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Öğe Evaluation of a Gravity Load Designed Reinforced Concrete Structure Failed Under Its Own Weight Due to Creep in Concrete(TRANS TECH PUBLICATIONS LTD, 2013) Kaltakci, Mevlut Yasar; Korkmaz, Hasan Husnu; Kamanli, Mehmet; Ozturk, Murat; Arslan, Musa HakanTurkish building stock is commonly composed of reinforced concrete moment resisting frames. Recent earthquakes in Turkey resulted thousands of failed or heavily damaged residential houses and office buildings. In addition of the earthquake failures, reinforced concrete structures may also failed only under their own weight. There are several examples such as Hicret Apartment in Diyarbakir (1983), Zumrut Apartment in Konya, in central Anatolia, Huzur Apartment in Istanbul (2007). On February 2nd, 2004 a 9-story reinforced concrete building in Konya (Zumrut Apartment) collapsed leaving 92 people dead. The first author of the paper was governmentally charged about the investigation of the failure causes. Carrot samples were taken from the concrete columns and steel samples were obtained from the disaster area. The dimensions of the structural members were determined. The structure was modeled in three dimensional space and vertical collapse analyses were conducted. The one of the main cause of failure was determined as the creep of the concrete occurred in excessively loaded columns. The main reasons of the damages and failures were determined to be the insufficiency in material quality, mistakes made in load selection and the inappropriate load-carrying dimensions. The construction mistakes and not obeying the design drawings are the other flaws. In this paper detailed information about the structure, creep analyses and vertical collapse analyze results were depicted in understandable format.Öğe Evaluation of different miniplates in fixation of fractured human mandible with the finite element method(MOSBY-ELSEVIER, 2007) Korkmaz, Hasan HusnuThe objective of this study was to develop a 3-dimensional finite element model ( FEM) to formulate biomechanical justification of the positioning of different plates to achieve stable fixation of a fractured mandible. Miniplate systems that give acceptable levels of rigidity were investigated, and recommendations about miniplate location, orientation, and type selection are made. A fracture near the body region was bridged with a variety of commonly used plate configurations. Number, positioning and type of the plate system parameters. The results of this fracture model support the advantage of 2-plate systems. Using a longer plate in the superior position and a shorter one in the inferior position produced a more stable condition. Number of screws or length of the miniplate had no significant effect on the stability of fractured segments. The results obtained from this study offer the choice of a particular plate size, thickness, design, or configuration for application and thus provide information for clinical use.Öğe Experimental study of strengthening of RC frames with column retrofitting(Selçuk Üniversitesi, 2014) Unal, Alptug; Balik, Fatih Suleyman; Bahadir, Fatih; Korkmaz, Hasan Husnu; Kaltakci, Mevlut Yasar; Kamanli, MehmetRecently, researches related with strengthening have been increased. In most of these studies, strengthening of reinforced concrete frames with inadequate earthquake resistance was searched. However, it is known that there are buildings with inadequate earthquake resistance as well as buildings with both inadequate earthquake resistance and inadequate axial load bearing capacity. A 1/3 geometric scaled reinforced concrete frame with inadequate earthquake resistance and inadequate axial load strength modeled as a sample building was strengthened with column retrofitting and tested under vertical and lateral loads. In this study, two 1/3 geometric scaled specimens were tested under the effect of reversible repeatable lateral loads simulating earthquake. One of these samples is a bare reinforced concrete frame representing buildings with inadequate earthquake resistance and axial load strength as well as including building defects without any strengthening which are frequently encountered in our country. The second experiment element was constructed in order to represent the buildings which necessitate strengthening due to earthquake loads and axial loads. In this specimen, the columns were strengthened by retrofitting from three sides. The hysteresis curves, envelope curves, rigidity, ductility and consumed energy graphs of these tested elements are given and the differences between them were investigated and interpreted. In the final section, the experimental results obtained were evaluated, interpreted and suggestions were made.