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    Approaches for design of lightweight steel structures, current controlling conditions, and the issues recommended to be emphasized in a prospective lightweight steel building code
    (PAMUKKALE UNIV, 2018) Gunes, Selma Aysegul; Ceribasi, Seyit
    Because of the absence of a comprehensive code for cold-formed steel constructions in Turkey sections, capacity, design, production and assembly of cold-formed lightweight steel buildings cannot be fully controlled. Especially during periods of high market demand, economic structures which are considered as standard in accordance with the market conditions are produced and built. Even though current design and manufacturing assumptions might differ for each company the design and manufacturing are done by experience-based assumptions. For the projects for which strict controls are requested, and which are mostly supported by the state, all examining of cold-formed lightweight steel buildings is done with various national and international regulations. In the scope of this article a brief introduction of lightweight steel structures, current usage patterns and common design and manufacturing details in Turkey are presented and an example of in-situ lightweight steel structure is designed. Design assumptions and element properties are investigated according to two widely-used international codes, and additionally including the current Turkish regulations, the controls are performed, and the model and analysis of the structure are achieved by using SAP2000. As a result of the study, a general way of overall inspection and control of cold formed lightweight structures has been tried to be reached according to national and international regulations.
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    Determining the optimum outrigger locations for steel tall buildings by using time history analyses
    (Wiley, 2021) İnam, İlhan Emre; Ceribasi, Seyit; Karapinar, Isil Sanri
    The outrigger system is an effective tall building system used at one or multiple locations of high-rise buildings. It is designed to control and minimize lateral displacement and to increase bending stiffness of the buildings by changing the load transfer mechanism of the structural systems. This paper presents a framework for estimation of the optimum location of the outriggers with structural engineering design approach. Three different sample high-rise buildings, 35-story 140-m, 40-story 160-m, and 45-m 180-m, were investigated. A time-history analysis method was used to examine the effects of earthquakes. In the first stage, the buildings were assumed to have one outrigger. The outrigger was put on each floor, and ETABS analysis models were created. For each different sample buildings, 35, 40, and 45 different analytical models were utilized for that stage, respectively. In the second stage, in case of outrigger in two positions, all combinations in which outriggers can be located in different positions were taken into consideration for only 40-story sample building. Considering all of the possible cases, where the steel high-rise building has 40 floors and the outriggers can be in two different locations, 780 different analysis models were used.
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    The effect of polypropylene, steel, and macro synthetic fibers on mechanical behavior of cementitious composites
    (Pontificia Univ Catolica Chile, Escuela Construccion Civil, 2021) Özsoy Özbay, Ayşe Elif; Erkek, Orhan; Ceribasi, Seyit
    Incorporation of fibers in concrete has been an efficient technique to prevent crack propagation, thus improving ductility, durability, toughness and strength of concrete. In this context, a comprehensive experimental study has been conducted concerning the compressive and flexural strength of fiber reinforced concrete, through preparing nine concrete batches with polypropylene fibers, steel fibers and macro synthetic fibers; and the hybrid forms combining polypropylene (PP) and steel, polypropylene and macro synthetic fibers. Fiber inclusion in concrete caused slight variations in compres-sive strength. However, the flexural strength for all sample sets was significantly increased. The highest values of strength increase relative to control concrete were 60.67%, 42.45% and 27.05% incorporating steel, polypropylene and macro syn-thetic fibers, respectively. It was also noted that the higher aspect ratio of steel fibers resulted with better flexural perfor-mance, among the steel fiber reinforced concrete samples. Hybrid forms of polypropylene-steel and polypropylene-macro synthetic fibers achieved the highest flexural strength compared with samples including single type of fiber. In blended groups, utilization of polypropylene fibers with steel fibers and with macro synthetic fibers resulted with 69.81% and 78.99% of increase in flexural strength relative to control specimens, respectively.
