Concrete Arch Dam Research Articles

Orthotropic Material and Anisotropic Damage Mechanics Approach for Numerically Seismic Assessment of Arch Dam–Reservoir–Foundation System

In contrast with modeling of the contraction joints, the performance and influence of lift joints are usually neglected in numerical analysis of concrete arch dams. In this paper, the seismic nonlinear response of a concrete arch dam–reservoir–foundation system is investigated with considering the effects of lift joints using orthotropic-based material. An anisotropic damage mechanics approach is introduced and modified to take into account the effects of weak horizontal planes between concrete lifts during the construction phase. This model is capable to consider the pre-softening behavior, the softening initiation criterion and anisotropic cracking behavior in mass concrete. The coupled equation of motion in dam–reservoir system is solved by staggered displacement method while the foundation rock is assumed as a mass-less and rigid mediums. The coupled system is excited using three-component ground motion in the maximum credible level. It is found that using orthotropic-based material increases crest displacements and also leads to more damage in the dam body in comparison with the case using the common isotropic-based material.

Coupled stress–seepage analysis of Karun III concrete arch dam

The response of a concrete arch dam is very much affected by the mechanisms of foundation rock behaviour. This type of dam is highly sensitive to displacements of its foundation owing to the low stiffness of the dam compared to the displacements of its foundation and abutments. Seepage is a load type which is distributed widely within foundation rock. Therefore, it could have important effects on displacements and stresses in the dam. In this paper, the Karun III double-curvature, 205 m high arch dam is selected as a case study. Effective stress analyses are carried out for the dam. The analysis results are compared with values recorded by instruments. Furthermore, the effects of some basic input parameters on the response of the dam are investigated. Subsequently, basic parameters are calibrated based on the initial investigation results, and the effective stress analysis is carried out for the Karun III dam by employing the modified parameters.

Structural identification of concrete arch dams by ambient vibration tests

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.

Earthquake response of concrete arch dams: a plastic–damage approach

SUMMARYThere are several alternatives to evaluate seismic damage‐cracking behavior of concrete arch dams, among which damage theory is the most popular. A more recent option introduced for this purpose is plastic–damage (PD) approach. In this study, a special finite element program coded in 3‐D space is developed on the basis of a well‐established PD model successfully applied to gravity dams in 2‐D plane stress state. The model originally proposed by Lee and Fenves in 1998 relies on isotropic damaged elasticity in combination with isotropic tensile and compressive plasticity to capture inelastic behaviors of concrete in cyclic or dynamic loadings. The present implementation is based on the rate‐dependent version of the model, including large crack opening/closing possibilities. Moreover, with utilizing the Hilber–Hughes–Taylor time integration scheme, an incremental–iterative solution strategy is detailed for the coupled dam–reservoir equations while the damage–dependent damping stress is included. The program is initially validated, and then, it is employed for the main analyses of the Koyna gravity dam in a 3‐D modeling as well as a typical concrete arch dam. The former is a major verification for the further examination on the arch dam. The application of the PD model to an arch dam is more challenging because the governing stress condition is multiaxial, causing shear damage to become more important than uniaxial states dominated in gravity dams. In fact, the softening and strength loss in compression for the damaged regions under multiaxial cyclic loadings affect its seismic safety. Copyright © 2013 John Wiley & Sons, Ltd.

Investigation of repeatability of digital surface model obtained from point clouds in a concrete arch dam for monitoring of deformations

Applicability of Terrestrial Laser Scanners/Scanning (TLS) in deformation measurement in dams is an active area of study. With the advance of modern technology, accuracy of measurements is much improved by developments in design of terrestrial laser scanners. Currently, this technology is used in large and complex engineering structures such as dams. Although TLS is a high cost technology, it is particularly used in monitoring of dam deformations, due to its speed in obtaining thousands of data points, ability to visualize the scanned object and its environment with high accuracy and ability to take long-range measurements. In order to determine the effect of change in water reservoir levels on body of the dam, TLS are used to take deformation measurements in different time intervals, where the water level was at maximum, minimum and medium levels. This paper provides an overview of terrestrial laser scanning technology for deformation monitoring. The concrete arch dam in Antalya Oymapinar, Turkey was used for case study. Four different scannings were performed in this dam in order to verify the replicability of TLS results on same water levels and equivalent conditions. Digital Surface Models reflecting dam surface have been created. Results obtained from surface model differences were examined using surface matching method.

