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Öğe An investigation of anchorage to the edge of steel plates bonded to RC structures(Techno-Press, 2016) Kara, Mehmet Emin; Fırat, F. K.; Sönmez, M.; Karabörk, T.This paper presents the results of an experimental study investigating the effects of anchorage systems used in externally bonded steel plates on the strength and ductility of reinforced concrete structures. In the literature, diagonal steel plates bonded to frames were designed to be more flexible than the connections to eliminate the possible effect of the connection flexibility. However, to better evaluate the performance of the strengthened structures, the strength and behavior of connections should also be considered. The purpose of this study was to experimentally investigate the effects of different connection types of steel plates bonded to the frame using anchors on the strengthened RC structures. For this purpose, eleven specimens were designed to simulate the interior and exterior connection behavior. Two of these were used as the control beams and remaining nine for the investigation of the functionality of the end steel plates. Experimental results show that the load carrying capacity of the strengthened beams is directly related to the connection types of the steel plates. For the interior connections, L-shaped end plates that were strengthened using steel anchors must have adequate stiffness to prevent its shape. While, for the exterior connections, the connection with three anchors carried more load than the other exterior connections.Öğe An investigation of anchoraged carbon fiber reinforced polymers bonded to concrete(2011) Kara, Mehmet Emin; Bayat, KıvançCarbon Fiber Reinforced Polymers (CFRP) is used for strengthening or retrofitting of RC structures frequently at last decades. Although there are studies about the stress distribution between CFRP plates and concrete, there are very limited amount of studies about the behaviours of anchorages that are applied to ends of CFRP plates used for connection. Connecting diagonal strips of CFRP to columns and beams of masonry infilled RC frames is a significant problem. In this study, two different anchoraging techniques namely fan and standard type that are found in its place at literature are compared with their pros and cons. Type and the number of anchorages are the main investigated parameters. RC beams without any tension reinforcement that are manufactured with a notch at the constant moment region are used in this study. As a result, increase in the number of fan type anchorages should be kept limited, if any other precautions did not took in to account. But increase in the number of standard anchorages are improved the strength and behaviour positively.Öğe An Investigation of fan type anchorages applied to end of CFRP strips(Techno-Press, 2013) Kara, Mehmet Emin; Yaşa, MustafaCFRP strips are widely used nowadays for repair/strengthening or capacity increase purposes. Sharp bending at the ends of the CFRP strips is frequently encountered at these applications. In this study, Reinforced Concrete (RC) beam specimens that were produced with 10 MPa compression strength concrete were strengthened by using bonded CFRP strips with end anchorages to tension region. The parameters that were investigated in this study are the width of the strip, the number of applied fan anchorages and whether additional layer of CFRP patch is used or not at the strip ends. Specimens were strengthened with 100 mm wide CFRP strips with one or two anchorages at the ends. In addition CFRP patch with two and three anchorages at the ends were tested for investigating the effect of the patches. Specimens that were strengthened with three anchorages at the ends with patches were repeated with 60 and 80 mm wide CFRP strips. The most successful result was obtained from the specimen that was strengthened with 80 mm wide CFRP strips with 3 end anchorages and patches among the others at the experimental program. The numbers of anchorages that were applied to ends of CFRP strips were more effective than the width of the CFRP strips onto strength and stiffness of the specimens. Due to limited space at the ends of the strips at most three anchorages could be applied.