Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Structural Design of Rc Structures From Sustainable Development Perspective(01. Izmir Institute of Technology, 2023) Gültepe, Ekin; Dönmez, CemalettinThe growth of the population and changing demands have become a significant problem due to the limited resources of the earth. Climate change has increased the occurrence of natural events and probable disasters due to insufficient infrastructure. The economic, environmental, and social aspects of the problem necessitate sustainable practices. On the other hand, probable disaster dictates design decisions to keep the physical environment intact and resilient. Hence, the expectations from the construction industry are high. The industry also needs to tackle the task of lowering the existing high consumption levels of natural resources and energy. Being resilient under seismic events is paramount for the areas that have high seismicity. The general trend of using less material for sustainability purposes conflicts with the resilient seismic design decisions which typically cause an increase in the initial consumptions. The studies on resilience and sustainability hint that there might be design opportunities that serve both purposes together. In this study, such an opportunity for RC residential buildings is focused. The resilience and energy cost of a conventional moment-resisting frame and the same frame with increased robustness through the addition of shear walls are studied. It is presumed in addition to the increased robustness, the thermal impact of the additional concrete mass will create an advantage for energy consumption in the life cycle of the building. The design decision for shear walls is based on the proposal by Hassan and Sozen (1997). Nonlinear time history analysis is performed for both frames according to Turkish Earthquake Regulation. Results show that the robust frame has the needed resilience. The energy analysis shows that the frame with shear walls has significantly higher consumption initially. However, when the thermal impact of the concrete is included in the full life cycle, the energy consumption difference reduces from 18% to 4%. As a result, it could be stated that providing sufficient robustness to the structure by shear walls at targeted locations provides an opportunity to have a resilient and sustainable structure with a minor increase in total energy cost throughout the life cycle of the structure.Master Thesis Effect of Column-Beam Moment Capacity Ratios on the Frame Plastic Failure Mechanism(01. Izmir Institute of Technology, 2023) Akhtari, Rohullah; Dönmez, CemalettinThe strong-column weak-beam design ratio plays a crucial rule to design the structures particularly for high seismic region. Interestingly, the ratio to be used is still under spotlight for research. Observations and analytical studies have demonstrated that the ratio's effectiveness varies with some parameters. One of these parameters is the number of stories in a building. The failure mechanism of the structures depends on this ratio and the design ratio efficiency seems to change as building's stories increases. This efficiency also seem to saturate at a point depending on number of stories. In this study, three case studies have been assessed and analyzed. Each case study contains three reinforced concrete frames with different strong-column weak-beam design ratios that varies from 1.2 to 3.0. For each case study, the design ratios are ranged into three parts: (i) ratios between 1.2 to 1.5; (ii) ratios between 1.5 to 2.0; (iii) ratios between 2.0 to 3.0. The Turkish Earthquake Regulation (2018) has been utilized for the design procedures. The pushover and time-history analysis of frames were performed using OpenSees software framework (McKenna et al., 2010). Columns have been modeled with fiber sections and the beams have been modeled with concentrated rotational springs at the ends. Both members are accepted to be linear in between. The plastic hinge occurrence at the end of members were monitored to observe the frames' failure mechanism.Master Thesis Evaluation of Effective Stiffness Procedures in Seismic Design of Reinforced Concrete Frames(01. Izmir Institute of Technology, 2021) Şenol, Duygu; Dönmez, CemalettinThis study investigates the success of the effective stiffness procedures defined for the design of reinforced concrete frames in seismic design regulations. The emphasis will be on the effort to model success relations. The origins of the effective stiffness approach could be identified in the effort to use the equal displacement rule for seismic design purposes. The equal displacement rules dictate that if a system's effective stiffness at the sustained drift levels could be identified, the linear and nonlinear system deflection demands are approximately equal. The nonlinear displacement response of a system could be obtained using this "estimated" stiffness value at the sustained displacement levels from the elastic analysis of the system. Hence, there is no consensus about defining the effective stiffness, and different approaches exist for its calculation. In this study, the effective stiffness approaches of the Turkish Earthquake Code (2018), Canadian Standards Association Design of Concrete Structures (CSA A.23.3-14), New Zealand Concrete Structures Standard (NZS3101-2006), Eurocode 8 (EN 1998-3), Building Code Requirement for Structural Concrete of American Concrete Institute (ACI318-19) and Sozen's Method are investigated in terms of effort in their execution to the success of the result. In order to provide a comparison in reference to measured values, the evaluation is based on the shaking table tests of a ten-story-three-bay reinforced concrete frame model. The numerical analysis is performed using the OpenSees platform. The model is formed by defining nonlinear rotational springs at the element ends. The effective stiffness definitions are performed per each regulation, and the results are compared with the test results. Also, a suite of ground motions is selected, and time history analyses are performed using each effective stiffness approach. Results are compared in terms of the maximum and envelope drift levels of the frames obtained by each approach.Master Thesis Seismic Analysis of an Ancient Lighthouse by Meso-Scale Modeling Technique(01. Izmir Institute of Technology, 2020) Gözün, Safiyullah Üveys; Özdemir, İzzet; Dönmez, CemalettinModeling masonry structures has always been a difficult subject due to the lack of information about the behavior, the heterogeneity of the masonry materials and complex geometries of masonry structures. In terms of the computational costs and complexity, several methods are proposed in the literature. In this thesis, the capabilities of the meso-scale modeling technique are investigated by means of two experiments selected from the literature and the seismic response of an ancient lighthouse. Brick and mortar type structure is idealized as expanded units surrounded by zero thickness cohesive interfaces representing the mortar behavior. This means that the failure of mortar layers is considered explicitly by means of cohesive surfaces whereas the mechanical response of expanded units is described by Drucker-Prager/Cap model. This approach is used to simulate the in-plane and the outof-plane behavior of masonry walls reported in the literature. After validating the models with the experimental results, implicit-dynamic time history analyses of an ancient lighthouse are conducted by using 2 different earthquake records. The influence of mortar properties on the energy dissipation mechanisms and collapse pattern of the structure are investigated by means of a parametric study. As an attempt to identify the critical earthquake level corresponding to the initiation of sliding within the lighthouse, a set of additional analyses are conducted with scaled earthquake records.Master Thesis Stiffnes Requirements of Shear Diaphragms Used To Brace Steel I-Beams(Izmir Institute of Technology, 2017) Akbaba, Andaç; Dönmez, Cemalettin; Eğilmez, Oğuz ÖzgürThe 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) Vardaroğlu, Mustafa; Eğilmez, Oğuz Özgür; Dönmez, Cemalettin; Dönmez, Cemalettin; Eğilmez, Oğuz ÖzgürLateral 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, CemalettinEvery 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, CemalettinReinforced 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, CemalettinCurrent 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.