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Modal analysis of concrete arch dam–reservoir–foundation rock systems is a challenging task. The complexities arise mainly due to computing mode shapes encountered when solving an eigenvalue problem with asymmetric generalized mass and stiffness matrices. Moreover, the problem becomes complicated when wave propagation is occurring due to the inclusion of water compressibility and foundation rock mass. In the present study, a computational tool is especially developed for this purpose. The theoretical background is explained initially. Subsequently, dynamic analysis of the Morrow Point arch dam–reservoir–foundation rock system is carried out with different values of reservoir bottom absorption coefficient. In addition, some of the modal characteristics of such systems, including resonant frequencies and natural periods, are discussed. The main objective is to perform these analyses by modal analysis. However, the direct method of analysis is also carried out in each case as a basis for comparison from the perspectives of accuracy and efficiency.

Dams are among the most important and largest engineering structures used to supply potable and agricultural water, hydro-power and prevention of seasonal floods. Human experience has shown than where damage occurs in these megastructures, there would be incompensable financial, environmental and fatal losses. Therefore, the issue of safety and proper performance of dams are the vital importance both in terms of designing the new structures or health monitoring of the old structures. This subject is more particular importance in the case of concrete arch dams; since, in the absence of identification of small and minor damages, with the growth and spread of structural damages a general failure may be occurred in these infrastructures with considerable human and financial losses. Nevertheless, concrete arch dams have been less broadly considered in the investigation, and the most of the researches have included simple structures with a low-degree-of-freedom. Therefore, the main objective of this paper is to study the effects of structural damages (including the intensity and location) on the modal properties of these engineering systems. For this purpose, the modal characteristics of the structure, such as the natural frequencies and the shape-modes, are initially computed using finite element model on a concrete arch dam. Considering different scenarios for damage including: nine different locations (on different vertical and horizontal locations). The modal characteristics of the system would be then determined before and after the occurrence of damage. In the presented research, the effects of damages at three levels of arch dam body on the modal parameters of the system, are investigated. The comparison of the structural modal parameters of the intact and damaged states show that, firstly, the natural frequencies of the system have less sensitivity than mode-shapes of the system, and also the damages in the top and middle have more effective than the corners zones on the modal features of the arc-dam body.

To evaluate the real working behaviour of high arch dams, the in-situ monitoring data-based inversion of deformation parameters is essential. The frequently used hydraulic, seasonal, and time model cannot accurately interpret the viscoelastic deformation behaviour of concrete dams. The main purpose of this paper is to propose a hydraulic, exponential, seasonal, and time (HEST) statistical model to conduct the multi-point zonal intelligent inversion of viscoelastic parameters of high arch dams. The extreme learning machine (ELM) is used to establish the nonlinear relationship between viscoelastic parameters and finite element method-calculated total hydraulic displacement. The particle swarm optimization is improved by three strategies and is then used to search the optimal viscoelastic parameters from the ELM model, according to the HEST model-separated total hydraulic displacement. An engineering example of the Jinping-I arch dam has demonstrated the good performance of the proposed HEST model and inversion method. In the water level stable stage, the abnormal increase of dam radial displacement, which is measured by the plumb line monitoring system, can be reasonably interpreted by the air temperature annual drop effect and dam concrete's hysteretic deformation, and the latter can be reasonably represented by the step-type exponential function-based hysteretic hydraulic component, which occupies a proportion of 20–30%. The inverted instantaneous elastic moduli of concrete in the four clustered zones of the dam body are 44.8, 48.8, 30.8 and 41.0 GPa, respectively, and other viscoelastic parameters are linearly proportional to these. The inverted parameters in the central of the dam body are the highest, followed by the crest region, while smaller values are obtained for dam regions near the foundation. With the utilization of deformation spatial association, the zonal intelligent inversion can effectively avoid the interference of the location of used dam displacement monitoring points.

Displacement monitoring data modeling is important for evaluating the performance and health conditions of concrete dams. Conventional displacement monitoring models of concrete dams decompose the total displacement into the water pressure component, temperature component, and time-dependent component. And the crack-induced displacement is generally incorporated into the time-dependent component, thus weakening the interpretability of the model. In the practical engineering modeling, some significant explaining variables are selected while the others are eliminated by applying commonly used regression methods which occasionally show instability. This paper proposes a crack-considered elastic net monitoring model of concrete dam displacement to improve the interpretability and stability. In this model, the mathematical expression of the crack-induced displacement component is derived through the analysis of large surface crack’s effect on the concrete dam displacement to improve the interpretability of the model. Moreover, the elastic net method with better stability is used to solve the crack-considered displacement monitoring model. Sequentially, the proposed model is applied to analyze the radial displacement of a gravity arch dam. The results demonstrate that the proposed model contributes to more reasonable explaining variables’ selection and better coefficients’ estimation and also indicate better interpretability and higher predictive precision.

