An effective load increment method for multi modal adaptive pushover analysis of buildings

K. Türker,E. Irtem 국제구조공학회 2007 Structural Engineering and Mechanics, An Int'l Jou Vol.25 No.1

In this study, an effective load increment method for multi modal adaptive non-linear static (pushover) analysis (NSA) for building type structures is presented. In the method, lumped plastisicity approach is adopted and geometrical non-linearties (second-order effects) are included. Non-linear yield conditions of column elements and geometrical non-linearity effects between successive plastic sections are linearized. Thus, load increment needed for formation of plastic sections can be determined directly (without applying iteration or step-by-step techniques) by using linearized yield conditions. After formation of each plastic section, the higher mode effects are considered by utilizing the essentials of traditional response spectrum analysis at linearized regions between plastic sections. Changing dynamic properties due to plastification in the system are used on the calculation of modal lateral loads. Thus, the effects of stiffness changes and local mechanism at the system on lateral load distribution are included. By using the proposed method, solution can be obtained effectively for multi-mode whereby the properties change due to plastifications in the system. In the study, a new procedure for determination of modal lateral loads is also proposed. In order to evaluate the proposed method, a 20 story RC frame building is analyzed and compared with Non-linear Dynamic Analysis (NDA) results and FEMA 356 Non-linear Static Analysis (NSA) procedures using fixed loads distributions (first mode, SRSS and uniform distribution) in terms of different parameters. Second-order effects on response quantities and periods are also investigated. When the NDA results are taken as reference, it is seen that proposed method yield generally better results than all FEMA 356 procedures for all investigated response quantities.

Vibration based damage identification of concrete arch dams by finite element model updating

Temel Türker,Alemdar Bayraktar,Barış Sevim 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.13 No.2

Vibration based damage detection is very popular in the civil engineering area. Especially, special structures like dams, long-span bridges and high-rise buildings, need continues monitoring in terms of mechanical properties of material, static and dynamic behavior. It has been stated in the International Commission on Large Dams that more than half of the large concrete dams were constructed more than 50 years ago and the old dams have subjected to repeating loads such as earthquake, overflow, blast, etc.,. So, some unexpected failures may occur and catastrophic damages may be taken place because of theloss of strength, stiffness and other physical properties of concrete. Therefore, these dams need repairs provided with global damage evaluation in order to preserve structural integrity. The paper aims to show the effectiveness of the model updating method for global damage detection on a laboratory arch dam model. Ambient vibration test is used in order to determine the experimental dynamic characteristics. The initial finite element model is updated according to the experimentally determined natural frequencies and mode shapes. The web thickness is selected as updating parameter in the damage evaluation. It is observed from the study that the damage case is revealed with high accuracy and a good match is attained between the estimated and the real damage cases by model updating method.

Stochastic Approach on Safe Designing of Double Layer Grid Space Structure against Member Length Imperfections

Hakan T. Türker 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.3

The imperfections in Double Layer Grid Space Structure (DLGSS) threaten the safety of designs. The imperfections in the member length of DLGSS may result from human-based causes such as manual cuts, tolerance sensitivity in CNC cuttings and variation in temperature. Therefore, analyzing the impacts of imperfections is vital to ensure the safety of DLGSS systems. Thus, a safe design of DLGSS against member length imperfections is the main focus of this paper. A novel and practical safe design approach, which considers member length imperfections, has been proposed based on linear elastic and probabilistic analyses methods. The impacts of member length imperfections on the DLGSS behavior were also evaluated in detail. Variation in positions of imperfect members, initial size of length imperfections (longer or shorter than the ideal size) and number of imperfect members were selected as the parameters to be analyzed. A 3D computer program, which considers the initial length imperfections of members, has been codded to analyze the space trusses. The impact of imperfection on a space structure was investigated by repeating the simulations for stochastic dispersion of imperfect member position and initial member length imperfection. The results revealed that initial length imperfection might have a considerable impact on the DLGSS behavior. The DLGSS systems can safely be designed by employing the proposed design approach to overcome the defi ned imperfections.

