Reinforced Concrete Containment Research Articles

Identification and assessment of seismic damage for RC containment structures considering prestressing effect

Containment structures shall remain viable even after strong ground motions to save lives and valuables. Therefore, the current study exploits the prestressing effect to mitigate seismic damage and prevent function and structural failure during seismic events. The seismic response of the studied reinforced concrete containment (RCC) structure is well captured and investigated. The results reveal that the prestressing could significantly mitigate the seismic damage and the RCC structure’s bottom is the most vulnerable region. Hence, the prestressing value might be designed to mitigate the seismic damage of the RCC structure not only to keep its integrity under overpressure. Moreover, damage assessment using different damage indices has been presented, and a modification for the Park-Ang damage index has been formulated. Furthermore, a new formula has been proposed to predict the RCC structure’s damage ratio accurately, and a new classification for the damage states has been developed to identify the performance level.

Structural Health Monitoring for Reinforced Concrete Containment Using Inner Electrical Resistivity Method

Nuclear power plants (NPPs) are considered as the main source for generating electricity nowadays in some countries. The effect of impact of heavy fully loaded aeroplane such as (Boeing 747-200c) causes leakage of the radiation through the cracks generated on the external RC containment of NPPs, and this leads to severe damage for humans and cities. In this research paper, external RC containment is modeled using ANSYS and hit by Boeing 747-200c which is the heavier aeroplane compared to other jets and causes severe damage for external RC containment. In addition, the impact location for Boeing 747-200c is considered at 30 m vertical height. RC containment response was studied after the impact of an aeroplane and a proposed structural health monitoring technique is applied using embedded sensors in order to detect and locate the embedded cracks that is generated due to the effect of impact of heavy aeroplane. It was concluded that RC containment is intact except for the impact region which is damaged. An experimental program was applied on a part of the element in ANSYS which is away from the impact region. Four specimens were cast using heavy weight concrete in laboratory. Three cracked specimens consist of different lengths of vertical cracks which represent different times of impact in order to replicate crack propagation as in ANSYS. The cracks are simulated inside laboratory specimens using failure criteria. The parameters used in detecting the cracks for specimens are the percentage change in electrical resistivity and Decimal Logarithm Resistivity Anisotropy (DLRA) at which they give a good indication for the presence of the crack.

The capacity loss of a RCC building under mainshock-aftershock seismic sequences

Reinforced concrete containment (RCC) building has long been considered as the last barrier for keeping the radiation from leaking into the environment. It is important to quantify the performance of these structures and facilities considering extreme conditions. However, the preceding research on evaluating nuclear power plant (NPP) structures, particularly considering mainshock-aftershock seismic sequences, is deficient. Therefore, this manuscript serves to investigate the seismic fragility of a typical RCC building subjected to mainshock-aftershock seismic sequences. The implementation of the fragility assessment has been performed based on the incremental dynamic analysis (IDA) method. A lumped mass RCC model considering the tri-linear skeleton curve and the maximum point-oriented hysteretic rule is employed for IDA analyses. The results indicate that the seismic capacity of the RCC building would be overestimated without taking into account the mainshock-aftershock effects. It is also found that the seismic capacity of the RCC building decreases with the increase of the relative intensity of aftershock ground motions to mainshock ground motions. In addition, the effects of artificial mainshockaftershock ground motions generated from the repeated and randomized approaches and the polarity of the aftershock with respect to the mainshock on the evaluation of the RCC are also researched, respectively.

Seismic Fragility of a Typical Containment under Bidirectional Earthquake Excitations

Existing research to predict seismic fragility of Reinforced Concrete Containment (RCC) buildings does not take into account the impact of its inelastic bidirectional interaction arising from bidirectional horizontal ground motions. Hence, this study attempts to present a reliable and feasible method for fragility of the RCC subject to bidirectional ground motions. Three bidirectional load histories due to inelastic bidirectional interaction are firstly introduced to determine displacement-based failure limits for this structure. Nine bidirectional earthquake Intensity Measures (IMs) are developed to perform the bidirectional Incremental Dynamic Analysis (IDA). For the selection of an optimum method for fragility under bidirectional earthquake excitations, three fragility analysis methods are conducted and their results are compared. Results show that the maximum likelihood method yields better fragility results than the other two methods. The safety factor method for fragility cannot get the aleatory randomness properly. Besides, the first-mode geometric mean spectral acceleration SaGM (T1) is found to strongly correlate with the demand measure for the RCC and is suggested for deriving fragility curves for such structures under bidirectional earthquake excitations.

