Browsing by Author "MERTOL, Halit Cenan"
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Item COMPRESSIVE AND TENSILE BEHAVIORS OF STEEL FIBER REINFORCED CONCRETE(2015-06-26) ABDUSSALAM, Alfadhil. A. Gheit. Alfadhil; MERTOL, Halit Cenan; BARAN, EraySteel fiber reinforced concrete (SFRC) is a concrete mixture containing discontinuous, discrete steel fibers that are randomly dispersed and uniformly distributed. The quality and quantity of steel fibers influence the mechanical properties of concrete. It is in general accepted that the addition of steel fibers significantly increases tensile toughness and ductility, also slightly enhances the compressive strength. The benefits of using steel fibers become apparent after concrete cracking because the tensile stress is then redistributed to fibers. The objective of this study is to investigate the compressive and tensile behavior of steel fibers in reinforced concrete by conducting an experimental program consisting of load testing on various specimens made from conventional concrete (CC) and steel fiber reinforced concrete (SFRC). Test series consisted of cylindrical compression (100×200 and 150×300 mm) and prismatic modulus of rupture (150×150×600 mm) specimens. Tensile tests on reinforcing bars surrounded by prismatic concrete specimens were also performed. The variables used in these tests were lengths (500, 1000, and 1500 mm) and cross sectional dimensions (60×60, 100×100,150×150, 200×200 mm) of the prismatic concrete specimens around reinforcing bar. Load-deflection behaviors were obtained and evaluated to develop the compressive and tensile stress-strain relationships of SFRC. Experimental load-deflection relationships obtained from modulus of rupture tests were compared to the predicted load-deflection curves determined using compressive and tensile stress-strain curves obtained in this research. Also the stress-strain relationships available in the literature were used predict the behavior.Item DEVELOPMENT OF CUSTOM LOAD AND RESISTANCE FACTORS FOR DESIGN OF REINFORCED CONCRETE STRUCTURES(2021-07-10) ELOSTA, İbrahim; MERTOL, Halit CenanThe load and resistance factors used nowadays in the design of reinforced concrete structures were developed before this century. Using these factors from the past significantly penalizes the design of reinforced concrete structures constructed using materials having better quality control and loads having better predictions of occurrences today. The purpose of this study was to develop a tool that determined the load and resistance factors depending on the statistical data (bias and covariance) related to current materials (concrete and steel) and current prediction of loads (dead, live, etc.) and the target reliability index. The First Order Second Moment (FOSM) and Monte Carlo Simulation (MSC) were the methods used as the structural reliability models. The first method was used to determine the resistance parameters for different failure modes. These resistance parameters (biases and covariances) were calculated using 20 million random variables using MCS Method to determine reliability index values. Finally, a program using Microsoft Excel Software was developed to determine custom load and resistance factors to design reinforced concrete members. Based on the input date for biases and covariances of resistance, dead, and live loads; failure modes of the beams and column members; and the target reliability index, the produced program selects custom load factors for your project.Item ENHANCING CIVIL ENGINEERING EDUCATION USING ACTIVE LEARNING TECHNIQUES(2013-08-14) ÇALIŞKAN, Nihan Tuğba; MERTOL, Halit CenanIn the last few decades the civil engineering prefession has rapidly developed to be able to adapt to changing conditions in various areas worldwide. Besides, the 21st century students are also completely different from the students who lived in the 20th century. The advances in technology have a great influence on these students. They don’t know the life before computer, cell phones etc. The traditional educational methods containing passive teaching methods no longer work for current students. Most of the students in this century are active learners and active teaching methods should be used to be able to get good performance from these students. In this study computer games, hands-on-practices, experiments, laboratory works used as active teaching methods and applied on different courses such as Statics, Dynamics, Strength of Materials, and Fundamentals of Reinforced Concrete, and the change in students’ performance is evaluated.Item EVALUATION OF ENHANCED PUSHOVER ANALYSIS PROCEDURES FOR REGULAR AND IRREGULAR REINFORCED CONCRETE BUILDINGS(2022-01-14) ELSHARIDA, Mohamed; MERTOL, Halit CenanAn important aspect of performance-based design methodologies can be regarded as the accuracy of predictions of seismic demands parameters. Making improvements to this aspect of the design-based methodologies is undeniably desirable. Recently, several Enhanced Pushover Analysis (EPA) procedures that take into account the influence of higher modes have been proposed. As most of these procedures have been applied to regular building frames; there remains a need to verify the efficiency of such procedures on the evaluation of irregular building frames. The EPA procedures, namely the Consecutive Modal