Öğe Comparison of seismic performance of RC frames strengthened with four different techniques(2012) Altın, Sinan; Anıl, Özgür; Kara, Mehmet Emin; Kopraman, KopramanThe purpose of this experimental study is to compare the strengthening techniques that are applied to non ductile low rise RC frames under seismic loads. In this study, 1/3 scale, one-bay, one-storey, nonductile RC frames with masonry infill walls were strengthened using four different techniques and are tested experimentally under reversed cyclic lateral loading. The four frames were constructed with masonry infill walls and three were strengthened with a mesh reinforced mortar layer, CFRP and steel strips wrapping, respectively. The remaining one without any extra strengthening was tested as a reference. A final specimen of the experimental program was strengthened with RC infill instead of masonry infill. Strength, stiffness, storey drift, ductility and failure modes of the specimens were evaluated and compared experimentally. Each strengthening technique proved to have different types of effectiveness on the lateral strength and stiffness of non ductile RC frames. Different strengthening techniques changed the ultimate lateral strengths and stiffnesses within the ranges of 53% to 381% and 82% to 601%, respectively.Öğe Eğilme etkisi altındaki soğukta şekil verilmiş çelik konik çatı kirişlerinin sonlu elemanlar modellemesine etki eden parametrelerin incelenmesi(Niğde Ömer Halisdemir Üniversitesi, 2024) Oruç, Ramazan; Kara, Mehmet EminBu çalışmada soğukta şekil verilmiş çelik kiriş elemanların doğrusal olmayan nümerik modellemesinin deneysel veriler ile doğrulanması amaçlanmıştır. C harfi formunda kesiti olan kirişlerden oluşturulan ve konik çatıya benzetilen deney elemanı test edilmiştir. Nümerik çalışmada ise deney elemanları farklı ağ tipleri, boyutları ve büyütme katsayıları kullanılarak modellenmiştir. Ayrıca, global ve lokal geometrik kusurlar gibi değişkenlerin analize etkisi değerlendirilmiş ve model doğrulanmıştır. Belirlenen modelin analizlerinden elde edilen sonuçlar, deneyde elde edilen sonuçlar ile karşılaştırılmıştır. Analitik modelin doğrulanmasında global kusurların tek başına yeterli olmadığı, lokal etkilerin de tanımlanması gerektiği sonucuna ulaşılmıştır.Öğe Experimental and numerical study on effectiveness of various tie-rod systems in brick arches(Elsevier, 2016) Ural, Ali; Fırat, Fatih Kürşat; Tuğrulelçi, Şükran; Kara, Mehmet EminArch-type structures have long been used to span large openings. In many historical masonry structures, the stability of the arches or pillars upon which the arches rest has been ensured by wood or iron tension members, commonly called tie-rods. Limited studies in the literature and earthquake reconnaissance reports have already verified the critical role of tie-rods on seismic behavior of arch-type structures. Iron tie-rods in many historic arches are nowadays susceptible to damages due to excessive corrosion. Similarly, strong seismic excitations or large differential foundation settlements may result in severe damage, in the form of buckling or fracturing, on tie-rods of many historic arches. In such cases, the replacement of the damaged tie-rods using a practical, reliable and effective technique is essential to retain the stability of the structure. To the best knowledge of authors, there is no published work in literature on this specific restoration work. The main objective of this study is to investigate both experimentally and numerically the viability, practicality and efficiency of five different replacement techniques proposed for the tie-rods in historic masonry arches. With this aim, six masonry arches, one reference with no tie-rod and five repaired using various tie-rod connection details, were tested under compressive load. Using the actual nonlinear properties of the masonry units and mortar, which are determined as specified by the current national specifications, a numerical study was also conducted using a commercially available structural analysis program and the test results are compared by the numerical results. In this study, the experimental results are presented in comparison with these numerical results and comments on the tie-rods used on the arches are given in consideration of the obtained results. Furthermore, recommendations are offered to solve the problems of tie-rod applications encountered in restoration works.