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Yilmazturk, Sema Melek. "Three Dimensional Dynamic Response Of A Concrete Gravity Dam." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615455/index.pdf.
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Hydroelectric power is a commonly used alternative source of energy in developing countries. In this regard, concrete gravity dams are the most preferred dam type especially with the developments in the engineering industry. Roller compacted concrete became more popular in dam construction due to its advantages of speed and economy. Several methods are used for the design of concrete gravity dams by analyzing the dam response under static and dynamic loads. This study provides three dimensional linear dynamic analysis of roller compacted concrete gravity dam with a complete dam-foundation-water interaction by using EACD-3D-08 program. Foundation flexibility was included with damping and mass using boundary elements. Three dimensional solid elements were used for the idealization of the dam and water with using finite element methods. Compressibility of water with reservoir absorption was studied. In the light of USACE, performance criteria of linear analyses were assessed. Parametric study was conducted to determine the most influential parameters on the dam response. The importance and necessity of three dimensional analyses were investigated by comparing with linear two dimensional analyses. Linear analyses were then compared with three dimensional nonlinear analyses. In conclusion, the realistic dam seismic response can only be obtained by using three dimensional linear analyses with full interaction of dam-foundation-water.
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Simic, Milan. "Earthquake analysis of concrete gravity dam-foundation systems." Thesis, University of Bristol, 1994. http://hdl.handle.net/1983/418224c4-bc34-4ec8-a39e-ec5d7a6f1d4f.
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Abuladze, Vissarion. "Numerical analysis and shape optimisation of concrete gravity dams." Thesis, London South Bank University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336375.
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The Finite Element and Boundary Element Methods are both well established numerical techniques for analysing a wide range of engineering problems. In the present thesis these numerical techniques are used for obtaining a more realistic picture of various characteristics of concrete gravity dams. The present work addresses the behaviour of gravity dams under static loading, and the developed analysis procedure/computer package can cater for a wide range of dam characteristics including: the three-dimensional behaviour of a gravity dam-foundation-abutments system; the non-linear behaviour of a dam and foundation materials; the sequential construction of a dam and impounding of the reservoir loading on the structure; the effect on stresses of interfaces and joints existing between a dam and its foundation, and in the body of a dam itself; the action of pore water pressure within the foundation, at the dam-foundation interface, and in the body of a gravity dam; etc. Using the purpose written computer package which can cater (in an efficient and accurate way) for the influence of all such factors, mathematical programming methods are, then, used to produce a powerful tool for the shape optimisation of gravity dams leading to safe, functional and economical solutions to the problem. In the course of developing the computer program, much care has been exercised as regards the appropriate selection of the finite element types, mesh configurations and mesh densities, in order to reflect (in an efficient fashion) the variation of stress gradients in the body of a gravity dam. In order to reduce high costs associated with a full three-dimensional analysis, a rather efficient method is developed which enables one to carry out equivalent twodimensional computer runs which will effectively simulate the actual three-dimensional behaviour of gravity dams in, for example, narrow valleys. The proposed approach reduces the dimensionality of an actual problem by one, thus, eliminating the main disadvantage of the finite element method in terms of high solution costs for threedimensional problems. As a result, the proposed method makes the solution procedure highly cost effective. By coupling the finite element-boundary element (FEBE) techniques, which can cater for the material non-linearities in the appropriate regions of the foundation, an attempt is made to by-pass the individual disadvantages of both these numerical techniques. It has, then, been possible to exploit the advantages of reducing the dimensionality of the foundation region by one using the boundary element technique, and, hence, come up with significant savings in terms of computer running times. Anisotropic tangent constitutive models for plain concrete under a general state of biaxial static monotonic loading for, both, plane-stress and plane-strain states of stresses are proposed which are simple in nature, and use data readily available from uniaxial tests. These models have been implemented into the computer program which is, then, used to investigate the influence of the step-by-step construction of the dam and the sequential impoundment of the reservoir loading on the state of stresses. The non-linear program is also used to analyse various characteristics of Bratsk concrete gravity darn (in Russia). The correlations between the numerical results and extensive field measurements on this darn, have been found to be encouraging. Isoparametric quadratic interface finite elements for analysing the darnfoundation interaction problem have also been developed. These elements have zero thickness and are based on an extension of the linear interface elements reported by others. The numerical problems of ill-conditioning (usually associated with zero thickness elements) are critically investigated using test examples, and have been found to be due to inadequate finite element mesh design. Non-linear elastic tangent constitutive models for simulating the shear stress-relative displacement behaviour of interfaces have also been developed, and are used to analyse the effects of including interface elements at the dam-foundation region of contact. It is shown that the inclusion of interface elements in the numerical analyses of the dam-foundation system leads to rather significant changes in the magnitudes of the critical tensile stresses acting at the heel of the dam, which have previously been evaluated (by others) using a rigid dam-foundation interconnection scheme. Effects of pore water pressure, acting as a body force throughout the foundation, the dam-foundation interface and the body of a gravity dam, are also critically studied, with the pore pressure values predicted by seepage analysis. Using an extensive set of numerical studies, a number of previously unresolved issues as regards the influence of pore pressures on the state of stresses are clarified. The effect of drainage on the state of stresses within the body of a dam is investigated, and an insight is also given into the effect of the uplift acting at the lift lines between successive layers of Roller Compacted Concrete (ReC) dams. A shape optimisation procedure for gravity dams based on the penalty function method and a sequential unconstrained minimisation technique is also developed. A number of shape optimisations of idealised gravity dams are carried out in order to compare the numerical results with previously available analytical solutions. The present work also caters for the effects of foundation elasticity and uplift on the optimal shape of a gravity dam. A numerical example is provided covering the shape optimisation of a hollow gravity dam. Finally, the shape optimisation of an actual dam (i.e. Tvishi gravity dam in Georgia) using the presently proposed procedures is carried out with the fmal results compared with those available from the project design team. Wherever possible. numerical outputs have been checked against available small or full scale test data or previously reported closed form solutions. Throughout this thesis very encouraging correlations between the present predictions and such experimental and theoretical data have been obtained.
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Cai, Qingbo. "Finite element modelling of cracking in concrete gravity dams." Thesis, Pretoria : [s.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-01302008-160623.
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Amirkolai, Mohsen Ghaemian. "Dam-reservoir interaction effect on the seismic response of concrete gravity dams /." *McMaster only, 1997.
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Sundström, Max, and Max Ivedal. "Stress and Sliding Stability Analysis of Songlin Rock-Filled Concrete Gravity Dam." Thesis, Uppsala universitet, Elektricitetslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-305249.