Long-term service status of a large-scale arch dam is affected by variations of loads and material properties with randomness and fuzziness. This study aims to resolve the problems of a variety of uncertain variables that coexist in the reliability assessment of arch dams. Firstly, a time-varying non-probabilistic reliability (N-PR) solution method of the arch dams is proposed based on the convex set model. Subsequently, non-probabilistic target reliability indexes are put forward according to the defined probabilistic reliability indexes during long-term operation of the arch dams. Afterwards, a fuzzy prediction index is formulated based on the mixed statistical model and the Info-gap model under the most unfavorable reservoir water depth, so as to timely find defects and avoid the potential failure of the arch dams. Numerical simulation on the Jinping I arch dam is conducted to validate the proposed methods. The possible failure modes and the long-term N-PR of the world’s highest arch dam is appraised, and the fuzzy prediction indexes are concluded. Research results can provide a feasible way for large-scale arch dam reliability and safety assessment.

This study aims to explore the correlation between the seismic response indices of high arch dam with and without cantilever reinforcement strengthening. The nonlinear dynamic responses of the 289-m-high Baihetan dam located in southwestern China, to three-component endurance time acceleration histories are investigated. The dynamic responses, including damage distribution, displacement, and joint opening, are statistically analyzed. Furthermore, the proposed seismic response indices, including the global and local damage volume ratios, the average joint opening, and the displacement of the crown cantilever are studied. By comparing the seismic response indices with and without reinforcement, the effects of cantilever reinforcement on the changing trend and range of the seismic response indices are discussed. Subsequently, the correlation curves of the seismic response indices are demonstrated, and the correlation calculated with reinforcement between the seismic response indices is identified. To provide a better correlation analysis, the correlation of each seismic response index is classified. Numerical results show that the changing trend of correlation of the damage indices v. the upstream displacement is different from that of the damage indices v. the downstream displacement. When the peak ground acceleration is approximately 0.5 g, cantilever reinforcement has a significant effect on limiting damage development in the middle-upper part of the downstream face. However, cantilever reinforcement has a limited effect on the correlation between each seismic response index under different peak ground accelerations.

Temperature monitoring and control is of great significance to ensure concrete quality during the construction of dam concrete. In this study, a 3D thermal field restructuring method is developed for the complex evolution process of thermal field in dam concrete during construction, based on real-time temperature monitoring. The proposed method is related to the ordinary Kriging interpolation and the distributed optical fiber temperature sensing (DTS) technology. Based on the temperature monitoring of the Wudongde (WDD) super-high arch dam, the 3D thermal field can be acquired effectively and fast by the proposed restructuring method. The results indicate the temperature difference between the temperature measured by thermometers and the restructured temperature is within 1 °C. The evolution process of the restructured 3D thermal field for the WDD arch dam is in good agreement with the site situation. In addition, the uncertainty, cons and pros of the proposed method and the optimal layout of temperature sensors are further discussed. Although the proposed thermal field restructuring method has some limitations, it is believed to be a valuable tool for acquiring the 3D thermal field and thermal gradient of dam concrete.

Behavior prediction of concrete arch dams requires the interpretation of monitoring data from instrument measurement. Mathematical models based on artificial intelligence algorithms provide an effective approach to interpret the dam behavior from the monitoring data, which can be utilized to model dam displacement as a function of water level, irreversible time effect, and thermal. In our recent study, an improved mathematical model base on kernel-extreme learning machines (KELM) algorithm with long-term daily air temperature monitoring data series has been successfully applied to the displacement prediction modeling of concrete gravity dams. Considering the important contribution of thermal effect on concrete arch dam deformation, the present paper concerns the applicability of the proposed method in the behavior prediction of concrete arch dams. For the sake of improving the efficiency of the mathematical model, the parameters which are crucial to the performance of KELM are selected by the Jaya optimization algorithm. The performance of the proposed automatic parameter optimization-based Jaya-KELM model was compared with the traditional statistical model and other intelligent algorithms. Results demonstrate that the proposed method is a promising and powerful approach for the behavior prediction modeling of concrete arch dams.

Predicting the structural response efficiently and quickly is a major focus in civil engineering. For concrete dams, due to the structure’s complexity, it is difficult to obtain the structural performance timely through a large number of calculations. In this paper, the relationship between structural responses and seismic intensity mesures (IMs) is established under the framework of endurance time analysis method (ETAM) with its good accuracy and high efficiency. Baihetan arch dam is selected as a case study, and the dam-reservoir-foundation system is excited under fourteen sets of endurance time acceleration functions (ETAFs) which are generated through the response spectra of ground motion records. The results show that, compared with displacement-dependent damage indices (DIs), damage-dependent DIs can better reflect damage characteristics of the arch dam under different damage levels. Among the ETA-related IMs, the combined spectral acceleration is the most practical and proficient, followed by acceleration spectral intensity (ASI) and effective peak acceleration (EPA). For high arch dam, the influence of the higher order modes should be fully taken into account when establishing the correlation between the structural response and the IMs. The sufficiency of IMs based on structural response should also be fully demonstrated.

The detection of post-earthquake damage inside concrete dams has recently attracted great interest in academia and industry. A novel electromechanical impedance (EMI) method using embedded EMI sensors (EMISs) is proposed in this paper to detect earthquake-induced damage within concrete dams. The basic concept of the proposed EMI method is to use high-frequency excitations to monitor local changes in the monitored dams caused by damage. Based on the effective impedance, a three-dimensional (3D) EMI model for embedded EMISs is proposed. Then, a new damage-sensitive feature factor is derived based on the proposed 3D EMI model. A high arch dam model with embedded EMISs is studied experimentally. Moreover, shaking table tests are conducted on the dam model. The proposed 3D EMI method is used to monitor the evolution of earthquake-induced damage inside the dam model. The experimental results demonstrate the efficiency and feasibility of the proposed EMI method for detecting earthquake-induced damage in concrete dams.

