Water Length and Height Effects on the Earthquake Behavior of Arch Dam-Reservoir-Foundation Systems

Baris¸ Sevim,Ahmet Can Altuns¸ik,Alemdar Bayraktar,Mehmet Akköse,Yusuf Calayir 대한토목학회 2011 KSCE Journal of Civil Engineering Vol.15 No.2

In this study, water length and height effects on the earthquake behavior of arch dam-reservoir-foundation systems are purposed. The study can be classified into two parts. In the first part, in order to obtain a realistic 3D arch dam-reservoir-foundation model,water length effects on the behavior of the arch dam systems are investigated. For this purpose a double curvature arch dam is modeled by forming four different water lengths related to dam Height (H) as H, 2H, 3H and 4H. Each model is analyzed in time domain and the realistic model is obtained according to the analyses results. In the second part, water height effects on the behavior of the arch dam system are investigated. The arch dam obtained from first part of the study is modeled by forming four different water heights related to dam Height (H) as 0H, 0.33H, 0.66H and H. The behavior of the dam, reservoir and foundation are expressed in terms of displacements using Lagrangian approach. The foundation is taken into account as massless; behavior of reservoir is assumed to be linearly elastic, inviscid and irrotational. In this study, all systems are modeled by ANSYS finite element program and analyses are performed using IMPVALL/I-ELC180 component of Imperial Valley (1940) earthquake. Dynamic equations of motions are solved by using Newmark integration algorithm. It is seen that both water length and height affect the earthquake behavior of the arch dams considerably.

Investigation of water length effects on the modal behavior of a prototype arch dam using operational and analytical modal analyses

Baris Sevim,Alemdar Bayraktar,Ahmet Can Altunisik 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.37 No.6

This study determines the water length effects on the modal behavior of a prototype arch dam using Operational and Analytical Modal Analyses. Achievement of this purpose involves construction of a prototype arch dam-reservoir-foundation model under laboratory conditions. In the model, reservoir length was taken to be as much as three times the dam height. To determine the experimental dynamic characteristics of the arch dam using Operational Modal Analysis, ambient vibration tests were implemented for empty reservoir and three different reservoir water lengths. In the ambient vibration tests,the dam was vibrated by natural excitations provided from small impact effects and the response signals were measured using sensitive accelerometers. Operational Modal Analysis software process signals collected from the ambient vibration tests, and Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification techniques estimated modal parameters of the dams. To validate the experimental results, 3D finite element model of the prototype arch dam was modeled by ANSYS software for empty reservoir and three different reservoir water lengths, and dynamic characteristics of each model were determined analytically. At the end of the study, experimentally and analytically identified dynamic characteristics compared to each other. Also, changes on the natural frequencies along to water length are plotted as graphs. Results suggest that reservoir water complicates the modal behavior of the arch dam significantly.

Near-fault ground motion effects on the nonlinear response of dam-reservoir-foundation systems

Bayraktar, Alemdar,Altunisik, Ahmet Can,Sevim, Baris,Kartal, Murat Emre,Turker, Temel Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.28 No.4

Ground motions in near source region of large crustal earthquakes are significantly affected by rupture directivity and tectonic fling. These effects are the strongest at longer periods and they can have a significant impact on Engineering Structures. In this paper, it is aimed to determine near-fault ground motion effects on the nonlinear response of dams including dam-reservoir-foundation interaction. Four different types of dam, which are gravity, arch, concrete faced rockfill and clay core rockfill dams, are selected to investigate the near-fault ground motion effects on dam responses. The behavior of reservoir is taken into account by using Lagrangian approach. Strong ground motion records of Duzce (1999), Northridge (1994) and Erzincan (1992) earthquakes are selected for the analyses. Displacements, maximum and minimum principal stresses are determined by using the finite element method. The displacements and principal stresses obtained from the four different dam types subjected to these nearfault strong-ground motions are compared with each other. It is seen from the results that near-fault ground motions have different impacts on the dam types.