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The construction of Songlin rock-filled concrete gravity dam, located in the Yunnan province, China began in the end of 2015. In this master thesis the finite element method (FEM) based software Abaqus has been used to perform a computational analysis on tension stresses, compression stresses and sliding stability for static conditions. One overflow section and one non-overflow section of the dam have been analysed. The results of the analysis have been evaluated by comparing with Chinese standards for dam safety and is intended to help engineers with making decisions in the construction process of the dam. The measured compressive stress values of both the overflow and non-overflow section are not evaluated to be within safe levels, further evaluation is required to ensure the safety of the dam. The dam is considered to be safe from vertical tension in the analysed region, however an extended evaluation including the whole dam base is recommended. The analysed cross-sections for sliding stability can be considered safe, but further analysis is required to make a conclusion of the sliding stability of the full dam base.
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Durieux, Johan Hendrik. "Development of a practical methodology for the analysis of gravity dams using the non-linear finite element method." Diss., Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-06232009-152815/.
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Johansson, Lukas, and Dan Valtersson. "Stability Analysis of Non-overflow Section of Concrete Gravity Dams : A Longtan Dam case study." Thesis, Luleå tekniska universitet, Geoteknologi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-70724.
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Fouhy, David, and Bayona Francisco Ríos. "Reliability-Based Analysis of Concrete Dams." Thesis, KTH, Jord- och bergmekanik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176867.
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Dams are designed and assessed based on traditional factor of safety methodology. Several drawbacks of this approach exist; for example varying failure probability for structures where the factor of safety is the same. This traditional factor of safety methodology imposes conservative assumptions in terms of both design and analysis. A probability-based analysis has been suggested to account for the omission of uncertainties and provide a less conservative analysis (Westberg & Johansson, 2014). Through the stability analyses of three existing dam structures, a minimum level of reliability or maximum failure probability may be calculated with the ultimate goal of defining a target safety index (β-target) for buttress and gravity dams. These analyses shall in turn contribute to the formulation of a probability-based guideline for the design and assessment of Swedish concrete dams. This probability-based guideline shall be known as the ‘Probabilistic Model Code for Concrete Dams.’ The calculations carried out in this study adhere to the methodologies and specifications set out in the preliminary draft of the Probabilistic Model Code for Concrete Dams. These methodologies encompass analyses within two dominating failure modes for concrete dams; sliding stability and overturning stability. Various load combinations have been modelled for each dam structure to account for the probabilistic failure of each dam under commonly occurring circumstances. A parametric study has been carried out in order to provide insight into the contribution that existing rock bolts provide to the stability of each dam. Furthermore, a study has been carried out into the existence of a persistent rock joint or failure plane in the rock foundation and the effects its presence would have on the sliding stability of a dam. Finally a discussion had been carried out in order to provide suggestions into the formulation of a target safety index through the data envisaged by our analyses for the design and assessment of Swedish concrete dams.
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Beser, Mehmet Resat. "A Study On The Reliability-based Safety Analysis Of Concrete Gravity Dams." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605786/index.pdf.
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Dams are large hydraulic structures constructed to meet various project demands. Their roles in both environment and the economy of a country are so important that their design and construction should be carried out for negligibly small risk. Conventional design approaches are deterministic, which ignore variations of the governing variables. To offset this limitation, high safety factors are considered that increase the cost of the structure. Reliability&ndashbased design approaches are probabilistic in nature since possible sources of uncertainties associated with the variables are identified using statistical information, which are incorporated into the reliability models. Risk analysis with the integration of risk management and risk assessment is a growing trend in dam safety. A computer program, named CADAM, which is based on probabilistic treatment of random loading and resistance terms using Monte&ndash
Carlo simulation technique, can be used for the safety analysis of gravity dams. A case study is conducted to illustrate the use of this program.
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Boberg, Björn, and David Holm. "FEM modeling of concrete gravity dams." Thesis, KTH, Vattendragsteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-99351.
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Sauvé, Ghislain. "Seismic analysis of uplifting concrete gravity dams." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59640.
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Rational and efficient numerical modelling procedures are required to simulate the dynamic behaviour of dam-foundation-reservoir systems. Significant nonlinear response mechanism such as uplifting of the dam under severe ground motion should be considered to obtain a realistic evaluation of seismic stability and structural behaviour.In this study, the performance of three different time-domain reservoir modelling procedures suitable for nonlinear analysis were investigated. These were an added mass approach based on the Westergaard method, and finite element formulations using either fluid pressures or displacements to represent the reservoir. The efficiency of various coordinate reduction procedures were studied to progressively reduce the number of degrees-of-freedom needed to properly represent the earthquake response of uplifting gravity dams. Parametric analyses of a typical two-dimensional model were carried out to determine the influence of key modelling assumptions on the structural response. The parameters considered were the intensity of uplift pressures and the mesh density at the dam-foundation interface, the relative stiffness of the dam and the foundation, and the height of the dam.
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Hatami, Kianoosh. "Effect of reservoir boundaries on the seismic response of gravity dams." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq30090.pdf.
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Venturelli, John. "Seasonal temperature and stress distributions in concrete gravity dams." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56758.
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Seasonal thermal stresses have been found to contribute significantly to the long term degradation of strength and stiffness of concrete dams located in northern regions. Moreover, thermal stresses and strains must be evaluated to define the initial loading conditions for seismic safety analyses. In this study, finite element procedures to model the thermal response of concrete gravity dams are presented. Heat transfer and structural models of a typical dam-foundation-reservoir system are developed. The reservoir, foundation, and air temperature variations, as well as solar radiation, are evaluated from data collected from different sources. The rate of convergence of the numerical solution is examined, and a methodology to identify the critical temperature states and to compute the related stresses, considering creep, is presented.Extensive parametric analyses are then performed to determine the relative influence of (i) the geometrical, thermal, and mechanical properties of the dam, (ii) the reservoir, foundation and air temperature distributions, and (iii) the heat supply from solar radiation, on the stress-strain response of the system. Temperature states to define critical stress conditions for structural safety analysis are determined.
Significant thermal stresses occur in the vicinity of the exposed surfaces of the dam. The typical depth of frost penetration is about 6m. The parameters which affect the surface stresses most are the air temperature distribution and the height of the dam, while for the frost penetration they are the solar radiation, convection coefficient, and conduction coefficient.
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Bhattacharjee, Sudip Sankar. "Static and seismic fracture analyses of concrete gravity dams." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=42301.
