Seismic safety assessment of eynel highway steel bridge using ambient vibration measurements

Altunisik, Ahmet Can,Bayraktar, Alemdar,Ozdemir, Hasan Techno-Press 2012 Smart Structures and Systems, An International Jou Vol.10 No.2

In this paper, it is aimed to determine the seismic behaviour of highway bridges by nondestructive testing using ambient vibration measurements. Eynel Highway Bridge which has arch type structural system with a total length of 216 m and located in the Ayvaclk county of Samsun, Turkey is selected as an application. The bridge connects the villages which are separated with Suat U$\breve{g}$urlu Dam Lake. A three dimensional finite element model is first established for a highway bridge using project drawings and an analytical modal analysis is then performed to generate natural frequencies and mode shapes in the three orthogonal directions. The ambient vibration measurements are carried out on the bridge deck under natural excitation such as traffic, human walking and wind loads using Operational Modal Analysis. Sensitive seismic accelerometers are used to collect signals obtained from the experimental tests. To obtain experimental dynamic characteristics, two output-only system identification techniques are employed namely, Enhanced Frequency Domain Decomposition technique in the frequency domain and Stochastic Subspace Identification technique in time domain. Analytical and experimental dynamic characteristic are compared with each other and finite element model of the bridge is updated by changing of boundary conditions to reduce the differences between the results. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of highway bridges. After finite element model updating, maximum differences between the natural frequencies are reduced averagely from 23% to 3%. The updated finite element model reflects the dynamic characteristics of the bridge better, and it can be used to predict the dynamic response under complex external forces. It is also helpful for further damage identification and health condition monitoring. Analytical model of the bridge before and after model updating is analyzed using 1992 Erzincan earthquake record to determine the seismic behaviour. It can be seen from the analysis results that displacements increase by the height of bridge columns and along to middle point of the deck and main arches. Bending moments have an increasing trend along to first and last 50 m and have a decreasing trend long to the middle of the main arches.

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.

Development of engineering software to predict the structural behavior of arch dams

Altunisik, Ahmet Can,Kalkan, Ebru,Basaga, Hasan Basri Techno-Press 2018 Advances in computational design Vol.3 No.1

In this study, it is aimed to present engineering software to estimate the structural response of concrete arch dam. Type-1 concrete arch dam constructed in the laboratory is selected as a reference model. Finite element analyses and experimental measurements are conducted to show the accuracy of initial model. Dynamic analyses are carried out by spectrum analysis under empty reservoir case considering soil-structure interaction and fixed foundation condition. The displacements, principal stresses and strains are presented as an analysis results at all nodal points on downstream and upstream faces of dam body. It is seen from the analyses that there is not any specific ratio between prototype and scaled models for each nodal point with different scale values. So, dynamic analyses results cannot be generalized with a single formula. To eliminate this complexity, the regression analysis, which is a statistical method to obtain the real model results according to the prototype model by using fitting curves, is used. The regression analysis results are validated by numerical solutions using ANSYS software and the error percentages are examined. It is seen that 10% error rates are not exceeded.

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

Ahmet Can Altunisik,Alemdar Bayraktar,Süleyman Adanur,Arman Domaniç,Baris Sevim 국제구조공학회 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. Kömürhan Highway Bridge constructed with balanced cantilever method and located on the 51st km of Elaz-Malatya, Turkey, highway over F rat 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.

Experimental identification of box girder bridge model under undamaged and damaged conditions considering time effect

Ahmet Can Altunisik 사단법인 한국계산역학회 2016 Computers and Concrete, An International Journal Vol.18 No.4

In this paper, it is aimed to evaluate the structural behavior of box girder bridge model under undamaged and damaged conditions considering time effect between June 2009 and February 2015 using ambient vibration tests. For this purpose, a scaled bridge model is constructed and experimental measurements are performed to determine the damage and time effect on dynamic characteristics such as natural frequencies, mode shapes and damping ratios. In the ambient vibration tests, natural excitations are provided and the response of the bridge model is measured. The signals collected from the tests are processed by Operational Modal Analysis; and the dynamic characteristics of the bridge model are estimated using Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods. Measurement time, frequency span and effective mode number are selected by considering similar studies found in the literature. To expose the damage and time effect on dynamic characteristics, four experimental measurement cases are considered between 2009 and 2015. The first measurement case is conducted on June 2009 under undamaged conditions. The second and third measurement cases are performed on October 2010 under undamaged and damaged conditions to emerge the damage and time effect, respectively. The fourth measurement tests are carried out on February 2015 to display the time effect on the dynamic characteristics considering same damage condition in third measurements. At the end of the study, experimentally identified dynamic characteristics are compared with each other to investigate the damage and time effects. It can be stated that the both of Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are very useful to identify the dynamic characteristics of the bridge model. Maximum differences obtained as 11.98% and 112.24% between Case 1 and Case 2, 10.30% and 26.24% between Case 2 and Case 3, 12.36% and 401.50% between Case 3 and Case 4 for natural frequencies and damping ratios, respectively. It is seen that damages and environmental conditions affect the structural behavior of concrete bridges, substantially. Also, time dependent environmental conditions such as temperature, humidity and ageing are as important as cracks and damages.

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.

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.

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.

Damages of minarets during Erciş and Edremit Earthquakes, 2011 in Turkey

Bayraktar, Alemdar,Altunisik, Ahmet Can,Muvafik, Murat Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.14 No.3

This paper illustrates the damages of reinforced concrete and masonry minarets during October 23 (Erci?) and November 9 (Edremit), 2011 Van earthquakes in Turkey. Erci? and Edremit are townships located 90km and 18km from Van city center in Turkey, respectively. Ground accelerations and response spectrums for these earthquakes are given in this paper. A total of 63 reinforced concrete and masonry minarets are heavily damaged or collapsed in the city center and villages nearby after both earthquakes. Because of the fact that there is no Turkish standard and specification directly related to design of minarets, nearly all of the constructions are carried out by workers using only their own technical knowledge. So, all of the non-engineering reinforced concrete and masonry minarets completely collapsed or damaged heavily. From the study, it is seen that the damages are due to several reasons such as site effect, location, and length of the fault, reduction in cross section and formation of the discontinuity, use of plain reinforcement steel, use of concrete with insufficient strength, existence of short lap splices and incorrect end hook angle, larger mass and stiffness concentrations on some region, longitudinal reinforcements discontinuity, cracks at the cylindrical body, and damage of spire and end ornament. In addition to these reasons, the two earthquakes hit the minarets within seventeen days, causing progressive damage. So, the existing design and construction practices should be improved to provide sufficient earthquake performance. Also, it is recommended that there should be a safe distance between the minaret and surrounding structures to reduce the loose of life after earthquake.