SENSITIVITY OF DYNAMIC BEHAVIOUR OF THE FE MODEL: CASE STUDY FOR THE IGNALINA NPP REACTOR BUILDING

2008 ◽  
Vol 14 (2) ◽  
pp. 121-129 ◽  
Author(s):  
Romualdas Baušys ◽  
Gintautas Dundulis ◽  
Rimantas Kačianauskas ◽  
Darius Markauskas ◽  
Sigitas Rimkevičius ◽  
...  
Keyword(s):  
Dynamic Behaviour ◽  
Free Field ◽  
Response Spectra ◽  
Element Model ◽  
Sensitivity Study ◽  
Fe Model ◽  
Model Case ◽  
Global Dynamic ◽  
Wall Stiffness ◽  
Reactor Building

The 3D thin‐walled finite element model of Ignalina NPP Unit 2 reactor building was developed aimed at the evaluation of the global dynamic behaviour with a focus on the seismic response. The model comprises description of the monolithic structures, while prefabricated frame structures are ignored and replaced by external masses. Sensitivity study of the selected dynamic characteristics of the model with respect to data uncertainties is considered. Uncertainty of the model is considered in terms of masses of removed structures and wall stiffness. Seismic input is represented by the site specific free‐field ground response acceleration spectra. The sensitivity study concerns variations of frequencies and acceleration of in‐structure horizontal response spectra at specified points. Maximal bending moments are also considered. It was obtained that the reactor level is not sensitive to the uncertainties considered, while discernable sensitivity was detected at the top level of the structure. Santrauka Pateikta Ignalinos atominės elektrinės pastato erdvinio baigtinių elementų dinaminio modelio kūrimo koncepcija, išnagrinėtas šio modelio jautrumas keičiamoms masėms ir sienų standumui. Parodyta, kaip šie keičiami dydžiai turi įtaką dažniams, horizontaliems tam tikrų nagrinėjamų taškų atsako spektrams, lenkimo momentų persiskirstymui ir jų didžiui.

Detailed Finite Element Modeling of US EPR™ Nuclear Island for Seismic SSI Analysis

2010 ◽  
Author(s):  
Mansour Tabatabaie ◽  
Basilio Sumodobila ◽  
Calvin Wong ◽  
Daniel E. Fisher ◽  
J. Todd Oswald
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Response Spectra ◽  
Element Model ◽  
Lumped Mass ◽  
Standard Design ◽  
The Us ◽  
Reactor Building ◽  
Fixed Base ◽  
Stick Model

The US EPR™ standard design currently under development by AREVA consists primarily of a nuclear island (NI) and several other significant structures outside of and in close proximity to the NI. The NI structures consist of the Reactor Building (RB), Fuel Building (FB), Safeguard Building 1 (SB1), Safeguard Building 2/3 (SB2/3), Safeguard Building 4 (SB4), and Reactor Building Internal Structures (RBIS) — all of which share a common foundation basemat. The Nuclear Island is embedded approximately 11.6 m below the ground surface. Seismic soil-structure interaction (SSI) analysis of nuclear power plants is often performed in the frequency domain using a lumped-mass stick and/or coarse finite element model of the structure. These models are designed to capture the global dynamic response of the system, the results of which provide the inertia forces that are used for foundation stability assessment as well as input to a static detailed finite element model of the structure for design. The in-structure response spectra is calculated from a separate dynamic analysis of detailed structural model on fixed base excited by the base motion developed from the SSI analysis or often by including single-degree-of-freedom (SDOF) oscillators representing the local response in the stick/coarse finite element SSI models. With recent advances in computer software and hardware technologies, it is now possible to perform SSI analysis of detailed structural models in the frequency domain. This paper presents the results of the seismic SSI analysis of the US EPR™ nuclear island using both a stick and detailed finite element representation of the structure. The soil profile corresponds to a medium stiff soil case used for the standard design. Because the EPR™ nuclear island is a complex, unsymmetric structure, the stick model consists of multiple interconnected sticks developed and calibrated against a detailed finite element model of the structure on a fixed base. Both models are analyzed using SASSI [1]. The results of the detailed finite element model in terms of maximum accelerations and response spectra, as well as total interstory forces and moments, are calculated and compared with those of the lumped-mass stick model.