Vibration based damage detection in a scaled reinforced concrete building by FE model updating

Temel Türker,Alemdar Bayraktar 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.14 No.1

The traditional destructive tests in damage detection require high cost, long consuming time, repairing of damaged members, etc. In addition to these, powerful equipments with advanced technology have motivated development of global vibration based damage detection methods. These methods base on observation of the changes in the structural dynamic properties and updating finite element models. The existence, location, severity and effect on the structural behavior of the damages can be identified by using these methods. The main idea in these methods is to minimize the differences between analytical and experimental natural frequencies. In this study, an application of damage detection using model updating method was presented on a one storey reinforced concrete (RC) building model. The model was designed to be 1/2 scale of a real building. The measurements on the model were performed by using ten uni-axial seismic accelerometers which were placed to the floor level. The presented damage identification procedure mainly consists of five steps: initial finite element modeling, testing of the undamaged model, finite element model calibration, testing of the damaged model, and damage detection with model updating. The elasticity modulus was selected as variable parameter for model calibration, while the inertia moment of section was selected for model updating. The first three modes were taken into consideration. The possible damaged members were estimated by considering the change ratio in the inertia moment. It was concluded that the finite element model calibration was required for structures to later evaluations such as damage, fatigue, etc. The presented model updating based procedure was very effective and useful for RC structures in the damage identification.

Structural evaluation of Aspendos (Belkıs) Masonry Bridge

Temel Türker 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.4

In this study, the structural performance of a seven span masonry arch bridge was evaluated. Investigations were performed on Aspendos (Belkıs) Masonry Arch Bridge which was located on road of Aspendos Acropolis City in Antalya, Turkey. The old bridge was constructed in the early of fourth century AD, but it was exposed to the earthquakes in this region and the overloading by the river water. The old bridge was severely damaged and collapsed by probably an earthquake many years ago and a new bridge was then reconstructed on the remains of this old bridge by Seljuk in the 13th century. The bridge has also been affected from overflowing especially in the spring of each year, so some protective measures should be taken for this monumental bridge. Therefore, the structural performance under these loading has to be known. For this purpose, an initial finite element model was developed for the bridge and it was calibrated according to ambient vibration test results. After that, it was analyzed for different load cases such as dead, live, earthquake and overflow. Three load combinations were taken into account by deriving from these load cases. The displacements and the stresses for these combination cases were attained and compared with each other. The structural performance of Aspendos Masonry Arch Bridge was determined by considering the demand-capacity ratio for the tensile stress of the mortar used in Aspendos Masonry Arch Bridge. After these investigations, some concluding remarks and offers were presented at the end of this study.

Structural and Molecular Orbital Properties of Some Boroxine Derivatives-A Theoretical Study

Lemi Türker,Selçuk Gümüş,Taner Atalar 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.10

In the present study, firstly, the variations of the geometric parameters induced by different substituents on boroxine skeleton (symmetrically H, CH3, Cl, F, NO2 substituted boroxines) are investigated by using B3LYP/6-31G(d,p), RHF/6-31G(d,p), and MP2/6-31G(d,p) levels of the theory. The second objective is to estimate the substituent effect on the molecular aromaticity of boroxine derivatives using energetic and NICS criteria. Moreover, the effects of different theoretical levels on NICS values have been investigated in a systematic approach. Lastly, a rotational analysis has been performed to investigate the effect of rotation around the B-Me and B-NO2 bonds on total energy of the system. It has been found that electron withdrawing substituents contribute the aromaticity of boroxine affirmatively. Conversely, electron donors make the system less aromatic. Also, the theoretical vibrational spectra for these boroxine derivatives are presented and compared with the experimental data from the literature.