To assess safety of a dam in an earthquake, establishing the performance evaluation index of the arch dam is significant. The finite-element model based on the 289 m-high Baihetan Dam in Southwest China is taken as a case for seismic response analysis, in which the radiation damping of infinite foundation and opening of contraction joints are taken into consideration. Using the incremental dynamic analysis (IDA) approach, a three-component earthquake scaled to 12 increasing intensity levels is applied to the model, and the seismic response of the model is analysed. In this paper, it is proposed to study the damage based on the monolith, so the monolith damage volume ratio and monolith damage area ratio are suggested to determine the most severe part of the dam. Meanwhile, to help identifying the damage of the dam, the response results of contraction joints are extracted to analyse the potential relationship between the proposed indexes, providing a reference for exploring new detection indexes and damage evaluation indexes. In order to explore the possibility of the simplified layout of dam damage monitoring, the dam body is partitioned according to the results of monolith damage development.

Purpose The purpose of this study is to develop and verify a methodology for a zoned deformation prediction model for super high arch dams, which is indeed a panel data-based regression model with the hierarchical clustering on principal components. Design/methodology/approach The hierarchical clustering method is used to highlight the main features of the time series. This method is used to select the typical points of the measured ambient and concrete temperatures as predictors and divide the deformation observation points into groups. Based on this, the panel data of each zone can be established, and its type can be judged using F and Hausman tests successively. Then hydrostatic–temperature–time–season models for zones can be constructed. Through the comparative analyses of the distributions and the fitted coefficients of these zones, the spatial deformation mechanism of a dam can be identified. A super high arch dam is taken as a case study. Findings According to the measured radial displacements during the initial operation period, the investigated pendulums are divided into four zones. After tests, fixed-effect regression models are established. The comparative analyses show that the dam deformation conforms to the natural condition. The factors such as the unstable temperature field and the nonlinear time-dependent effect have obvious effects on the dam deformation. The results show the efficiency of the proposed methodology in zoning and prediction modeling for deformation of super high arch dams and the potential to mining dam deformation mechanism. Originality/value A zoned deformation prediction model for super high arch dams is proposed where hierarchical clustering on principal component method and panel data model are combined.

This study presents the monitoring and assessment technology of a large arch dam, the Fei-Tsui arch dam in Taiwan, from both seismic response data and ambient vibration measurement collected from a wireless sensing system. Subspace identification (considering inputs) and stochastic subspace identification (output-only) are both used to extract the dynamic characteristics of the dam. Variation of the system natural frequencies of the dam with respect to reservoir water level is investigated. The system transfer function between the earthquake input and the response of the dam body is also investigated using the ARX model. By combining ambient vibration survey, seismic response data, and static monitoring, the safety assessment of the dam structure can be made.

Gallery cracks occur commonly in concrete dams, but their cracking mechanism has yet to be effectively revealed. In this paper, the actual temperature, stress change history and cracking process of a gallery area were uncovered, based on the safety monitoring data of cracks in a super-high arch dam. In addition, the basic development and change laws, as well as the corresponding cracking mechanism, were analyzed, and the real causes and influential factors of cracks at the site were revealed, which will provide a reference for the prevention of cracks in similar projects in the future.

The overall mechanical behavior of the structure of an arch dam is comprehensively reflected by the vibration modal information included in measured vibration response. Hence, the results obtained from inverting material parameters based on measured vibration data are often superior to those based on static monitoring data. In this study, a dynamic inversion method for the material parameters of a high arch dam and its foundation is proposed on the basis of the measured vibration response. First, an arch dam prototype test is conducted to obtain the measured dynamic displacement response as input. Then, a stochastic subspace identification method based on singular entropy is formulated to determine the modal parameters. Second, a dynamic elastic modulus (DEM) with a great influence on the modal parameters is selected as the material parameter to be inverted. Then, a response surface model (RSM), which reflects the nonlinear relationship between the material and modal parameters of each zone, is constructed. Latin hypercube sampling is used to generate the sample library of the DEM. The RSM is fitted by modal parameters calculated on the basis of the arch dam finite element model (FEM) and is applied to replace the FEM. Finally, the optimization mathematical model of the inversion of the DEM is established. Then, the objective function is optimized through a genetic algorithm, and the optimal combination of the DEM in each zone is inverted. The modal parameters of the arch dam calculated by inversion results are consistent with those measured by variation law and values. Therefore, the inversion results are reasonable and reliable. This method provides a new idea for determining the material parameters of a high arch dam and its foundation during the operation period.

Simulation of the infinite foundation is a key issue in the seismic response analysis of high dams. This paper studies how the major characteristics of foundation models influence the nonlinear dynamic response of arch dams when the radiation damping effect is taken into account. The nonlinear dynamic responses of the 217 m high Yebatan arch dam under construction in China is performed as a numerical example. Several key factors, including truncated size, material damping and non-uniformity of the foundation, are analyzed comprehensively. The results show that the material damping and the size of the foundation affect the dynamic response of the dam when the incident wave method is used. Neglect of the material damping of the foundation is proposed to solve this problem, and its rationality is verified. In addition, the results show that the realistic non-uniformity of the foundation should be considered in the earthquake response of arch dams.