Floor Response Spectra of Loviisa NPP Reactor Buildings

2010 ◽  
Author(s):  
Jukka Ka¨hko¨nen ◽  
Pentti Varpasuo
Keyword(s):  
Material Properties ◽  
Nuclear Power ◽  
Ground Motions ◽  
Response Spectra ◽  
Primary Circuit ◽  
Fe Model ◽  
Floor Response Spectra ◽  
Modal Damping ◽  
Reactor Building ◽  
Circuit Components

For the updated seismic probabilistic risk assessment of the Loviisa nuclear power plant in Finland, knowledge of reactor building floor response spectra were needed. For this purpose a large finite element (FE) model of the reactor building was constructed. The model included all the major primary circuit components. The FE -model was parameterized and the Latin hypercube method was utilized to construct sixty samples of reactor building. Parameters used were material properties for concrete and steel, modal damping and the ground motion. The ground motions were derived from the seismic studies conducted for the Loviisa site. Following results were achieved in this analysis: The probabilistic spectra were determined for different elevations in the reactor building as well as for the representative locations in the main mechanical components that were explicitly modeled.

scholarly journals Alternative scheme for frequency response function measurement of experimental-analytical dynamic substructuring

2019 ◽  
Vol 13 (2) ◽  
pp. 4946-4957
Author(s):  
W. I. I. Wan Iskandar Mirza ◽  
M. N. Abdul Rani ◽  
M. A. Yunus ◽  
R. Omar ◽  
M. S. Mohd Zin
Keyword(s):  
Dynamic Behaviour ◽  
Synthesis Method ◽  
Element Model ◽  
Impact Testing ◽  
Fe Model ◽  
Function Measurement ◽  
Alternative Scheme ◽  
Dynamic Substructuring ◽  
3D Elements ◽  
Analytical Dynamic

The accuracy of the predicted dynamic behaviour of an assembled structure using the frequency based substructuring (FBS) method is often found to be diverged from the experimental counterparts. The divergence which has become the paramount concern and major issue for   structural dynamicists is because of the unreliable experimental FRF data of the interfaces of substructures, arising from the limited resources of appropriate excitation points and accelerometer attachments in the vicinity of the interfaces. This paper presents an alternative scheme for FRF measurement of the experimental FRF data of substructures. In this study, an assembled structure consisting of two substructures were used, namely substructure A (Finite element model) and substructure B (Experimental model). The FE model of substructure A was constructed by using 3D elements and the FRFs were derived via the FRF synthesis method. Specially customised bolts were used to allow the attachment of accelerometers and excitation to be made at the interfaces of substructure B, and the FRFs were measured by using impact testing. Both substructures A and B were then coupled by using the FBS method and the coupled FRF was validated with the measured FRF counterparts. This work revealed that the proposed scheme with specially customized bolts has led to a significant enhancement and improvement in the FBS predicted results.  

Generation of In-Structure Response Spectra Considering Secondary System Mass Interaction

2003 ◽  
Author(s):  
Thomas Ma ◽  
Quazi Hossain ◽  
Farhang Ostadan
Keyword(s):  
Finite Element ◽  
Response Spectra ◽  
Element Model ◽  
Analytical Models ◽  
Secondary System ◽  
Model Case ◽  
Floor Slab ◽  
Vertical Stiffness ◽  
Structure Response ◽  
Heavy Equipment

With the advancement in computer capabilities, seismic soil-structure interaction (SSI) models of nuclear facility structures are no longer limited to few lumped masses on beam stick elements. Nowadays, more rigorous finite element models (FEMs) are often used for SSI analyses to predict the response of the structure as well as to develop in-structure response spectra for seismic qualification of equipment. However, in these models, it is not practical to accurately and explicitly represent the floor slabs that are often of composite design and has openings, because such a representation would require a large number of elements. For this reason, the SSI global models typically do not include such level of detail to accurately represent the vertical stiffness of the slabs, and vertical in-structure response spectra are often developed using a floor slab and equipment representation that essentially ignores the interaction between the equipment and the slab. For heavy equipment, this may result in an excessively conservative design. Thus, there is a need for a practical approach to develop vertical in-structure response spectra that would include the beneficial effects of interaction between the equipment and the floor slab. Such an approach can be especially effective for a facility with a large number of floor-mounted heavy equipment that require seismic qualification. One such approach has been proposed and studied here by applying it on a hypothetical, but a realistic structure. In this study, the vertical in-structure response spectra for floor-mounted equipment were generated using a new pseudo-substructure method without increasing the size of the finite element model of the primary structure and avoiding numerous secondary analyses of subsystems. To evaluate the effectiveness of this new method, vertical in-structure response spectra (IRS) were generated using three SSI analytical models: (i) the Accurate Model (Case I) that explicitly represents the equipment mass, the vertical flexibility of the equipment, and the vertical flexibility of the floor slab; (ii) the Conventional Model (Case II) that ignores the interaction between the equipment and the floor slab; and (iii) the New Model (Case III) that is capable of capturing most of the effects of the interaction between the equipment and the floor slab, but without additional elements representing the floor slab. In this paper, a description of the three models, the analytical approach, and a comparison of the response motions generated by the three models are presented and discussed.