Öğe An Experimental Study on Reinforced Concrete Infilled Frames with Openings(TRANS TECH PUBLICATIONS LTD, 2013) Balik, Fatih Suleyman; Korkmaz, Hasan Husnu; Kamanli, Mehmet; Bahadir, Fatih; Korkmaz, Serra Zerrin; Unal, AlptugIn the last decade, seven major earthquakes caused significant casualties and extensive structural failures. Thousands of RC buildings were severely damaged or collapsed in Turkey due to various deficiencies. This has initiated experimental studies on strengthening methods and intensive researches regarding the rehabilitation of reinforced concrete structures by introducing reinforced concrete infill walls were carried out. Strengthening of reinforced concrete frames by cast-in-place reinforced concrete infills is commonly used in practice. Many structures were also repaired using this technique after the recent earthquakes. In this experimental research, six, one-bay/two-story, 1/3-scaled non-ductile, undamaged reinforced concrete (RC) frames were constructed and tested to investigate the behavior of frames strengthened by introducing infills with or without openings. The test specimens were subjected to reversed cyclic quasi-static lateral loading. The specimens were constructed with the most commonly observed deficiencies in residential RC buildings in Turkey. The first specimen was the reference bare specimen and contained no strengthening. The other specimens were infilled with RC panels with openings having different ratios and configurations. Strength, stiffness and storey drifts of the test specimens were measured and compared. Test results indicated that infilled RC frames displayed significantly higher lateral strength and stiffness than the non-ductile bare frame considerably.Öğe Performance improvement studies of masonry houses using elastic post-tensioning straps(JOHN WILEY & SONS LTD, 2007) Turer, Ahmet; Korkmaz, Serra Zerrin; Korkmaz, Hasan HusnuUnreinforced masonry houses are composed of building blocks with weak inter-binding action between them which commonly possess low tensile strength. The principal tensile stresses generated by out-of-plane bending and in-plane shear forces cannot be tolerated well and leads to heavy structural damage and brittle collapse beyond linear capacity of the material. Remedies such as externally applied mesh reinforcement and post-tensioning improves post and pre-cracking performances; however, yielding of reinforcement material or shortening of walls due to cracking causes loss of integrity and post-tensioning force. This paper discusses a research programme on earthquake strengthening of masonry houses using post-tensioning by elastomeric straps and related shaking table tests on 1/10 scale single storey rural dwelling models. The aim of the study is to assess the use and effectiveness of post-tensioning rubber straps at several different configurations especially for houses with heavy earth roofs supported on wooden logs. Full-scale application can be conducted using scrap automobile tyres, which might be implemented as an economic and environment friendly alternative strengthening technique for poor residents of low-cost dwellings. The performance and validity of the proposed strengthening techniques were tested on 1/10 scale models using a simplistic shaking table. The structural performance of the reinforced models with vertical post-tensioning rubber straps was significantly improved as compared to the original specimen; the results were even better when vertical and horizontal straps were used. Obtained results show promise for seismic strengthening using rubber straps for post-tensioning. Copyright (C) 2006 John Wiley & Sons, Ltd.Öğe Rehabilitation of Infilled Reinforced Concrete Frames with Thin Steel Plate Shear Walls(ASCE-AMER SOC CIVIL ENGINEERS, 2016) Akin, Emre; Korkmaz, Serra Zerrin; Korkmaz, Hasan Husnu; Diri, ErsanDifferent rehabilitation methods have been suggested for system improvement of existing deficient reinforced concrete building stock in seismic hazard areas. Although the use of steel plate shear walls for the rehabilitation of steel frames is common, their application to deficient reinforced concrete frames is not as common. In this study, the efficiency of steel plate shear walls on deficient reinforced concrete frames having hollow clay tile infill walls is investigated. Five one-bay, two-story 1/3 scaled RC frames were subjected to quasistatic lateral loading. The results indicated that significant improvement may be achieved in the lateral frame response. Lateral load-carrying capacities and energy dissipation capacities were considerably increased. However, a local shear strengthening of deficient columns may be required since shear demand on the columns increases considerably owing to tension field forces of the steel plate shear walls. (C) 2016 American Society of Civil Engineers.