Browsing by Author "Mertol, Halit Cenan"
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Article A site survey of damaged RC buildings in İzmir after the Aegean sea earthquake on October 30, 2020(Gradevinar, 2023-06-10) Mertol, Halit Cenan; Tunç, Gökhan; Akış, TolgaAn earthquake with a magnitude of Mw = 6.6 and a depth of approximately 16.5 km occurred on 30 October 2020 off the cost of Samos, a Greek island 35 km southwest of Seferihisar, a town in İzmir. The earthquake caused several collapses and severe structural damage in approximately 6,000 buildings, specifically in the Bayraklı District in İzmir Bay. This paper presents the observations and findings of a technical team that visited the earthquake-affected areas immediately after an earthquake. Eleven partially or fully collapsed buildings and several severely damaged reinforced concrete buildings were investigated. Based on the site observations, we observed that almost all of the collapsed or severely damaged reinforced concrete buildings in the region were built between 1975 and 2000. Site observations also confirmed that the construction of these collapsed or damaged buildings did not conform to the requirements outlined in the Turkish Earthquake Codes used at the time. The failures and severe damage to buildings in earthquake-affected areas are primarily related to inadequate reinforcement configuration, poor material quality, the absence of geotechnical studies, and framing problems related to their lateral load-carrying systems. Therefore, it is recommended that all the buildings located in and around İzmir Bay, particularly those built between 1975 and 2000, be structurally evaluated to prevent any further loss of life and property during future earthquakes.Item EXPERIMENTAL AND ANALYTICAL INVESTIGATION ON IMPACT BEHAVIOR OF CONVENTIONAL AND STEEL FIBER REINFORCED CONCRETE BEAMS(2022-02-22) Najah, Azdeen Saleh; Mertol, Halit Cenan; Tuncay, KağanThis research investigated the experimental and analytical behavior of unreinforced and reinforced concrete beams cast using conventional concrete (CC) and steel fiber reinforced concrete (SFRC) under impact loading. Dramix ZP-305 type steel fibers were used for SFRC. Half of the beam specimens were unreinforced and the others were reinforced using one 8 mm diameter steel reinforcement fixed at center of specimen cross section. Cylinder concrete compressive strengths used in this study were 12 and 26 MPa for CC specimens and 35 MPa for SFRC specimens. Beam specimens had 60×60×500, 100×100×500, and 150×150×500 mm dimensions. The specimens were tested under impact loading using a drop-hammer testing apparatus having a weight of 58.5 N. This weight was dropped from various heights (1.20, 2.00, and 2.95 m for unreinforced specimens and 2.95, 3.00, and 3.04 m for reinforced specimens) based on specimen sizes. The slow motion videos of the tested specimens were recorded using a high-speed camera having a frame rate of 2000 fps. Experimental velocity-time relationships for hammer were obtained by analyzing of recorded impact videos using the TEMA Motion Analysis Software. Beams, hammer, and supports were modeled in ANSYS Finite Element Analysis Program and parameters related to modeling were calibrated based on the test results. Riedel, Hiermaier, and Thoma (RHT) Concrete Model was used in ANSYS Dynamic Explicit AUTODYN solver. The results were compared to the experimental studies on CC and SFRC in this research and input parameters of the model were modified. Comparisons of the experimental and modeling results indicated that velocity-time relationships of hammer showed very good agreement for various concrete compressive strengths and dimensions of specimens. It can be concluded that the calibrated concrete model presented in this study could provide some general guidelines for predicting the behavior of reinforced and unreinforced CC and SFRC under impact loading.Item FATIGUE BEHAVIOR OF PRESTRESSED STEEL FIBER REINFORCED CONCRETE BEAMS(2022-02-25) Abdelmola, Saad; Mertol, Halit CenanFatigue behavior of prestressed steel fiber reinforced concrete beams is investigated in this research. The test series consisted of three singly prestressed beams having 180×250×3500 mm dimensions. The main parameter in the testing program was the type of concrete (conventional or steel fiber reinforced). Two types of steel fibers (Dramix ZP 305 and Dramix 4D) with the same weight ratios were used in the testing program. One specimen was cast using conventional concrete and other two specimens were cast using steel fiber reinforced concrete. The specimens were subjected to four point bending. Initially the specimens were cracked. Fatigue loading was applied to the specimens up to 2000 k cycles. The fatigue loading was stopped and load-deflection relationship of each specimen was obtained at predetermined cyclic intervals. These load-deflection relationships were evaluated in terms of stiffness and flexural toughness. The results indicate that the use of steel fiber reinforced concrete increases both the stiffness and flexural toughness of the beams slightly under cyclic loading compared to that of conventional concrete specimens. Experimentally obtained load-deflection relationships were compared to the load-deflection relationships obtained from sectional analyses using the proposed models in the literature and best fit stress-strain models were determined.Item FINITE ELEMENT ANALYSIS OF CONCRETE ENCASED STEEL COMPOSITE COLUMNS AND REINFORCED CONCRETE BEAMS(2022-01-11) Othman, Mohammed Moatasem Othman; Tunç, Gökhan; Mertol, Halit CenanThe composite structural system includes two major structural systems which are concrete structural system and steel structural system. In this study, two specimens have been modeled in LS-DYNA software to study the seismic efficiency and vulnerability of the composite column-beam joints against shear and axial failures based on the experimental tests that were conducted at the laboratory. The first specimen was with High Ductility (HD) and the second one was with Low Ductility (LD), and the reinforcement designed according to the Turkish Earthquake Code (TEC 18), then the results have been compared with the results of experimental specimens. The study investigated the cracks and failure patterns, load-deflection envelope, dissipation, and degradation of simulated models. Also, another 12 specimens have been conducted and simulated in the LS-DYNA which is based on the two models to assess the performance of the frame with alteration of several parameters such as steel section availability, concrete grade, steel section type, and ductility. The results show that the finite element models provide an approached result to the experimental test, also, it indicates that the specimen with high ductility shows slightly better seismic performance than the low ductility specimen. Moreover, the parametric study demonstrates that the steel availability in the frame regardless of the type of the steel is the most important parameter to improve the frame’ seismic performance, then the concrete grade comes as the second parameter regarding significance, while the steel section type and transfer reinforcement ratio in a composite column do not show a significant impact.Item STRUCTURAL EVALUATION OF BUILDINGS UNDER URBAN TRANSFORMATION IN ANKARA(2022-01-25) Çamurdan, Asil Tuğana; Mertol, Halit CenanMost structures in Turkey are located in earthquake zones and are subjected to risk of collapse under earthquake loads, especially the structures constructed before 1999 Adapazarı Earthquake. After this earthquake, new regulations related to materials, analysis, design, construction, and auditing provided design and construction of safer structures. For the buildings constructed before this date, a need to investigate the condition of these old buildings was arisen throughout Turkey whether they needed a strengthening or demolishing and reconstruction process, under the name “urban transformation.” This study was performed to evaluate the steps used on structural evaluation of buildings under urban transformation. The structural evaluation reports of 39 buildings in Ankara prepared by various building inspection organizations were reviewed and the results were compared in terms of many aspects such as concrete strengths, allowable soil strengths, earthquake forces, unsafe column numbers and their shear forces, etc. and a relationship was established related to the collected data. Graphs related to reasons why these buildings were considered unsafe. The findings of this study may be used to generalize the condition of evaluation of buildings under urban transformation in other cities of Turkey.