Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Author: search.filters.author.Dönmez, CemalettinPublisher: search.filters.publisher.Izmir Institute of Technology

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Now showing 1 - 5 of 5
  • Master Thesis
    Stiffnes Requirements of Shear Diaphragms Used To Brace Steel I-Beams
    (Izmir Institute of Technology, 2017) Akbaba, Andaç; Dönmez, Cemalettin; Eğilmez, Oğuz Özgür; Dönmez, Cemalettin; Eğilmez, Oğuz Özgür; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The buckling capacity of steel I-beams can be increased by providing lateral bracing along the length of the beams by either cross-frames or diaphragms. Metal sheeting that is often used in steel building and bridge constructions to support the fresh concrete, acts like a shear diaphragm and provides continuous bracing to steel beams. In building industry, metal deck forms are considered as a lateral support to the beams. However, due to their flexible connection detail between the girder and shear diaphragm, metal deck forms are not considered as a brace source for bridge construction industry. But with the recent studies, by improvements of the flexible connection details, metal decking can be used as a bracing system. An adequate bracing system must possess sufficient stiffness and strength. A computational study was conducted to investigate stiffness requirements of shear diaphragms used to brace stocky and slender steel I-beams. Both doubly and singly symmetric sections were studied. The computational study consists of eigenvalue buckling analyses on perfectly straight twin-girder system braced by shear diaphragms and large deformation analyses with imperfect girders with different configurations of girder sections and spans. A three dimensional computer programme was utilized to perform analytical studies. Analytical model is verified by a full-scale twin-girder system laboratory test that is carried out on a previous study. Stiffness requirements have been proposed for shear diaphragms used to brace stocky and slender steel I-beams.
  • Master Thesis
    Strength Requirements of Shear Diaphragms Used To Brace Steel I-Beams
    (Izmir Institute of Technology, 2014) Eğilmez, Oğuz Özgür; Eğilmez, Oğuz Özgür; Dönmez, Cemalettin; Dönmez, Cemalettin; Eğilmez, Oğuz Özgür; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Lateral torsional buckling, also known as flexural torsional buckling is a failure mode that often controls the design of I-shaped steel beams during construction. In order to increase the lateral torsional buckling capacity of the girders in this stage, discrete or continuous bracing systems are often utilized in building and bridge constructions. Light gauge metal decking acts like a shear diaphragm and provides continuous lateral bracing to the beams. The building industry has long relied on metal decking to laterally support the beam top flanges. Bridge construction industry does not consider metal decking as a brace source due to the flexible connection between the girder and the diaphragm. However, recent studies have shown that metal sheeting can also be used in the bridge industry as construction bracing as long as the flexibility of the connections can be controlled by modifications. An adequate bracing system must possess sufficient strength and stiffness to control deformations and brace forces. A parametrical study was conducted to investigate the stiffness and strength of shear diaphragms used to brace stocky and slender steel I-beams. This thesis focuses on the strength requirements. The parametrical study consists of eigenvalue buckling analyses and large displacement analyses on a twin girder shear diaphragm system with various girder and metal deck configurations. A three-dimensional finite element analysis program was selected for the analyses. In the model metal deck-girder connections and the connection between adjacent decks are modeled respectively. Finite element model is verified by a full-scale twin-girder buckling test as the part of a previous study. According to the numerical study an equation is proposed for the estimation of the brace forces in the deck connections. The equation is shifted for possible deck and girder configurations.
  • Master Thesis
    Estimation of Frequency Response Fuction for Experimental Modal Analysis
    (Izmir Institute of Technology, 2008) Karakan, Eyyüb; Dönmez, Cemalettin; Dönmez, Cemalettin; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Every structural system has unique dynamic parameters based on the mass, stiffness and the damping characteristics. If the system is linear and time invariant, dynamic parameters could be shown to be measured and formulated by the Frequency Response Function (FRF). The study of defining the dynamic parameters of a system thru well designed experiments and analysis is called experiment modal analysis. Experimental modal analysis has two major study areas which are modal testing and modal parameter estimation. FRFs are calculated based on the measured data in modal experiment and it is main input to the modal parameter estimation. Based on the measured/synthesized FRF dynamic parameters of the structures considered could be obtained In this study basics of the experimental modal analysis is studied. The primary objective is to see the effects of various testing and analysis parameters on the synthesis of FRF. This goal is achieved by testing and discussion of several simple structural systems.In the thesis general information about experimental modal analysis is presented.The experiment and the modal analysis results of the of the studied systems, which are simple beam, H-frame, square plate and 2D frame, is presented. Selected parameters that are effective on the FRF synthesis is discussed. These parameters are the attachment of the accelerometers, the tip hardness of the impact hammer and the digital signal processing errors such as leakage, windowing, filtering and averaging. The hammer and accelerometers calibrations will be discussed briefly as well. The results are discussed in order to provide some guidance for understanding the effects of the selected parameters on the FRFs.
  • Master Thesis
    Effect of Infill Wall Stiffness Variations on the Behavior of Reinforced Concrete Frames Under Earthquake Demands
    (Izmir Institute of Technology, 2013) Sönmez, Egemen; Dönmez, Cemalettin; Dönmez, Cemalettin; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Reinforced concrete (RC) structures with infill walls are the most common building types in earthquake-prone regions of Turkey. Due to the complications in modeling the infill wall - frame interaction, they are generally neglected in structural design. However, presence of the infill walls has been proved to affect stiffness, strength and behavior of the structures significantly. Effects of infill walls may be either beneficial or detrimental under seismic demands. Infill walls typically increase the stiffness and strength of the structures. This situation may be advantageous for nonductile buildings up to a certain limit. However, brittle nature and variety of failure modes of infill walls may cause unforeseen and irreversible damages. Particularly, softstory mechanisms may occur due to drift concentrations at lower stories. An organized stiffness distribution along the height of the structure may help mitigating these negative effects. The main purpose of the study is to investigate the effects of stiffness variations in infill walls to the behavior of the frames. In order to achieve the purpose, an analytical software that supports an infill model, was selected. The software is calibrated and verified by simulating a series of experiments. Afterwards, a planar, fivestory, five-bay reinforced concrete frame was designed with common deficiencies observed in residential buildings in Turkey. The performance of the bare frame (BF) was determined using pushover analysis. Then, two types of infilled frames were obtained by introducing infill walls into two bays. The infill walls of the first infilled frame (IF-1) had a uniform stiffness and strength distribution along the height of the frame. In the second infilled frame (IF-2), the stiffness and strength of the infill walls had a decreasing profile from the bottom to the top story. By this distribution, drift concentration at the lower stories was aimed to be mitigated. Nonlinear dynamic and pushover analyses were performed on the frames. The results indicated that the organized stiffness distribution of IF-2 mitigated the drift concentrations and improved he seismic performance of the frame.
  • Master Thesis
    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.