The Dynamic Evaluation of Rock Slope Stability Considering the Effects of Microseismic Damage

A state-of-the-art microseismic monitoring system has been implemented at the left bank slope of the Jinping first stage hydropower station since June 2009. The main objectives are to ensure slope safety under continuous excavation at the left slope, and, very recently, the safety of the concrete arch dam. The safety of the excavated slope is investigated through the development of fast and accurate real-time event location techniques aimed at assessing the evolution and migration of the seismic activity, as well as through the development of prediction capabilities for rock slope instability. Myriads of seismic events at the slope have been recorded by the microseismic monitoring system. Regions of damaged rock mass have been identified and delineated on the basis of the tempo-spatial distribution analysis of microseismic activity during the periods of excavation and consolidation grouting. However, how to effectively utilize the abundant microseismic data in order to quantify the stability of the slope remains a challenge. In this paper, a rock mass damage evolutional model based on microseismic data is proposed, combined with a 3D finite element method (FEM) model for feedback analysis of the left bank slope stability. The model elements with microseismic damage are interrogated and the deteriorated mechanical parameters determined accordingly. The relationship between microseismic activities induced by rock mass damage during slope instability, strength degradation, and dynamic instability of the slope are explored, and the slope stability is quantitatively evaluated. The results indicate that a constitutive relation considering microseismic damage is concordant with the simulation results and the influence of rock mass damage can be allowed for its feedback analysis of 3D slope stability. In addition, the safety coefficient of the rock slope considering microseismic damage is reduced by a value of 0.11, in comparison to the virgin rock slope model. Our results demonstrate that microseismic activity induced by construction disturbance only slightly affects the stability of the slope. The proposed feedback analysis technique provides a novel method for dynamically assessing rock slope stability and can be used to assess the slope stability of other similar rock slopes.

Analysis and Back-Analysis for Temperature Field of Concrete Arch Dam During Construction Period Based on Temperature Data Measured by DTS

Based on the observed temperature information of arch dam, the mathematical and mechanical methods are combined usually with dam engineering theory to capture in real time and evaluate in time the developing status and space-time distribution of arch dam temperature, and implement the back analysis for temperature control measures. It is an important step for dam construction and safe operation. Some methods, namely transient temperature-field simulation, thermodynamic parameters back-calculation, and model correction, are used synthetically to solve the above problem. A method is proposed to back calculate the thermodynamic parameters of arch dam by use of the temperature data obtained by the distributed optical fiber temperature sensor (DTS). A problem is studied to couple the simulated temperature field by finite element method (FEM) and the observed temperature field by the DTS. A method is presented to update dynamically the FEM model on the basis of the observed temperature field. An actual engineering is analyzed by the proposed method. It is shown that the DTS system can implement the real-time observation of concrete arch dam temperature field. According to the observed temperature field by the DTS and the updated numerical simulation model of the temperature field, scientific guidance can be given during the pouring process of the arch dam, and reliable data can be provided to analyze and evaluated arch dam safety.

Coupled elasto-plasticity damage constitutive models for concrete

The paper is to design and construct a coupled elasto-plasticity damage constitutive model for concrete. Based on the energy dissipation principle, the Hsieh-Ting-Chen four-parameter yield function is used. The model can reflect different strength characteristics of concrete in tension and compression, and reduce the limitation and lacuna of the traditional damage constitutive models for concrete. Furthermore, numerical test for concrete stress-strain relation under uniaxial tension and compression is given. Moreover, the damage process of concrete gravity dam is calculated and analyzed in seismic load. Compared with other damage constitutive models, the proposed model contains only one unknown parameter and the other parameters can be found in the Hsieh-Ting-Chen four-parameter yield function. The same damage evolution law, which is used for tension and compression, is good for determining stress-strain constitutive and damage characteristics in complex stress state. This coupled damage constitutive models can be applied in analyzing damage of concrete gravity dam and arch dam.

Numerical prediction of swelling in concrete arch dams affected by alkali-aggregate reaction

A chemo-damage model is presented for anisotropic swelling analysis of concrete arch dams affected by alkali-aggregate reaction (AAR). The model combines the AAR kinetics and the plastic-damage model, and the chemical and mechanical phases are coupled. A redistributing weight function, determined by the applied stresses in the concrete, is introduced to control the AAR-induced anisotropic expansion of the concrete. Creep strain is also included in the approach using the Kelvin–Voigt model. Accelerated tests, in which the specimens are confined with steel rings and subjected to axial loads, are first analyzed using the proposed model. The computed strains of the specimens are in good agreement with the experimental measured strains. The application to the AAR-affected Kariba dam is then carried out. The radial and vertical displacements of the dam due to AAR are reproduced with sufficient accuracy. The stresses within the dam are significantly redistributed during the AAR process. Severe cracking and damage appear to occur in the dam heel and the downstream face on both sides of the dam-foundation interface. It demonstrates Kariba dam is facing an increased risk of collapse associated with the increasing compressive stresses within the dam and developing cracks on both sides of the downstream face during the development of AAR.