During concrete dam construction, concrete temperature monitoring and control is key to ensuring dam concrete quality and construction safety. In this study, a 2D thermal field restructuring method relating to the Kriging temperature interpolation is proposed. Based on dam site monitoring data of distributed optical fiber, the results indicated that the proposed restructuring method can be applied to effectively and quickly obtain 2D real thermal field. The evolution law of thermal field in early ages and temperature differences of concrete blocks based on the thermal field data are obtained. It also can be concluded that the proposed restructuring method could help obtain accurate and reliable restructuring monitoring data. Keywords: 2D thermal field, Restructuring method, Distributed optical fiber, Kriging, Concrete dam

This paper aims to define the non-linear response for concrete arch gravity dams, considering seismic actions as main external destabilizing actions. The plastic degradation theory has been used to define the reduction of the elasto-plastic modulus during the hysteretic cycles. The parameters to apply the model are obtained from the literature and numerical analysis. In this sense, working with a reduction of the elasto-plastic modulus is useful to define the displacement of the structure. The seismic input has been obtained from probabilistic and deterministic seismic hazard analyses. For that, a series of several earthquakes have been chosen to perform the time–history analysis. The response of the structure blocks under four earthquakes has been made using a step-by-step direct integration. An application to Rules Dam has been made to test the method. Results of the seismic analysis provide several specific accelerations for concrete arch gravity dams. Results of the structural show that in 2D analysis the maximum non-linear dam displacements reach value up to 27 cm, whereas for 3D analysis they reach up to 7 cm. Moreover, these cyclic displacements produce several accumulations of plastic deformations and cracks.

The probabilistic risk of arch dam failure under thermal loading is studied. The incorporated uncertainties, which are defined as random variables, are associated with the most affecting structural (material) properties of concrete and thermal loading conditions. Karaj arch dam is selected as case study. The dam is numerically modeled along with its foundation in three-dimensional space; the temperature and thermal stress distribution is investigated during the operating phase. The deterministic thermal finite element analysis of the dam is combined with the structural reliability methods in order to obtain thermal response predictions, and estimate the probability of failure in the risk analysis context. The tensile overstressing failure mode is considered for the reliability analysis. The thermal loading includes ambient air and reservoir temperature variations. The effect of solar radiation is considered by an increase in the ambient temperatures. Three reliability methods are employed: the first-order second-moment method, the first-order reliability method, and the Monte-Carlo simulation with Latin Hypercube sampling. The estimated failure probabilities are discussed and the sensitivity of random variables is investigated. Although most of the studies in this line of research are used only for academic purposes, the results of this investigation can be used for both academic and engineering purposes.

The aim of this study is to propose a cracking analysis method for a super high arch dam based on fracture toughness. A local cracking problem of the Xiluodu super-high dam is first introduced in detail in terms of the related horizontal cracking propagation risk during the construction period and the effect on overall stability during the operational period. An engineering procedure is then proposed to define the cracking stability and analyze the effects of crack repair for super high arch dams. This procedure is based on comparing the stress intensity factor KI, obtained using a 3D fracture mechanics approach and numerical simulation, with the experimentally obtained fracture toughness of site-cast fully-graded concreteKIC. The three cracking states of stability, critical stability and crack propagation are defined by the analysis method. The proposed engineering procedure is then applied to predict the cracking risk and effect to the Xiluodu arch dam at elevation level (EL) 358.8–361.8 m. The predictions on cracking stability correlate well with field site deformation monitoring evidence.

It is widely accepted that plastic optical fibers will have broad application prospect in the field of structural health monitoring because the fiber is not easy to break like silica optical fibers and it also has excellent characteristics such as large diameter, good toughness, high plasticity and low cost. In order to monitor the location, width and direction of cracks in concrete dam, quantitative crack monitoring method of concrete dam based on POF-OTDR is studied theoretically and experimentally. Firstly, mathmatical model of quantitative crack monitoring is established through a lot of model tests. Then double-POF crack monitoring method is presented and validated experimentally after analysing possible layout methods. Based on this interpretation, a reasonable POF network layout scheme for crack monitoring is proposed. Finally, network structure for a concrete arch dam is discussed based on numerical calculation.

Mastering the real temperature distribution of the concrete dam is the basis for solving the problem of temperature control and crack prevention. In this paper, Distributed Temperature Sensing (DTS) technology was applied to temperature monitoring of a high-arch dam under construction in southwest China. In order to obtain a more comprehensive temperature distribution of the dam, optical fiber layout principles for arch dams were studied, and horizontal and vertical optical fiber layout schemes were first proposed according to these principles. The real temperature variation processes of the dam were obtained in real time with a line temperature measurement pattern instead of a point temperature measurement pattern. Additionally, a framework of distributed optical fiber data acquisition and remote transmission was proposed. Interconnection of multiple DTS hosts and remote transmission of temperature data were realized. Then, two-dimensional temperature fields of a typical dam block in different ages and longitudinal profiles of dam blocks with embedded fibers were reconstructed based on large amounts of temperature monitoring data and the Kriging difference algorithm. Temperature field reconstruction results showed that the temperature distribution law of the concrete arch dam was in accordance with the actual situation.

