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In this paper, to improve the mechanical behavior of DeepCwind semi-submersible floating offshore wind turbine (FOWT) platform mooring lines, the nonlinear catenary cables of the platform were divided into multi-segment and intermediate buoys. Mathematical formulations of the boundary element method (BEM) governing the dynamics of mooring line systems with buoy devices were described. This study was applied to the OC4-DeepCwind semi-submersible FOWT platform, which is designed for a 200-meter water depth with mooring lines consisting of three catenary steel chain cables at 120° angles to each other. The dynamic response of the multi-segment catenary mooring lines with different buoy radiuses and different positions along the cables was investigated. The full-scale platform was modeled in ANSYS-AQWA software, and the simulations were performed under harsh offshore conditions. The mooring line's general arrangement, tension, strain and uplift force for different buoy radiuses and their position along the cable are presented and discussed. Moreover, platform motions in three directions (surge, heave, and pitch) were also analyzed. It was concluded that by correctly selecting the buoy volume and position along the cable, the tension of the cable may be reduced by up to 45%. By incorrectly selecting the buoy, the results caused adverse effects. [ABSTRACT FROM AUTHOR]

In this research, a numerical investigation on the hydrodynamic response of a semisubmersible platform, developed by DeepCwind consortium, equipped with the National Renewable Energy Laboratory 5-MW reference wind turbine, and a typical 6-MW wind turbine is conducted. The main objective is to develop a numerical model validated by experimental test results of a semisubmersible platform with mooring lines made of various materials. A commercial software package is employed to model the floating platforms, and a coupled dynamic analysis is carried out on floater motions, mooring lines, and their interactions. The 5-MW numerical model is verified using experimental results of the reduced 1/50th scale semisubmersible platform model conducted by DeepCwind consortium. The results from the numerical model are also compared with FAST programme developed by the National Renewable Energy Laboratory, where an acceptable agreement is achieved to benchmark the parametric study presented herein. A semisubmersible platform with 6-MW wind turbine is designed through hydrostatic and hydrodynamic analyses, using the general arrangement, main structure, and mooring system from the verified 5-MW numerical model. A parametric study is carried out to study the influence of different parameters on the hydrodynamic response of the platform, including total mass, mooring material properties, and wave characteristics. Various mooring lines are examined with particular attention to polymer and synthetic materials to determine which is the most suitable for this platform. Results reveal that using the synthetic mooring lines due to their low Young's modulus provide better performance for the platform compared with other materials investigated in this research. [ABSTRACT FROM AUTHOR]

The paper proposes a new approach for optimal design structures equipped with tuned mass dampers (TMDs) with large mass ratios. The approach is based on minimizing the frequency response function (FRF) of displacement response of the structure as well as the acceleration of the TMD that leads to almost equal modal damping ratios in the first and second mode of vibration. Furthermore, two regression equations are proposed to predict the optimum TMD properties. It is concluded that choosing the optimum TMD parameters as suggested in this study provides up to 94% reduction in the maximum FRF of structural displacement. [ABSTRACT FROM AUTHOR]

This article focuses on evaluating thermal performance of different types of residential buildings in Mediterranean climate (Csa) of Iran. The aim is to identify the main design parameters in nine research cases, selected from three distinct periods of history with different architectural styles, and evaluating thermal performance of these buildings. To that end, a library study was carried out to identify the most influential passive design strategies and to highlight their impact on thermal comfort and energy efficiency of residential buildings. A field survey was conducted to determine the most common types of average-income houses in Csa climate of Gorgan, Iran, with a historical overview from 19th century to present. Nine buildings were selected to study from three different period of times including the years from 1850 to 1925, 1925 to 1979 and 1979 to present. A three-dimensional numerical model was developed to assess the impact of four main design parameters including orientation, geometrical properties, openings and materials on indoor thermal comfort for each case, using Design Builder commercial software package. The correlation between these design variables and thermal comfort was presented; the results reveal that the contemporary residential buildings are not designed as efficient as traditional houses in this area, in terms of passive energy saving techniques. [ABSTRACT FROM AUTHOR]

In this paper, the second-order hydrodynamic force on fixed and floating tandem cylinders has been calculated and different parameters have been taken into consideration. An incident wave is diffracted by the fixed cylinder, and as a result low-frequency waves radiate toward the floating cylinder and cause low-frequency second-order hydrodynamic forces to act on the surface of the floating cylinder. The interactions between the fixed and floating cylinders have been investigated by changing the distance between them, as well as the draft and radius of the floating cylinder. By employing perturbation series analysis over the wetted surface, the second-order wave excitation force has been calculated. The maximum force applied on the floating cylinder becomes non-dimensional when considering it with and without the fixed cylinder. The results showed the effect that the existence of the fixed cylinder had on the increase in the second-order forces is quite evident where, for a significant parameter of the floating cylinder, the force in the heave direction was enhanced by up to 1.55 times. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer bars are gaining increased use in the construction market as a replacement to steel reinforcement for concrete structures. However their use as compression members is limited due to their mechanical properties, typically low flexural rigidity, so that local buckling may occur relatively at low stress levels. Their premature rupture in reinforced concrete (RC) columns could be eliminated by enhancing the columns’ response elastically and concentrating damage to the externally installed, replaceable post-tensioned structural fuses. This paper is part of a larger numerical and experimental investigation to develop and validate design methods for a rocking aramid fiber reinforced polymer (AFRP) reinforced concrete column. The numerical study, implemented using the Extreme Loading for Structures software, consists of a total of thirteen columns. The columns were subjected to axial load followed by cyclic lateral load up to failure to examine the effectiveness of the rocking connection and overall response. The effect of key variables such as longitudinal bar ratio, structural fuse sizes and tie spacing was investigated. Ductility and energy dissipation gains of the rocking AFRP RC columns were compared to that of the conventionally reinforced steel column, and expected performance of the rocking connection was achieved. [ABSTRACT FROM AUTHOR]