Representation of bolted joints in a structure using finite element modelling and model updating

2020 ◽  
Vol 14 (3) ◽  
pp. 7141-7151 ◽  
Author(s):  
R. Omar ◽  
M. N. Abdul Rani ◽  
M. A. Yunus
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Model Updating ◽  
Complex Structure ◽  
Bolted Joints ◽  
Model Parameters ◽  
Fe Model ◽  
Bolted Joint ◽  
Fe Modelling ◽  
Joint Structure

Efficient and accurate finite element (FE) modelling of bolted joints is essential for increasing confidence in the investigation of structural vibrations. However, modelling of bolted joints for the investigation is often found to be very challenging. This paper proposes an appropriate FE representation of bolted joints for the prediction of the dynamic behaviour of a bolted joint structure. Two different FE models of the bolted joint structure with two different FE element connectors, which are CBEAM and CBUSH, representing the bolted joints are developed. Modal updating is used to correlate the two FE models with the experimental model. The dynamic behaviour of the two FE models is compared with experimental modal analysis to evaluate and determine the most appropriate FE model of the bolted joint structure. The comparison reveals that the CBUSH element connectors based FE model has a greater capability in representing the bolted joints with 86 percent accuracy and greater efficiency in updating the model parameters. The proposed modelling technique will be useful in the modelling of a complex structure with a large number of bolted joints.

Finite Element Analysis of the Distributed Vibration Absorbers for Structural Noise Control

2005 ◽  
Author(s):  
Ashwini Gautam ◽  
Chris Fuller ◽  
James Carneal
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Base Plate ◽  
Element Model ◽  
Fe Model ◽  
Vibration Absorbers ◽  
Element Analysis ◽  
Poroelastic Media ◽  
Hexahedral Elements ◽  
Component Models

This work presents an extensive analysis of the properties of distributed vibration absorbers (DVAs) and their effectiveness in controlling the sound radiation from the base structure. The DVA acts as a distributed mass absorber consisting of a thin metal sheet covering a layer of acoustic foam (porous media) that behaves like a distributed spring-mass-damper system. To assess the effectiveness of these DVAs in controlling the vibration of the base structures (plate) a detailed finite elements model has been developed for the DVA and base plate structure. The foam was modeled as a poroelastic media using 8 node hexahedral elements. The structural (plate) domain was modeled using 16 degree of freedom plate elements. Each of the finite element models have been validated by comparing the numerical results with the available analytical and experimental results. These component models were combined to model the DVA. Preliminary experiments conducted on the DVAs have shown an excellent agreement between the results obtained from the numerical model of the DVA and from the experiments. The component models and the DVA model were then combined into a larger FE model comprised of a base plate with the DVA treatment on its surface. The results from the simulation of this numerical model have shown that there has been a significant reduction in the vibration levels of the base plate due to DVA treatment on it. It has been shown from this work that the inclusion of the DVAs on the base plate reduces their vibration response and therefore the radiated noise. Moreover, the detailed development of the finite element model for the foam has provided us with the capability to analyze the physics behind the behavior of the distributed vibration absorbers (DVAs) and to develop more optimized designs for the same.

scholarly journals Bond Behaviour of Near-Surface Mounted Strips in RC Beams—Experimental Investigation and Numerical Simulations

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4362
Author(s):  
Renata Kotynia ◽  
Hussien Abdel Baky ◽  
Kenneth W. Neale
Keyword(s):  
Concrete Strength ◽  
Element Model ◽  
Steel Reinforcement ◽  
Reinforcement Ratio ◽  
Experimental Program ◽  
Fe Model ◽  
Bond Behaviour ◽  
Near Surface ◽  
Cfrp Laminates ◽  
Near Surface Mounted