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Smeared crack analysis models, based on nonlinear fracture mechanics concepts, have been developed to investigate the fracture behaviour of concrete gravity dams. The proposed constitutive models have been implemented in a finite element analysis computer program for nonlinear static and seismic analyses of plain concrete structures. Extensive verifications of the computational models have been carried out by studying the nonlinear static response of notched concrete beams, a model concrete dam, and a full scale concrete gravity dam: all experimentally or numerically investigated in the past. Seismic fracture and energy response of Koyna Dam, a classic example of seismic induced cracking in concrete dams, has also been studied. Finally, the seismic fracture behaviour of a typical concrete gravity dam has been investigated, considering severe ground motions and winter temperature effects as expected in Eastern Canada. Reduced frequency independent models of dynamic interactions in the dam-reservoir-foundation system have been considered in the nonlinear seismic analyses.
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Krounis, Alexandra. "Uncertainty in Sliding Stability Analyses of Existing Concrete Gravity Dams with Bonded Concrete-Rock Interfaces." Licentiate thesis, KTH, Jord- och bergmekanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-131430.
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Safety assessment of existing dams becomes more and more important with their increasing age. In addition, new regulations, due to climate changes and changes in knowledge, demand a re-evaluation of the existing dams’ safety. One of the failure modes considered in safety assessments of concrete gravity dams is sliding at the dam-foundation contact. Sliding failure is assumed to occur when the applied load exceeds the shear strength of the interface. Thus, the shear strength of the concrete-rock interface will ultimately determine if sliding of the dam will occur or not and it is, therefore, of utmost importance to be able to quantify it. The shear strength of concrete-rock interfaces is in general defined based on the Mohr-Coulomb shear strength criterion, which is governed by the cohesion, friction angle and normal stress along the interface. This simplified model of the shear strength is subject to several uncertainties, due for example to the natural variability of the involved parameters, statistical errors etc. In addition, analyses are commonly performed using the averaged values of cohesion, friction angle, normal and shear stresses, based on the assumption of ductile failure. This may be incorrect for bonded or partly bonded interface since test results show that bonded concrete-rock cores exhibit brittle behaviour. The uncertainties related to bonded or partly bonded interfaces are taken into account in the Swedish guidelines, RIDAS, for by treating all concrete-rock interfaces as unbonded, i.e. the effect of cohesion is not included when evaluating the shear strength of the interface. This is a conservative method, but it may lead to expensive and unnecessary strengthening of existing dams. Other deterministic guidelines/regulations, e.g. FERC, allow the use of cohesion but apply higher target safety factors when both the cohesive and the frictional strength are taken into account. To evaluate the adequacy of using cohesion in sliding stability analyses of concrete dams, the effect of the uncertainties on the calculated sliding stability of the dam has to be assessed. This thesis highlights several uncertainties related to bonded concrete-rock interfaces. However, the thesis focuses mainly on increasing the knowledge regarding the model uncertainty due to the brittle failure mechanism in combination with a possible spatial variability of cohesion. The magnitude of the model uncertainty is studied using numerical analyses. Its influence on the assessed behaviour of a hypothetical dam monolith is then evaluated using probability based methods. A conclusion drawn from this particular case, but which is likely to be generalized to other dam-foundation systems, is that the ductile sliding failure is too coarse an approximation of the failure behaviour of dams with bonded interfaces and could lead to an overestimation of dam safety. In addition, the potential spatial variability of cohesion along the interface further diminishes the validity of the ductile failure model. Areas that require further research in order to take into account the most significant uncertainties related to bonded interfaces include the definition of the ratio of bonded area to total area and its influence on sliding stability. The statistical uncertainty due to the limited number of tests also needs to be studied.QC 20131015
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Tofangchi, Mahyari Abbas-Ali. "Static and seismic rehabilitation of concrete gravity dams by post-tensioning." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=26430.
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Post-tensioning rehabilitation technique is often used to improve the static and dynamic stability of concrete gravity dams. The required post-tensioning force has often been estimated from the gravity method using simple static rigid body equilibrium. However, the application of linear and nonlinear (fracture) analysis techniques using the finite element method could be advantageous to optimize the design of post-tensioning strengthening schemes, specially under seismic loads where controlled damage is an acceptable performance criterion.In this study, the flood and seismic safety evaluations of prestressed dams were carried out using the gravity method, and linear and fracture finite element methods. Two typical concrete gravity dam models, 35 m and 90 m in heights, were examined. The performance of different post-tensioning modelling techniques such as the equivalent force method, and bonded/unbonded cable elements was examined in finite element analyses. A new nonlinear analysis methodology using displacement control was studied to determine the required amount of post-tensioning forces under flood condition. Sliding stability (local and global), overstressing, and controlled damage requirements were considered to develop post-tensioning design criteria in rehabilitation of concrete gravity dams. Various schemes of post-tensioning cable layouts were examined in seismic analyses.
The different prestressing modelling techniques present almost identical static and seismic structural behaviours. The material properties of the horizontal joint at the dam-foundation interface, and the tendon layouts were found the key prestressing design parameters. Linear finite element analyses predict higher required prestressing forces compared to other analysis methods. In general, flood resistant: design of prestressing also presents adequate seismic performance for small dams. However, additional partial prestressing is required near the downstream face of higher dams to prevent cracking at this location.
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Horyna, Tomas. "Reliability analysis of base sliding of concrete gravity dams subjected to earthquakes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0016/NQ46355.pdf.
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Løkke, Arnkjell. "Earthquake Analysis of Concrete Gravity Dams : Review and Modernization of Two Analysis Procedures." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for konstruksjonsteknikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23539.
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A two-stage procedure has been proposed for the elastic analysis phase of seismic design and safety evaluation of concrete gravity dams: (1) response spectrum analysis (RSA) in which the peak value of response is estimated directly from the earthquake design spectrum; and (2) response history analysis (RHA) of a finite element idealization of the dam monolith. Both analysis procedures include the effects of dam-water foundation interaction, known to be important in the earthquake response of dams.Presented in this thesis are two important developments that have now been added to the computer program EAGD-84, implementing the RHA procedure: (1) a set of Matlab modules ? including an easy-to-use graphical user interface (GUI) ? has been developed, providing users with the capability of pre-processing input and post-processing analysis output from EAGD-84 in the Matlab scripting language; (2) a more complete set of compliance data that govern the interaction between the dam and the foundation region has been incorporated in the program. These developments greatly improve the accessibility and functionality of the EAGD-84 program, and provide users with sufficient control over the overall damping in the dam-water-foundation system to ensure consistency with recent research. The above mentioned RSA procedure has likewise been modernized. A number of enhancements have been made to the procedure, the most significant being: (1) a more complete set of data for the parameters that characterize dam-foundation interaction has been computed and implemented; and (2) to enhance the accuracy of the procedure, a correction factor for computing beam stresses on the downstream face of the dam has been developed. In addition, a comprehensive evaluation of the accuracy of the RSA procedure has been conducted, demonstrating that it estimates stresses close enough to the "exact" results (determined by RHA) to be satisfactory for the preliminary phase in the design of new dams and in the safety evaluation of existing dams. The accuracy achieved by the procedure is noteworthy, especially considering the complicated effects of dam-water-foundation interaction and reservoir bottom absorption on the dynamics of the system, and the number of approximations necessary to develop the procedure. The updated version of the computer program EAGD-84, the new Matlab modules and the GUI, as well as a new report presenting the updated RSA procedure, have all been made publicly available through the Pacific Earthquake Engineering Research (PEER) Center.
