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Mechanical Behavior of Hybrid Fiber Reinforces Concrete Under Direct Tension
(Izmir Institute of Technology, 2020) Çetin, Fatma Şirin; Saatcı, Selçuk; Erdem, Tahir Kemal; Saatçi, Selçuk; Erdem, Tahir Kemal; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
Using different fiber types together, called hybrid fiber reinforced concrete, may cause a mutual synergic response between fiber matrixes. Due to these synergic effects of different fiber combinations, the mechanical behavior of concrete may perform differently than single fiber reinforced concrete. In this study, the effects of fiber hybridization in the direct tension behavior of concrete mixtures obtained by using three different types of steel fiber and polyvinyl alcohol (PVA) fiber were investigated. In this scope, total of 50 dog bone shaped, notched specimens were cast for 10 different mixtures and tested under direct tension. Average tensile stress-crack width responses of concrete specimens were investigated. It was found that the addition of PVA fiber to 35 mm long single hook end and 60 mm long double hook end steel fiber mixtures with a volume ratio of 0.75% did not considerably change the tensile behavior post cracking. As a result of adding PVA fibers to 60 mm single hook steel fiber mixtures with a volume ratio of 1.25%, cracking stresses were decreased and post cracking behavior was adversely affected. Addition of PVA fibers to 60 mm single hook steel fiber mixture with 0.75% volumetric ratio was found to increase post cracking stress levels.
Effects of Shear Reinforcement on the Impact Behavior of Reinforced Concrete Slabs
(Izmir Institute of Technology, 2014) Arsan, Yonca; Saatci, Selçuk; 01. Izmir Institute of Technology
Design of reinforced concrete (RC) members against impact loads is required for many structures such as industrial facilities, military protective structures, and infrastructures. This study presents experimental investigation for strengthening RC slabs under impact loads using shear reinforcement. Slabs were strengthened against punching shear with two methods: using shear studs as shear reinforcement and using steel fiber reinforced concrete (SFRC) instead of plain concrete. Eight RC slabs with dimensions of 2150x2150x150 mm were tested. Four of the specimens, two identical pairs, were cast with shear studs around the point of impact. Remaining four specimens, again two identical pairs, were cast with 1% steel fibers. Pairs in each group contained two different levels of longitudinal reinforcement. For each pair, one specimen was tested under static loading, whereas its identical twin was tested under impact loads. Specimens were tested with a test setup that provides simply supported conditions. Support loads, displacements, accelerations, and strains on bars were measured during the tests. The study revealed that using shear studs and SFRC prevents brittle punching shear failure for both static and impact loading. Specimens with steel fibers reached the highest load carrying capacity for static test while specimens with shear reinforcement carried a smaller load for large deformations. Specimens with SFRC displayed a close to static behavior under impact loading, influenced only slightly by inertial forces due to impact. Specimens with shear studs were largely influenced by inertial forces and scabbing occurred at some areas. Specimens with steel fibers endured more impacts compared to control specimens and specimens with shear studs due to their higher energy dissipating capabilities.
Dynamic Behavior of Reinfor Ced Concrete Frames With Infill Walls
(Izmir Institute of Technology, 2011) Çankaya, Mehmet Alper; Dönmez, Cemalettin; Dönmez, Cemalettin; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
Current practices utilize infill walls as insulation or partition material but not as a structural material. The main reason for this choice is the complexity of the partition wall-frame interaction behavior. Therefore infill walls typically ignored in the structural designs. However, existence of partition walls heavily effect stiffness, strength and behavior of structures. The main purpose of the presented study is the investigation of the dynamic parameters of reinforced concrete frames with and without infill walls. Moreover, lateral strength, stiffness and energy dissipation properties of the frames are also studied. In order to achieve the purpose four planar, one-bay, four story RC frames with 1/5 scale are designed, constructed and tested. In the frames main parameters are selected as presence of partition walls and ductile/non-ductile reinforcement detailing. Experiments are consisted of static and dynamic tests. In static tests each frame subjected to lateral loads that were applied at the each story level to provide a lateral loading increasing with height. Lateral load levels were controlled by the drift levels in the first story. Dynamic tests were performed at the end of each deformation level and modal analysis methods are utilized. Analyses have shown that existence of partition walls in the frame increased the natural frequencies of the frames. However, reinforcement detailing did not have a significant effect on natural frequencies. It is also observed that the natural frequencies of the frames decreased with increasing damage level. On the other hand, presence of partition walls effected the damaged behavior of the frames and drift is observed to concentrate to the first story with the increasing level of damage. And finally stiffness, strength and energy dissipation properties of frames with partition walls are observed to be dramatically higher than the frames without partition walls.

Master Degree / Yüksek Lisans Tezleri

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