Uncertainty Quantification and Sensitivity Analysis of Concrete Structure Using Multi-Linear Regression Technique

Dimensionless analysis of pulse-like effects on the seismic behavior of a dam based on wavelet-decomposed near-fault ground motions

A large part of the dynamic force acted on the dam is the hydrodynamic force induced by dam and reservoir interaction which increases the seismic response of dam. Also, the water level has essential role in the creation of induced hydrodynamic force in reservoir because of interaction. In this paper, in order to investigation of the sensitivity of the seismic performance of system, Monte Carlo simulation with Latin Hypercube Sampling is used in which the reservoir height was selected as random input and the dam crest displacement, maximum value of hydrodynamic pressure and 1st and 3rd principle stresses in heel and toe of dam were considered as output responses and the sensitivity of responses were reliably examined under seismic loading. Considering of Pine Flat concrete gravity dam as case study, a finite element model is developed and implemented into a computer code using Ansys software for seismic analysis of system. Consider to obtained results, it is revealed that the reservoir height how can effect on seismic behaviour of system due to earthquake. Investigation of the obtained results it is obvious that the increasing of reservoir height around the greater than 70% height of full reservoir, considerable increase the seismic response of concrete dam body.

Uncertainty quantification in a resonant nonlinear MEMS structure

This paper proposes an approach to assess and predict the seismic risk of existing concrete gravity dams (CGDs) considering the ageing effect. The combination of fragility function and cumulative absolute velocity (CAV) depending on two failure states has been used in the analysis. It represents the time-variant degradation of the concrete structure and the conditional change of structural vulnerability in the case of the seismic excitation. Therefore, the seismic risk assessment captures here the nonlinear dynamic behavior of a concrete gravity dam through the fragility analysis. Incremental dynamic analysis for the fragility curves is adopted to state the performance of the dam in terms of different intensity measures. To assess the capacity of the aged concrete gravity dam, this research introduces a way to estimate the CAVlimit of CGDs with varying time. For a case study, an existing concrete gravity dam in Korea has been taken into consideration to apply this approach. The numerical finite element model is validated by optimizing the recorded field data. The proposed approach and its findings will be helpful to CGDs operators to ensure whether a dam needs to stop after a specific time using the extracted mathematical model. Furthermore, as this mathematical model is the function of time, the operator can get an idea about dam conditions at any specific time and can take necessary steps.

The implementation of resilience-enhancing strategies on existing concrete gravity dams is a task of primary importance for the society. This aim can be achieved by estimating the risk of concrete dams against multi-hazards and by improving the structural control. Focusing the attention only on the seismic hazard, numerical models assume great importance due to the lack of case studies. However, for the same reason, numerical models are characterised by a high level of uncertainty which must be reduced by exploiting all available information. In this way reliable predictive models of the structural behaviour can be built, thus improving the seismic fragility estimation and the dam control. In this context, the observations recorded by the monitoring systems are a powerful source of information. In this thesis two Bayesian frameworks for Structural Health Monitoring (SHM) of existing concrete gravity dams are proposed. On the one hand, the first proposed framework is defined for static SHM, so the dam displacements are considered as Quantity of Interest (QI). On the other hand, a dynamic SHM framework is defined by assuming the modal characteristics of the system as QI. In this second case an innovative numerical algorithm is proposed to solve the well-known mode matching problem without using the concept of system mode shapes or objective functions. Finally, a procedure based on the Optimal Bayesian Experimental Design is proposed in order to design the devices layout by optimizing the probability of damage detection. In all the three procedures the general Polynomial Chaos Expansion (gPCE) is widely used in order to strongly reduce the computational burden, thus making possible the application of the proposed procedure even without High Performance Computing (HPC). Two real large concrete gravity dams are analysed in order to show the effectiveness of the proposed procedures in the real world. In the first part of the thesis an extended literature review on the fragility assessment of concrete gravity dams and the application of SHM is presented. Afterwards, the statistical tools used for the definition of the proposed procedures are introduced. Finally, before the presentation of SHM frameworks, the main sources of uncertainties in the numerical analysis of concrete gravity dams are discussed in order to quantify their effects on the model outputs.

Almost all high-rise buildings have been constructed in the Republic of Armenia for past twenty-five years are Reinforced Concrete (RC) shear wall–frame structures, where shear walls provide most of the stiffness of buildings. The walls in these buildings are designed to sustain earthquake and wind loads. Vulnerability of them during earthquake action depends on many different factors. Some of them are the openings and its location in the walls. Usage of ground stories as parking and garages is demanded large openings in shear walls therefore determination of ultimate sizes of openings is important problems for designers. In this paper, FEM (Finite Element Method) models are used for investigation of stress-strain state of RC wall–frame buildings with various openings in the walls under action of seismic forces. Limitation of size and position of openings are considered in the paper taking into account of building code of Armenia. Various schemes of openings are considered in the article. The existing experimental data of shear walls were performed in various laboratories have been compared with our numerical investigation of RC models based on nonlinear computer analyses. Dynamic analyses of structures using accelerograms are showed sequence of damages in RC wall-frame models. The recommendations for limitation of ratio area of an opening to the whole area of a wall are proposed at the end of the article.

