Süleyman Adanur

Comparison of near-fault and far-fault ground motion effects on geometrically nonlinear earthquake behavior of suspension bridges

This paper presents a comparison of near-fault and far-fault ground motion effects on geometrically nonlinear earthquake behavior of suspension bridges. Boğaziçi (The First Bosporus) and Fatih Sultan Mehmet (Second Bosporus) suspension bridges built in Istanbul, Turkey, are selected as numerical examples. Both bridges have almost the same span. While Boğaziçi Suspension Bridge has inclined hangers, Fatih Sultan Mehmet Suspension Bridge has vertical hangers. Geometric nonlinearity including P-delta effects from self-weight of the bridges is taken into account in the determination of the dynamic behavior of the suspension bridges for near-fault and far-fault ground motions. Near-fault and far-fault strong ground motion records, which have approximately identical peak ground accelerations, of 1999 Chi-Chi, 1999 Kocaeli, and 1979 Imperial Valley earthquakes are selected for the analyses. Displacements and internal forces of the bridges are determined using the finite element method including geometric nonlinearity. The displacements and internal forces obtained from the dynamic analyses of suspension bridges subjected to each fault effect are compared with each other. It is clearly seen that near-fault ground motions are more effective than far-fault ground motion on the displacements and internal forces such as bending moment, shear force and axial forces of the suspension bridges.

Determination of Water Level Effects on the Dynamic Characteristics of a Prototype Arch Dam Model using Ambient Vibration Testing

This study investigated the water level effects on the dynamic characteristics of a prototype arch dam model using ambient vibration testing were investigated. Achievement of this purpose involved construction of a prototype arch dam-reservoir-foundation model under laboratory. The dam body was constructed with 60 cm height. Ambient vibration tests on the arch dam estimated its natural frequencies, mode shapes and damping ratios for different water levels. In the ambient vibration tests, ambient excitations are provided from small impact effects and the responses of the arch dam are measured. It can be stated from the study that natural frequencies are not overly changed among 0–30 cm water levels; however they are increased for higher water levels. The difference between the first natural frequencies of the arch dam obtained from empty reservoir (H = 0 cm) and full reservoir (H = 60 cm) is about 20–25%.

Modal Parameter Identification of a Prototype Arch Dam Using Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification Techniques

In this study, dynamic characteristics of a prototype arch dam-reservoir-foundation model are determined by operational modal analysis method using frequency and time domain techniques. For this purpose, a prototype arch am-reservoir-foundation model is constructed in laboratory conditions. Ambient vibration tests were conducted to the arch dam to identify its natural frequencies, mode shapes, and damping ratios. Natural excitations such as small impact effects were used to vibrate the arch dam. Sensitivity accelerometers were used to collect signals from the measurements. Measurements were recorded for empty and full reservoirs. The signals collected from the tests were processed by operational modal analysis software, and the dynamic characteristics of the dam were estimated using enhanced frequency domain decomposition and stochastic subspace identification techniques. The dynamic characteristics obtained from both techniques are close to each other. It can be stated that the both enhanced frequency domain decomposition and stochastic subspace identification techniques are very useful to identify the modal parameter of the prototype arch dam. In addition, it is observed that there is 20–25 % difference between natural frequencies for empty and full reservoirs.

Dynamic Characteristics of an Arch Dam Model before and after Strengthening with Consideration of Reservoir Water

AbstractThis technical note presents an investigation about the changing of dynamic characteristics of an arch dam model before and after strengthening considering reservoir water. To this end, an arch dam-reservoir-foundation model has been constructed in the laboratory. Ambient vibration tests have been performed on the damaged and strengthened arch dam models for empty and full reservoir to determine the effect of water on the dynamics characteristics. Enhanced frequency domain decomposition method has been used to extract the dynamic characteristics. Finally, the dynamic characteristics obtained from the damaged and strengthened dam models have been compared to with each other. Also, the natural frequencies for damaged and strengthened models are compared to detect the effect of strengthening application on the frequencies. Results indicate that the natural frequencies and damping ratios are changed with the full reservoir. However, mode shapes are not changed. Results also show that the natural frequ...

