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Öğe THE BEHAVIOR OF INFILLED STEEL FRAMES UNDER REVERSE CYCLIC LOADING(HONG KONG INST STEEL CONSTRUCTION, 2014) Kaltakci, M. Yasar; Koken, AliThe objective of this study was to make an experimental investigation on the behavior of nine steel frames with various infill characteristics under reverse cyclic loading. The test specimens, which were one-story steel frames, had the frame length/height ratios (1/h) of 1, 1/2, and 2. The infill characteristics of the specimens were assigned as i) no infill, ii) brick wall infill, iii) brick wall+plaster infill. The specimens were tested under reverse cyclic loading representing the seismic loading in the horizontal direction, and the displacement values obtained during the tests were measured and recorded in a digital manner. At the end of the tests, the infilled frames were evaluated in terms of failure types, strength envelopes, energy consumption characteristics, and stiffness decreases by comparing the test results.Öğe EFFECT OF CIRCULAR HOLES ON CROSS-PLY LAMINATED COMPOSITE PLATES(SPRINGER HEIDELBERG, 2009) Arslan, H. Murat; Kaltakci, M. Yasar; Yerli, Huseyin R.In this study, an analysis of fiber-reinforced, laminated composite plates containing circular holes has been carried out. First, the stress state of a layer in a laminated plate is studied. After obtaining the stress state for each layer due to uniaxial loading of a plate, the stress concentrations around a circular hole are studied. A number of diagrams are drawn to show the stress concentrations around a hole, for layers having different oriented fibers, using different material pairs with different E-1/E-2 ratios (ratio of elasticity modulus of fiber direction to that of transverse direction). Graphs are given for various E-1/E-2 values, for the circumferential stress values around the hole versus angular location of points, and for two different fiber orientation angles. Second, the failure of the laminated composite plate is studied. To determine the 'first-ply failure" of a laminated plate, Tsai-Hill failure criterion is employed to find minimum bearing circumferential stresses and where they occur as a function of fiber orientation angle.Öğe Experimental and Analytical Analysis of RC Frames Strengthened Using RC External Shear Walls(SPRINGER HEIDELBERG, 2011) Kaltakci, M. Yasar; Arslan, M. Hakan; Yilmaz, Ulku S.In this study, we have investigated the application of an external RC shear wall as a method of improving the performance of reinforced concrete (RC) frames in an earthquake. We produced a series of eight RC frames, each of which was modeled at a 1/3 scale with two floors and two spans. These frames were of the same size and had design and construction deficiencies commonly encountered in the RC buildings in Turkey. We tested four of the eight frames without any strengthening, under reversed cyclic lateral loadings resembling earthquake loads. The remaining four frames we tested under the same conditions after strengthening them with RC external shear walls. We arranged the axial force loads applied to the columns of the test models in two different ways to result in tensile and compression failure. The test results were analyzed on the basis of a comparison using static push over analysis. The results of the experimental tests and analytical studies showed that the RC external shear wall improved the seismic character of the existing RC frame as much as RC infill walls, therefore this method can be used as an alternative strengthening method. Also, the method provides effective, practical and economical strengthening that minimizes the need for additional works and does not restrict the use of the RC building.Öğe An experimental study on strengthening of vulnerable RC frames with RC wing walls(TECHNO-PRESS, 2012) Kaltakci, M. Yasar; Yavuz, GunnurOne of the most popular and commonly used strengthening techniques to protect against earthquakes is to infill the holes in reinforced concrete (RC) frames with fully reinforced concrete infills. In some cases, windows and door openings are left inside infill walls for architectural or functional reasons during the strengthening of reinforced concrete-framed buildings. However, the seismic performance of multistory, multibay, reinforced concrete frames that are strengthened by reinforced concrete wing walls is not well known. The main purpose of this study is to investigate the experimental behavior of vulnerable multistory, multibay, reinforced concrete frames that were strengthened by introducing wing walls under a lateral load. For this purpose, three 2-story, 2-bay, 1/3-scale test specimens were constructed and tested under reversed cyclic lateral loading. The total shear wall (including the column and wing walls) length and the location of the bent beam bars were the main parameters of the experimental study. According to the test results, the addition of wing walls to reinforced concrete frames provided significantly higher ultimate lateral load strength and higher initial stiffness than the bare frames did. While the total shear wall length was increased, the lateral load carrying capacity and stiffiiess increased significantly.