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Broberg, Lisa, and Malin Thorwid. "Evaluation of Failure Modes for Concrete Dams." Thesis, KTH, Betongbyggnad, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-169708.
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The safety of a concrete dam is ensured by designing according to failure criteria, for all combinations of loads using safety factors. Today in Sweden, RIDAS, the Swedish power companies’ guidelines for dam safety, is used for the design of dams and is based on BKR, the National Board of Housing, Building and Planning. Swedish dams are designed to resist two global failure modes; sliding and overturning. Combination of failure modes, that should be considered in the design of concrete dams, is however fairly unknown. Since 2009 the Eurocodes was adopted and came into force 2011. The Eurocodes have replaced BKR in the design of most structures in Sweden where the partial factor method is used to ensure safety in the design. The objective of this report was to examine if the design criteria for concrete dams in today’s condition are enough to describe real failure modes. The other objective was to analyse if Eurocode is comparable to RIDAS in dam design. The stated questions were answered by performing a literature study of known dam failures and analytical calculations for different types of concrete gravity dams, with varying geometry and loading conditions. The programs CADAM and BRIGADE were also used as calculation tools to further analyse if failure occurred as expected. The results from the analytical calculations together with the performed FE analysis indicate that limit turning does occur and often generate lower safety factors compared to overturning. Limit turning is similar to overturning failure although it accounts for material failure in the rock. This design criterion is therefore, highly dependent on the quality of the rock and requires investigations of the foundation to be a good estimation of the real behaviour of the dam body. From the compilation of reported failures the conclusion was that the current design criteria are adequate. However, the real challenge lies in ensuring that the construction of dams is correctly performed to fulfil the stated criteria. A transition to Eurocode appears to be reasonable for the stability criterion. A modification of the partial factors is nevertheless necessary to obtain result corresponding to RIDAS, especially for the overturning criteria.För att uppnå säkra dammkonstruktioner, för alla lastkombinationer, dimensioneras dammar enligt bestämda brottvillkor som ska uppfylla en viss säkerhetsfaktor. Idag används RIDAS, för dimensionering av dammar i Sverige. RIDAS Kraftföretagens riktlinjer för dammsäkerhet, är baserat på BKR, Boverkets konstruktionsregler. I Sverige dimensioneras dammar för att motstå de två globala brottmoderna glidning och stjälpning. Frågan som behöver besvaras är om det finns eller kan finnas några kombinationer av brottmoder som borde beaktas vid dimensionering av dammar. 2009 antogs Eurokoderna och trädde i kraft 2011. Eurokoderna har ersatt BKR vid dimensionering av de flesta konstruktioner i Sverige. I Eurokod används partialkoefficienter för att garantera säkra konstruktioner. Syftet med denna rapport var att undersöka om dagens brottkriterium är tillräckliga för att beskriva hur dammar går till brott. Rapporten behandlar även möjligheten att övergå från att dimensionera dammar enligt RIDAS till att dimensionera enligt Eurokod. För att besvara detta genomfördes en litteraturstudie av rapporterade dammbrott. Dessutom genomfördes analytiska beräkningar för flera olika typer av dammar med varierande geometri och lastfall. Programmen CADAM och BRIGADE användes som ytterligare verktyg för att analysera brottmoderna. Enligt resultat från de analytiska beräkningarna tillsammans med FE-beräkningarna ansågs limit turning inträffa och genererade i högre grad en lägre säkerhetsfaktorer i jämförelse med stjälpning. Limit turning kan förklars som delvis stjälpande och inkluderar brott av bergmassan. Brottmodet är dock beroende av kvalitéten hos berget och det krävs undersökningar av grunden för att kunna göra en god uppskattning av dammens verkliga beteende. Sammanställningen av tidigare brott visade att nu gällande brottkriterier är lämpliga och troligtvis tillräckliga. Utmaningen är istället att säkerställa att konstruktionerna är korrekt utförda och därmed uppfyller dessa brottkriterier. En övergång till Eurokod tycks vara möjlig för de globala brottmoderna, dock är det väsentligt att partialkoefficienterna justeras för att uppnå resultat som överensstämmer med RIDAS, särskilt för stjälpning.
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Mir, Riyaz Ahmad. "An experimental investigation into the seismic induced failure of moderately high concrete gravity dams." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239139.
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Dankers, Clyde Lleland. "A framework for the evaluation of the structural safety of existing concrete gravity dams." Master's thesis, Faculty of Engineering and the Built Environment, 2019. http://hdl.handle.net/11427/31226.
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Addressing the aging and deterioration of dams is a relatively new challenge in the dam engineering field in South Africa. The average life expectancy of a dam is approximately 50 years, but they can normally be used for much longer periods than this. Maintenance and rehabilitation are vital to ensure that they achieve their design service lives and for the extension of their service lives. The rehabilitation of dams to extend their service lives and/or to ensure that they comply with modern stability criteria can be an extremely lengthy and costly exercise. It would therefore be valuable to do some research into the process of evaluating the structural safety of dams. The focus of this research study is specifically on the evaluation of the structural safety of large concrete gravity dams. The purpose of the research is to investigate the most commonly used and accepted methods to evaluate the structural safety of concrete gravity dams and develop a framework that can be used for the evaluation of the structural safety of concrete gravity dams. For the purpose of this research study, an existing large concrete gravity dam was evaluated as a case study. The dam is approximately 93 years old and provides water to the nearby local municipality for domestic purposes. According to the first and second Dam Safety Evaluation (DSE) reports the dam does not comply with modern stability criteria for concrete gravity dams. The findings of these dam safety evaluation reports led to the dam being labelled as essentially “unsafe” in the case of the occurrence of a large flood. Typically, this would mean that the dam must be rehabilitated to improve its safety. However, some engineers believe that this is not the case and that major rehabilitation is not necessary. In this research study a framework for the evaluation of the structural safety of existing concrete gravity dams was developed based on lessons learnt from the literature review and the case study. This recommended framework can be useful as a guide for future safety evaluations of existing concrete gravity dams. The potential benefits of using this recommended framework includes avoiding unnecessary rehabilitation work, as well as significant time and cost savings.