Jinping-I high arch dam is the highest arch dam (305 m) in the world, but the topography of its left and right sides of the arch is not symmetrical, which has a great impact on the overall stability of the arch dam. Based on the geomechanical model test and nonlinear numerical simulation, the evolution processes of cracks and failure during overloading in dam body and faults are demonstrated. Three safety factors of Jinping-I are gained and compared with other high arch dams. The safety factor of crack (K1) is 2.5, the factor of initial nonlinear deformation (K2) is 4.5 and the factor of the ultimate bearing capacity (K3) of Jinping-I is 7.5, indicating that the project has a high inherent safety. Treatments of foundation and weak zones are proved to be effective and then suggestions for reinforcement are given. Additionally, the relationships between model test and numerical simulation based on the deformation reinforcement theory are studied, which verifies that the unbalanced force is an effective indicator for cracking.

Determining vibration characteristics constitutes the first step in calibrating the finite element model in an old arch dam analysis. These characteristics provide the required information for a proper dynamic analysis of the coupled fluid-structure system used for risk assessment purposes. This paper investigates the detailed vibration characteristics of arch dams with heterogeneous material by applying random field theory. A group of six double-curvature arch dams are studied herein. The spatial material distribution using different correlation lengths is compared, and the response dispersion is quantified. An experimental meta-model design is developed for a specific class of dams, with an approximate analytical solution being derived. Ultimately, an iterative, random field-based system identification technique is proposed for old arch dams.

The internal damage of the model during the geomechanical model test is difficult to be detected. The failure and instability process of the arch dam are always accompanied by a large number of acoustic emission (AE) signals, which is related to the number of cracks in the model. AE technique was applied in the geomechanical model test of Mengdigou arch dam to analyze its failure process and overall stability. Noise filtering was conducted based on spectrum analysis of AE signal waveform . Parameter analysis was performed after noise filtering. The overall stability of the dam was evaluated by three characteristic overload safety factors: the crack initiation factor K 1 , nonlinear deformation factor K 2 and ultimate load factor K 3 , which were studied by AE parameter analysis. The failure process of Mengdigou arch dam was analyzed by the statistical analysis of AE hits and the wave velocity variation before and after test. AE analysis results were compared with the displacement and video monitoring results at the same time to verify the correctness of the evaluation method based on AE technique. The results showed that the failure process of the dam and foundation was well described by the AE technique, and the three safety factors of Mengdigou arch dam were defined more clearly. And as for Mengdigou arch dam, the fracture occurred at the dam heel area in the early stage of loading and the abutment of right bank was better than the left. The foundation damage was not serious after test and the overall instability was determined by instability of dam. Based on AE technique, the three overload safety factors was determined more clearly: K1 = 1.5–2.0, K2 = 4.5–5.0, and K3 = 11–11.5, which provided an important reference for the Mengdigou arch dam construction.

This paper proposes an improved dynamic stability analysis for abutment of dam (IDSAM) by combining interface boundary element with partitioned finite element (PFE-IBE). The total yield of the control area is taken as the instability criterion, and the area is made up of contact point pairs controlling the structural surface. The full structural surface yield state of the structural surface of the dam abutment rock mass was taken into account. The strength reduction coefficient corresponding to the full structural surface yield was taken as the safety factor of dam abutment stability. In this way, the damage of the structural surface can be reflected more accurately and intuitively, eliminating the impact of human factors on the valuation of the safety factor. Three calculation methods are used to evaluate the abutment stability of the Shapai Arch Dam, including pseudo-static method, the combination between finite element method and rigid body limit equilibrium method, and the proposed IDSAM. The comparison of results shows that the dam abutment safety factor obtained by IDSAM (left 2.4, right 3.0) ranges between those obtained by pseudo-static method (left 2.116, right 2.945) and finite element rigid body limit equilibrium method (left 2.429, right 3.182). Hence, the safety factor acquired by our method is rational. Considering the nonlinear characteristics of rock mass discontinuity, IDSAM reflects the operating state of the arch dam, shedding new light on the evaluation of aseismatic safety.

This study investigates the local and global stability of the Luzzone Dam. Two finite element models were built, one with foundation rock, the other without. The purpose of this was to demonstrate a potential gulf between rigid connection modelling, and rock–structure interaction (RSI). Strand7 is not a traditional geotechnical finite element model (FEM) program, though performed well when modelling radial displacement on the Luzzone Dam. Generally, the percentage between a rigid base and RSI model displacement was 10%. This result was validated against previous numerical models on the structure. Static loads produced a radial displacement on the crown structure of 9.01 cm. Uneven stress distributions at the base of the structure were shown to be the most unpredictable result. With rigid base connections, these loads produced peak tensile stresses of 10.7 MPa. This was greater than its dynamic counterpart, asking questions about fully fixed restraints. It is noted that this is above yield and should be investigated further. Special attention will be devoted to determining the failure criteria in the simulated dams to suggest better practical guide lines for the practical engineers on site.