Öğe An experimental study on the strengthening of non-ductile reinforced concrete frames via external shear wall(TAYLOR & FRANCIS LTD, 2012) Kaltakci, M. Yasar; Ozturk, MuratThe most common method for strengthening reinforced concrete frames that have insufficient earthquake resistance is the addition of reinforced concrete (RC) shear walls to the structural system. In recent years, the idea of constructing the shear walls not inside but outside the building was preferred and applied in order to decrease the cost of strengthening processes and without limiting the utilisation of the building. The most important problem of this application is that the architectural requirements of buildings can be hindered because of the shear walls constructed out of the axes; this can be solved by connecting the exterior shear walls to the existing frame using coupling beams and leaving a certain spacing between them. In this study, the contribution of the strengthening method called 'external shear wall application via coupling beam' on the behaviour of the existing frame under lateral loading conditions was investigated. For this purpose, one reference frame, one reference shear wall and two frames strengthened with external shear walls using coupling beams were produced and tested under reversed-cyclic lateral loading. The strengthened frames were constructed by connecting the external shear wall to the frame by making RC and steel coupling beam applications to determine the behaviour differences between them. In conclusion, the strengthening method made a considerable contribution to the frame that was insufficient against earthquake effects in terms of lateral load carrying capacity, rigidity and energy dissipation capacity.Öğe A new approach on the strengthening of primary school buildings in Turkey: An application of external shear wall(PERGAMON-ELSEVIER SCIENCE LTD, 2008) Kaltakci, M. Yasar; Arslan, M. Hakan; Yilmaz, Ulku S.; Arslan, H. DeryaConsiderable life and property losses have occurred because of the devastation due to the earthquakes happened in Turkey during the last 10 years. Especially, the damages that occurred on the public buildings were more serious and irrevocable when compared with the damages that took place oil private buildings. In Turkey, primary school buildings constitute a large portion of the public buildings. Unfortunately, these buildings faced with heavy damages during the last earthquakes. The strengthening of existing primary school buildings in accordance with new contract specifications, thereby reducing losses of life and property to a minimum in case of an earthquake, has become one of the important issues on the agenda of the Turkish government. However, the strengthening of the primary school buildings by using the available methods is so difficult, because the strengthening works take a long time, the user of these buildings are obliged to evacuate the buildings and also there occurs extra costs caused by the additional repairs and renovations within the buildings when these methods are used. In this study, a new strengthening type of reinforced concrete buildings namely "external reinforced concrete shear wall" application method is discussed. For this purpose, three typical projects, which have been built commonly, are mentioned. The structural deficiencies observed in these buildings are given. In the experimental stage of this study, all experimental programme is formed in order to evaluate the performance of the external shear wall application. In the experimental schedule, four reinforced concrete test specimens are produced by using the design and detailing data of the considered school buildings. According to these tests, the strengthening and system improvement performed through adding external reinforced concrete shear wall to the reinforced concrete buildings will add improved behaviour, strength and rigidity to the system with its low cost besides the ease of construction and application. Since these buildings are detached and located in a multi-purpose garden, constructed as typical projects and have special architectural layout, developing this method for the existing primary school buildings will be able to be implemented in most of the primary school buildings Without my problems. (C) 2007 Elsevier Ltd. All rights reserved.Öğe Predicting the flexural behaviour of reinforced concrete and lightweight concrete beams by ANN(NATL INST SCIENCE COMMUNICATION-NISCAIR, 2012) Kamanli, Mehmet; Kaltakci, M. Yasar; Bahadir, Fatih; Balik, Fatih S.; Korkmaz, H. Husnu; Donduren, M. Sami; Cogurcu, M. TolgaIn this study, artificial neural network (ANN) method is used to predict the deflection values of beams and compared with the experimental results of a testing series. For this purpose six reinforced concrete beams with constant rectangular cross-section are prepared and tested under pure bending. The concrete of the test specimens is casted using the lightweight aggregates obtained from volcanic sediments. The lightweight concrete has some advantages comparing the traditional concrete, such as less self weight, less earthquake forces due to decreased mass, good sound and thermal insulation. The use of lightweight concrete in the construction industry is popular due to various advantages. The neural network procedure is applied to determine or predict the deflection values of 1/1 scaled model beams. The analytical results are compared with the test results and further predictions, including different mix designs can be possible at the end of the study. As a result, while the statistical values RMSE, R-2 and MAE from training in ANN model are found as 0.266, 99.2% and 0.216, respectively, these values are found in testing as 0.370, 96.47% and 0.419, respectively.