Mevlut Yasar Kaltakci

Results and lessons learned from the buildings which failed under their own weight in Turkey

The Zumrut Apartment Building in Turkey collapsed completely and suddenly on February 2, 2004, killing 92 people. A few months later, on October 29, 2004, cracks occurred on two reinforced concrete columns in the basement of the Altinbasak Apartment Building, about 500 m away from the Zumrut Building. In both cases the collapses occurred spontaneously, and were not related to an earthquake or other external causes. At the end of the investigations performed in situ and on the project documents, the main reasons for the collapse and damage were determined to be the mistakes made in the design load selection, the inappropriate dimensions of the load-carrying members, poor material quality, and poor soil conditions. The main aim of this study was to investigate the causes of the collapse and damage to these two buildings by considering the significant mistakes made during the design and construction stages. In addition, the research and observations performed on the buildings and the results from tests made on specimens taken from them, will be presented in this paper. A discussion of the values obtained from computer models of the buildings using the finite element method is also presented, and their relationship to the damages observed in the buildings, especially on the vertical load-bearing members.

Artificial neural network design for behaviours of reinforced concrete column under axial load and comparison of experimental study

Construction (building) sector is one of the sectors which adapt the rapid development of the technology. Especially in frame (skeleton) systems, very serious studies on columns that are vertical conveyors (carriers) are being done. Generally, these studies are implemented by experimentally and computer software is used in these studies as they offer good results. Artificial neural network (ANN) has been used in several engineering application areas including civil engineering. The use of ANN to predict the behaviour of reinforced concrete (R/C) members, using the vast amount of experimental data as a test-bed for learning and verification of results, proved to be available method for carrying out parametric studies. In the present study, columns under the axial load were manufactured from concrete that has been produced without carrying out the standards. Load conveying capacities and tension-unit deformation relationships of columns manufactured with different geometrical and equipment (outfit) properties and same cross-section area have been investigated. At the same time, research has been done via modelling by using ANN that is one of techniques of artificial intelligence and gained importance in recent years. SPSS statistical packet program is used to evaluate the results of this research. After comparisons of results obtained in the experiments, it has been determined that square column samples have the most axial load conveying capacity. It has also been determined that number of displacement is less in samples of columns wrapped (winded) with fret comparing to samples of columns wrapped with stirrup. The same results are obtained after modelling by ANN. As the result of statistical analyses that have been done in %5 reliability interval between data obtained from experiments and ANN, it has been seen that ANN can be used as reliable method.

Evaluation of a Gravity Load Designed Reinforced Concrete Structure Failed under its Own Weight due to Creep in Concrete

Turkish 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.

Strengthening of Reinforced Concrete Frames Not Designed According to TDY2007 with External Shear Walls

Recently 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 didnt 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.