Finite element model updating of Kömürhan highway bridge based on experimental measurements

Bayraktar, Alemdar,Altunisik, Ahmet Can,Sevim, Baris,Turker, Temel Techno-Press 2010 Smart Structures and Systems, An International Jou Vol.6 No.4

The updated finite element model of K$\ddot{o}$m$\ddot{u}$rhan Highway Bridge on the Firat River located on the $51^{st}$ km of Elazi$\breve{g}$-Malatya highway is obtained by using analytical and experimental results. The 2D and 3D finite element model of the bridge is created by using SAP2000 structural analyses software, and the dynamic characteristics of the bridge are determined analytically. The experimental measurements are carried out by Operational Modal Analysis Method under traffic induced vibrations and the dynamic characteristics are obtained experimentally. The vibration data are gathered from the both box girder and the deck of the bridge, separately. Due to the expansion joint in the middle of the bridge, special measurement points are selected when experimental test setups constitute. Measurement duration, frequency span and effective mode number are determined by considering similar studies in literature. The Peak Picking method in the frequency domain is used in the modal identification. At the end of the study, analytical and experimental dynamic characteristic are compared with each other and the finite element model of the bridge is updated by changing some uncertain parameters such as material properties and boundary conditions. Maximum differences between the natural frequencies are reduced from 10% to 2%, and a good agreement is found between natural frequencies and mode shapes after model updating.

Investigation of water length effects on the modal behavior of a prototype arch dam using operational and analytical modal analyses

Sevim, Baris,Bayraktar, Alemdar,Altunisik, Ahmet Can Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.37 No.6

This study determines the water length effects on the modal behavior of a prototype arch dam using Operational and Analytical Modal Analyses. Achievement of this purpose involves construction of a prototype arch dam-reservoir-foundation model under laboratory conditions. In the model, reservoir length was taken to be as much as three times the dam height. To determine the experimental dynamic characteristics of the arch dam using Operational Modal Analysis, ambient vibration tests were implemented for empty reservoir and three different reservoir water lengths. In the ambient vibration tests, the dam was vibrated by natural excitations provided from small impact effects and the response signals were measured using sensitive accelerometers. Operational Modal Analysis software process signals collected from the ambient vibration tests, and Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification techniques estimated modal parameters of the dams. To validate the experimental results, 3D finite element model of the prototype arch dam was modeled by ANSYS software for empty reservoir and three different reservoir water lengths, and dynamic characteristics of each model were determined analytically. At the end of the study, experimentally and analytically identified dynamic characteristics compared to each other. Also, changes on the natural frequencies along to water length are plotted as graphs. Results suggest that reservoir water complicates the modal behavior of the arch dam significantly.

Structural identification of concrete arch dams by ambient vibration tests

Sevim, Baris,Altunisik, Ahmet Can,Bayraktar, Alemdar Techno-Press 2013 Advances in concrete construction Vol.1 No.3

Modal testing, widely accepted and applied method for determining the dynamic characteristics of structures for operational conditions, uses known or unknown vibrations in structures. The method's common applications includes estimation of dynamic characteristics and also damage detection and monitoring of structural performance. In this study, the structural identification of concrete arch dams is determined using ambient vibration tests which is one of the modal testing methods. For the purpose, several ambient vibration tests are conducted to an arch dam. Sensitive accelerometers were placed on the different points of the crest and a gallery of the dam, and signals are collected for the process. Enhanced Frequency Domain Decomposition technique is used for the extraction of natural frequencies, mode shapes and damping ratios. A total of eight natural frequencies are attained by experimentally for each test setup, which ranges between 0-12 Hz. The results obtained from each ambient vibration tests are presented and compared with each other in detail. There is a good agreement between the results for all measurements. However, the theoretical fundamental frequency of Berke Arch Dam is a little different from the experimental.

Near-fault ground motion effects on the nonlinear response of dam-reservoir-foundation systems

Alemdar Bayraktar,Ahmet Can Altuni ik,Baris Sevim,Murat Emre Kartal,Temel Türker 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.28 No.4

Ground motions in near source region of large crustal earthquakes are significantly affected by rupture directivity and tectonic fling. These effects are the strongest at longer periods and they can have a significant impact on Engineering Structures. In this paper, it is aimed to determine near-fault ground motion effects on the nonlinear response of dams including dam-reservoir-foundation interaction. Four different types of dam, which are gravity, arch, concrete faced rockfill and clay core rockfill dams, are selected to investigate the near-fault ground motion effects on dam responses. The behavior of reservoir is taken into account by using Lagrangian approach. Strong ground motion records of Duzce (1999), Northridge (1994) and Erzincan (1992) earthquakes are selected for the analyses. Displacements, maximum and minimum principal stresses are determined by using the finite element method. The displacements and principal stresses obtained from the four different dam types subjected to these nearfault strong-ground motions are compared with each other. It is seen from the results that near-fault ground motions have different impacts on the dam types.

