Earthquake response of isolated cable-stayed bridges under spatially varying ground motions

Sevket Ates,Kurtulus Soyluk,A. Aydin Dumanoglu,Alemdar Bayraktar 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.31 No.6

A comprehensive investigation of the stochastic response of an isolated cable-stayed bridge subjected to spatially varying earthquake ground motion is performed. In this study, the Jindo Bridge built in South Korea is chosen as a numerical example. The bridge deck is assumed to be continuous from one end to the other end. The vertical movement of the stiffening girder is restrained and freedom of rotational movement on the transverse axis is provided for all piers and abutments. The longitudinal restraint is provided at the mainland pier. The A-frame towers are fixed at the base. To implement the base isolation procedure, the double concave friction pendulum bearings are placed at each of the four support points of the deck. Thus, the deck of the cable-stayed bridge is isolated from the towers using the double concave friction pendulum bearings which are sliding devices that utilize two spherical concave surfaces. The spatially varying earthquake ground motion is characterized by the incoherence and wavepassage effects. Mean of maximum response values obtained from the spatially varying earthquake ground motion case are compared for the isolated and non-isolated bridge models. It is pointed out that the base isolation of the considered cable-stayed bridge model subjected to the spatially varying earthquake ground motion significantly underestimates the deck and the tower responses.

Earthquake response of isolated cable-stayed bridges under spatially varying ground motions

Ates, Sevket,Soyluk, Kurtulus,Dumanoglu, A. Aydin,Bayraktar, Alemdar Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.31 No.6

A comprehensive investigation of the stochastic response of an isolated cable-stayed bridge subjected to spatially varying earthquake ground motion is performed. In this study, the Jindo Bridge built in South Korea is chosen as a numerical example. The bridge deck is assumed to be continuous from one end to the other end. The vertical movement of the stiffening girder is restrained and freedom of rotational movement on the transverse axis is provided for all piers and abutments. The longitudinal restraint is provided at the mainland pier. The A-frame towers are fixed at the base. To implement the base isolation procedure, the double concave friction pendulum bearings are placed at each of the four support points of the deck. Thus, the deck of the cable-stayed bridge is isolated from the towers using the double concave friction pendulum bearings which are sliding devices that utilize two spherical concave surfaces. The spatially varying earthquake ground motion is characterized by the incoherence and wave-passage effects. Mean of maximum response values obtained from the spatially varying earthquake ground motion case are compared for the isolated and non-isolated bridge models. It is pointed out that the base isolation of the considered cable-stayed bridge model subjected to the spatially varying earthquake ground motion significantly underestimates the deck and the tower responses.

Earthquake response of isolated cable-stayed bridges under spatially varying ground motions

Sevket Ates,Kurtulus Soyluk,A. Aydin Dumanoglu,Alemdar Bayraktar 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.32 No.1

A comprehensive investigation of the stochastic response of an isolated cable-stayed bridge subjected to spatially varying earthquake ground motion is performed. In this study, the Jindo Bridge built in South Korea is chosen as a numerical example. The bridge deck is assumed to be continuous from one end to the other end. The vertical movement of the stiffening girder is restrained and freedom of rotational movement on the transverse axis is provided for all piers and abutments. The longitudinal restraint is provided at the mainland pier. The A-frame towers are fixed at the base. To implement the base isolation procedure, the double concave friction pendulum bearings are placed at each of the four support points of the deck. Thus, the deck of the cable-stayed bridge is isolated from the towers using the double concave friction pendulum bearings which are sliding devices that utilize two spherical concave surfaces. The spatially varying earthquake ground motion is characterized by the incoherence and wavepassage effects. Mean of maximum response values obtained from the spatially varying earthquake ground motion case are compared for the isolated and non-isolated bridge models. It is pointed out that the base isolation of the considered cable-stayed bridge model subjected to the spatially varying earthquake ground motion significantly underestimates the deck and the tower responses.

Finite element model updating effect on the structural behavior of long span concrete highway bridges

A.C. Altunisik,A. Bayraktar 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.14 No.6

In this paper, it is aimed to determine the finite element model updating effects on the structural behavior of long span concrete highway bridges. Birecik Highway Bridge located on the 81stkm of Şanlıurfa-Gaziantep state highway over Fırat River in Turkey is selected as a case study. The bridge consist of fourteen spans, each of span has a nearly 26m. The total bridge length is 380m and width of bridge is 10m. Firstly, the analytical dynamic characteristics such as natural frequencies and mode shapes are attained from finite element analyses using SAP2000 program. After, experimental dynamic characteristics are specified from field investigations using Operational Modal Analysis method. Enhanced Frequency Domain Decomposition method in the frequency domain is used to extract the dynamic characteristics such as natural frequencies, mode shapes and damping ratios. Analytically and experimentally identified dynamic characteristics are compared with each other and finite element model of the bridge is updated to reduce the differences by changing of some uncertain parameters such as section properties, damages, boundary conditions and material properties. At the end of the study, structural performance of the highway bridge is determined under dead load, live load, and dynamic loads before and after model updating to specify the updating effect. Displacements, internal forces and stresses are used as comparison parameters. From the study, it is seen that the ambient vibration measurements are enough to identify the most significant modes of long span highway bridges. Maximum differences between the natural frequencies are reduced averagely from %46.7 to %2.39 by model updating. A good harmony is found between mode shapes after finite element model updating. It is demonstrated that finite element model updating has an important effect on the structural performance of the arch type long span highway bridge. Maximum displacements, shear forces, bending moments and compressive stresses are reduced %28.6, %21.0, %19.22, and %33.3-20.0, respectively.