Öğe Strengthening of Gravity Load Designed Reinforced Concrete Frames With the External RC Shear Walls(TRANS TECH PUBLICATIONS LTD, 2013) Bahadir, Fatih; Kamanli, Mehmet; Korkmaz, Hasan Husnu; Balik, Fatih Suleyman; Unal, Alptug; Korkmaz, Serra ZerrinTurkey is situated on a very earthquake zone of the world namely Alp-Himalayan Earthquake Zone. Several destructive earthquakes resulted in high dead losses in the last century. Turkish building stock consisted of nonductile RC framed structures commonly 3 to 7 stories. The common properties of the existing structures is the poor lateral resistance. The residental buildings with poor earthquake resistance must be rehabilitated with a rapid, economical, feasible and effective strengthening methods. The external shear wall addition to the existing poor frame is studied experimentally in this study. 6 specimens were tested under reversed cyclic lateral loading simulating the seismic action. The first specimen was the reference specimen and didn't contain any strengthening and tested to see reference behaviour. The other specimens were strengthened with external shear walls with or without openings. The size of the openings is a parameter in the study. Secons specimen didn't contain any opening. Columns of the frames also jacketed with reinforced concrete. The maximum lateral load carrying capacity, ductility capacities, energy consuption capacities, improvement in the lateral rigidities were investigated.Öğe Strengthening of Reinforced Concrete Frames Not Designed According to TDY2007 With External Shear Walls(TRANS TECH PUBLICATIONS LTD, 2013) Unal, Alptug; Kaltakci, Mevlut Yasar; Balik, Fatih Suleyman; Korkmaz, Hasan Husnu; Bahadir, Fatih; Korkmaz, Serra Zerrin; Kamanli, MehmetRecently repair and strengthening of existing buildings become a popular research topic. The strengthening of buildings necessitates the evacuation of the structure. On the other hand, school, hospital type structures must continue their function. In this study exterior shear wall addition to the existing exterior frames is proposed. Since the application is applied to the exterior of the building, the structure can continue its function during the application. In this study, 1/3 scaled 4 specimens were tested under reversed cyclic loading simulating the seismic action. First reference specimen was the bare frame and didn't contain a strengthening and tested to see the reference behavior. Specimens have several design mistakes to represent the existing older structures. The other specimens retrofitted with different configurations. The second specimen was strengthened with exterior shear walls and contained a window opening. The last specimen was also retrofitted with exterior shear wall but the shear walls were divided into two pieces. The load-displacement curves, envelope curves, relative displacement curves, energy absorption curves and rigidity curves were presented and compared within the paper. In the conclusion, the capacity increase of the frame was discussed and several recommendations were presented.Öğe The Structural Damages and Collapse Types in Turkey, Observed After the Recent Earthquake(TRANS TECH PUBLICATIONS LTD, 2013) Korkmaz, Serra Zerrin; Korkmaz, Hasan HusnuIn the last decade, the earthquakes in Turkey caused thousands of loss of life. The most unfortunate case was happened in 1999 Marmara earthquake and more than 20000 people lost their life. Recently an earthquake of magnitude 7.2 occurred in Van city and 600 dead toll was reported. Following the earthquake, the author was visited the earthquake region. In this study field reconnaissance survey the causes of failures observed on reinforced concrete (RC) structures were summarized. The main problem was the construction quality especially the concrete production process. The steel detailing was also a big problem for the region. The failed or damaged buildings were included several non-seismic details. The observed problems of damaged or collapsed buildings were short column formations, soft or weak stories, inadequate lateral confinements reinforcement, use of plain undeformed bars, poor material and concrete quality, lap spilice problems, strong beam-weak columns and weak beam-column joints.
