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.

Structural response of concrete gravity dams under blast loads

Sevim, Baris,Toy, Ahmet Tugrul Techno-Press 2020 Advances in concrete construction Vol.9 No.5

Concrete dams are important structures due to retaining amount of water on their reservoir. So such kind of structures have to be designed against static and dynamic loads. Especially considering on critical importance against blasting threats and environmental safety, dams have to be examined according to the blast loads. This paper aims to investigate structural response of concrete gravity dams under blast loads. For the purpose Sarıyar Concrete Gravity Dam in Turkey is selected for numerical application with its 85 m of reservoir height (H), 255 m of reservoir length (3H), 72 m of bottom and 7 m of top widths. In the study, firstly 3D finite element model of the dam is constituted using ANSYS Workbench software considering dam-reservoir-foundation interaction and a hydrostatic analysis is performed without blast loads. Then, nearly 13 tons TNT explosive are considered 20 m away from downstream of the dam and this is modeled using ANSYS AUTODYN software. After that explicit analyses are performed through 40 milliseconds. Lastly peak pressures obtained from analyses are compared to empirical equations in the literature and UFC 3-340-02 standard which provide unified facilities criteria for structures to resist the effects of accidental explosions. Also analyses' results such as displacements, stresses and strains obtained from both hydrostatic and blasting analysis models are compared to each other. It is highlighted from the study that blasting analysis model has more effective than the only hydrostatic analysis model. So it is highlighted from the study that the design of dams should be included the blast loads.

Geometrical dimensions effects on the seismic response of concrete gravity dams

Sevim, Baris Techno-Press 2018 Advances in concrete construction Vol.6 No.3

This study presents the effects of geometrical dimensions of concrete gravity dams on the seismic response considering different base width/dam height (L/H) ratios. In the study, a concrete gravity dam with the height of 200 m is selected and finite element models of the dam are constituted including five different L/H ratios such as 0.25, 0.5, 0.75, 1.00, 1.25. All dams are modeled in ANSYS software considering dam-reservoir-foundation interaction. 1989 Loma Prieta earthquake records are applied to models in upstream-downstream direction and linear time history analyses are performed. Dynamic equilibrium equations of motions obtained from the finite element models of the coupled systems are solved by using Newmark time integration algorithm. The seismic response of the models is evaluated from analyses presenting natural frequencies, mode shapes, displacements and principal stresses. The results show that the L/H ratios considerably affect the seismic response of gravity dams. Also, the model where L/H ratio is 1.00 has more desirable results and most appropriate representation of the seismic response of gravity dams.

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.

Effects of the vertical component of ground motion on the seismic performance of Bhakra Gravity Dam

Sevim, Baris,Altunisik, Ahmet Can,Gunaydin, Murat Techno-Press 2021 Advances in concrete construction Vol.12 No.3

In this paper, the earthquake component effects on the seismic performance of Bhakra Gravity Dam in India are investigated. For the purpose, Bhakra Dam is modeled two-dimensionally considering dam-reservoir-foundation interaction. In the finite element modeling, dam and foundation are represented by PLANE182 elements in ANSYS with different material properties, and fluid is considered with FLUID29 elements. This type of element provides translation and pressure degrees of freedom. Linear time history analyses on the dam are performed by considering components of the 1991 Uttarkashi and 1999 Chamoli (NW Himalaya) Earthquakes in India. During the analyses firstly the horizontal component of earthquakes are applied to system and results are obtained, and then both of horizontal and vertical components are applied to the systems together. In the analyses, element matrices are computed using the Gauss numerical integration technique. The Newmark method is used in the solution of the equation of motions. Also, Rayleigh damping is considered. The seismic performance of Bhakra Dam is examined and presented by dynamic characteristics, displacements, principal stresses, and demand-capacity ratios. The results showed that the vertical components of the earthquake significantly affect the response of the dam. The results show that the vertical component with the horizontal component cause biggest tensile stresses compared to only the horizontal component for both earthquakes. However, displacement response is changed depending on the ground motion. As a conclusion of this study it can be said that the vertical component changes the structural response of the dam on both of the good and bad behaviors.