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Iqbal, Ali. "Probability of Failure for Concrete Gravity Dams for Sliding Failure - Proposal to solution for the eleventh ICOLD Benchmark workshop." Thesis, KTH, Jord- och bergmekanik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-100538.
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Safety of dams can be evaluated based on the risk analysis methodologies that accounts for estimation of the risks associated to the dam-reservoir system. For this purpose it is important to estimate the probability of load events and probability of failure for several failure modes. The following thesis emphasises on estimation of the probability of one specific failure mode, i.e. “sliding failure” for a concrete gravity dam. The main idea behind this thesis was to analyse the estimation of the probability of sliding failure of an existing dam by obtaining the relationships among the different load events, factors of safety associated to those events and the probability of failure estimated using numerical simulation techniques together with different reliability methods. The analysed dam is taken from theme C of the eleventh ICOLD Benchmark workshop on numerical analysis of dams. The thesis covers the methodology for estimating the probability of failure of a given concrete gravity dam with five water levels, considering the sliding failure mode along the dam-foundation interface along with the estimation of factors of safety for each water level and with two different drainage conditions. First order second moment Taylor’s Series Approximation is being used as Level 2 reliability method and Monte Carlo simulation as Level 3 reliability method to estimate the probability of failure against sliding of the dam. Conclusions are drawn in the end by comparing the results obtained from factor of safety estimation and probability of failure for each water level and drainage condition, followed by suggestions for further research in the context of sliding stability of concrete dams.
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Leão, Marcio Fernandes. "Análise tensão deformação de uma barragem de concreto em solo residual preponderantemente anisotrópico." Universidade do Estado do Rio de Janeiro, 2015. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=9394.
Full textAbstract:
Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de JaneiroEstudos de fundações de obras de arte, como barragens de concreto-gravidade e barragens de terra, devem contemplar todos os esforços atuantes no maciço de fundação, principalmente as tensões e as deformações esperadas durante todo o processo construtivo e no período pós-construtivo. Quando essas estruturas são apoiadas sobre rochas de boa sanidade, a escolha do barramento geralmente favorece a implantação de barragens de concreto. Entretanto, quando os maciços de fundação são formados por solos, a opção técnica geralmente mais bem aceita é quanto à utilização de barragens de terra. Em ambos os casos, as análises de estabilidade e de deformação são desenvolvidas por métodos analíticos bem consolidados na prática. Nas condições mais adversas de fundação, seja em rochas ou em solos com marcante anisotropia e estruturas reliquiares herdadas da rocha-mãe, a utilização de modelos constitutivos anisotrópicos em análises por elementos finitos propicia simulações mais realistas dessas feições estruturais, contribuindo para o seu melhor conhecimento. O presente trabalho teve por objetivo demonstrar a utilização de um modelo constitutivo anisotrópico no estudo da fundação da Barragem San Juan, localizada na República Dominicana, que foi concebida como uma estrutura tipo concreto-gravidade apoiada sobre solos residuais jovens altamente anisotrópicos. Nessa obra, apesar de sua pequena altura, a presença marcante de descontinuidades ensejou um estudo mais detalhado do comportamento tensão-deformação da fundação, levando em conta o levantamento detalhado da atitude das descontinuidades presentes no maciço e os resultados de ensaios de resistência em planos paralelos e normais às descontinuidades. Para a estimativa de deformações, os respectivos módulos de Young (Es) foram estimados com base em correlações com a resistência à penetração SPT desenvolvidas nesta dissertação, a partir de um estudo estatístico baseado em várias publicações disponíveis na literatura. As análises numéricas por elementos finitos foram desenvolvidas através do programa Plaxis 2D, utilizando-se como modelo constitutivo aquele denominado The Jointed Rock Model, que é particularmente recomendado para análises de estabilidade e deformação de materiais anisotrópicos. Os resultados das análises numéricas foram comparados com as análises de equilíbrio limite elaboradas para o projeto executivo da referida barragem, pelo programa Slope, utilizando o método rigoroso de Morgenstern e Price, que se mostrou conservador. Os resultados das análises numéricas mostraram sua inequívoca versatilidade para a escolha de opções de reforço da fundação, através de dentes que objetivavam o aumento das condições de estabilidade da barragem.
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Sevieri, Giacomo [Verfasser], Hermann G. [Akademischer Betreuer] Matthies, and Falco Anna [Akademischer Betreuer] De. "The seismic assessment of existing concrete gravity dams : FE model uncertainty quantification and reduction / Giacomo Sevieri ; Hermann G. Matthies, Anna De Falco." Braunschweig : Technische Universität Braunschweig, 2021. http://d-nb.info/1225038251/34.
Full text
26
Divoux, Patrick. "Modélisation du comportement hydro-mécanique des discontinuités dans les structures et les fondations rocheuses : application aux barrages en béton." Université Joseph Fourier (Grenoble ; 1971-2015), 1997. http://www.theses.fr/1997GRE10192.
Full textAbstract:
Les incidents et les accidents survenus a des barrages en beton, ainsi que les resultats d'auscultation, ont montre que leur stabilite depend tres largement du comportement mecanique des zones les plus faibles de l'ensemble vallee-barrage. Localises au niveau des discontinuites dans la structure et dans le rocher, ces points faibles sont principalement les failles des zones d'appui, les reprises de betonnage dans le barrage, le contact beton-rocher au niveau de la fondation et les joints de plots du barrage. Nous avons travaille a la modelisation du comportement de ces zones avec les elements finis particuliers que sont les elements d'interface. Un grande partie de ce rapport est consacree a la connaissance du comportement de ces elements, aux hypotheses emises lors de leur formulation et aux difficultes numeriques associees a la prise en compte de comportements fortement non-lineaires. Le mode de construction, les techniques de clavage et de drainage des barrages en beton en font des ouvrages particuliers dont la modelisation est rendue difficile avec les codes aux elements finis classiques. Le code de calcul gefdyn a ete le support du developpement d'outils et de methodes d'analyse du comportement des barrages en beton et des fondations rocheuses. Appliquees aux barrages de puyvalador et de puylaurent, ces methodes permettent de prendre en compte les principales non-linearites du comportement des ouvrages et de mieux comprendre leur fonctionnement. Ces calculs fournissent des renseignements exploitables sur le plan pratique et sur le plan theorique.
27
Seghir, Abdelghani. "Contribution à la modélisation numérique de la réponse sismique des ouvrages avec interaction sol-structure et interaction fluide-structure : application à l'étude des barrages poids en béton." Phd thesis, Université Paris-Est, 2010. http://tel.archives-ouvertes.fr/tel-00627044.
