Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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  • Conference Object
    Improving the Ductility of Steel I-Beams Through the Use of Glass Fiber Reinforced Polymers
    (Curran Associates, 2010) Eğilmez, Oğuz Özgür; Alkan, Deniz; Özdemir, Timur
    Flange and web local buckling in beam plastic hinge regions of steel moment frames can prevent beam-column connections from achieving adequate plastic rotations under earthquake-induced forces. Reducing the flange-web slenderness ratios (FSR/WSR) of beams is the most effective way in mitigating local buckling as stipulated in the latest seismic design specifications. However, existing steel moment frame buildings with beams that lack the adequate slenderness ratios set forth for new buildings are vulnerable to local member buckling and thereby system-wise instability prior to reaching the required plastic rotation capacities specified for new buildings. This paper presents results from a research study investigating the cyclic behavior of steel I-beams modified by a welded haunch at the bottom flange and reinforced with glass fiber reinforced polymers at the plastic hinge region. Cantilever I-sections with a triangular haunch at the bottom flange and FSR higher then those stipulated in current design specifications were analyzed under reversed cyclic loading. Beam sections with different depth/width and flange/web slenderness ratios (FSR/WSR) were considered. The FEA results revealed that the GFRP reinforcement moderately improves the plastic local behavior of steel I-beams.
  • Conference Object
    Citation - Scopus: 1
    Stiffness and Strength of Shear Diaphragms Used for Stability Bracing of Slender Beams
    (Curran Associates, 2014) Eğilmez, Oğuz Özgür; Akbaba, Andaç; Vardaroğlu, Mustafa
    Light gage metal decking is often used in structures as concrete deck formwork, roof cladding or siding. In the steel building and bridge industries, decking acts like a shear diaphragm and provides continuous lateral bracing to the top flange of non-composite beams and girders that they are attached to. The building industry has long relied on the in-plane stiffness and strength of metal decking to brace steel beams during construction. Although the current AASHTO LRFD specifications do not allow bridge deck forms to be relied upon as a bracing source for steel bridge I-girders, recent studies have demonstrated that deck forms can significantly increase the buckling capacity of bridge girders by providing a relatively simple modification to the connection. Shear diaphragm bracing of steel I-beams have been studied in the past. These studies mainly focused on beams with stocky webs. The purpose of the study outlined in this paper is to enhance the understanding of both the stiffness and strength of shear diaphragms used to brace slender steel I-beams. The parameters that are investigated include diaphragm stiffness, sheet thickness, number of side-lap fasteners, flange width, and web slenderness ratio. Beams with web slenderness ratios of 100 to 160 and span/depth ratios of 10, 15, and 20 are considered. A simple finite element analytical (FEA) model is utilized in the study. The results indicate that web slenderness ratio does not have a major effect on fastener forces and the strength behavior of shear diaphragms is dependent on the number of side-lap fasteners. The findings of the study will be used to develop strength and stiffness requirements for shear diaphragms used to brace slender steel beams
  • Conference Object
    Overt information operations during peacetime
    (Curran Associates, 2012) Tekir, Selma
    Information superiority is the most critical asset in war making. It directly addresses the perception of the opponent and in the long term the will of him to act. Sun Tzu's classical text states this fact by the concept of deception as the basis of all warfare. The success in warfare then is dependent on being aware of what's happening, accurately realizing the context. This is the intelligence function in broad terms and mostly open source intelligence as it provides the context. Competitive intelligence is based mainly on open sources and day by day the open source share in the intelligence product is increasing. Present diversified open sources & services represent a methodology shift in war. The two preceding ways have been overt physical acts against military targets in wartime and covert information operations conducted throughout peacetime against even nonmilitary targets respectively. The present methodology must be overt (open) information operations during peacetime. This coincides with a metaphor change as well. It proposes a transformation from a war metaphor into a game metaphor in which there are some playing rules. In fact, the existence of such rules helps in drawing the boundary of the field of competitive intelligence and thus making it a profession. Game metaphor is safer to adopt than war as it's easier to take responsibility in public disclosure scenarios in this case. By following this metaphor, you continue to stay in the boundary of legitimate competition. In other terms, you make a conscious preference in terms of war intensities by choosing to avoid the more intense war forms limited conflict, and actual warfare respectively. Finally, this preference is in accordance with the fundamental point of the Sun Tzu's entire argument: The vision of victory without fighting. To summarize, open source domination in the competitive intelligence lays the ground for the game metaphor that represents a transformation in warfare. The apparent outcome is overt information operations during peacetime. It emerges as the most important tool to fight against deception, thus success in information warfare in the contemporary world.