Arch dam stability is one of the main engineering challenges that must be met in the early stages of investigations and design of the dam. The highest degree of stability can be achieved if the dam 's structure formed in best layoutsand the free ends of the dam body, defined by the crest, restrictsespecially if the dam is affected seismically. This research study falls under the auspices of the second phase of concrete dam construction, i.e. design stage.Nonlinear finite element analysis is performed in order to investigate the structural behaviors of the four models of double curvature concrete arch dam. Three-dimensional models of arch dams are prepared to utilizing Revit, the building information modeling software. Subsequently, the four models are linked to the finite element’s tools package of Abaqus 6.13 for the purposes of discretization and structural analyses. The models have the same mechanical properties and basic dimensions and differ only in the form and physical appearance of a crest (crest shape).Amplified of crest shape caused a slight movement of the dam center of the mass to be optimally positioned, and thus the new center of mass supports the stability of the dam. The varying effects of crest configurations on the whole dam structure response were discovered according to the results of maximum and minimum principal stresses along the crown cantilever path as well as to the displacements response along the crest path of the arch dam. Strengthening or amplified crest dimensions could decrease arch dam thickness for a certain value and can reduce the response of the displacement to about 30 percent.The results indicated a reduction in the undesired movement between the adjacent cantilevers at the contraction joint zone, so a marvelous response was remarked in both of triangle upward edges crest and triangle downward edges crest models.

This paper focuses on presenting a complete study on the dynamic behavior of Cahora Bassa dam (Mozambique), a 170 m high double curvature arch dam which has been under continuous vibrations monitoring since 2010. The installed Seismic and Structural Health Monitoring system was designed to continuously record acceleration time series in several locations in the dam body (crest gallery) and near the dam-rock interface, under ambient/operational vibrations and during seismic events, using uniaxial and triaxial accelerometers. The system was complemented with the development of software for automatic modal identification and automatic detection of seismic vibrations. The numerical simulations are carried out using a 3D finite element program, based on a solid-fluid coupled formulation to simulate the dam-reservoir-foundation system, considering dam-water dynamic interaction and propagation of pressure waves throughout the reservoir. The main experimental outputs are presented and compared with results from 3D finite element analysis, including the evolution of identified natural frequencies over time, vibration mode shapes, and the seismic response in accelerations. Finally the non-linear seismic behavior of Cahora Bassa dam is studied for an input accelerogram with a 0.6 g peak acceleration, considering the joints movements and a damage model for concrete.

Arch dams have delicate sections thanks to their curvature. The fact that these dams are large, costly and construction takes many years increases the importance of the structure. Mistakes and / or accidents that may occur during the construction of such structures may occur major loss of life and property. Considering the volumes, masses and slenderness of arch dams, they can be significantly affected by dynamic forces such as changing water pressure, temperature, wind and earthquakes. The level of these effects and to what extent they affect the dam can be determined by the analysis to be made to finite element model created by computer. Since Finite Element Analysis is based on certain assumptions, the results obtained should be compared and / or verified with the results obtained by experimental methods. One of the most suitable methods preferred in many engineering structures is the experimental modal analysis method. Within the scope of the study, experimental vibration tests were carried out in order to evaluate and determine the structural behavior of the double curvature Deriner Arch Dam, which has a body height of 249m and a crest length of 720m. Experimental measurements were carried out with accelerometers placed in appropriate places in order to obtain the mode shapes of the dam. The dynamic characteristics of the dam were determined using OMA software. The first seven natural frequencies of the Deriner arch dam were obtained in the range 1.60-4.10Hz. As a result of the negotiations with the DSI 26th Regional Directorate, the acceleration data obtained from the existing accelerometer system of the dam was instantly taken and a continuous monitoring process was initiated. This data was transferred to the web-based monitoring site and a structural condition monitoring platform was created.

The RFPA3D is used to establish a fine finite element model of 6.63 million elements, which realizes the fine simulation of the stability of the Xiluodu arch dam under layered, overall, multiworking conditions and multistress fields, and the cracking and failure process under overload. The structural design scheme of the arch dam and the corresponding foundation treatment design are evaluated. The model fully reflects the measures of dam shape structure design, angle fitting structure design, and foundation concrete replacement in the Xiluodu arch dam technical design stage. The RFPA3D adopts the mesoelement elastic damage model, which considers the Mohr–Coulomb criterion of shear fracture and the maximum tensile failure criterion, and assumes that the mechanical properties of the element satisfy Weibull distribution to consider its heterogeneity. The simulation results show that, under normal load conditions, the dam foundation surface after comprehensive reinforcement has better overall stability, the stress and deformation of the dam body have good symmetry, and the overload factor of crack initiation under overload calculation K1 = 2P0 (P0 is normal water load), the nonlinear deformation overload factor K2 = 3.5–4P0, and the limit load factor K3 = 7.5–8.0P0, dam safety can be satisfied. The RFPA3D is used to establish a superlarge fine model to study the overall stability of the high arch dam, which provides an effective method for analysis and research of other large hydraulic projects in the world.