This paper presents an investigation of the bond mechanism between carbon fibre reinforced polymer (CFRP) laminates, concrete and steel in the near-surface mounted (NSM) CFRP-strengthened reinforced concrete (RC) beam-bond tests. The experimental program consisting of thirty modified concrete beams flexurally strengthened with NSM CFRP strips was published in. The effects of five parameters and their interactions on the ultimate load carrying capacities and the associated bond mechanisms of the beams are investigated in this paper with consideration of the following investigated parameters: beam span, beam depth, longitudinal tensile steel reinforcement ratio, the bond length of the CFRP strips and compressive concrete strength. The longitudinal steel reinforcement was cut at the beam mid-span in four beams to investigate a better assessment of the influence of the steel reinforcement ratio on the bond behaviour of CFRP to concrete bond behaviour. The numerical analysis implemented in this paper is based on a nonlinear micromechanical finite element model (FEM) that was used for investigation of the flexural behaviour of NSM CFRP-strengthened members. The 3D model based on advanced CFRP to concrete bond responses was introduced to modelling of tested specimens. The FEM procedure presents the orthotropic behaviour of the CFRP strips and the bond response between the CFRP and concrete. Comparison of the experimental and numerical results revealed an excellent agreement that confirms the suitability of the proposed FE model.

Finite Element Model of Human Cochlea Considering of the Helicotrema Size

2013 ◽  
Vol 456 ◽  
pp. 576-581 ◽  
Author(s):  
Li Fu Xu ◽  
Na Ta ◽  
Zhu Shi Rao ◽  
Jia Bin Tian
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Basilar Membrane ◽  
Round Window ◽  
Element Model ◽  
Oval Window ◽  
Fe Model ◽  
Cochlear Duct ◽  
Human Cochlea ◽  
Set Up

A 2-D finite element model of human cochlea is established in this paper. This model includes the structure of oval window, round window, basilar membrane and cochlear duct which is filled with fluid. The basilar membrane responses are calculated with sound input on the oval window membrane. In order to study the effects of helicotrema on basilar membrane response, three different helicotrema dimensions are set up in the FE model. A two-way fluid-structure interaction numerical method is used to compute the responses in the cochlea. The influence of the helicotrema is acquired and the frequency selectivity of the basilar membrane motion along the cochlear duct is predicted. These results agree with the experiments and indicate much better results are obtained with appropriate helicotrema size.

A coupled FE model for the joint resolution of the shallow water and the groundwater flow equations

2014 ◽  
Vol 24 (7) ◽  
pp. 1553-1569 ◽  
Author(s):  
H.G. Rábade ◽  
P. Vellando ◽  
F. Padilla ◽  
R. Juncosa
Keyword(s):  
Groundwater Flow ◽  
Shallow Water ◽  
Free Surface Flow ◽  
Element Model ◽  
Surface Flow ◽  
Fe Model ◽  
Content Type ◽  
Flow Equations ◽  
Natural Watersheds ◽  
Joint Resolution

Purpose – A new coupled finite element model has been developed for the joint resolution of both the shallow water equations, that governs the free surface flow, and the groundwater flow equation that governs the motion of water through a porous media. The paper aims to discuss these issues. Design/methodology/approach – The model is based upon two different modules (surface and ground water) previously developed by the authors, that have been validated separately. Findings – The newly developed software allows for the assessment of the fluid flow in natural watersheds taking into account both the surface and the underground flow in the way it really takes place in nature. Originality/value – The main achievement of this work has dealt with the coupling of both models, allowing for a proper moving interface treatment that simulates the actual interaction that takes place between surface and groundwater in natural watersheds.

Finite Element Mesh Generator Applying Constraints’ Propagation and Isoparametric Mapping

1991 ◽  
Author(s):  
J. Rodriguez ◽  
M. Him
Keyword(s):  
Finite Element ◽  
Mesh Generation ◽  
Element Model ◽  
Finite Element Mesh ◽  
Fe Model ◽  
Element Analysis ◽  
Element Mesh ◽  
Mesh Generator ◽  
Generation Algorithm ◽  
Essential Input

Abstract This paper presents a finite element mesh generation algorithm (PREPAT) designed to automatically discretize two-dimensional domains. The mesh generation algorithm is a mapping scheme which creates a uniform isoparametric FE model based on a pre-partitioned domain of the component. The proposed algorithm provides a faster and more accurate tool in the pre-processing phase of a Finite Element Analysis (FEA). A primary goal of the developed mesh generator is to create a finite element model requiring only essential input from the analyst. As a result, the generator code utilizes only a sketch, based on geometric primitives, and information relating to loading/boundary conditions. These conditions represents the constraints that are propagated throughout the model and the available finite elements are uniformly mapped in the resulting sub-domains. Relative advantages and limitations of the mesh generator are discussed. Examples are presented to illustrate the accuracy, efficiency and applicability of PREPAT.

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