aquaculture in Iranian Northern provinces was surveyed. Utilizing researches held in fisheries research centers and existence of aquaculture experts in vicinity, activation of veterinary organization in production and post production, and entering new brood stocks with desirable growth are the main strategies for developing rainbow trout and Chinese carps culture in Iranian Northern provinces. In sturgeon fishes culture, independence of farms from fingerlings produced by governmental complex and diversification the cultured fishes using new species and hybrids can develop this part of aquaculture. Avoiding illegal fishing in sea and rivers, preserving the population of Caspian Sea fishes, entering new fish species which their resources are decreased extremely to breeding and fingerling production cycle, and using pike perch and bream while they migrate to Anzali Lagoon from Caspian Sea, instead of freshwater brood stocks will cause the output of sea enhancement and sea ranching activities to increase, and fisheries return coefficient of these fishes will rise. Using quantitative matrix and scoring method, it was defined that aquaculture in Iranian Northern provinces are extremely approved and acceptable and the score of strengths is more than weaknesses and opportunities more than threats. By using strategic management, these activities can be more developed

Study of some biological characteristics of golden grey mullet (Liza aurata) in Iranian Coastal waters of the Caspian Sea

During last 65 years the catch of mullets had increasing trends with some fluctuations in the Iranian coastal water of the Caspian Sea .In this period about 138 thousand tons of mullets have been caught. Mullet’s account for 35% of total catch annually .In recent years species composition of mullets has chanched in the Iranian coastal water of the Caspian Sea and catch composition of golden grey mullet increased from 76% in 1995 to 98% in 2006. In this survey some biological characteristics of golden grey mullet have been studied in Iranian coastal water of the Caspian Sea .Fish samples have been gathered from commercial catch of beach seine cooperatives monthly in Iranian coastal water of the Caspian Sea over 2006 and 2007. In the laboratory fishes have been measured biometrically and biological parameters have been calculated .Also catch statistics of mullets during 2006-2007 have been obtained and discussed. Results showed that the catch of mullets in beach seine cooperatives during 2006 and 2007 was 4181 and 3685 tons respectively that golden grey mullet contribute 99% and 98% of the catch composition of mullets respectively. Length range of golden grey mullet caught by beach seine cooperatives was 19-50.2 cm with mean length of 32.7 ± 6.4 (± SD) and weight range was 67-1475 gr with mean weight of 411 ± 255 gr. The age structure of this species was comprised 2-10 years old fish with mean age of 4.42 years old. In this survey totally the sex ratio of male: female of golden grey mullet was 356: 434 that was significant variation from equal sex ratio. Pick of the spawning in Guilan province was in October and in Mazandaran and Golestan provinces was in November. In October the proportion of spawning females declined from western area (Guilan province) towards eastern parts (Golestan province).The highest proportion of spawning females was in December in Golestan province. The highest GSI index value was observed in September and October and it was decreased in November and December and it was consistent during January till April. The mean absolute fecundity was 700881±429987 eggs with minimum and maximum fecundity of 200112 and 2282862 eggs respectively. The Lm 50% for female golden grey mullet was calculated as 33.6 cm

Study on biology (age, feeding and, reproductive) of (Cyprinus carpio, Linnaeus 1758) in south coastal line Caspian Sea (Iranian waters)