Effects of dentin moisture on the push-out bond strength of a fiber post luted with different self-adhesive resin cements

Sevinç Aktemur Türker,Emel Uzunoğlu,Zeliha Yılmaz 대한치과보존학회 2013 Restorative Dentistry & Endodontics Vol.38 No.4

Objectives: This study evaluated the effects of intraradicular moisture on the pushoutbond strength of a fibre post luted with several self-adhesive resin cements. Materials and Methods: Endodontically treated root canals were treated with oneof three luting cements: (1) RelyX U100, (2) Clearfil SA, and (3) G-Cem. Roots werethen divided into four subgroups according to the moisture condition tested: (I) dry:excess water removed with paper points followed by dehydration with 95% ethanol,(II) normal moisture: canals blot-dried with paper points until appearing dry, (III)moist: canals dried by low vacuum using a Luer adapter, and (IV) wet: canals remainedtotally flooded. Two 1-mm-thick slices were obtained from each root sample and bondstrength was measured using a push-out test setup. The data were analysed using atwo-way analysis of variance and the Bonferroni post hoc test with p = 0.05. Results:Statistical analysis demonstrated that moisture levels had a significant effect on thebond strength of luting cements (p < 0.05), with the exception of G-Cem. RelyX U100displayed the highest bond strength under moist conditions (III). Clearfil SA had thehighest bond strength under normal moisture conditions (II). Statistical ranking ofbond strength values was as follows: RelyX U100 > Clearfil SA > G-Cem. Conclusions:The degree of residual moisture significantly affected the adhesion of luting cements toradicular dentine.

Influence of a glide path on the dentinal crack formation of ProTaper Next system

Sevinç Aktemur Türker,Emel Uzunoğlu 대한치과보존학회 2015 Restorative Dentistry & Endodontics Vol.40 No.4

Objectives: The aim was to evaluate dentinal crack formation after root canal preparation with ProTaper Next system (PTN) with and without a glide path. Materials and Methods: Forty-five mesial roots of mandibular first molars were selected. Fifteen teeth were left unprepared and served as controls. The experimental groups consist of mesiobuccal and mesiolingual root canals of remaining 30 teeth, which were divided into 2 groups (n = 15): Group PG/PTN, glide path was created with ProGlider (PG) and then canals were shaped with PTN system; Group PTN, glide path was not prepared and canals were shaped with PTN system only. All roots were sectioned perpendicular to the long axis at 1, 2, 3, 4, 6, and 8 mm from the apex, and the sections were observed under a stereomicroscope. The presence/absence of cracks was recorded. Data were analyzed with chi-square tests with Yates correction. Results: There were no significant differences in crack formation between the PTN with and without glide path preparation. The incidence of cracks observed in PG/PTN and PTN groups was 17.8% and 28.9%, respectively. Conclusions: The creation of a glide path with ProGlider before ProTaper Next rotary system did not influence dentinal crack formation in root canals.

TG Index, its Graphical Matrix Representation and Application on Polyenes

Selçuk Gümüş,Lemi Türker 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.5

A novel topological index (TG Index) has been introduced. The graphical matrix representation of the TG index includes the use of directed subgraphs for the first time in graph theory literature. The application of the TG index on certain properties of polyenes yielded very well correlation data.

Seismic response of concrete gravity dam-ice covered reservoir-foundation interaction systems

K. Haciefendioglu,A. Bayraktar,T. Türker 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.4

This paper examines the ice cover effects on the seismic response of concrete gravity damreservoir-foundation interaction systems subjected to a horizontal earthquake ground motion. ANSYS program is used for finite element modeling and analyzing the ice-dam-reservoir-foundation interaction system. The ice-dam-reservoir interaction system is considered by using the Lagrangian (displacementbased) fluid and solid-quadrilateral-isoparametric finite elements. The Sar yar concrete gravity dam in Turkey is selected as a numerical application. The east-west component of Erzincan earthquake, which occurred on 13 March 1992 in Erzincan, Turkey, is selected for the earthquake analysis of the dam. Dynamic analyses of the dam-reservoir-foundation interaction system are performed with and without ice cover separately. Parametric studies are done to show the effects of the variation of the length, thickness, elasticity modulus and density of the ice-cover on the seismic response of the dam. It is observed that the variations of the length, thickness, and elasticity modulus of the ice-cover influence the displacements and stresses of the coupled system considerably. Also, the variation of the density of the ice-cover cannot produce important effects on the seismic response of the dam.