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Torsional parameters importance in the structural response of multiscale asymmetric-plan buildings
Bakas, Nikolaos,Makridakis, Spyros,Papadrakakis, Manolis Techno-Press 2017 Coupled systems mechanics Vol.6 No.1
The evaluation of torsional effects on multistory buildings remains an open issue, despite considerable research efforts and numerous publications. In this study, a large number of multiple test structures are considered with normally distributed topological attributes, in order to quantify the statistically derived relationships between the torsional criteria and response parameters. The linear regression analysis results, depict that the center of twist and the ratio of torsion (ROT) index proved numerically to be the most reliable criteria for the prediction of the modal rotation and displacements, however the residuals distribution and R-squared derived for the ductility demands prediction, was not constant and low respectively. Thus, the assessment of the torsional parameters' contribution to the nonlinear structural response was investigated using artificial neural networks. Utilizing the connection weights approach, the Center of Strength, Torsional Stiffness and the Base Shear Torque curves were found to exhibit the highest impact numerically, while all the other torsional indices' contribution was investigated and quantified.
Baka, Aikaterini D.,Uzunoglu, Nikolaos K. Occupational Safety and Health Research Institute 2014 Safety and health at work Vol.5 No.3
Investigation and analysis of accidents are critical elements of safety management. The over-riding purpose of an organization in carrying out an accident investigation is to prevent similar accidents, as well as seek a general improvement in the management of health and safety. Hundreds of workers have suffered injuries while installing, maintaining, or servicing machinery and equipment due to sudden re-energization of power lines. This study presents and analyzes two electrical accidents (1 fatal injury and 1 serious injury) that occurred because the power supply was reconnected inadvertently or by mistake.
Torsional parameters importance in the structural response of multiscale asymmetric-plan buildings
Bakas, Nikolaos,Makridakis, Spyros,Papadrakakis, Manolis 테크노프레스 2016 Multiscale and multiphysics mechanics Vol.1 No.4
The evaluation of torsional effects on multistory buildings remains an open issue, despite considerable research efforts and numerous publications. In this study, a large number of multiple test structures are considered with normally distributed topological attributes, in order to quantify the statistically derived relationships between the torsional criteria and response parameters. The linear regression analysis results, depict that the center of twist and the ratio of torsion (ROT) index proved numerically to be the most reliable criteria for the prediction of the modal rotation and displacements, however the residuals distribution and R-squared derived for the ductility demands prediction, was not constant and low respectively. Thus, the assessment of the torsional parameters' contribution to the nonlinear structural response was investigated using artificial neural networks. Utilizing the connection weights approach, the Center of Strength, Torsional Stiffness and the Base Shear Torque curves were found to exhibit the highest impact numerically, while all the other torsional indices' contribution was investigated and quantified.
Growth and Properties of Electrodeposited Transparent Al-doped ZnO Nanostructures
O. Baka,L. Mentar,M. R. Khelladi,A. Azizi 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.12
Al-doped zinc oxide (AZO) nanostructures were fabricated on fluorine-doped tin-oxide (FTO)- coated glass substrates by using electrodeposition. The effects of the doping concentration of Al on the morphological, microstructural, electrical and optical properties of the nanostructures were investigated. From the field emission scanning electron microscopy (FE-SEM) observation, when the amount of Al was increased in the solution, the grains size was observed to decreases. The observed changes in the morphology indicate that Al acts as nucleation centers in the vacancy sites of ZnO and destroys the crystalline structure at high doping level. Effectively, the X-ray diffraction (XRD) analysis indicated that the undoped and the doped ZnO nanostructures has a polycrystalline nature and a hexagonal wurtzite structure with a (002) preferential orientation. The photoluminescence (PL) room-temperature measurements showed that the incorporation of Al in the Zn lattice can improve the intensity of ultraviolet (UV) emission, thus suggesting its greater prospects for use in UV optoelectronic devices.
Nikolaos Bakas 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.61 No.1
The recently introduced index Ratio Of Torsion (ROT) quantifies the base shear amplification due to torsional effects on shear cantilever types of building structures. In this work, a theoretical proof based on the theory of elasticity is provided, depicting that the ratio of torsion (ROT) is independent of the forces acting on the structure, although its definition stems from the shear forces. This is a particular attribute of other design and evaluation criteria against torsion such as center of rigidity and center of strength. In the case of ROT, this evidence could be considered as inconsistent, as ROT is a function solely of the forces acting on structural members, nevertheless it is proven to be independent of them. As ROT is the amplification of the shear forces due to in-plan irregularities, this work depicts that this increase of internal shear forces rely only on the structural topology. Moreover, a numerical verification of this theoretical finding was accomplished, using linear statistics interpretation and nonlinear neural networks simulation for an adequate database of structures.
Aikaterini D. Baka,Nikolaos K. Uzunoglu 한국산업안전보건공단 산업안전보건연구원 2014 Safety and health at work Vol.5 No.3
Investigation and analysis of accidents are critical elements of safety management. The over-ridingpurpose of an organization in carrying out an accident investigation is to prevent similar accidents, aswell as seek a general improvement in the management of health and safety. Hundreds of workers havesuffered injuries while installing, maintaining, or servicing machinery and equipment due to sudden reenergizationof power lines. This study presents and analyzes two electrical accidents (1 fatal injury and1 serious injury) that occurred because the power supply was reconnected inadvertently or by mistake.