Sequential Ground Motion Effects on the Behavior of a Base-Isolated RCC Building

The sequential ground motion effects on the dynamic responses of reinforced concrete containment (RCC) buildings with typical isolators are studied in this paper. Although the base isolation technique is developed to guarantee the security and integrity of RCC buildings under single earthquakes, seismic behavior of base-isolated RCC buildings under sequential ground motions is deficient. Hence, an ensemble of as-recorded sequential ground motions is employed to study the effect of including aftershocks on the seismic evaluation of base-isolated RCC buildings. The results indicate that base isolation can significantly attenuate the earthquake shaking of the RCC building under not only single earthquakes but also seismic sequences. It is also found that the adverse aftershock effect on the RCC can be reduced due to the base isolation applied to the RCC. More importantly, the study indicates that disregarding aftershocks can induce significant underestimation of the isolator displacement for base-isolated RCC buildings.

Stress–Strain State and Vibrations of a Complex-Shaped Containment Shell Under Nonstationary Loads

The dynamic behavior of a reinforced-concrete containment shell of a nuclear power plant under the combined effect of an internal pressure jump due to a reactor breakdown and seismic load due to a design-basis earthquake is analyzed. The finite-element method and Dipros software are used. A modal analysis is performed followed by numerical solution of the equations of motion of the containment to determine the post-accident stress–strain state of its structures. It is shown that the maximum stress intensity in the leaktight steel liner does not exceed its yield strength (i.e., the integrity of the liner is maintained, and the containment keeps performing its functions and meets the radiation safety requirements)

Damage accumulation of a base-isolated RCC building under mainshock-aftershock seismic sequences

Strong aftershocks have the potential to induce greater structural damage for Nuclear Power Plant (NPP) structures. In order to ensure the safety and integrity of Reinforced Concrete Containment (RCC) buildings, the base isolation technique is proposed to reduce the effects of earthquake shaking on the building and avoid damage of the structure under earthquakes. However, none of the studies have focused on evaluating the seismic performance of RCC buildings with isolation for mainshock-aftershock seismic sequences. The aim of this paper is to thoroughly investigate the structural damage of RCC buildings with Lead Rubber Bearing (LRB) isolators under seismic sequences. A suite of twenty-eight artificial sequential ground motions is developed to investigate the influence of considering aftershocks on the performance of RCC buildings with isolators for both design-basis and beyond-designbasis earthquake shaking. The results reveal that strong aftershocks would induce greater damage for the RCC without isolators under beyond-design-basis earthquake. While, base isolation can protect the RCC building under seismic sequences being damaged even for beyond-design-basis earthquake shaking. The IDA results of base-isolated RCC demonstrate that isolators also increase the structural reserve capacity significantly under both mainshocks and seismic sequences.

Seismic analyses of a RCC building under mainshock–aftershock seismic sequences

A large mainshock may trigger numerous aftershocks within a short period, and nuclear power plant (NPP) structures have the probability to be exposed to mainshock–aftershock seismic sequences. However, the researchers focused on seismic analyses of reinforced concrete containment (RCC) buildings under only mainshocks. The aim of this paper is to thoroughly investigate the dynamic responses of a RCC building under mainshock–aftershock seismic sequences. For that purpose, 10 as-recorded mainshock–aftershock seismic sequences with two horizontal components are considered in this study, and a typical three-dimensional RCC model subjected to the selected as-recorded seismic sequences is established. Peak ground accelerations (PGAs) of mainshocks equal to 0.3g (safe shutdown earthquake load-SSE load) are considered in this paper. The results indicate that aftershocks have a significant effect on the responses of the RCC in terms of maximum top accelerations, maximum top displacements and accumulated damage. Furthermore, in order to preserve the RCC from large damage under repeated earthquakes, local damage and global damage indices are suggested as limitations under only mainshocks.

Seismic Testing and Verification for 30 Tons Scaled-Down Model of Reinforced Concrete Containment Vessel

The scaled-down model of Reinforced Concrete Containment Vessel (RCCV) for Advanced Boiling Water Reactor (ABWR) building, whose weight is 30 tons, is the biggest seismic test in Taiwan, until now. The design and stress analysis of the testing model is following the ASME-359 code. This experimental test can be the basis to check whether the scaled-down RCCV is safe or not when it undergoes the fictitious seismic loading came from shaking table. The other object of this test is getting the experimental data of dynamic responses, such as accelerations and displacements, to verify the validity of numerical model.