Pushover (CMP), Dynamic Load Pattern (DLP), and Single‐Run Multimode Pushover (SMP), have been applied to regular steel moment resisting frames in literature. The purpose of this study is to comparatively assess the efficiency and capability of these EPA procedures to estimate the seismic demands of twelve regular and irregular special reinforced concrete (RC) moment-resisting frames having various number of stories (4, 8, 12, 16, 20, and 24). The structural responses given by the EPA methods are then compared with the benchmark results achieved from the Nonlinear Time History Analysis (NLTHA). For the sake of comparison, the conventional pushover analyses based on the first-mode and uniform lateral load pattern are also demonstrated. The results indicate that the DLP and CMP methods can predict the seismic demands of regular and irregular buildings with a higher level of accuracy than the SMP procedure. Consequently, the DLP and CMP procedures were found to be better alternatives for obtaining practically reasonable estimations of seismic demands of building frames where the influence of higher modes is significant.Item EVALUATION OF MODIFIED AND EXTENDED PUSHOVER METHODS FOR RC BUILDINGS HAVING SETBACK IRREGULARITY(2022-09-12) HASAN, Ghadeer; MERTOL, Halit CenanIrregular configurations of reinforced concrete buildings were frequently identified as one of the main causes of failures during previous earthquakes. The setback irregularity which occurs due to abrupt reduction of the lateral dimension of the building at specific levels of elevation may be catastrophic for buildings having various heights. Engineers are more likely to adopt simplified nonlinear static analytical procedures such as pushover analysis when evaluating the seismic performance of reinforced concrete buildings due to its ease in application. The use of conventional pushover analysis methods provides acceptable results low-rise buildings. However, these methods do not provide sufficient results for mid- and high rise buildings whose behavior under seismic actions is not only governed by the fundamental mode shape. To overcome this problem, some advanced methods considering the effects of higher mode shapes were proposed by various researchers. However, the applicability of these methods to three dimensional high-rise buildings having setback irregularity was not addressed in the literature. In this study, a total of 6 mid- and high-rise building models having setback irregularity at various locations were analyzed using nonlinear pushover analysis methods namely the Inverted Triangular Lateral Load Pattern (TLP) according to ASCE 7-22, First Modal Shape Lateral Load Pattern (FLP), Uniform Lateral Load Pattern (ULP), Modified Upper Bound Method (MUB), and Extended Upper Bound Method (EUB), to evaluate the applicability of these methods. The results obtained using these methods were compared to the Nonlinear Time History Analysis Method (NLTHA) which provided benchmark solutions to the problems. Three of the building models had 6 stories and the other three had 12 stories. The story heights of the models were all 4.5 m at the ground story and 3.2 m for the rest of the stories. All models had four bays in both plan view directions with a typical length of 6 m each. One model of each height level was a regular building and used for comparison purposes. Other two models of each height level had setback irregularity in various locations of the elevation in one direction. The results were assessed for seismic demand variables such as lateral displacements, interstory drift ratios, and plastic hinge rotations. The EUB method also provided more accurate results of interstory drift ratios of all irregular building models compared to those of the conventional pushover analysis procedures (TLP, FLP, and ULP). Conventional pushover methods were not sufficient to predict the plastic hinge rotations at the upper stories of the 6 and 12 story building models, whereas the EUB method provided reasonable estimates of these plastic hinge rotationsfor irregular buildings.Item EXPERIMENTAL ANALYSIS OF THE BEHAVIOR OF COMPOSITE COLUMN-REINFORCED CONCRETE BEAM JOINTS(2022-01-21) Dakhil, Abdulrrahman; TUNÇ, Gökhan; MERTOL, Halit CenanThis thesis is dedicated to improving our understanding and assessment of the seismic efficiency and vulnerability of the SRC column to RC beam joints in composites, and their ability to dissipate seismic energy through inelastic deformations. In this study, experimental aspects regarding the seismic performance of high ductility and low ductility steel-concrete composite frame were investigated. A literature review was performed, leading to the development of a new column-beam joint. The basic design parameter in this study was ductility, which is considered a conceptual framework in Efficiency-Base Seismic Engineering. Thus, attention was focused on assuring various ductility ranges of composite joints, which can be all obtained through a detailed study of the Turkish Earthquake Code (TEC 18). After identifying deficiencies and the energy dissipation capacity in the new proposed joints, two half scaled frames with specific ductility related designs were built, instrumented, tested, and analyzed. The specimens were tested under displacement-controlled lateral cyclic loading that incorporated constant axial