Seismic behavior of three dimensional concrete rectangular containers including sloshing effects

Mirzabozorg, H.,Hariri-Ardebili, M.A.,Nateghi A., R. Techno-Press 2012 Coupled systems mechanics Vol.1 No.1

In the present paper, the three-dimensional model of a typical rectangular concrete tank is excited using an artificial and a natural three components earthquake ground motion and the staggered displacement method is utilized for solving the coupled problem of the tank-contained liquid system in time domain. In the proposed method, surface sloshing of the liquid is taken into account in addition to the impulsive term and the appropriate damping values are applied on both of them. The resulted responses are compared with those obtained from the ABAQUS finite element software. It is found that the convective term affects responses extensively and must be considered in seismic design/safety assessment of storage tanks. In addition, the utilized method for solving the coupled problem is stable during the conducted general dynamic analyses and is able to capture the expected phenomena.

The reason of cracking in bottom gallery of SefidRud Buttress Dam and earthquake and post earthquake performance

Mirzabozorg, Hasan,Ghaemian, Mohsen,Roohezamin, Amirhossein Techno-Press 2019 Structural monitoring and maintenance Vol.6 No.2

Present study concerns the safety evaluation of SefidRud dam's block No. 18 regarding probable crack propagation in the foundation gallery under a MCE record. Accordingly, a 3D finite element model of the block in companion with the reservoir and the foundation is modeled. All the associated thermal and structural parameters are derived via calibration with the records of thermometers and pendulums installed inside the dam body. The origination of the cracks and their whereabouts are determined by primary thermal and static analyses and through a linear dynamic analysis the potential failure zone and their extent and level are studied. The foundation gallery is the most probable zone among the other intensive tensile stress area to compromise the dam stability. Therefore, the nonlinear analysis of this risky region is inevitable. The results depict the permissible expansion of the cracks inside the gallery even under another future earthquake in MCE level. As a consequence, the general dam performance is assessed safe in spite of the seepage flow rate growth from the gallery fractures.

Nonlinear behavior of concrete gravity dams and effect of input spatially variation

Mirzabozorg, H.,Kianoush, R.,Varmazyari, M. Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.3

In the present article, effect of non-uniform excitation due to spatially variation of seismic input on nonlinear response of concrete gravity dams is considered. The reservoir is assumed compressible. Isotropic damage mechanics approach is used to model static and dynamic nonlinear behavior of mass concrete in 2D space. The validity of utilized nonlinear model is considered using available theoretical results under static and dynamic conditions. The tallest monolith of Pine Flat dam is selected as a case study. Two cases are analyzed for considering the effect of limited wave propagation velocity on seismic behavior of the dam-reservoir system in which travelling velocities are chosen as 2000 m/s and infinity. It is found that tensile damage in neck and toe regions and also, in the vicinity of the base increase when the system is excited non-uniformly.

Damage mechanics approach and modeling nonuniform cracking within finite elements for safety evaluation of concrete dams in 3D space

Mirzabozorg, H.,Kianoush, R.,Jalalzadeh, B. Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.1

An anisotropic damage mechanics approach is introduced which models the static and dynamic behavior of mass concrete in 3D space. The introduced numerical approach is able to model non-uniform cracking within the cracked element due to cracking in Gaussian points of elements. The validity of the proposed model is considered using available experimental and theoretical results under the static and dynamic loads. No instability and stress locking is observed in the conducted analyses. The Morrow Point dam is analyzed including dam-reservoir interaction effects to consider the nonlinear seismic behavior of the dam. It is found that the resulting crack profiles are in good agreement with those obtained from the smeared crack approach. It is concluded that the proposed model can be used in nonlinear static and dynamic analysis of concrete dams in 3D space and enables engineers to define the damage level of these infrastructures. The performance level of the considered system is used to assess the static and seismic safety using the defined performance based criteria.

Nonlinear behavior of concrete gravity dams and effect of input spatially variation

H. Mirzabozorg,R. Kianoush,M. Varmazyari 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.3

In the present article, effect of non-uniform excitation due to spatially variation of seismic input on nonlinear response of concrete gravity dams is considered. The reservoir is assumed compressible. Isotropic damage mechanics approach is used to model static and dynamic nonlinear behavior of mass concrete in 2D space. The validity of utilized nonlinear model is considered using available theoretical results under static and dynamic conditions. The tallest monolith of Pine Flat dam is selected as a case study. Two cases are analyzed for considering the effect of limited wave propagation velocity on seismic behavior of the dam-reservoir system in which travelling velocities are chosen as 2000 m/s and infinity. It is found that tensile damage in neck and toe regions and also, in the vicinity of the base increase when the system is excited non-uniformly.

Damage mechanics approach and modeling nonuniform cracking within finite elements for safety evaluation of concrete dams in 3D space

H. Mirzabozorg,R. Kianoush,B. Jalalzadeh 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.1

An anisotropic damage mechanics approach is introduced which models the static and dynamic behavior of mass concrete in 3D space. The introduced numerical approach is able to model non-uniform cracking within the cracked element due to cracking in Gaussian points of elements. The validity of the proposed model is considered using available experimental and theoretical results under the static and dynamic loads. No instability and stress locking is observed in the conducted analyses. The Morrow Point dam is analyzed including dam-reservoir interaction effects to consider the nonlinear seismic behavior of the dam. It is found that the resulting crack profiles are in good agreement with those obtained from the smeared crack approach. It is concluded that the proposed model can be used in nonlinear static and dynamic analysis of concrete dams in 3D space and enables engineers to define the damage level of these infrastructures. The performance level of the considered system is used to assess the static and seismic safety using the defined performance based criteria.