Öğe Experimental investigation on cfrp-to-concrete bonded joints across crack(2010) Anıl, Özgür; Belgin, Ça?atay M.; Kara, Mehmet EminBonding of carbon fiber reinforced polymer (CFRP) composites has become a popular technique for strengthening concrete structures in recent years. The bond stress between concrete and CFRP is the main factor determining the strength, rigidity, failure mode and behavior of a reinforced concrete member strengthened with CFRP. The accurate evaluation of the strain is required for analytical calculations and design processes. In this study, the strain between concrete and bonded CFRP sheets across the notch is tested. In this paper, indirect axial tension is applied to CFRP bonded test specimen by a four point bending tests. The variables studied in this research are CFRP sheet width, bond length and the concrete compression strength. Furthermore, the effect of a crack-modeled as a notch-on the strain distribution is studied. It is observed that the strain in the CFRP to concrete interface reaches its maximum values near the crack tips. It is also observed that extending the CFRP sheet more than to a certain length does not affect the strength and the strain distribution of the bonding. The stress distribution obtained from experiments are compared to Chen and Teng's (2001) analytical model.Öğe Hysteretic behavior of RC shear walls strengthened with CFRP strips(Elsevier, 2013) Altın, Sinan; Anıl, Özgür; Kopraman, Yağmur; Kara, Mehmet EminThe purpose of this study was to investigate the hysteretic behavior of shear deficient reinforced concrete (RC) walls that were strengthened with carbon fiber reinforced polymer (CFRP) strips. Totally, 1/2 scale five specimens with 1.5 aspect ratio walls were constructed. One of them was tested without any retrofitting as a reference specimen and four of them were retrofitted specimens with CFRP strips. All of the specimens were tested under cyclic lateral loading. CFRP strips with different configurations were tested like X-shaped, horizontal and parallel strips or combinations of them. All of the CFRP configurations were symmetrically bonded to both sides of the shear wall and were anchoraged to the wall. The research focuses on the effect of using CFRP strips for enhancing strength and increasing ductility of the non-seismic detailed shear walls. Test results shows that all of the CFRP strip configurations significantly improves the lateral strength, energy dissipation and deformation capacity of the shear deficient RC walls. The specimen that was strengthened with X-shaped CFRP strips was failed with premature shear failure. The specimen that was strengthened with horizontal strips was showed flexural hysteretic behavior and plastic hinge was developed at the wall base. CFRP strips were controlled shear crack propagation and resulted in improvement of displacement capacity. (C) 2012 Elsevier Ltd. All rights reserved.Öğe Infill wall effects on the dynamic characteristics of RC frame systems via operational modal analysis(Techno Press, 2020) Kömür, Mehmet Aydın; Kara, Mehmet Emin; Deneme, İbrahim Ö.This paper presents an experimental study on the dynamic characteristics of infilled reinforced concrete (RC) frames. A 1/3-scaled, one-bay, three-storey RC frame was produced and tested by using operational modal analysis (OMA). The experiments were performed on five specimens: one reference frame with no infill walls and four frames with infill walls. The RC frame systems included in?ll walls made of hollow clay brick, which were constructed in four different patterns. The dynamic characteristics of the patterns, including the frequency, mode shapes and damping ratios in the in-plane direction, were obtained by 6 accelerometers. Twenty-minute records under ambient vibration were collected for each model, and the dynamic characteristics were determined using the ambient vibration testing and modal identification software (ARTeMIS). The experimental studies showed that the in?ll walls significantly affected the frequency value, rigidity and damping ratio of the RC frame system.Öğe Investigation of conical roof beam under vertical loads: Experimental and parametric studies(Elsevier Ltd, 2025) Oruç, Ramazan; Kara, Mehmet EminThis study presents experimental and numerical analyses to investigate the bending behavior of cold-formed steel (CFS) conical roof beams under vertical loads. The effects of radial beam orientation (face-to-face and face-to-back) and the spacing between circular beams (4500 mm, 1800 mm, 900 mm) on moment capacity, buckling modes, and deformation behavior were examined. Six single-span beam systems were tested, and it was observed that decreasing the spacing between circular beams increased the moment capacity and altered the buckling modes. The face-to-back orientation of radial beams reduced lateral displacement and rotation angles. Experimental results were validated using finite element analysis, and parametric studies were conducted. The parametric analyses revealed that decreasing the height-to-thickness (h/t) ratio of radial beams increased the moment capacity, while the thickness of circular beams had a limited effect. The results were compared with AISI S100–16 standards and an additional method to estimate local and distortional buckling capacities more accurately within the existing DSM approach.