Seepage criteria based optimal design of water retaining structures with reliability quantification utilizing surrogate model linked simulation-optimization approach

Seismic fragility curves have been introduced as key components of seismic probabilistic risk assessment studies. They express the probability of failure of mechanical structures conditional to a seismic intensity measure and must take into account various sources of uncertainties, the so-called epistemic uncertainties (i.e., coming from the uncertainty on the mechanical parameters of the structure) and the aleatory uncertainties (i.e., coming from the randomness of the seismic ground motions). For simulation-based approaches we propose a methodology to build and calibrate a Gaussian process surrogate model to estimate a family of nonparametric seismic fragility curves for a mechanical structure by propagating both the surrogate model uncertainty and the epistemic ones. Gaussian processes have indeed the main advantage to propose both a predictor and an assessment of the uncertainty of its predictions. In addition, we extend this methodology to sensitivity analysis. Global sensitivity indices such as aggregated Sobol' indices and kernel-based indices are proposed to know how the uncertainty on the seismic fragility curves is apportioned according to each uncertain mechanical parameter. This comprehensive uncertainty quantification framework is finally applied to an industrial test case consisting of a part of a piping system of a pressurized water reactor.

Seismic stability of concrete gravity dams strengthened by rockfill buttressing

Uncertainty quantification and sensitivity analysis are essential for improving the modeling and estimation of greenhouse gas emissions in livestock farming to evaluate and reduce the impact of uncertainty in input parameters to model output. The present study is a comprehensive review of the sources of uncertainty and techniques used in uncertainty analysis, quantification, and sensitivity analysis. The search process involved rigorous selection criteria and articles retrieved from the Science Direct, Google Scholar, and Scopus databases and exported to RAYYAN for further screening. This review found that identifying the sources of uncertainty, implementing quantifying uncertainty, and analyzing sensitivity are of utmost importance in accurately estimating greenhouse gas emissions. This study proposes the development of an EcoPrecision framework for enhanced precision livestock farming, and estimation of emissions, to address the uncertainties in greenhouse gas emissions and climate change mitigation.

Hydraulic structures such as gravity dams are classified as essential structures, and have the vital role in providing strong and safe water resource management. Three major aspects must be considered to achieve an effective design of such a structure: 1) The building cost, 2) safety, and 3) accurate analysis of seepage characteristics. Due to the complexity and non-linearity relationships of the seepage process, many approximation theories have been developed; however, the application of these theories results in noticeable errors. The analytical solution, which includes the difficult conformal mapping procedure, could be applied for a simple and symmetrical problem only. Therefore, the objectives of this paper are to: 1) develop a surrogate model based on numerical simulated data using SEEPW software to approximately simulate seepage process related to a hydraulic structure, 2) develop and solve a linked simulation-optimization model based on the developed surrogate model to describe the seepage occurring under a concrete gravity dam, in order to obtain optimum and safe design at minimum cost. The result shows that the linked simulation-optimization model provides an efficient and optimum design of concrete gravity dams.

An improved numerical manifold method for crack propagation of concrete gravity dams under seismic loads

Concrete gravity dams continued to develop in Indonesia even though the population is still smaller than embankment dams. Until 2021 there consist of 16 concrete gravity dams or about 7% of all dams in Indonesia. The utilization of concrete gravity dams in Indonesia is 75% for hydropower or as many as 12 dams. Concrete gravity dam is a high-risk structure so the design of concrete gravity dams must be referred to the guidelines where applicable in Indonesia and internationally with approval from Dam Safety Organization. In Indonesia, the construction of concrete gravity dams cannot be separated from the participation of design consultants from developed countries such as the UK, Japan, US, Canada, Korea, and China. Indonesian Water Resource Guidelines 2009 is formal reference that must be adhered to by all design and construction planners in Indonesia, so that designs that refer to the guidelines and manuals from foreign countries must go through a comparison and evaluation process to meet the design acceptance criteria in accordance with the Indonesian Water Resource Guidelines 2009. Comparison processes include load conditions, design concepts, seismic analysis methods, stability and stress analysis methods, and stability and stress acceptance criteria. As a results of comparison, we can get information that the Indonesian Water Resource Guidelines 2009 apply stability and stress acceptance criteria more conservative. As consequence, the investment cost for the construction of concrete gravity dams in Indonesia is becoming more expensive.Keywords: dams, concrete gravity, guidelines, comparation, stability.

1. A method was developed for estimating the reliability of concrete gravity dams under seismic actions within the framework of the linear spectral theory of seismic stability. 2. The method approximately takes into account the effect of all main factors determining the strength and reliability of the structure: earthquake intensity and frequency, service life of the dam, its various operating regimes, deformation and strength characteristics of the material of the dam and base, character of limit states, etc. 3. An analysis of the probabilistic characteristics of the random variables figuring in the equation for seismic inertial loads and corresponding numerical experiments showed that substantial simplifications are possible at a number of stages of the solution, making the method rather simple. 4. At present (when the standard reliability for concrete dams has still not been legalized) the method permits assessing the role of various factors and comparing variants of the structures, and in the future (when a standard reliability is assigned) it will permit estimating the reliability with consideration of the probabilistic characteristics of all main parameters of the problem. 5. The given examples of the calculation showed the effect of certain factors on the reliability of dams under an unusual combination of loads.

System identification of concrete gravity dams using artificial neural networks based on a hybrid finite element–boundary element approach