The Caspian Sea is the biggest lacustrine water source. Common carp is very important commercially in south coastal line of Iranian Caspian Sea waters, especially in east coastal line, because eighty percent annual catch of this species has been caught in this area in particular. Despite the common carp importance and value in Iran, but there is a little information about its biology in natural system. This study is comprehensive research on reproduction, growth and feeding. The specimens were caught by beach seine net in coastal line of Iranian waters. The fork length ranged between 5.6 and 2866.2 g. The b value of the length-weight relationship ranged from 2.843 to 2.924 for female and male, respectively. The age composition of the specimens was from 1 to 11 year. The Gonadosomatic ratio (GSR) changed from 2 to 12. There were two peaks of GSR in April and December, so that the latter peak was much shorter than the first that. Fecundity variations were high and ranged 77448 to 430745 eggs. It observed linear significant correlation in fecundity- weight (r=0.98) and fecundity-length (r=0.88) relationships. Average growth in length was described with the Von Bertalanffy growth model: L (t) = 60.5(1-exp (0.19(t-0.65). The percent of empty stomach and prey dominant evaluated during different seasons by specific formula result showed that in Cyprinus carpio prey Molluscs was dominated and specific food items. Empty stomachs in winter and spring were higher and lower, respectively

Artificial propagation and Culture of Rutilus frisii kutum of Autumn form for restocking

The Kutum, Rutilus frisii kutum, is one of the most important bony fishes in Iranian coastal of Caspian Sea. Its harvest range is between 9000-10000 tons in a year, nearly 60% of the income of Bony fish fishery produced by kutum fishery. The stock of this species reduced drastically in 1982 and the catch slumped to the less than 250 tons in a year. Kutum spawning grounds deterioration, illegal catch, and lack of restocking program were the main cause of the decline. This Spices in nature comprised by two distinct form, autumn and spring form. It is worth to be mentioned, by the effect of Caspian Sea Bony fishes Research Center s experts in 1983, artificial spawning and releasing the fries to the sea were commenced and the catch steadily improved. But all activities concerning restocking of kutum concentrated in spring form, as at present about 260 million its fries are released into sea for restocking by Iranian Fisheries Organization, but for above reasons and lack of restocking program, the populations of autumn form gravely shrinked and neared to be extinct. Therefore, to enhance the biodiversity and boost fishers livelihood of kutum in Caspian Sea this project implemented by cooperation of Iranian Fisheries Organization (IFRO) and Caspian Environment Program (CEP) in Aquaculture Institute (Inland Waters). In this project, brooders caught from Anzali lagoon and maintained in two different condition, include of floating cages in Anzali lagoon and earthen ponds in Sefidrud Fisheries Research Station. The results showed that there weren’t significant differences between two maintenance statuses in maturation period and other reproductive characteristics of brooders. The ratio of male to female was 1 to 1.4. Minimum and maximum weight measured 1450 to 3100 g (with average of 1850 g) in female and 670 to 1900 g (with average of 1165 g) in male, respectively. The first natural spawning of brooders occurred in the end of January in temperature of 8 till 10 °C in concrete ponds. Also, some of maintained brooders in earthen ponds spawned in February. The average number of absolute, function and relative fecundity determined 88565 16809, 73805 14008 and 48670 12056, respectively. For artificial spawning, male and female brooders injected by pituitary gland with dose of 2-3 and 4-5 mg/kg body weight, respectively. Approximately, 10 and 8 present of female were over-ripe and immature in March (artificial spawning time), respectively. More than 59 % of injected female brooders induced to spawning in first stage after 10-12 hours and 13 % of them in twice stage and 7-8 hours after first stage. And also, 27.6% of females didn’t positive response to injection. Dry method used for eggs fecundity and incubation period lasted 7- 10 days in 14-16 °C. In totally, eggs fertilization were more than 95% and the average of eggs fertilization percent in throughout of period measured more than 92.7 6 %. Eyed eggs appearance occurred 3 days after fecundity and its mean was 92.7 15.1%. Larvae after yolk sac absorption feed with dry milk for 4-5 days and then introduced into fertilized earthen ponds (500 m2 and equipped to aerators) in intensive condition and fed with micro pellet food for 3-4 month. In finally, more than 1.8 million fries of 1-2 g and some more than 5 g produced and released into Anzali lagoon to its restocking for first time. It is expected that continuing of restocking process of autumn form kutum by Iranian Fisheries Organization eventuate to population increasing of this form in Caspian Sea in future