Murat Ozturk

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.

Prediction of tensile capacity of adhesive anchors including edge and group effects using neural networks

Abstract Adhesive anchors are widely used in seismic strengthening applications to add new structural members or sections to existing concrete members due to their high tensile and compressive strengths, low cost, and easy and fast installation. To safely design such anchors, it is very important to know their pullout capacity under axial tensile forces. This paper explores the pullout capacity of both single and groups of adhesive anchors loaded in tension in uncracked concrete. Quadruple anchor groups were considered for group effect. To this end, 142 single anchor tests including edge effect (located near a concrete edge) and 175 quadruple group anchor tests (totally 317 tests) were obtained from literature. The formulated three-layered artificial neural network method (ANN) was trained using 75% of the data set by using different learning algorithms. The methods were tested with the remaining 25%. The variables taken into account in this study are anchor diameter, embedment length, concrete compressive strength, concrete body height, edge distance (for single anchors), and anchor spacing (for group anchors). It was determined that experimental data can be estimated to a notably close extent via the ANN model.

Sudden Complete Collapse of Zumrut Apartment Building and the Causes

AbstractIn 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.

An Experimental Study on the Strengthening of RC Frames with Soft Storey Irregularities with Different Types of Steel Diagonals

When the loss of life and property is considered, it is clear that special precautions must be taken against the earthquakes among the natural disasters. Post-earthquake observations, especially those made in the developing countries, reveal that there are many reasons for the damage and loss of life, not just one. The formation of soft storey irregularity is one of the most important factors among them. In this study, it is aimed to propose an alternative strengthening method to eliminate the adverse effects of the formation of a soft storey irregularity. Four identical frames with two stories and single span were constructed and tested under reverse cyclic loading which simulates the earthquake. The first frame among them was prepared by bonding bricks as an infill wall on two stories and it was considered to be the reference frame. In the 2nd frame, the formation of soft storey irregularity was facilitated by removing the infill wall on the lower story and the behavioral differences were examined. The remaining two frames were strengthened by using steel elements in two different diagonal shapes on the lower story. As a result, the experimental study showed that the strengthening with steel diagonal elements increased the lateral load-carrying capacity of the frame with soft storey behavior by 250% and the energy dissipation by 120% and also provided better results than the reference frame.

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.

Estimation of Tensile Capacity of Single Anchors Including Edge Effect Using Neural Networks

The demand for more flexibility in the design and strengthening of concrete structures has resulted in an increased use of anchoring systems. Adhesive anchors are widely used in seismic strengthening applications to add new structural members or sections to existing concrete members. To safely design such anchors, it is very important to know their tensile capacity under axial tensile forces. This paper explores the pullout capacity of single adhesive anchors loaded in tension in un-cracked concrete. To this end 142 single anchor tests including edge effect (located near a concrete edge) were obtained from literature. The formulated three-layered artificial neural network method (ANN) was trained using 75% of the data set by using different learning algorithms. The methods were tested with the remaining 25% of the data set. The variables taken into account in this study are anchor diameter, embedment length, concrete body height and edge distance. It was determined that experimental data can be estimated to a notably close extent via the ANN model.

An experimental study on the strengthening of non-ductile reinforced concrete frames via external shear wall

The 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.