Öğe Rehabilitation of heavily earthquake damaged masonry building using steel straps(TECHNO-PRESS, 2008) Altın, Sinan; Kuran, Fikret; Anıl, Özgür; Kara, Mehmet EminThe purpose of this study is to develop a rehabilitation technique for heavily earthquake damaged masonry buildings. A full scale one storey masonry building with window and door openings was manufactured and tested on the shock table by applying increased amplitude free vibration up to the point where heavy earthquake damage was observed. Damaged test building was rehabilitated with vertical and diagonal steel straps and then tested again. The effectiveness of improvements obtained by the rehabilitation technique was investigated. Steel straps improved the lateral strength and stiffness of masonry walls and limited the lateral displacement of building. Stability of the masonry walls were also improved by the steel straps. Steel straps reduced the natural period of the earthquake damaged masonry building and prevented the failure of the building at the same amplitude of free vibration.Öğe Strengthening of RC shear walls with CFRP strips(The Hong Kong Polytechnic University, 2016) Altın, Sinan; Anıl, Özgür; Kopraman, Yağmur; Kara, Mehmet EminThe purpose of this study was to investigate the hysteretic behavior of shear deficient reinforced concrete (RC) walls that were strengthened with carbon fiber reinforced polymer (CFRP) strips. Totally, ½ scale five specimens with 1.5 aspect ratio walls were constructed. One of them was tested without any retrofitting as a reference specimen and four of them were retrofitted specimens with CFRP strips. All of the specimens were tested under cyclic lateral loading. CFRP strips with different configurations were tested like X-shaped, horizontal and parallel strips or combinations of them. All of the CFRP configurations were symmetrically bonded to both sides of the shear wall and were anchoraged to the wall. The research focuses on the effect of using CFRP strips for enhancing strength and increasing ductility of the non-seismic detailed shear walls. Test results shows that all of the CFRP strip configurations significantly improves the lateral strength, energy dissipation and deformation capacity of the shear deficient RC walls. The specimen that was strengthened with X-shaped CFRP strips was failed with premature shear failure. The specimen that was strengthened with horizontal strips was showed flexural hysteretic behavior and plastic hinge was developed at the wall base. CFRP strips were controlled shear crack propagation and resulted in improvement of displacement capacity. Copyright © 2016 Department of Civil and Environmental Engineering & Research Institute for Sustainable Urban Development, The Hong Kong Polytechnic University.Öğe Tire encasement and granular column stability(ASTM International, 2020) Terzi, Niyazi Uğur; Erensoy, Can; Yılmaztürk, Ferruh; Kara, Mehmet Emin; Özsoy Ünlü, MürüvvetGranular columns derive their load capacity from the confinement offered by the surrounding soil. However, lateral support can be problematic in extremely soft soil. Granular columns, when embedded in very soft clay, may bulge because of a lack of confinement offered by the surrounding soil. To avoid these problems, additional confinement can be provided by using geogrid or geosynthetic encasement. This study investigates a method of encasement construction with the aim of using waste tires to build columns. Without any recycling pretreatment, waste tires were used as material for stone encasement. Tires were stacked vertically to form a column frame structure and were bonded together using infinite screws and tightened with bolts. The diameter of the stone columns was that of a nominal car tire in all tests. A similar geosynthetically encased stone column with identical geometrical properties was also tested. Load tests were performed on both geotextile and tire-encased columns in a clay bed medium under incremental surcharge loads. To measure the bucking deformations of the column section using photogrammetric methods, unconfined loading tests were conducted under the same loading conditions. Results obtained from small-scale laboratory tests show that tire encasement makes the stone columns stiffer and stronger than traditional geotextile-encased stone columns.
