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.

A smeared crack model for seismic failure analysis of concrete gravity dams considering fracture energy effects

Hariri-Ardebili, Mohammad Amin,Seyed-Kolbadi, Seyed Mahdi,Mirzabozorg, Hasan Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.1

In the present paper, a coaxial rotating smeared crack model is proposed for mass concrete in three-dimensional space. The model is capable of applying both the constant and variable shear transfer coefficients in the cracking process. The model considers an advanced yield function for concrete failure under both static and dynamic loadings and calculates cracking or crushing of concrete taking into account the fracture energy effects. The model was utilized on Koyna Dam using finite element technique. Dam-water and dam-foundation interactions were considered in dynamic analysis. The behavior of dam was studied for different shear transfer coefficients considering/neglecting fracture energy effects. The results were extracted at crest displacement and crack profile within the dam body. The results show the importance of both shear transfer coefficient and the fracture energy in seismic analysis of concrete dams under high hydrostatic pressure.

A smeared crack model for seismic failure analysis of concrete gravity dams considering fracture energy effects

Mohammad Amin Hariri-Ardebili,Seyed Mahdi Seyed-Kolbadi,Hasan Mirzabozorg 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.1

In the present paper, a coaxial rotating smeared crack model is proposed for mass concrete in three-dimensional space. The model is capable of applying both the constant and variable shear transfer coefficients in the cracking process. The model considers an advanced yield function for concrete failure under both static and dynamic loadings and calculates cracking or crushing of concrete taking into account the fracture energy effects. The model was utilized on Koyna Dam using finite element technique. Damwater and dam-foundation interactions were considered in dynamic analysis. The behavior of dam was studied for different shear transfer coefficients considering/neglecting fracture energy effects. The results were extracted at crest displacement and crack profile within the dam body. The results show the importance of both shear transfer coefficient and the fracture energy in seismic analysis of concrete dams under high hydrostatic pressure.

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.

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.

Force density ratios of flexible borders to membrane in tension fabric structures

Asadi, H.,Hariri-Ardebili, M.A.,Mirtaheri, M.,Zandi, A.P. Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.6

Architectural fabrics membranes have not only the structural performance but also act as an efficient cladding to cover large areas. Because of the direct relationship between form and force distribution in tension membrane structures, form-finding procedure is an important issue. Ideally, once the optimal form is found, a uniform pre-stressing is applied to the fabric which takes the form of a minimal surface. The force density method is one of the most efficient computational form-finding techniques to solve the initial equilibrium equations. In this method, the force density ratios of the borders to the membrane is the main parameter for shape-finding. In fact, the shape is evolved and improved with the help of the stress state that is combined with the desired boundary conditions. This paper is evaluated the optimum amount of this ratio considering the curvature of the flexible boarders for structural configurations, i.e., hypar and conic membranes. Results of this study can be used (in the absence of the guidelines) for the fast and optimal design of fabric structures.

Force density ratios of flexible borders to membrane in tension fabric structures

H. Asadi,M. A. Hariri-Ardebili,M. Mirtaheri,A. P. Zandi 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.6

Architectural fabrics membranes have not only the structural performance but also act as an efficient cladding to cover large areas. Because of the direct relationship between form and force distribution in tension membrane structures, form-finding procedure is an important issue. Ideally, once the optimal form is found, a uniform pre-stressing is applied to the fabric which takes the form of a minimal surface. The force density method is one of the most efficient computational form-finding techniques to solve the initial equilibrium equations. In this method, the force density ratios of the borders to the membrane is the main parameter for shape-finding. In fact, the shape is evolved and improved with the help of the stress state that is combined with the desired boundary conditions. This paper is evaluated the optimum amount of this ratio considering the curvature of the flexible boarders for structural configurations, i.e., hypar and conic membranes. Results of this study can be used (in the absence of the guidelines) for the fast and optimal design of fabric structures.

Seismic mitigation of substation cable connected equipment using friction pendulum systems

Reza Karami Mohammadi,Masoud Mirtaheri,Mojtaba Salkhordeh,Erfan Mosaffa,Golsa Mahdavi,Mohammad Amin Hariri-Ardebili 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.6

Power transmission substations are susceptible to potential damage under seismic excitations. Two of the major seismic failure modes in substation supplies are: the breakage of brittle insulator, and conductor end fittings. This paper presents efficient isolation strategies for seismically strengthening of a two-item set of equipment including capacitive voltage transformer (CVT) adjacent to a Lightning Arrester (LA). Two different strategies are proposed, Case A: implementation of base isolation at the base of the CVT, while the LA is kept fixed-base, and Case B: implementation of base isolation at the base of the LA, while the CVT is kept fixed-base. Both CVT and LA are connected to each other using a cable during the dynamic excitation. The probabilistic seismic behavior is measured by Incremental Dynamic Analysis (IDA), and a series of appropriate damage states are proposed. Finally, the fragility curves are derived for both the systems. It is found that Friction Pendulum System (FPS) isolator has the potential of decreasing flexural stresses caused by intense ground motions. The research has shown that when the FPS is placed under LA, i.e. Case B (as oppose to Case A), the efficiency of the system is improved in terms of reducing the forces and stresses at the bottom of the porcelain. Several parametric studies are also performed to determine the optimum physical properties of the FPS.