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.

Assessment of damages on a RC building after a big fire

Ada, Mehmet,Sevim, Baris,Yuzer, Nabi,Ayvaz, Yusuf Techno-Press 2018 Advances in concrete construction Vol.6 No.2

This paper presents a case study about the damages on the structural elements of a cast in place reinforced concrete (RC) building after a big fire which was able to be controlled after six hours. The fire broke off at the $2^{nd}$ basement floor of the building, which has five basements, one ground, and two normal floors. As a result of intensely stocked ignitable materials, it spread out to the all of the upstairs. In visual inspection, most of the typical fire damages were observed (such as spalling, net-like cracks, crumbled plasters, bared or visible reinforcement). Also, failures of the $2^{nd}$ basement columns were encountered. It has been concluded that the severity failures of the columns at the $2^{nd}$ basement caused utterly deformation of the building, which is responsible for the massive damages on the beam-column connections. All of the observed damages were categorized related to the types and presented separated regarding the floors. Besides to the visual inspection, the numerical analysis was run to verify the observed damaged on the building for columns, beams, and the connection regions. It is concluded from the study that several parameters such as duration of the fire, level of the temperature influence on the damages to the RC building. Also, it is highlighted by the study that if the damaged building is considered on the overall structural system, it is not able to satisfy the minimum service requirements neither gravity loads nor earthquake conditions.

Optimal sensor placements for system identification of concrete arch dams

Altunisik, Ahmet Can,Sevim, Baris,Sunca, Fezayil,Okur, Fatih Yesevi Techno-Press 2021 Advances in concrete construction Vol.11 No.5

This paper investigates the optimal sensor placements and capabilities of this procedure for dynamic characteristics identification of arch dams. For this purpose, a prototype arch dam is constructed in laboratory conditions. Berke arch dam located on the Ceyhan River in city of Osmaniye is one of the highest arch dam constructed in Turkey is selected for field verification. The ambient vibration tests are conducted using initial candidate sensor locations at the beginning of the study. Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are used to extract experimental dynamic characteristics. Then, measurements are repeated according to optimal sensor locations of the dams. These locations are specified using the Effective Independence Method. To determine the optimal sensor locations, the target mode shape matrices which are obtained from ambient vibration tests of the selected dam with a large number of accelerometers are used. The dynamic characteristics obtained from each ambient vibrations tests are compared with each other. It is concluded that the dynamic characteristics obtained from initial measurements and those obtained from a limited number of sensors are compatible with each other. This situation indicates that optimal sensor placements determined by the Effective Independence Method are useful for dynamic characteristics identification of arch dams.

Numerically and empirically determination of blasting response of a RC retaining wall under TNT explosive

Toy, Ahmet Tugrul,Sevim, Baris Techno-Press 2017 Advances in concrete construction Vol.5 No.5

Blast loads may considerably affect the response of structures. In previous years, before computer analysis programs, the parameters of blast effects were calculated with empirical methods, consequently some researchers had proposed equations to find out the phenomenon. In recent year's computer analysis programs have developed already, so detailed solutions can be made numerically. This paper describes the blasting response of the structures using numerical and empirical methods. For the purpose, a reinforced concrete retaining wall is modelled using ANSYS Workbench software, and the model is imported to ANSYS AUTODYN software to perform explicit analyses. In AUTDYN software, a sum of TNT explosive is defined 5,5 m away from the wall and solution is done. Numerical results are compared with those of obtained from empirical equations. Similar study is also considered for equal explosive which is the 4 m away from the wall. The results are represented by graphics and contour diagrams of such as displacements and pressures. The results showed that distance of explosive away from the wall is highly affected the structural response of it.