Öğe Prediction of force reduction factor (R) of prefabricated industrial buildings using neural networks(TECHNO-PRESS, 2007) Arslan, M. Hakan; Ceylan, Murat; Kaltakci, M. Yasar; Ozbay, YuekselThe force (load) reduction factor, R, which is one of the most important parameters in earthquake load calculation, is independent of the dimensions of the structure but is defined on the basis of the load bearing system of the structure as defined in earthquake codes. Significant damages and failures were experienced on prefabricated reinforced concrete structures during the last three major earthquakes in Turkey (Adana 1998, Kocaeli 1999, Duzce 1999) and the experts are still discussing the main reasons of those failures. Most of them agreed that they resulted mainly from the earthquake force reduction factor, R that is incorrectly selected during design processes, in addition to all other detailing errors. Thus this wide spread damages caused by the earthquake to prefabricated structures aroused suspicion about the correctness of the R coefficient recommended in the current Turkish Earthquake Codes (TEC - 98). In this study, an attempt was made for an approximate determination of R coefficient for widely utilized prefabricated structure types (single-floor single-span) with variable dimensions. According to the selecting variable dimensions, 140 sample frames were computed using pushover analysis. The force reduction factor R was calculated by load-displacement curves obtained pushover analysis for each frame. Then, formulated artificial neural network method was trained by using 107 of the 140 sample frames. For the training various algorithms were used. The method was applied and used for the prediction of the R rest 33 frames with about 92% accuracy. The paper also aims at proposing the authorities to change the R coefficient values predicted in TEC - 98 for prefabricated concrete structures.Öğe The seismic improvement and control of weak concrete frames with partial concrete shear walls(SAGE PUBLICATIONS LTD, 2014) Kaltakci, M. Yasar; Yavuz, GunnurControlling the lateral movement of buildings under earthquake effects is very important to prevent total collapse and therefore reinforced concrete (RC) shear walls are used to obtain the lateral stability of such buildings. In this study, the usability of partial RC shear walls to strengthen buildings with weak earthquake behavior was investigated. The basic parameters of the study were determined to be the ratio of shear wall height to shear wall length (H-w/L-w) and whether the upper inflection point of the bent bar, a steel bar commonly used in the beams of RC buildings in Turkey, is integrated into or bent outside of the partial shear wall section. Three units of two-story, double-span weak RC frames were produced at a one-third scale. Two of these three frames were then strengthened by partial shear walls integrated on both sides of the central column. Strengthened and non-strengthened specimens were tested under reversed-cyclic lateral loading. The frame systems strengthened via partial RC shear walls showed significant improvement in strength and stiffness. No debonding was observed in the anchorage rods used in the shear wall-foundation connection.Öğe Stress concentrations of symmetrically laminated composite plates containing circular holes(SHIRAZ UNIV, 2006) Kaltakci, M. Yasar; Arslan, H. M.In this study, an analysis of fiber reinforced, symmetrically laminated composite plates containing circular holes has been carried out. First, the stress state of a layer in a laminated plate is studied. After obtaining the stress state for each layer due to the uniaxial loading of a plate, the stress concentrations around a circular hole are studied. A number of diagrams are drawn to show the stress concentrations around a hole for layers having different oriented fibers using different material pairs with different E-1/E-2 ratios (ratio of elasticity modulus of fiber direction to that of transverse direction). Graphs are given for various (E1E2)-E-/ values for the circumferential stress values around the hole versus angular location of points for two different fiber orientation angles. Second, the failure of the laminated composite plate is studied. To determine the "firstply failure" of a laminated plate, Tsai-Hill failure criterion is employed to find minimum bearing circumferential stresses and where they occur as a function of the fiber orientation angle.Öğe Sudden Complete Collapse of Zumrut Apartment Building and the Causes(ASCE-AMER SOC CIVIL ENGINEERS, 2013) Kaltakci, M. Yasar; Kamanli, Mehmet; Ozturk, Murat; Arslan, M. Hakan; Korkmaz, H. HusnuIn recent years, buildings and structures in Turkey have frequently failed or suddenly sustained damage because of their own weight or other loads. The most dramatic failure was the Zumrut Apartment Building disaster: a 9-story RC building in Konya that collapsed on February 2, 2004, leaving 92 people dead. This study will investigate the cause of the building damage and failure. The significant mistakes made during the design and construction of the building will also be considered. This study was divided into three sections: site investigation, analytical study, and experimental study. The evaluation of the building failure relating to the vertical load-bearing members will be presented using observations from the site investigations, the test results obtained from specimens taken from the failed building, and the findings of an analytical study involving modeling the building using the finite-element method.