Buckling strength of thin-shell concrete arch dams

An investigation has been undertaken on the buckling strength of concrete arch dams in the form of thin shells of single and double curvature. When subjected to the hydrostatic pressure exerted by the retained water, the shell experiences predominantly compressive internal actions, which can result in buckling failure of the thin shell. There are many factors influencing the buckling strength of the arch dam. These include the shape of the valley, the geometry of the arch surface, the degree of bulging of the arch, shell-thickness variation and support conditions. The present study makes use of FEM modelling to determine the influence of key parameters on the critical buckling pressure of cylindrical and elliptic-paraboloidal arch dams. For cylindrical arch dams, design curves giving information on factors of safety against buckling are presented. By comparing the results for the elliptic paraboloid with those for the parabolic cylindrical arch, the benefits of double curvature are evaluated.

Seismic deformation and seismic resistance analysis of Shapai Roller Compacted Concrete Arch Dam based on field monitoring and dynamic finite element method

Shapai Roller Compacted Concrete (RCC) Arch Dam is the highest RCC arch dam of the 20th century in the world with a maximum height of 132 m, and it is the only concrete arch dam near the epicentre of Wenchuan earthquake on May 12th, 2008. The seismic damage to the dam and the resistance of the dam has drawn great attention. This paper analyzed the response and resistance of the dam to the seismic wave using numerical simulations with comparison to the monitored data. The field investigation after the earthquake and analysis of insitu data record showed that there was only little variation in the opening size at the dam and foundation interface, transverse joints and inducing joints before and after the earthquake. The overall stability of the dam abutment resistance body was quite good except a little relaxation was observed. The results of the dynamic finite element method (FEM) showed that the sizes of the openings obtained from the numerical modeling are comparable with the monitored values, and the change of the opening size is in millimeter range. This study revealed that Shapai arch dam exhibited high seismic resistance and overload capacity in the Wenchuan earthquake event. The comparison of the monitored and simulated results showed that the numerical method applied in this paper well simulated the seismic response of the dam. The method could be useful in the future application on the safety evaluation of RCC dams.

Nonlinear Response of High Arch Dams to Nonuniform Seismic Excitation Considering Joint Effects

Nonuniform excitation due to spatially varying ground motions on nonlinear responses of concrete arch dams is investigated. A high arch dam was selected as numerical example, reservoir was modelled as incompressible material, foundation was assumed as mass-less medium, and all contraction and peripheral joints were modelled considering the ability of opening/closing. This study used Monte-Carlo simulation approach for generating spatially nonuniform ground motion. In this approach, random seismic characteristics due to incoherence and wave passage effects were investigated and finally their effects on structural response were compared with uniform excitation at design base level earthquake. Based on the results, nonuniform input leads to some differences than uniform input. Moreover using nonuniform excitation increase, stresses on dam body.

Wave passage and incoherency effects on seismic response of high arch dams

The effects of incoherency and wave-passage on the nonlinear responses of concrete arch dams are investigated in this study. A double curvature arch dam is selected as a numerical example. The reservoir is modeled as a compressible material and the foundation is modeled as a massless medium. Ground motion time-histories are artificially generated using the Monte Carlo simulation approach. Four different finite element models (FEM) are considered: uniform excitation; incoherence effect; wave passage effect; and both incoherence and wave passage effects. It was revealed that modeling multiple-supports excitation could have a significant impact on the structural response of the dam by inducing a pseudo-static effect. Also, it was concluded that the coherency effect overshadows the wave passage effect and the results obtained from non-uniform excitation of FEM, including the wave passage effect, is close to the results of the FEM when it is uniformly excited.

The Diagnostic Method of Concrete Dam Monitoring Information Valid Interval

On the basis of the analysis of the displacement of concrete dam and its related influential factors, based on the evolvement of nonlinear dynamics of concrete dam, it can effectively identify the mutations position of measured value and the attribute interval of dynamical system applied with the wavelet analysis, dynamic structural mutation theory and other numerical analysis methods. When detecting after separating structural mutation sequence, it can finally get the relative stable displacement time series of dynamical structure, so it can realize the diagnostic separation of the monitoring information effective interval. At the end of the paper, through applying a certain concrete arch dam, it is proved that the proposed method of concrete dam mutations diagnosis of is of great significance for the real-time monitoring of the workability state of a dam.

