Since the earthquakes in Northridge and Kobe in 1994 and 1995, respectively, many investigations have been carried out towards improving the strength and ductility of steel beam to column pre- and post-Northridge connections. In order to achieve these objectives, recent researches are mainly focused on three principles: reducing the beam section to improve the beam ductility, adding different kinds of slit damper to beam and column flanges to absorb and dissipate the input earthquake energy in the connection and strengthening the connection area using additional elements such as rib plates, cover plates, and flange plates to keep the plastic hinges away from the column face. This paper presents a reduced beam section approach via the introduction of multilongitudinal voids (MLV) in the beam web for various beam depths varying from 450 mm to 912 mm. ANSYS finite element program was used to simulate the three different sizes of SAC sections: SAC3, SAC5, and SAC7. Results showed an improvement in the connection ductility since the input energy was dissipated uniformly along the beam length and the total rotation of the connection was over four percent radian.
Wave propagation in unbounded domains is one of the important engineering problems. There have been many attempts by researchers to solve this problem. This paper intends to shed a light on the finite point method, which is considered as one of the best methods to be used for solving problems of wave propagation in unbounded domains. To ensure the reliability of finite point method, wave propagation in unbounded domain is compared with the sinusoidal unit point stimulation. Results indicate that, in the case of applying stimulation along one direction of a Cartesian coordinate, the results of finite point method parallel to the stimulation have less error in comparison with the results of finite element method along the same direction with the same stimulation.
In die-casting molds, heat-checking is the typical failure mechanism. Optimizing the parameters that decrease this failure venture should be considered when designing and heat treating steels. The quality of die steels and their treatment continue to improve. This research investigated properties of the traditional materials 1.2343 and 1.2344 and the new steels (Dievar and TOOLOX 44) when applied to the die-casting mold specimens, after different experimental cycles. Also microstructures of the mentioned materials were analyzed by scanning electron microscopy (SEM) test. Chrome-molybdenum-silicon-vanadium steels have good hardening ability in oil and in air. Therefore, the hot-work steels have considerable toughness and plastic attributes through both regular and higher temperatures. So, it is a good traditional die-casting material. However, another special die steel, such as Dievar, is a particularly developed steel grade; its exclusivity profile is exceptional due to its chemical composition and the use of the latest production techniques. Dievar has good heat-checking and gross-cracking resistance as a result of both high toughness and good hot strength. An additional material, a new prehardened tool steel known as TOOLOX 44, exhibits control of the failure described above by optimizing the parameters of impact toughness that could reduce the heat-checking failures. A variety of heat treatment parameters exist for various reasons because the heat treatment operation is performed by a variety of companies. This issue of the diversity in heat treatments is resolved by TOOLOX 44; this steel is quenched and tempered in delivered state.
Fixed offshore jackets are principal substructures widely used in offshore industries. An accurate consideration in finding an advantageous alternative to traditional steel material in the construction of this essential structure could be very efficient. The focus of this study is to simplify the construction procedures and to increase the serviceability life of the offshore jacket. To this aim, as a new low-cost material, high-specific-strength steel has been considered. With using ANSYS software, transient dynamic analysis has been implemented on two hypothesized three-legged jackets located in the Persian Gulf region. It is assumed that the modeled jackets are made of traditional steel and high-specific-strength steel material. The effects of an extreme wave load and a supply vessel impact load have been considered for the structural analysis. It has been shown that structural performances of the high-specific-strength steel jacket under the effects of the mentioned loads, are better compared to the traditional steel jacket.Análise dinâmica transitória da plataforma de alta resistência com onda marítima e carga de impacto de embarcação RESUMO. Plataformas fixas são as principais subestruturas usadas em industrias marítimas. Uma procura precisa em encontrar alternativas vantajosas para o aço tradicional nas construções dessas estruturas poderia ser de extrema eficácia. O foco deste estudo é simplificar os procedimentos de construção e aumentar a manutenção das plataformas. Para este objetivo, um novo material de baixo custo e com alta resistência foi considerado. Usando o software ANSYS, a análise dinâmica foi implementada em duas hipotéticas plataformas de três pernas, localizadas no Golfo Pérsico. É suposto que os modelos das plataformas são feitos de aço tradicional e do aço de alta resistência. Os efeitos de impactos de ondas e de embarcações foram considerados para a análise estrutural. Foi demonstrado que os desempenhos da plataforma de alta resistência na questão dos efeitos dos impactos foram melhores em comparação com as plataformas tradicionais.
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