Determination of the restoration effect on the structural behavior of masonry arch bridges

A.C. Altunisik,A. Bayraktar,A.F. Genc 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.16 No.1

In this paper, it is aimed to investigate the restoration effect on the structural behavior of masonry arch bridges. Dandalaz masonry arch bridge located on the 4km east of Karacasu town of Aydin, Turkey is selected as a numerical example. The construction year of the bridge is not fully known, but the bridge is dated back to 15th century. Considering the current situation, it can be easily seen that the structural elements such as arch, side walls and timber blocks are heavily damaged and the bridge is unserviceable. Firstly finite element model of the bridge is constituted to reflect the current situation (before restoration) using building survey drawings. After, restoration project is explained and finite element model is reconstituted (after restoration). The structural responses of the bridge are obtained before and after restoration under dead load, live load and dynamic earthquake loads. For both conditions, maximum displacements, maximum-minimum principal stresses and maximum-minimum elastic strains are given with detail using contours diagrams and compared with each other to determine the restoration effect. From the study, it can be seen that the maximum internal forces are consisted under dynamic loads before and after restoration. Also, the restoration projects and studies have important and positive effects on the structural response of the bridge to transfer these structures to future.

Effect of Zinc Content and Cutting Tool Coating on the Machinability of the Al‑(5–35) Zn Alloys

Şenol Bayraktar,Ali Paşa Hekimoğlu 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.4

In this study, Al-5Zn, Al-15Zn, Al-25Zn and Al-35Zn alloys containing 5, 15, 25 and 35 wt% Zn, respectively were producedby permanent mold casting. Their microstructures and mechanical properties were investigated using metallographyand universal hardness and tensile tests. Cutting tests of the alloys produced were carried out in a vertical machining center. During the tests, the cutting forces were continuously measured and saved by a software. The roughness of the machinedsurfaces of the alloy samples was measured accordance with the standard of ISO 4287. It was observed that Al-(5–15)Znalloys exhibit single phase (aluminum rich α) microstructure while Al-(25–35)Zn alloys exhibit two-phase microstructureconsisting of α and zinc rich η. As the zinc content increased the hardness and tensile strength of the alloys increased, buttheir elongation to fracture decreased. Cutting force, surface roughness, formation of built-up edge (BUE) and built-uplayer (BUL), and the size of the chip occurring in the machining of the alloys decreased with increasing zinc content. Themachining of the Al-(5-35)Zn alloys with uncoated WC tools results in both lower cutting forces and better surface qualitycompared to titanium-aluminum-nitride (TiAlN) coated tools. The changes in the cutting properties of the tested alloys withthe increasing zinc content were discussed in the based on changes in structural and mechanical properties.

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.

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

Haciefendioglu, K.,Bayraktar, A.,Turker, T. Techno-Press 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 dam-reservoir-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 Sariyar 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.

Seismic analysis of arch dams including dam-reservoir interaction via a continuum damage model

Karaton, M.,Calayir, Y.,Bayraktar, A. Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.22 No.3

In this study, the earthquake damage response of the concrete arch dams was investigated including dam-reservoir interaction. A continuum damage model which is a second-order tensor and includes the strain softening behavior was selected for the concrete material. Fluid-structure interaction problem was modeled by Lagrangian approach. Sommerfeld radiation condition was applied to the truncated boundary of reservoir. The improved form of the HHT-${\alpha}$ time integration algorithm was used in the solution of the equations of motion. The arch dam Type 5 was selected for numerical application. For the dynamic input, acceleration records of the 10 December 1967 Koyna earthquake were chosen. These records were scaled with earthquake acceleration scale factor (EASF) and then used in the analyses. Solutions were obtained for empty and full reservoir cases. The effects of EASF and damping ratio on the response of the dam were studied.

Ferrous Alloys : DEFORMATION BEHAVIOUR OF HADFIELD STEEL AT VARIOUS STRAINS STRAIN RATES AND TEMPERATURES

F . A . Khalid,E . Bayraktar,C . Levaillant 대한금속재료학회 ( 구 대한금속학회 ) 1995 Advanced Material and Processing Vol.3 No.-