Full textAbstract:
La modélisation des problèmes d'interactions sol-structure et fluide-structure couvre plusieurs domaines de recherche très actifs qui traitent une multitude d'aspects tels que la géométrie non bornée du sol et dans certains cas du fluide stocké, les effets dissipatifs visqueux et radiatifs, l'application du chargement sismique, le choix des variables de base, les propriétés algébriques des systèmes d'équations résultant du couplage,... etc. Dans le présent travail, différents modèles numériques de couplage sol-structure et fluide-structure ont été examinés. Les limites de troncature géométrique du sol et du fluide on été traitées avec des éléments infinis dont les performances ont été comparées à celles des conditions de radiations. Le problème de vibrations libres couplées des systèmes fluide-structure a été résolu en introduisant de nouvelles techniques de symétrisation efficaces. De plus, une nouvelle formulation symétrique en éléments de frontière a été proposée. Cette formulation permet de produire une matrice symétrique définie positive et aboutit ainsi à un système algébrique similaire à celui qui découle de la discrétisation en éléments finis. La matrice bâtie dite "raideur équivalente" peut facilement être assemblée ou couplée avec les matrices de la formulation en éléments finis. Toutes les applications qui ont servi soit à comparer des modèles soit à valider les programmes développés, ont été effectué es dans le cas des barrages poids en béton. Ce cas constitue un problème de couplage fluide-sol-structure typique
28
El-Aidi, Bahaa. "Nonlinear earthquake response of concrete gravity dam systems." Thesis, 1989. https://thesis.library.caltech.edu/2510/1/El-aidi_b_1989.pdf.
Full textAbstract:
The earthquake response of concrete gravity dam systems is investigated with emphasis on the nonlinear behavior associated with tensile concrete cracking and water cavitation. A single dam-monolith is considered and is assumed to respond independently as a two-dimensional system under plane stress conditions. The two-dimensional assumption is also extended to model the compressible water body impounded upstream of the dam. Standard displacement-based finite element techniques are used to spatially discretize the field equations and produce a single symmetric matrix equation for the dam-water system. Energy dissipation in the reservoir, through radiation in the infinite upstream direction and absorption at the bottom, is approximately accounted for, and a set of numerical examples is presented to demonstrate the accuracy of the present formulation in modeling the linear earthquake response of infinite reservoirs. An approximate procedure to account for dam-foundation interaction is incorporated based on the response of a rigid plate attached to a three-dimensional viscoelastic half-space.
Water cavitation is modeled by a smeared approach which uses a bilinear pressure-strain relation. It is shown that the water response becomes dominated by spurious high frequency oscillations upon closure of cavitated regions, and improved results can be obtained by using some stiffness-proportional damping in the water reservoir. As demonstrated in an example analysis of Pine Flat Dam (linear dam), cavitation occurs in the upper part of the reservoir along the dam face, unlike other investigations which show cavitated regions at considerable distances from the dam, and both the tensile pressure cutoffs and compressive impacts have a minor effect on the dam response.
Tensile cracks are incorporated using the smeared crack approach, and sliding along closed cracks is allowed. Coupling effects inherent in the finite element formulation are explained, and their influence on open and closed cracks is investigated. Propagation of cracks is monitored in an interactive environment which uses an equivalent strength criterion and allows for user input; remeshing is avoided. The algorithm adopted here produces narrow cracks, unlike many other investigations which show large zones of cracking. An extensive numerical study of Pine Flat Dam demonstrates some interesting features of the nonlinear response of the system, identifies potential failure mechanisms, and reveals a number of difficulties that the analysis encounters. Although no instability of the dam occurs, the numerical difficulties will have to be overcome before definite conclusions regarding stability can be made. It is shown that cracking reduces the hydrodynamic pressures in the reservoir and, hence, reduces water cavitation.
29
Sooch, Gurinderbir Singh. "Methodologies for Seismic Assessment of Concrete Gravity Dam-Foundation Systems." Thesis, 2011. http://spectrum.library.concordia.ca/440513/1/Sooch_M.A.Sc_S2012.pdf.
Full textAbstract:
The number and size of hydroelectric dams have increased greatly across the Canadian landscape since 1910. The concrete gravity dams should perform satisfactorily during a seismic event as in case of failure, the release of impounded reservoir water can cause catastrophic damage in the downstream communities. Traditionally the foundation in a dam is modeled by a sub-structuring approach for the purpose of seismic performance analysis. The main disadvantage of sub-structuring approach is that it cannot be used for solving nonlinear dynamic problems. Therefore, in that case seismic response analysis must be carried out in time domain as it allows inclusion of nonlinear behavior in a system. In this study, different earthquake input mechanisms has been studied considering the following models A) massless foundation , B) free-field earthquake input at dam foundation interface and C) deconvolved earthquake input model. Deconvolution is a mathematical process which allows the adjustment of the amplitude and frequency contents of an earthquake ground motion applied at the base of the foundation to achieve the desired output at the dam-foundation interface. It has been observed that the existing procedures of deconvolution are inadequate for the high frequency earthquake records. A Modified deconvolution procedure has been proposed here for efficient deconvolution of high frequency earthquake records.The above discussed input mechanisms are studied in more detail with two different geometrical models. It has been found that model C is the most rational and accurate one compared to the other models.
In the second part of this study elastic and inelastic analysis of dams with different geometries has been performed to study the existing guidelines for the seismic assessment of dams. The performance of the dam models has been assessed using both the high frequency and low frequency earthquake records scaled at 0.35g. Based on the study it can be concluded that the different numerical models induce slight differences in the results relating to the tensile damage in dam foundation system. However, the results are consistent with each other. Also, the results from the linear elastic analysis provided valuable insight about seismic performance of concrete gravity dams but they fail to account for the existing deterioration in the dam.
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陳立洲. "Study on the Gravity Check Dam of Reinforced Concrete Frame Filled with Sediment." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/79772069807375553272.
Full textAbstract:
碩士國立中興大學
水土保持學系
87
To avoid the drawbacks of traditional check dam (i.e., mass usage of concrete, higher cost, and unbalance of heart hydraulic), this study proposed the design of "Gravity Check Dam of Reinforced Concrete Frame Filled with Sediment". This new design combines Counterfort Retaining Wall and reinforced concrete for their benefits of low cost and high tension-resistance. Four sections were included in the research: designs of dam configuration, analysis of stability, flume experiment, and cost analysis. In the flume experiment of "Gravity Check Dam of Reinforced Concrete Frame Filled with Sediment ", the result was concluded by placing the dam model in the flow condition without sedimentation. The dam structure is stable and without movement under the following experimental condition: maximum flow discharge of 0.006 cms, flume slope of 3.55%, and overflow depth of 4.2cm.
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Chen, Ming-Chi, and 陳明吉. "The Optimum Method for Cross Section Design and Structural Analysis of Concrete Gravity Dam." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/03470461095168502284.