Effect on Vibroengineering of Material Deterioration in a Scale-Down Reinforced Concrete Containment Vessel Specimen

This study is aim to evaluate the natural frequency variation of the scale-down reinforced concrete containment vessel specimen under accelerated corrosion conditions. A plastic ring was sealed around the perimeter of the cylindrical vessel bottom with the 3.5 % NaCl solution to achieve the accelerated corrosion test. Concrete resistivity, open circuit potential, corrosion rate and natural frequencies were tested and discussed in this study. Test results presented that the accelerated corrosion method with a direct 60 voltage applied was a suitable method for estimating and accelerating the concrete vessel specimen. Therefore, the changes in natural frequencies were consistent with the material degradation of the concrete vessel specimen. The natural frequencies decreased with the increasing corrosion rate or decreasing resistivities for the specimen at higher mode, but would be no change for the specimen at the natural frequency of 1st mode.

Damage mechanism and response of reinforced concrete containment structure under internal blast loading

Reinforced concrete containment (RC) is the most significant component of the nuclear power plant. It may lead to serious disaster owning to the leakage of radioactive materials as the reasons of internal explosion of reinforced concrete containment caused by earthquakes, fires, gas explosions or terrorist attacks, etc.The objective of this paper is to investigate the behavior of reinforced concrete containment, numerical simulation taking into account fluid–solid coupling interaction is conducted for the analysis on the dynamic responses of reinforced concrete containment under internal blast loading using LS–DYNA software, especially focusing on its damage mechanism.The generation and the propagation of blast wave and its effect on a containment structure are discussed using Arbitrary Lagrangian Eulerian (ALE) algorithm and multiple material models. The analysis results of the containment have been compared by empirical equations. Parametric studies have also been performed for internal detonation under different scale distances at a standoff distance of 20m in the RC containment. The results indicate that the influences of scale distances and mesh qualities of structure on dynamic response and damage mechanism of the structure are analyzed to assess the structural anti-explosion capability.

Conclusions of the EPRI Concrete Containment Research Program

Six years of EPRI sponsored research aimed at studying the overpressure behavior of reinforced and prestressed concrete containments has brought about the development of a test-validated methodology for the prediction of concrete containment capacity and leakage. The results of many large scale panel tests in the EPRI program and the Sandia 1:6 Scale Reinforced Concrete Containment Test have been instrumental in supporting this work. This paper describes the development of the leakage prediction criteria and analysis guidelines by summarizing the EPRI research program and the conclusions that have been reached regarding concrete containment overpressure behavior. The methodology for predicting linear tearing consists of using ABAQUS-EPGEN (a general purpose finite element program co-sponsored by EPRI and Hibbitt, Karlsson, and Sorensen, Inc.) to perform 2D global analyses and then applying curves of liner strain magnification factors to the global liner strains. The 2D axisymmetric analysis procedure has been automated by the development of “library models” for two families of concrete containments commonly found in the United States. Post test conclusions of the Sandia 1:6 Scale Model experiment are also discussed in support of the leakage prediction methodology. Finally, the conclusions that have been reached with regard to liner tearing and subsequent equilibrium leakage in a quasi-static pressurization scenario are reviewed in the context of current industry operating procedures and regulatory requirements. The paper introduces the most recent work in the EPRI program which evaluates the uncertainties of the leakage prediction procedure and recasts the procedure in a probabilistic risk assessment framework for use with recent U.S. regulatory documents.

Construction of a [formula omitted] concrete containment model

This paper discusses the features and construction of a 1 6 - scale reinforced-concrete containment model that has been built at Sandia National Laboratories in Albuquerque, New Mexico. The model Light-Water-Reactor (LWR) containment building was designed and built to the American Society of Mechanical Engineers (ASME) code by United Engineers and Constructors, Inc. The containment model will be tested to failure to determine its response to static internal overpressurization. The results from testing the heavily instrumented containment will be used to assess the capability of analytical methods for predicting the performance of containments subject to severe accident loads as part of the US Nuclear Regulatory Commission's program on containment integrity. The scaled dimensions of the cylindrical wall and hemispherical dome are typical of a full-size containment. Features representative of a prototypical containment and included in the heavily reinforced model are equipment hatches, personnel airlocks, several small piping penetrations, and a thin steel liner attached to the concrete by headed studs.

Experimental testing and calculation of small diameter electrical conduits in prestressed reinforcedconcrete containment vessels of atomic power plants

Experimental testing and calculation of small diameter electrical conduits in prestressed reinforcedconcrete containment vessels of atomic power plants