The effect of short columns on the performance of existing buildings

Kocak, Ali Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.4

In this study, the seismic performance of a residential building which was damaged in the 1992 Erzincan (Turkey) Earthquake (Ms = 6.8) is performed. Damages on columns due to short columns are estimated analytically implementing the shear hinges and results are compared with the observed damages on the building after the earthquake. In seismic performance evaluation, a deformation based approach is adopted, whereby the structural behavior under external and seismic loads is evaluated. Furthermore, the effects of short columns formed by band windows in basement floors are investigated analytically. The sizes of band windows are parametrically changed in order to understand the effects of short columns on overall building behavior.

Earthquake performance of FRP retrofitting of short columns around band-type windows

Kocak, Ali Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.1

Due to design codes and regulations and the variety of building plans in Turkey, it is very often seen that band-type windows are left for ventilation and lightening of the basements of buildings which are used for various purposes such as workplaces and storage. Therefore when the necessary support measures cannot be given, short columns are subjected to very high shear forces and so damage occurs. One of the precautions to avoid the damage of short column mechanisms in buildings where band-type windows are in the basement is to strengthen the short columns with fiber reinforced polymer (FRP). In this study, the effect of the FRP retrofitting process of the short columns around band-windowed structures, which are found especially in basement areas, is analyzed in accordance with Turkish Seismic Code 2007 (TSC 2007). Three different models which are bare frame, frame with short columns and retrofitted short columns with FRP, are created and analyzed according to TSC 2007 performance analysis methods to understand the effects of band windows in basements and the effect of FRP retrofitting.

A CLASS OF MÖBIUS ITERATED FUNCTION SYSTEMS

Cakmak, Gokce,Deniz, Ali,Kocak, Sahin Korean Mathematical Society 2020 대한수학회논문집 Vol.35 No.3

We characterize Möbius functions mapping the unit disc of the complex plane contractively into itself. We then give a procedure to produce Möbius iterated function systems on the unit disc.

Elastoplastic Finite Element Analysis of Masonry Shear Walls

H. Orhun Koksal,Bilge Doran,A. Osman Kuruscu,Ali Kocak 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.2

Masonry is the most important construction material in Turkey. It has been used for public and residential buildings in the past several thousand years. A great number of well-preserved old masonry structures still exist proving that this form of construction can successfully resist loads and environmental impact. Traditionally, most major buildings were solid walled structures with the walls bearing directly on the ground. Engineers work hard to convert the highly indeterminate, ambiguous and nonlinear behavior of historic masonry construction into something which can be understood with mathematical certainty. Therefore, practical and accurate structural analysis techniques are needed for the preserve the historical monuments as a huge cultural heritage. This paper is focused on Nonlinear Finite Element (NLFE) modeling of masonry shear walls at a macro-level taking the geometric arrangement of constituents. In this study, 3D elasto-plastic Finite Element (FE) analysis for the masonry walls that subjected to the combinations of vertical and lateral loads, are determined to find a practical method. An original meshing procedure is introduced to consider the orthotropy along the two natural directions of the masonry while the material is still assumed to be isotropic. The paper further examines parameter studies carried out to show that the relation suggested for cohesion values of mortar joint masonry can also be adopted for the masonry walls with dry joints employing compressive stresses on the top surface of the wall despite using its compressive strength. The accuracy of the proposed approach is verified by simulating a series of experiments reported in the literature. Those papers include shear tests on masonry walls with both dry and mortar joints by Raijmakers and Vermeltfoort, Oliveira and Roca. Comparisons between the predicted and measured failure loads of the walls confirm that it is possible to reproduce the fundamental features of masonry shear walls with the proposed meshing scheme. Finally, the proposed approach is shown to fit quite well the experimental load-deformation plots of masonry walls with both dry- and mortar joint under shearcompression fracture.

The effect of mortar type and joint thickness on mechanical properties of conventional masonry walls

Zengin, Basak,Toydemir, Burak,Ulukaya, Serhan,Oktay, Didem,Yuzer, Nabi,Kocak, Ali Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.6

Masonry walls are of a complex (anisotropic) structure in terms of their mechanical properties. The mechanical properties of the walls are affected by the properties of the materials used in wall construction, joint thickness and the type of masonry bond. The carried-out studies, particularly in the seismic zones, have revealed that the most of the conventional masonry walls were constructed without considering any engineering approach. Along with that, large-scale damages were detected on such structural elements after major earthquake(s), and such damages were commonly occurred at the brick-joint interfaces. The aim of this study was to investigate the effect of joint thickness and also type of mortar on the mechanical behavior of the masonry walls. For this aim, the brick masonry walls were constructed through examination of both the literature and the conventional masonry walls. In the construction process, a single-type of brick was combined with two different types of mortar: cement mortar and hydraulic lime mortar. Three different joint thicknesses were used for each mortar type; thus, a total of six masonry walls were constructed in the laboratory. The mechanical properties of brick and mortars, and also of the constructed walls were determined. As a conclusion, it can be stated that the failure mechanism of the brick masonry walls differed due to the mechanical properties of the mortars. The use of bed joint thickness not less than 20 mm is recommended in construction of conventional masonry walls in order to maintain the act of brick in conjunction with mortar under load.

The effect of mortar type and joint thickness on mechanical properties of conventional masonry walls

Başak Zengin,Burak Toydemir,Serhan Ulukaya,Didem Oktay,Nabi Yüzer,Ali Kocak 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.6

Masonry walls are of a complex (anisotropic) structure in terms of their mechanical properties. The mechanical properties of the walls are affected by the properties of the materials used in wall construction, joint thickness and the type of masonry bond. The carried-out studies, particularly in the seismic zones, have revealed that the most of the conventional masonry walls were constructed without considering any engineering approach. Along with that, large-scale damages were detected on such structural elements after major earthquake(s), and such damages were commonly occurred at the brick-joint interfaces. The aim of this study was to investigate the effect of joint thickness and also type of mortar on the mechanical behavior of the masonry walls. For this aim, the brick masonry walls were constructed through examination of both the literature and the conventional masonry walls. In the construction process, a single-type of brick was combined with two different types of mortar: cement mortar and hydraulic lime mortar. Three different joint thicknesses were used for each mortar type; thus, a total of six masonry walls were constructed in the laboratory. The mechanical properties of brick and mortars, and also of the constructed walls were determined. As a conclusion, it can be stated that the failure mechanism of the brick masonry walls differed due to the mechanical properties of the mortars. The use of bed joint thickness not less than 20 mm is recommended in construction of conventional masonry walls in order to maintain the act of brick in conjunction with mortar under load.