Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Seismic Behavior of Steel I-Beams Modified by a Welded Haunch and Reinforced With Glass Fiber Reinforced Polymers(Izmir Institute of Technology, 2009) Özdemir, Timur; Eğilmez, Oğuz Özgür; Eğilmez, Oğuz Özgür; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyFlange and web local buckling in beam plastic hinge regions of welded steel moment frames (SMF) can prevent beam-column connections to achieve adequate plastic rotations under earthquake-induced forces. 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. Generally, high modulus carbon FRP (CFRP) laminates, with elastic modulus similar to that of steel, are preferred in strengthening applications. On the other hand, glass FRP (GFRP) has a much smaller modulus than that of steel, typically one order of magnitude less, which limits its use in strengthening applications. However, this modulus mismatch is an asset when the primary goal is to stabilize inelastic local buckling with the least possible strength increase in the section. In a steel-GFRP hybrid system, while the low modulus of GFRP will not allow a significant strength increase in the beam, the flexural strength of GFRP can provide bracing to the underlying steel, which is flowing plastically. In this research study, the cyclic behavior of steel beams modified by a triangular haunch welded to the beam bottom flange only and reinforced with GFRP laminates at beam flanges have been investigated by finite element analysis (FEA). Cantilever I-sections with flange-web slenderness ratios higher then those stipulated in current seismic design specifications are analyzed under reversed cyclic loading. Both bare beam sections and sections reinforced with GFRP are investigated. The effects of GFRP thickness, width, and length on stabilizing local buckling are investigated. The flexural resistance of the beams at column face, interlaminar shear stresses in GFRP strips, and shear stresses at beam-GFRP binding surface are examined. The results reveal that the plastic rotation capacity of steel beams can be enhanced by the use of GFRP strips.Master Thesis Seismic Behavior of Steel I-Beams Reinfor Ced With Glass Fiber Reinforced Polymer: an Experimental Study(Izmir Institute of Technology, 2010) Yormaz, Doruk; Eğilmez, Oğuz Özgür; Eğilmez, Oğuz Özgür; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyDesign guidelines, which are put into effect in the aftermath of the 1994 Northridge earthquake, require intermediate and special moment frames (IMF and SMF) be capable of maintaining 0.02 and 0.04 radians interstory drift, respectively without significant strength degradation and development of instability. However, local buckles in the plastic hinge region are major hindrances for the ductility capability and stability of the structural system. Thus, the research program aims to mitigate such inelastic instabilities by using glass fiber reinforced polymer (GFRP), which possesses elastic modulus roughly one order of magnitude less than that of steel. On the other hand, this elastic modulus discrepancy between GFRP and steel can be useful for stabilizing local buckles by means of the bracing effect of GFRP during plastic hinge formations. This thesis describes large-scale experimental study of the research program that investigates the seismic behavior of steel I-beams reinforced with GFRP. In this experimental study, four HE400AA beams with welded haunch (WH) modification and three HE500AA beams with no modification were tested under cyclic loading. The results of experimental study indicate that it does not seem possible to rely on GFRP reinforcement to increase the flexural resistance of connections at a rotation of 0.04 radians because the adhesive layer between steel and GFRP fails in rotations much lower than 0.04 radians. However, the seismic performance of the structure can be moderately improved with the bottom flange WH and GFRP reinforcement in order to maintain rotations without local buckles in accordance with the rotation demand of IMFs, which is 0.02 radians.