Full textAbstract:
碩士國立屏東科技大學
土木工程系碩士班
87
The optimum cross-section design for the non-overflow section of concrete gravity dam with size, stress and system stability constraints is presented. The optimization technique employed is based on the multipliers method. The dimensions of the dam are used as the design variables. The construction cost is used as the objective function. The constraint includes the structural stability conditions. Five typical examples available in the literatures are solved and compared. Based on the results of this study, it is concluded that the optimal design process can give more economic designs compared to the conventional design process. Once the optimal design problem is formulated and complemented into a software, many variations in the problem conditions and parameters can be studied in a relatively short time, which can lead to better designs.
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尤致閔. "The Drainage Hole and Vegetation Vessel in the Gravity Check Dam of Reinforced Concrete Frame with Sediment Backfilled." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/65671669338928429401.
Full textAbstract:
碩士國立中興大學
水土保持學系
90
In this study, experiments focused on the position of drainage holes at the downstream side of gravity check dam of reinforced concrete frame filled with sediment. This study discussed the hydraulic characteristics under the combinations of two types of backfill sediment, four drainage holes with different diameter, and three different water depths. The experiment result indicated that ： a. Experimental findings also discovered that the flow velocity within drainage hole was affected strongly by backfill sediment over than the water depth. b. The diameter of drainage hole was the main factor affecting the flow of drainage hole: larger the diameter the more discharge. c. In similar condition，the velocity of the filled with standard deviation 5.12 sediment is bigger than the standard deviation 9.31 sediment. d. The drainage hole would be arranged higher than the vegetation vessel. Based on the forces and structural analysis of the vegetation vessel ， the thickness of the vegetation vessel was 15 cm； the longitudinal steel bar of the was #4@20cm and the temperature steel bar was #3@20cm(see fig.1).
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Fang, Kuang-Yu, and 方光宇. "The Hydraulic Characteristics of Drainage Holes in the Gravity Check Dam of Reinforced Concrete Frame Filled with Sediment." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/23749976154177949329.
Full textAbstract:
碩士國立中興大學
水土保持學系
89
In this study, experiments focused on the position of drainage holes at the downstream side of gravity check dam of reinforced concrete frame filled with sediment. This study discussed the Hydraulic Characteristics under the combinations of two types of refilled sediment, four drainage holes with different diameter, and three different water depths. The experiment result indicated that the drainage hole would be arranged higher than the plant flume to avoid disturbance on the sand and plant inside flume. Experimental findings also discovered that the flow velocity within drainage hole was affected strongly by refilled sediment over than the water depth. Meanwhile, the diameter of drainage hole was the main factor affecting the flow velocity of drainage hole: larger the diameter the faster velocity.
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Zhu, Xueye. "Seismic behavior of cracked concrete gravity dams." Thesis, 2004. http://spectrum.library.concordia.ca/8004/1/NQ96955.pdf.
Full textAbstract:
Two models are proposed to analyze the seismic behavior of cracked concrete gravity dams in order to assess the safety against sliding and overturning. A proposed rigid model first designed for cracked concrete dams considers the geometry of the cracked dam and includes all possible modes of motion with 3 degrees-of-freedom. The other model proposed is a flexible finite element model, which represents a penalty approach, based on the incremental displacement constraint equations between the nodes on both sides of the crack. All governing equations and corresponding conditions for every mode of motion are derived for the rigid model. Verifications show that this simple rigid model is effective in the prediction of the seismic response of cracked dams. Its applications to the cracked Koyna Dam and a typical dam cracked at the base demonstrate its advantages of simplicity, accuracy and ability to reveal the important features of seismic behavior of cracked concrete dams. The flexible model is verified with available solutions, showing its very good applicability in estimation of the dynamic response of cracked concrete dams, owing to its adequate treatment of contact conditions at the crack. Its applications to Koyna Dam and a typical dam prove its adequacy to the cases of cracks at both the base and at a height. Computations with both proposed models show that the cracked Koyna Dam and the cracked typical dam are safe under the earthquakes considered provided the effective coefficient of friction is sufficient large. However, both models suggest that the rocking mode must be considered since it affects the sliding displacement even if the rocking itself is very small. The partial dam above the crack might experience drifting if severe impact occurs. Therefore even a large coefficient of friction cannot prevent sliding. The residual sliding displacement along the crack for a specific cracked dam depends on factors such as coefficient of friction, water level, peak acceleration of earthquake and its details. The consistency of two proposed models is noted when increasing the stiffness in the flexible model. This suggests that the rigid model is applicable to the case when the upper part of the cracked dam is very stiff, while the flexible model is capable of revealing more details of the seismic behavior of cracked dams.
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Yoneda, William James. "Studies on seismic behavior of concrete gravity dams." Thesis, 2005. http://hdl.handle.net/2429/16918.
Full textAbstract:
This Master's thesis presents three independent studies related to the safety of
concrete gravity dams.
1. Dam-Gate Hydrodynamic Interaction Study
2. Damping Study
3. Shear Key Study
The three studies are self-contained, presented independently in Chapters 2 - 4
of this thesis. Work on this thesis started in winter 2002. The analytical work
was completed in summer 2004. This thesis was written as part of the
Professional Partnership Program with the University of British Columbia and
British Columbia Hydro.
A modal analysis of a 2DOF simplified model representing a portion of an
existing gravity dam structure was performed. The main purposes of this study
were to evaluate the effect of dam-gate interaction on the hydrodynamic loads
and to evaluate the effect of varying the natural frequency of the gate. It was
found that the modal interaction between the dam and gate structures caused
variation in the hydrodynamic loads acting on the gate and upstream face of the
dam. One of the recommendations for retrofitting the gates is to decrease the
natural frequency of the gate to below the natural frequency of the dam. This
essentially increases the flexibility of the gate system and reduces the amount of
hydrodynamic loads generated on the gate and upstream surface of the dam.
An analytical study to test the Half-Power Bandwidth method of estimating
damping in concrete gravity dams was performed successfully. The objectives of
this study were to test this method of evaluating structural damping and to
recommend a reasonable estimate of structural damping in concrete gravity
dams. The damping values computed by this method were found to be much
lower than expected (less than 2%) and therefore, unrepresentative of the
damping that is likely believed to be present in the concrete gravity dams
analyzed in this study (approximately 5 - 10%).
An exploratory study involving the finite-element modeling of a shear key system
was performed. The stress patterns that developed in the finite element model
under applied horizontal load were similar to those exhibited in the early stages
of the cracking sequence presented by Bakhoum (1991). In order to model the
later stages of the cracking sequence, it would be necessary to implement nonlinear
material models that are capable of modeling loading beyond the linear
range to failure.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Pereira, Renato Miguel Rodrigues. "Probabilistic-based structural safety analysis of concrete gravity dams." Doctoral thesis, 2019. http://hdl.handle.net/10362/76842.