  • Conference Object
    Citation - WoS: 3
    Citation - Scopus: 4
    Recent Cyberwar Spectrum and Its Analysis
    (Curran Associates, 2012) Aslanoğlu, Rabia; Tekir, Selma
    War is an organized, armed, and often prolonged conflict that is carried on between states, nations or other parties. Every war instance includes some basic components like rising conditions, battlespace, weapons, strategy, tactics, and consequences. Recent developments in the information and communication technologies have brought about changes on the nature of war. As a consequence of this change, cyberwar became the new form of war. In this new form, the new battlespace is cyber space and the contemporary weapons are constantly being renovated viruses, worms, trojans, denial-of-service, botnets, and advanced persistent threat. In this work, we present recent cyberwar spectrum along with its analysis. The spectrum is composed of the Estonia Attack, Georgia Attack, Operation Aurora, and Stuxnet Worm cases. The methodology for analysis is to identify reasons, timeline, effects, responses, and evaluation of each individual case. Moreover, we try to enumerate the fundamental war components for each incident. The analysis results put evidences to the evolution of the weapons into some new forms such as advanced persistent threat. Another outcome of the analysis is that when approaching to the end, confidentiality and integrity attributes of information are being compromised in addition to the availability. Another important observation is that in the last two cases, the responsive actions were not possible due to the lack of the identities of the offending parties. Thus, attribution appears as a significant concern for the modern warfare. The current sophistication level of the cyber weapons poses critical threats to society. Particularly developed countries that have high dependence on information and communication technologies are potential targets since the safety of the critical infrastructures like; healthcare, oil and gas production, water supply, transportation and telecommunication count on the safety of the computer networks. Being aware of this fact, every nation should attach high priorities to cyber security in his agenda and thus behave proactively.
  • Conference Object
    Citation - WoS: 9
    Cyclic Testing of Steel I-Beams Reinforced With Gfrp
    (Curran Associates, 2011) Eğilmez, Oğuz Özgür; Yormaz, Doruk
    Flange and web local buckling in beam plastic hinge regions of steel moment frames can prevent beam-column connections from achieving adequate plastic rotations under earthquake-induced forces. This threat is especially valid for existing steel moment frame buildings with beams that lack adequate flange/web slenderness ratios. As the use of fiber reinforced polymers (FRP) have increased in strengthening and repair of steel members in recent years, using FRPs in stabilizing local instabilities have also attracted attention. Previous computational studies have shown that longitudinally oriented glass FRP (GFRP) strips may serve to moderately brace beam flanges against the occurrence of local buckling during plastic hinging. An experimental study was conducted at Izmir Institute of Technology investigating the effects of GFRP reinforcement on local buckling behavior of existing steel I-beams with flange slenderness ratios (FSR) exceeding the slenderness limits set forth in current seismic design specifications and modified by a bottom flange triangular welded haunch. Four European HE400AA steel beams with a depth/width ratio of 1.26 and FSR of 11.4 were cyclically loaded up to 4% rotation in a cantilever beam test set-up. Both bare beams and beams with GFRP sheets were tested in order to investigate the contribution of GFRP sheets in mitigating local flange buckling. Different configurations of GFRP sheets were considered. The tests have shown that GFRP reinforcement can moderately mitigate inelastic flange local buckling.