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    Modelling of infill walls in reinforced concrete buildings under low-amplitude vibrations
    (Emerald Group Publishing Ltd, 2021) Aras, Fuat; Akbas, Tolga; Ceribasi, Seyit; Catbas, Fikret Necati
    A study was undertaken to analyse the capability of conventional finite-element (FE) models to represent the actual dynamic behaviour of masonry infill walls in reinforced concrete (RC) buildings under ambient conditions. Two commonly used modelling techniques were examined - shell elements and diagonal compression struts. An existing non-symmetrical, six-storey RC building was used as a reference structure. The dynamic characteristics of the real building were determined by an ambient vibration survey. Two FE models of the building were then constructed and the dynamic characteristics of the building were determined numerically. Comparisons of the experimentally obtained dynamic properties and those obtained using each numerical model revealed the most appropriate method for visualising the dynamic behaviour of RC buildings under low levels of vibration. The dynamic behaviour of RC buildings under earthquakes and the use of code-based period estimation formulas were then analysed. The results showed that each modelling technique affected the predicted dynamic frequencies substantially; choosing the most suitable model depends on the level of vibration.
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    Probabilistic computation of the structural performance of moment resisting steel frames
    (TECHNO-PRESS, 2017) Ceribasi, Seyit
    This study investigates the reliability of the performance levels of moment resisting steel frames subjected to lateral loads such as wind and earthquake. The reliability assessment has been performed with respect to three performance levels: serviceability, damageability, and ultimate limit states. A four-story moment resisting frame is used as a typical example. In the reliability assessment the uncertainties in the loadings and in the capacity of the frame have been considered. The wind and earthquake loads are assumed to have lognormal distribution, and the frame resistance is assumed to have a normal distribution. In order to obtain an appropriate limit state function a linear relation between the loading and the deflection is formed. For the reliability analysis an algorithm has been developed for determination of limit state functions and iterations of the first order reliability method (FORM) procedure. By the method presented herein the multivariable analysis of a complicated reliability problem is reduced to an S-R problem. The procedure for iterations has been tested by a known problem for the purpose of avoiding convergence problems. The reliability indices for many cases have been obtained and also the effects of the coefficient of variation of load and resistance have been investigated.
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    Progressive Damage Analyses of Masonry Buildings by Dynamic Analyses
    (SPRINGER INTERNATIONAL PUBLISHING AG, 2020) Aras, Fuat; Akbas, Tolga; Eksi, Hizir; Ceribasi, Seyit
    This study investigates the effects of prescribed damage on the walls of masonry buildings by experimental and numerical methods. Ambient vibration survey method was applied to an existing, two-story, unreinforced masonry building to determine its dynamic characteristics, such as mode shapes and natural frequencies. Then, the walls on two exterior sides of the building were demolished, and dynamic testing was repeated for the damaged building. As the next step, the amount of damage on the building was increased by more impacts, and the dynamic characteristics of the heavily damaged building were identified. The results obtained from the undamaged, damaged and heavily damaged building were compared, and the damage effect on the natural frequencies of the building was noted. Besides, finite element analyses of the undamaged, damaged and heavily damaged buildings were performed. It was found that, the numerical models, constructed with code-based material properties, do not sufficiently represent the dynamic behavior of masonry buildings. Secondly, as the result of the sustained damage, while the experimental and the numerical modal analyses revealed the decrease in the dominant frequencies of the building, the difference between them increases with the severity of the damage. With the framework presented in this study, the behavior of masonry buildings can better be determined and used for analysis purposes.
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    Static and Dynamic Analyses of Thin Uniformly Loaded Super Elliptical FGM Plates
    (TAYLOR & FRANCIS INC, 2012) Ceribasi, Seyit
    Elastic and functionally graded (FGM) Kirchhoff plates are investigated in this study. Meshless approximate methods are employed for solution of plate equations. For static analysis, uniformly distributed load and clamped boundaries are assumed. Galerkin's method is used to solve the partial differential equation of plates. In addition, vibration characteristics of simply supported FGM plates are studied by using the Ritz method. The Poisson's ratios of plates are assumed to be constant, but Young's modulus varies functionally. The effective Young's modulus of the plates, made of isotropic ceramic and metal constituents with volume contents varying only in the thickness direction, is computed using the Mori-Tanaka homogenization technique. The objective here is to investigate the influence of volume fractions and the component materials on mechanical behavior of super elliptical plates.