Stochastic seismic response of Keban dam by the finite element method

Abstract In this study, stochastic seismic response of a rock-fill dam is investigated by finite element method. The Keban dam constructed in Elazig, Turkey is chosen as a numerical example. The interaction of the rock-fill dam with the reservoir is neglected, but not the foundation rock. The properties of the dam materials were taken from the dam project and assumed to be linearly elastic, homogenous and isotropic in the analysis. A stationary and ergodicity assumption are is made for stochastic seismic analysis. The E–W component of the Erzincan Earthquake recorded on March 13, 1992, Erzincan, Turkey is chosen as a ground motion since it occurred nearby the dam site. The component considered is applied to the dam in the horizontal direction. The seismic response of the Keban dam subjected to the Erzincan Earthquake is also obtained by the deterministic method. The results obtained from stochastic and deterministic analysis are compared to each other. It is seen that the results obtained from the stochastic analysis are smaller than those from the deterministic analysis.

Retrofitting Effect on the Dynamic Properties of Model-Arch Dam with and without Reservoir Water Using Ambient-Vibration Test Methods

AbstractContinuous health monitoring and regular condition assessment is of vital importance for engineering structures in general and especially for arch dams. These structures can be exposed to many different loads such as earthquake, blast, wind, ice, and water pressure, which may cause deterioration and loss of structural integrity. Such development may have severe economic consequence and, more importantly, may present a serious risk to public safety. Therefore, the structural behavior of arch dams must be monitored at regular intervals during their service life, although the overall failure rate of these dams is around 1%. Experimental measurements by ambient vibration test methods are among the most commonly preferred inspection techniques for the evaluation of structural performance and safety. The aim of this research is to examine the retrofitting effect on the dynamic properties of a damaged arch dam model, with and without reservoir water, after retrofitting with high-strength structural repai...

Estimation of Elasticity Modulus of a Prototype Arch Dam Using Experimental Methods

AbstractUsing experimental methods, this study presents the estimation of the dynamic and static (secant) elasticity modules of a prototype arch dam. These experimental methods are ambient vibration tests, uniaxial compression tests, and ultrasonic velocity tests. Implementation of the methods on a prototypical arch dam–reservoir–foundation model of the dam, constructed under laboratory conditions, allows estimation of the elasticity modules. Random impact loads excite the arch dam during ambient vibration testing, which creates response signals for measurement. Commercially available software transfers the signals, and processing those signals allows estimation of the experimental natural frequencies of the arch dam. Analysis of a three-dimensional (3D) finite element model (FEM) of the arch dam determines natural frequencies. The estimation of the elasticity modules of the arch dam arises from a comparison of the experimental and analytical frequencies. The uniaxial compression tests use several specime...

The effects of sediment on earthquake response of concrete gravity dams to asynchronous ground motion

The effects of the sediment on the earthquake response of concrete gravity dams subjected to horizontal and vertical asynchronous ground motion are investigated including dam-reservoir-sediment-foundation interaction in this paper. Dam-reservoir-sediment-foundation interaction is modeled by the finite element method. The equations of motion of the dam-reservoir-sediment-foundation system are determined using the Lagrangian approach. Solutions are obtained for dam-reservoir-foundation and dam-reservoir-sediment-foundation systems separately. Parametric studies were conducted in order to investigate the effects of the variation of Youngs modulus and thickness of the sediment on the dam response. Seismic wave velocities of 250, 3000 m/s and infinite are used in calculations. It is observed that stresses near the dam crest decrease considerably when the sediment is included in the analyses. The variation of the values of Youngs modulus and thickness of the sediment influences the stress component slightly.

Automated Model Updating of Historical Masonry Structures Based on Ambient Vibration Measurements

AbstractFinite-element (FE) model updating is a very effective procedure for determining the uncertainty parameters in a structural model and minimize differences between experimentally and analyti...

Ambient Vibration-Based System Identification of a Medieval Masonry Bastion for Health Assessment using Nonlinear Analyses

Abstract Earthquakes have underlined the need for health monitoring and safety assessment of engineering structures in general and especially historical heritage. These structures can be exposed to many different loads such as earthquake and wind that may cause the deterioration and loss of structural integrity. In this study, ambient vibration-based system identification of Zağanos Bastion is carried out for health assessment using linear and nonlinear analyses. 3D finite element analyses of the bastion are performed using relievo drawings and analytical dynamic characteristics are obtained. Ambient vibration tests are conducted on the bastion and experimental dynamic characteristics such as natural frequencies, mode shapes and damping ratios are determined. Enhanced Frequency Domain Decomposition Method in the frequency domain and Stochastic Subspace Identification Method in the time domain are used to extract the experimental dynamic characteristics. Maximum differences are minimized using some uncertain parameters to obtain the updated finite element model. Linear and nonlinear time history analyses are carried out using 1999 Kocaeli earthquake ground motion record to display the maximum displacements, stresses and local damage regions with detail. This study suggests that minor damage at the connection points and exterior surface will sustain under destructive earthquakes.