In order to overcome the defect that the general shaking table test can’t clarify the scale relationship between the prototype structure and the scale model in the damaged area based on the fully similar laws, we derived a method that can analyze the relationship between the prototype structure and the scale model in the damaged area based on non-fully similar lows and verified it. We selected the appropriate material (the emulation concrete material, ECM), which has a good scale relationship with the prototype material in the elastic stage, the crack appearance stage, and crack propagation stage (damage stage). We proposed some similar ratios to reveal the similar relationship between the prototype structure and the scale model in the elastic stage, the crack appearance stage, and the crack propagation stage. Especially, we proposed two similar ratios: cr and hr (deduced by the fracture toughness similarity requirements and the fracture energy similarity requirements, respectively) which can well reflect the similar relationship between the prototype structure and the scale model in the damaged area. In order to verify these ratios, we compared the results of the prototype structure numerical simulation with those of the shaking table test of the scale model. The results show that hr has higher accuracy for predicting the relationship between the prototype structure and the scale model in the damaged area.

According to the results of a dynamic prototype test for the surface outlet radial gate on the Jinping high arch dam during the flood discharging process, a novel cause of vibration fundamentally different from the traditional causes of flow-induced radial gate vibration, is analyzed for the first time. Under the condition that the flood is discharged only from mid-level outlets, an accompanying vibration of the surface outlet gate is induced by the vibration of the closely spaced mid-level outlet gates. It is counterintuitive that the most intense vibration occurs when the surface outlet gate is closed and, on the contrary, the vibration is reduced when the gate is opened and subjected to flow excitation. In order to analyze and explain this accompanying vibration phenomenon, a theoretical model is developed based on the conventional theory of passive vibration absorbers. The difference between the proposed and conventional theoretical models is that more complex load and damping conditions are considered, and more attention was paid to the dynamic behavior of the accessory structure. Then, the cause and mechanism for the surface outlet gate vibration is clarified in detail, based on the proposed theoretical model. The comprehensive analysis and mutual verification of the prototype test, theoretical derivation and numerical simulation, indicate that the clarification and the proposed theoretical model is reasonable and accurate. The research reported in this paper will be beneficial for the design, operation and maintenance of the hydraulic gates installed on high arch dams.

As an important feature, deformation analysis is of great significance to ensure the safety and stability of arch dam operation. In this paper, Jinping-I arch dam with a height of 305 m, which is the highest dam in the world, is taken as the research object. The deformation data representation method is analyzed, and the processing method of deformation spatiotemporal data is discussed. A deformation hybrid model is established, in which the hydraulic component is calculated by the finite element method, and other components are still calculated by the statistical model method. Since the relationship among the measuring points is not taken into account and the overall situation cannot be fully reflected in the hybrid model, a spatiotemporal hybrid model is proposed. The measured values and coordinates of all the typical points with pendulums of the arch dam are included in one spatiotemporal hybrid model, which is feasible, convenient, and accurate. The model can predict the deformation of any position on the arch dam. This is of great significance for real-time monitoring of deformation and stability of Jinping-I arch dam and ensuring its operation safety.

In the seismic analysis of arch dams, the heterogeneity of the foundation rock is always not included with the use of assumption of a homogeneous half-space. This study is devoted to the analysis of dam-water-foundation rock interaction considering a complex layered half-space. For this purpose, a novel scaled boundary finite element method (SBFEM) for the analysis of 3D dam-foundation interaction is developed. The novel SBFEM can satisfy the radiation damping rigorously of a complex layered half-space, which overcomes the limit of scaling requirements and broadens the application of the original SBFEM. In addition, two efficient models in the framework of SBFEM have been established in the early research, respectively, to solve hydrodynamic analysis of dam-water interaction and free-field motion of an infinite canyon. Thus, based on the substructure method, a SBFEM procedure and the corresponding program, named SBFEM-LEACD, is developed to solve the earthquake analysis of arch dams considering a complex layered half-space. The response of an arch dam at the design stage in southwest China, where the foundation rock is idealized as three kinds of model: homogeneous half-space, horizontal layered half-space and inclined half-space, is analyzed to demonstrate the effect of the complex layered half-space.

Considering that the displacement of super high arch dams is sensitive to temperature variations and dam temperature field is essentially modulated by the ambient temperature, a measured air temperature-based hydrostatic-thermal-time (HTT) displacement health monitoring (DHM) model of super high arch dams is proposed. To fully explore the complex nonlinearity between dam displacement and its explanatory variables and to improve the predictive accuracy of the model, twin support vector regression (TSVR) is introduced to establish HTT model. Due to the influence of TVSR parameters on model performance, a performance-improved TSVR is proposed by utilizing grey wolf optimizer (GWO) algorithm to determine the optimal TSVR parameters in this study. The availability of the proposed model is tested with measured data of a super high arch dam. Results show that, compared with the harmonic functions in the commonly-used hydrostatic-seasonal-time (HST) models, the detailed variation characteristics of thermal displacement can be better captured with the measured air temperature factors in the proposed HTT model. Meanwhile, the fitting and predicting accuracy of the performance-improved TSVR-based DHM model is significantly improved. And the proposed model has an excellent long-term predictive capability. The conclusion can be drawn that the proposed model is feasible and effective for the analysis and prediction of dam displacement.