Finite element model updating of Kömürhan highway bridge based on experimental measurements

Alemdar Bayraktar,Ahmet Can Altunisik,Baris Sevim,Temel Türker 국제구조공학회 2010 Smart Structures and Systems, An International Jou Vol.6 No.4

The updated finite element model of Kömürhan Highway Bridge on the Flrat River located on the 51st km of Elazl-Malatya highway is obtained by using analytical and experimental results. The 2D and 3D finite element model of the bridge is created by using SAP2000 structural analyses software, and the dynamic characteristics of the bridge are determined analytically. The experimental measurements are carried out by Operational Modal Analysis Method under traffic induced vibrations and the dynamic characteristics are obtained experimentally. The vibration data are gathered from the both box girder and the deck of the bridge, separately. Due to the expansion joint in the middle of the bridge, special measurement points are selected when experimental test setups constitute. Measurement duration, frequency span and effective mode number are determined by considering similar studies in literature. The Peak Picking method in the frequency domain is used in the modal identification. At the end of the study, analytical and experimental dynamic characteristic are compared with each other and the finite element model of the bridge is updated by changing some uncertain parameters such as material properties and boundary conditions. Maximum differences between the natural frequencies are reduced from 10% to 2%, and a good agreement is found between natural frequencies and mode shapes after model updating.

Modal testing and finite element model calibration of an arch type steel footbridge

Alemdar Bayraktar,Ahmet Can Altuni ik,Bari Sevim,Temel Türker 국제구조공학회 2007 Steel and Composite Structures, An International J Vol.7 No.6

In recent decades there has been a trend towards improved mechanical characteristics of materials used in footbridge construction. It has enabled engineers to design lighter, slender and more aesthetic structures. As a result of these construction trends, many footbridges have become more susceptible to vibrations when subjected to dynamic loads. In addition to this, some inherit modelling uncertainties related to a lack of information on the as-built structure, such as boundary conditions, material properties, and the effects of non-structural elements make difficult to evaluate modal properties of footbridges, analytically. For these purposes, modal testing of footbridges is used to rectify these problems after construction. This paper describes an arch type steel footbridge, its analytical modelling, modal testing and finite element model calibration. A modern steel footbridge which has arch type structural system and located on the Karadeniz coast road in Trabzon, Turkey is selected as an application. An analytical modal analysis is performed on the developed 3D finite element model of footbridge to provide the analytical frequencies and mode shapes. The field ambient vibration tests on the footbridge deck under natural excitation such as human walking and traffic loads are conducted. The output-only modal parameter identification is carried out by using the peak picking of the average normalized power spectral densities in the frequency domain and stochastic subspace identification in the time domain, and dynamic characteristics such as natural frequencies mode shapes and damping ratios are determined. The finite element model of footbridge is calibrated to minimize the differences between analytically and experimentally estimated modal properties by changing some uncertain modelling parameters such as material properties. At the end of the study, maximum differences in the natural frequencies are reduced from 22% to only %5 and good agreement is found between analytical and experimental dynamic characteristics such as natural frequencies, mode shapes by model calibration.

Construction stage analysis of Kömürhan Highway Bridge using time dependent material properties

Altunisik, Ahmet Can,Bayraktar, Alemdar,Sevim, Baris,Adanur, Suleyman,Domanic, Arman Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.2

The aim of this study concerns with the construction stage analysis of highway bridges constructed with balanced cantilever method using time dependent material properties. K$\ddot{o}$m$\ddot{u}$rhan Highway Bridge constructed with balanced cantilever method and located on the 51st km of Elazi$\check{g}$-Malatya, Turkey, highway over Firat River is selected as an application. Finite element models of the bridge are modelled using SAP2000 program. Geometric nonlinearity is taken into consideration in the analysis using P-Delta plus large displacement criterion. The time dependent material strength variations and geometric variations are included in the analysis. Elasticity modulus, creep and shrinkage are computed for different stages of the construction process. The structural behaviour of the bridge at different construction stages has been examined. Two different finite element analyses with and without construction stages are carried out and results are compared with each other. As analyses result, variation of internal forces such as bending moment, axial forces and shear forces for bridge deck and column are given with detail. It is seen that construction stage analysis has remarkable effect on the structural behaviour of the bridge.