M. Yasar Kaltakci

Stress concentrations and failure criteria in anisotropic plates with circular holes subjected to tension or compression

In this study, an investigation is carried out to determine the tensile and compressive stress concentrations and failure criteria for anisotropic composite plates with circular cut-outs. For these purposes, glass-epoxy and graphite-epoxy are used as a test material. A number of diagrams are drawn to illustrate the circumferential stress around the circumference of the cut-outs by using the various fiber orientation angle (α). The failure criteria and its location for anisotropic plates with and without cut-outs are determined by employing the modified distortion energy and Tsai-Hill failure theories respectively. A failure criteria is presented for predicting the externally applied tensile and compressive load which will initiate failure at the cut-outs. The location of the failure is also determined by using both theories and comparing them with each other. In addition, the stress concentration and failure location around the circumference of the cut-outs are determined for anisotropic plates with various fiber orientation angle (α).

The seismic improvement and control of weak concrete frames with partial concrete shear walls

Controlling the lateral movement of buildings under earthquake effects is very important to prevent total collapse and therefore reinforced concrete (RC) shear walls are used to obtain the lateral stability of such buildings. In this study, the usability of partial RC shear walls to strengthen buildings with weak earthquake behavior was investigated. The basic parameters of the study were determined to be the ratio of shear wall height to shear wall length (Hw/Lw ) and whether the upper inflection point of the bent bar, a steel bar commonly used in the beams of RC buildings in Turkey, is integrated into or bent outside of the partial shear wall section. Three units of two-story, double-span weak RC frames were produced at a one-third scale. Two of these three frames were then strengthened by partial shear walls integrated on both sides of the central column. Strengthened and non-strengthened specimens were tested under reversed-cyclic lateral loading. The frame systems strengthened via partial RC shear walls showed significant improvement in strength and stiffness. No debonding was observed in the anchorage rods used in the shear wall-foundation connection.

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 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.

Determination of the resistance characteristics of self-compacting concrete samples by artificial neural network

In this study, in order to determine the resistance characteristics of self-compacting concrete (SCC) samples, experiments were done in the Konya Cement Factory, Ready-mix Concrete Establishment. Four different mixture proportions were chosen in the experimental study. 24 samples of the 4 mixtures were selected in order to set the cube compression strength. For each mixture, these 24 samples were broken down within 28 days and the characteristics of cube compression strength were obtained. After 28 days, compression strength average was found to be 50.0300 MPa. A model of Artificial Neural Network (ANN) was designed for this study and the results were obtained in this model of ANN. Both experimental and ANN data was analyzed with SPSS statistical packet software. The result of statistical analysis (p=0.9972) has been done in 95% of confidence interval. It has been seen that the ANN can be used as reliable modelling method for similar studies.