Full textAbstract:
The construction and operation of dams, associated with the use of water resources,
aims generically at water supplying, the energy producing and, in many cases, flow regulating
and flood controlling.
Considering the dam dimensions and the potential risks associated with its structural
failure, due to the occupation of the downstream valley, and to the costs of the construction,
maintenance and rehabilitation, the use of probabilistic principles in its design, as it is
already performed for other type of structures, is justified considering adequate levels of
safety.
The objections shared throughout the dam engineering community, regarding the
difficulty in estimating the probability of failure for concrete dams, are expectedly overcome
by the failure mode and uncertainty modeling, allowing the application of probabilistic
principles for their safety analysis, based on conservative simplifications regarding the
structural behavior, namely: (i) the definition of the failure surface (dam-foundation
interface); (ii) the consideration of rigid body failure mechanisms; and (iii) the consideration
of the residual shear strength, given only by the frictional component, corresponding to a
limit analysis valid for ultimate limit states.
For that purpose, the failure modes are derived from the current construction and design
practice by comparing analytical and numerical models of a generic, though representative,
case study. The uncertainties involved in the safety of concrete dams are statistically
quantified, through the definition of probabilistic distributions for loads and material
properties, using, in addition to the elements found in the literature, the information
available at LNEC about those features, resulting from the monitoring of the concrete
dam behavior during the construction, first filling and operation periods.
This work explores the required tasks for the adoption of the partial safety factor method for the safety analysis of concrete gravity dams, at the design phase. Two representative
studies regarding the reliability-based design of concrete gravity dams and
partial safety factor calibration are presented, intending to stimulate the discussion on
the applicability of probabilistic principles for the design of concrete dams, as well as,
to influence the safety criteria to be considered in a future revision of the dam safety
regulation.
The obtained results confirm that the seismic load combination and the sliding failure
modes are the most conditioning situations. It is also observed that cross-sections profiles
flatter than currently used may be needed for high intensity seismic zones. Partial safety
factors that approximate reasonably the reliability-based results could be derived.
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Donlon, William Patrick Jr. "Experimental investigation of the nonlinear seismic response of concrete gravity dams." Thesis, 1989. https://thesis.library.caltech.edu/1982/1/Donlon_wp_1989.pdf.
Full textAbstract:
The nonlinear seismic response of concrete gravity dams is investigated experimentally through the use of small-scale models. Of primary interest is crack formation, crack opening and closing, and sliding along crack planes. Also of concern is the stability of the structure after cracking. Three small-scale models (length scale = 115) of a single monolith of Pine Flat Dam are tested to determine the extent of such behavior and its effect on structural stability. The models are constructed of one polymer-based and two plaster-based materials developed for these experiments. The plaster-based materials fulfill the strength, stiffness, and density requirements established by the laws of similitude, while the polymer-based material fulfills only the stiffness and density requirements and is used only in the lower part of the dam where cracking is not expected. The excitation is a modified version of the N00E component of the 1940 Imperial Valley earthquake, applied to each model's base in the stream direction through a vibration table with high-frequency capability. Tests are performed with and without water in the reservoir. The response of each earthquake test is presented in the form of acceleration and displacement time histories, Fourier spectra, and frames taken from high-speed films of the model's response. The results of the experiments indicate that the neck region of a concrete gravity dam is most susceptible to cracking, although crack profiles can differ as a result of variations in excitation, material properties, and construction techniques. These results also indicate alternate design techniques which could improve the seismic stability of a cracked gravity dam.
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Batta, Vinod. "Two-dimensional boundary element analysis of seismic cracking in concrete gravity dams." Thesis, 1995. http://spectrum.library.concordia.ca/5475/1/NN01273.pdf.
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Horyna, Tomáš. "Reliability analysis of base sliding of concrete gravity dams subjected to earthquakes." Thesis, 1999. http://hdl.handle.net/2429/9991.
Full textAbstract:
Concrete gravity dams are typically constructed in blocks separated by vertical contraction
joints. The design of straight concrete gravity dams is traditionally performed by assuming each
block to be independent, except for gravity dams in valleys with relatively small width to height
ratios. Understanding the 2-D behaviour of individual monoliths is thus considered relevant and
2-D models are usually employed in safety evaluations of existing dams.
During a strong seismic event, low to medium height concrete gravity dams tend to crack at the
base as opposed to tall dams, which attract high stresses and cracking at the level of a slope
change on the downstream side of a dam. The state-of-the-practice in the seismic evaluation of
concrete gravity dams requires that the failure mode of the dam monolith sliding at its base be
considered.
This study focused on the post-crack dynamic response of existing concrete gravity dams in
order to investigate their safety against sliding considering non-linear effects in the damfoundation
interface. Sliding response of a single monolith of a low to medium height concrete
gravity dam at the failure state was studied and, therefore, the monolith separated or unbonded
from its foundation was considered. The work included experimental, analytical and reliability
studies.
During the experimental study, a model of an unbonded concrete gravity dam monolith was
developed and tested using a shake table. The model, preloaded by a simulated hydrostatic
force, was subjected to a selected variety of base excitations. Other effects, such as
hydrodynamic and uplift pressures were not considered in the experiments. A strong influence
of amplitude and frequency of the base motions on the sliding response of the model was
observed during the tests.
Simple and more detailed numerical models to simulate the experiments were developed during
the analytical study. It was observed that a simple rigid model could simulate acceptably the
tests only in a limited range of excitation frequencies. A finite element (FE) model simulated
the experiments satisfactorily over a wider range of dominant frequencies of the base
accelerations.
The numerical models were used to simulate the seismic response of a 45 m high monolith of
a concrete gravity dam subjected to three different earthquake excitations for varying
reservoir's water level. The agreement between the results using the simple rigid and the FE
models was found acceptable.
The results of the numerical simulations were used in a reliability analysis to calculate
probabilities of failure of the 45 m high monolith. Probability of failure was defined here as an
annual chance of exceeding an allowable amount of the monolith's base sliding during an
earthquake. The peak ground acceleration (PGA), the characteristics of the time history, and the
reservoir's water level were considered as random parameters during this study. Using the FE
model, the annual probabilities of failure ranged from 1. 1E-8 for the mean PGA of 0.2g and 20
cm of allowable sliding to 1.3E-3 for the mean PGA of 0.6g and 1 cm of allowable sliding. The
probabilities of failure using the simple rigid model were found close to those using the FE
model. It was concluded that the computationally less demanding simple rigid model may be
adequately used in reliability calculations of low to medium height concrete gravity dam safety
against base sliding.