loading to create cyclic tension and compression facets across the joint area. The test parameters were column reinforcement ratios, joint aspect ratios, axial loads, and cyclic lateral loads. The test results proved that the SRC column–RC beam frames, employing an extra column reinforcement ratio, exhibit better seismic performance.Item FLEXURAL BEHAVIOR OF LIGHTLY AND HEAVILY REINFORCED STEEL FIBER CONCRETE BEAMS(2014-09-07) BELLO, Hussain Jibril; MERTOL, Halit Cenan; BARAN, ErayFlexural behavior of lightly and heavily reinforced steel fiber concrete beams was investigated in this research. Test series consisted of 20 singly reinforced beams (10 pairs of beams) having 180×250×3500 mm dimensions. The main parameters in the testing program were the type of concrete and the amount of longitudinal reinforcement. Ten different longitudinal reinforcement ratios (with a minimum of 0.2 and a maximum of 2.5%) covering the range from under-reinforced to over-reinforced beam behavior were used in the testing program. Two specimens were tested for each longitudinal reinforcement ratio, one specimen using ordinary plain concrete (PC) and another specimen using steel fiber reinforced concrete (SFRC). Load-deflection behaviors were obtained and evaluated in terms of ultimate load, service stiffness, post-peak stiffness, and toughness. The results indicate that the use of SFRC increases the ultimate load and service stiffness of the beams slightly compared to that of PC specimens. As reinforcement ratio increases, the ultimate deflection of SFRC specimens becomes significantly greater than that of PC specimens. For over-reinforced sections the post peak stiffness of the SFRC specimens is observed to be significantly lower than that of PC specimens. The toughness of SFRC specimens is greater than that of PC specimens with the difference being significantly larger for over-reinforced sections. Experimentally determined load-deflection relationships were compared to the load-deflection curves obtained from sectional analyses based on strain compatibility and best fit stress-strain relationships for SFRC in tension and compression in the literature are presented.Item FLEXURAL BEHAVIOR OF REINFORCED CONCRETE BEAMS HAVING VARIOUS LAYERS OF CONVENTIONAL AND STEEL FIBER REINFORCED CONCRETE(2015-10-25) FAEQ FAEQ, Mohammed Nozad; MERTOL, Halit Cenan; BARAN, ErayFlexural behavior of reinforced concrete beams having various layers of conventional concrete and steel fiber reinforced concrete were investigated in this study. Two groups of five beams having 180×250×3500 mm dimensions were tested under four-point loading to evaluate the flexural behavior. Both of these groups of beams were reinforced with 416 reinforcing bars. The main variable in this research was the concrete type of the layers throughout the height of the specimen. The height of the cross-section of the beams was divided into 5 layers, each having 50 mm thicknesses. In group "F" specimens, SFRC was added to the layers of a conventional concrete beam, starting from the bottom, instead of conventional concrete. In group "P" specimens, SFRC layers were added starting from the top of the beam cross section. The load-deflection relationships of the tested beams under flexure were evaluated based on ultimate load, service stiffness, post-peak slope, and toughness characteristics. An analytical work was carried out to predict the behavior of the tested beams using the proposed stress-strain relationships in the literature.Item STRENGTHENING DEFICIENT RC BUILDINGS USING EXTERNAL STEEL BRACES(2022-06-14) ERPEK, Berk; MERTOL, Halit CenanBased on Ministry of Environment and Urbanization of Turkey, there are 5 million earthquake resistant apartments out of a total of 19,5 million apartments in Turkey. Seven million apartments need urgent action for a strengthening solution or shall be demolished immediately. It is not possible to demolish and rebuild all these deficient structures. Strengthening them includes many complications. One of the most important complications is the replacement of the occupants from the deficient buildings during the construction process. Strengthening of existing reinforced concrete structures using external steel braces method is getting popular worldwide since it may be performed faster, cheaper and without impacting the inhabitants who live in these structures. The purpose of this research is to determine the effectiveness of external strengthening using steel braces for existing reinforced concrete buildings. Four building models having number of stories 3, 6, 9, and 12 were analytically investigated. These building models were designed as deficient buildings according to Turkish design codes. The performances of the deficient building models were evaluated using three different methods, Equivalent Static Earthquake Load, Pushover Analysis, and Time History Analysis. These deficient buildings were strengthened using external steel braces and the performances were evaluated using these methods. The results indicated all building models can effectively be strengthened using inverted-V configured external steel bracing system. Buildings up to 9 stories can be effectively strengthened using X configured steel bracing system. The most cost effective strengthening system was the one having one steel frame on each side of the building.