Strain-based seismic failure evaluation of coupled dam-reservoir-foundation system

Hariri-Ardebili, M.A.,Mirzabozorg, H.,Ghasemi, A. Techno-Press 2013 Coupled systems mechanics Vol.2 No.1

Generally, mass concrete structural behavior is governed by the strain components. However, relevant guidelines in dam engineering evaluate the structural behavior of concrete dams using stress-based criteria. In the present study, strain-based criteria are proposed for the first time in a professional manner and their applicability in seismic failure evaluation of an arch dam are investigated. Numerical model of the dam is provided using NSAD-DRI finite element code and the foundation is modeled to be massed using infinite elements at its far-end boundaries. The coupled dam-reservoir-foundation system is solved in Lagrangian-Eulerian domain using Newmark-${\beta}$ time integration method. Seismic performance of the dam is investigated using parameters such as the demand-capacity ratio, the cumulative inelastic duration and the extension of the overstressed/overstrained areas. Real crack profile of the dam based on the damage mechanics approach is compared with those obtained from stress-based and strain-based approaches. It is found that using stress-based criteria leads to conservative results for arch action while seismic safety evaluation using the proposed strain-based criteria leads to conservative cantilever action.

Extensometers results correction in concrete dams: A case study in RCC Zhaveh Dam

Ziaei, Ahad,Ahangari, Kaveh,Moarefvand, Parviz,Mirzabozorg, Hasan Techno-Press 2017 Structural monitoring and maintenance Vol.4 No.1

Since extensometers are used to determine the absolute deformation of foundation and abutments and all results are obtained in reference to the base rod, the accuracy of these results has been constantly a subject of debate. In this regard, locating and installing extensometers outside the range of effect zone is also another challenge. The main purpose of this paper is to investigate and modify extensometers results based on the mentioned issues. For this aim, the concrete RCC Zhaveh dam in Iran was selected as the case study. To study the results of extensometers installed in this dam, first, the 3DEC_DP 5.00 software was applied for numerical modeling. Parameters such as discontinuities, dead load and piezometric pressure in the interface of concrete and rock were considered. Next, using the results obtained from 6 extensometers in foundation and abutments and 4 clinometers in dam body, the numerical model was calibrated through back analysis method. The results indicate that the base rod is moved and is not recommended being used as the base point. In other words, because installation of base anchor outside the range of effect zone is not possible due to the operational and economic considerations, the obtained results are not accurate enough. The results indicate a considerable 2-3 mm displacement of the base rod (location of the base anchor) in reference to the real zero point location, which must be added to the base rod results.

Estimation of Probable Damages in Arch Dams Subjected to Strong Ground Motions using Endurance Time Acceleration Functions

M. A. Hariri-Ardebili,H. Mirzabozorg 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.2

In the present paper, nonlinear behavior of mass concrete using the smeared crack approach is combined with the Endurance TimeAnalysis (ETA) method for estimation of probable damages in arch dams when they are subjected to strong ground motions. ETAmethod is a time-history based dynamic pushover procedure for seismic analysis of structures in which they are subjected to a set ofintensifying artificial ground motions called Endurance Time Acceleration Functions (ETAFs). Numerical model of an arch damreservoir-foundation system was excited in maximum credible level using real ground motions and equivalent ETAFs. Cracked areaswithin the dam body are selected to compare ETA results with conventional nonlinear time-history analysis. Results show acceptableconsistency between two methods while using ETA method reduces the total cost of analysis considerably. In addition, continuumseismic performance of dam was evaluated when it’s subjected to ETAFs.

Coupled arch dam-reservoir-massed foundation problem under different earthquake input mechanisms

Varmazyari, M.,Sabbagh-Yazdi, S.R.,Mirzabozorg, H. Techno-Press 2021 Coupled systems mechanics Vol.10 No.5

The aim of the present study is to investigate a coupled arch dam-reservoir-massed foundation problem under two earthquake input mechanisms. The problem nonlinearity originates from opening/slipping of the vertical contraction joints of the dam body. The reservoir-structure interaction is taken into account assuming compressible reservoir. Also, the meshing approach (structured mesh vs. unstructured one) in the foundation medium is investigated. The Karoun-I double curvature arch dam is selected as a case study. Three components of the 1994 Northridge earthquake are selected as the free-field ground motion. A deconvolution analysis in 3D space is conducted to adjust the amplitude and frequency contents of the earthquake ground motion applied to the bottom of the massed foundation to determine the desired acceleration response at various points on the dam-foundation interface taking into account the coupling between the foundation and the structure. It is found that in the deconvolved earthquake input models, the maximum tensile and the compressive stresses increase by 19% and 12%, respectively in comparison with those of the free-field input models. In addition, modeling foundation using the unstructured mesh decreases the maximum compressive stresses within the dam body by about 20% in comparison with that obtained using the structured mesh model. In the same way, the maximum crest displacements in the horizontal direction decreases by about 30%.