Effects of near-fault ground motions in seismic performance evaluation of a symmetric arch dam

Near-fault ground motion effects in comparison with far-fault ground motions on seismic performance of a symmetry concrete arch dam are investigated. Various sets of near-fault and far-fault ground motions with approximately identical peak ground acceleration were used for analyses of coupled system. For this purpose the Karaj arch dam was selected as case study and two different options were considered for dam-foundation interaction. In the first case, foundation rock was assumed rigid, and in the second case foundation rock was simulated as a massless medium. The behavior of the dam and foundation was expressed in terms of displacement, and the reservoir was modelled based on fluid elements. The seismic performance evaluation of the arch dam was performed using demand-capacity ratios obtained from linear analyses.

Study on Deformation-Based Seismic Performance Index of Arch Dams

Concrete arch dams are critical structures, the failure of which would lead to catastrophic effects on a regional scale. Considering the uncertainty characteristics of earthquake and the self-adjustment of inner force of arch dams, it’s necessary to investigate the seismic performance index of arch dam for holistically evaluating the seismic safety of arch dam-foundation system subjected to high intensity seismic excitations. By considering the contraction joints movement and concrete material nonlinearity, a series of dynamic response-history analyses of arch dam were carried out under increasing levels of earthquakes. Based on these analyses, the performance index of crest deformation is recommended for the seismic safety assessment of arch dam. And several performance stages of seismic response including the opening of contraction joints and the distribution of concrete damage are also investigated.

Numerical modeling of arch dam under blast loading

The damage of unallowable blast induced vibrations on the concrete structures results in a decrease in the safety of its structures. This paper develops a three dimensional anisotropic dynamic damage model for Dagangshan arch dam subjected to blast loading. The multiple damage failure criteria are adopted as the failure criteria of the dynamic damage evolution of concrete. From the simulation of the dynamic damage process in the arch dam due to the blast loading, some process fields of the dynamic displacement, the dynamic stress, dynamic damage distribution and other necessary information for the safety evaluation are obtained. The results obtained using the proposed model show that the nonlinear behavior of concrete dams can be satisfactorily predicted. This will provide a reasonable theoretical support on the safety evaluation of the capability of concrete arch dams against blast loading and useful information for further research in these areas.

Damage assessment of a concrete arch dam through nonlinear incremental dynamic analysis

Damage assessment of concrete arch dams is carried out through nonlinear Incremental Dynamic Analysis (IDA) of a typical arch dam. In this study the Morrow Point arch dam is subjected to a set of 12 three-component earthquakes each scaled to 12 increasing intensity levels. The dam–foundation interaction effects have been investigated by varying foundation's modulus of elasticity to be equal and half of dam concrete's modulus of elasticity. Damage propagation through the dam body is investigated and various IDA curves are created. The performance and various limit-states of the dam structure are examined based on the obtained results. Simple damage indices are proposed through comparison of response demands in earthquake analysis with the determined structural capacities. It was found that the proposed damage indices can properly indicate state of damage in the dam body.

Study on Concrete Dam Temperature Evaluation Based on Distributed Optical Fiber Temperature

The dam concrete material properties wre influenced by the implementation of temperature control measures on site. The weekly temperature evaluation system has been set up in order to evaluate current temperature control measures, combining with the distributed optical fiber temperature control techniques and construction technical requirements. The system has been applied to a concrete arch dam under construction in southwest China which established multi-objective fuzzy mathematical model by synthetic weighting method that was a combination of experts scoring method and entropy weight method. Practice shows that the system can estimate weak link of this week and give guidance to the temperature control’s adjustment of the following week.

Reservoir Fluctuation Effects on Seismic Response of High Concrete Arch Dams Considering Material Nonlinearity

Reservoir fluctuation effects on seismic response of concrete arch dams are investigated. Structure nonlinearity is originated from material nonlinearity due to tensile cracking and compression crushing of mass concrete using William-Warnke failure surface in principal stress state and reservoir is assumed compressible. An arch dam is selected as case study and TABAS earthquake record is used to excite the finite element model of dam-reservoir-foundation. It is found that principal stresses on upstream and downstream faces increase significantly with reservoir dewatering. Responses of dam in nonlinear model have special intricacies, but the extension of cracked areas develops meaningfully with decreasing reservoir water.