The Baixo Sabor dam is a concrete double-curvature arch dam, 123 m high, located in the north-east of Portugal, which is being monitored by a dynamic monitoring system that comprises 20 uniaxial accelerometers. The paper starts with the description of the structure and of the installed monitoring equipment, as well as the monitoring software used to process the data that is continuously retrieved from site through an internet connection. Then, the results obtained during the system’s first six months of operation are presented, which include the characterization of acceleration levels for major events, such as the opening of spillway gates after intense rain, and the evolution of the dam modal properties (natural frequencies, modal damping ratios and mode shapes) during the reservoir first filling. In particular, the continuous characterization of the dam modal properties during important variations of the water level is a very unique experimental result (up to the authors knowledge, this is the first journal paper describing the continuous tracking of the modal parameters of a dam during its first filling), which is particularly interesting for the calibration of numerical models that take into account water-structure interaction. Additionally, it should be noted that the accurate tracking of the modal properties, in quite demanding conditions motivated by the very low vibration levels, associated to the massive nature of the structure, and by the presence of harmonics induced by the turbines of the hydroelectric power plant, was only possible thanks to the use of a carefully designed installation and advanced processing methodologies. At the end of the paper, it is presented a comparison between the results estimated with ambient excitation and the ones obtained with a forced vibration test and also predicted by a numerical model that includes the water effect with the added mass technique.

Temperature plays a significant part in the cracking phenomenon of mass concrete structures, and therefore thermal analysis is of major importance, especially during construction, due to the heat of hydration of the cement. A transient coupled 3D finite element analysis of the thermal behaviour of Alqueva dam during construction is presented in this paper. The method used for the thermal analysis is described in detail, along with the simulation of the different actions. The thermal state of the dam is affected not only by climatic actions but also by concrete’s constituent materials and by the construction methods. The chemo-thermal problem is solved using a heat transfer model. An exponential function was calibrated taking into account the heat of hydration of the cement at 3, 7 and 28 days and the function obtained was then used to establish the chemical affinity relationship. The temperatures predicted using the numerical model are compared with the actual temperatures recorded in situ. Despite the uncertainties characteristic of this type of problem, results lead to the conclusion that the methodology applied in this paper can be effectively used for the chemo-thermal analysis of concrete arch dams, which is particularly relevant during the construction phase.

During its long process of serving time, roller compacted concrete (RCC) arch dam effected by the comprehensive combination of many factors shows a typical time-varying characteristic on its structure and material properties, which is objectively reflected in the prototype monitoring data. On the basis of the analysis on influence variables of dam deformation and the working mechanism of the RCC arch dam, in this paper, time-varying early-warning model for the RCC arch dam is established by introducing time-varying factors into hydrostatic pressure components and expanding temperature components, then the modeling method of time-varying early-warning model above is proposed combined with the partial least squares algorithm and genetic algorithm.

This paper is a preliminary attempt to examine nonlinear structural responses of an arch dam to an underwater explosion (UNDEX) shock loading based on numerical simulation. The numerical simulation is based upon the explicit dynamics finite element program ABAQUS/Explicit. Both the dam-reservoir interaction and the contraction-joint non-linearity are considered. Our research has underlined the importance of the shear keys to the integrity of the arch dam. Failures of the shear keys make each monolith more independent and thus the dam structure as a whole more flexible. Two major failure modes of the arch dam have been identified: (a) a break-off failure of the monolith closest to the explosive source, and (b) tensile cracking of the dam base concrete. The presented simulation procedure based upon ABAQUS/Explicit is time-efficient and relatively undemanding owing to its cut-off computational strategy. We believe that it is more suitable for a large-scale three-dimensional UNDEX simulation involving an arch dam than the full-process simulation procedure.

Arch dams appear vulnerable to underwater-explosion (UNDEX) shock loadings due to their relatively thin bodies. Many seismic analyses have highlighted the significant nonlinear joint contac...

Effective deformation monitoring is vital for the structural safety of super-high concrete dams. The radial displacement of the dam body is an important index of dam deformation, which is mainly influenced by reservoir water level, temperature effect, and time effect. In general, the safety monitoring models of dams are built on the basis of statistical models. The temperature effect of dam safety monitoring models is interpreted using approximate functions or the temperature values of a few points of measurement. However, this technique confers difficulty in representing the nonlinear features of the temperature effect on super-high concrete dams. In this study, a safety monitoring model of super-high concrete dams is established through the radial basis neural network (RBF-NN) and kernel principal component analysis (KPCA). The RBF-NN with strong nonlinear fitting capacity is utilized as the framework of the model, and KPCA with different kernels is adopted to extract the temperature variables of the dam temperature dataset. The model is applied to a super-high arch dam in China, and results show that the Hybrid-KPCA -RBF-NN model has high fitting and prediction precision and thus has practical application value.

A methodology is proposed for static safety evaluation of concrete arch dams during their construction and operation phases. It includes foundation modeling, stage-construction process, thermal post-cooling analysis, realistic behavior of contraction and peripheral joints, reservoir filling, and operational thermal loading. The structural stability and safety is assessed using safety indices. The proposed methodology is applied to a typical concrete arch dam. The dam is three-dimensionally modeled along with its foundation using finite element method. Different foundation properties are investigated in homogeneous and inhomogeneous conditions including distinct soft rock layers. The stability and safety of the dam-foundation system is evaluated through some analysis cases, which show the importance of various features presented in the model.