• Nuclear Engineering and Technology
• /
• v.48 no.3
• /
• pp.805-819
• /
• 2016

The numerical simulation methodologies to evaluate the structural behaviors of prestressed concrete containment vessels (PCCVs) have been substantially developed in recent decades. However, there remain several issues to be investigated more closely to narrow the gap between test results and numerical simulations. As one of those issues, the effects of no stiffness inside unbonded tendon ducts on the behavior of PCCVs are investigated in this study. Duct holes for prestressing cables' passing are provided inside the containment wall and dome in one to three directions for general PCCVs. The specific stress distribution along the periphery of the prestressing duct hole and the loss of stiffness inside the hole, especially in an unbonded tendon system, are usually neglected in the analysis of PCCVs with the assumption that the duct hole is filled with concrete. However, duct holes are not small enough to be neglected. In this study, the effects of no stiffness inside the unbonded tendon system on the behaviors of PCCVs are evaluated using both analytical and numerical approaches. From the results, the effects of no stiffness in unbonded tendons need to be considered in numerical simulations for PCCVs, especially under internal pressure loading.

• Nuclear Engineering and Technology
• /
• v.55 no.12
• /
• pp.4504-4517
• /
• 2023

After a loss of coolant accident (LOCA) in the prestressed concrete containment vessels (PCCVs) of nuclear power plants, the coupling of temperature and pressure can significantly affect the mechanical properties of the PCCVs. However, there is no consensus on how this coupling affects the failure mechanism of PCCVs. In this paper, a simplified finite element modeling method is proposed to study the effect of temperature and pressure coupling on PCCVs. The experiment results of a 1:4 scale PCCV model tested at Sandia National Laboratory (SNL) are compared with the results obtained from the proposed modeling approach. Seven working conditions are set up by varying the internal and external temperatures to investigate the failure mechanism of the PCCV model under the coupling effect of temperature and pressure. The results of this paper demonstrate that the finite element model established by the simplified finite element method proposed in this paper is highly consistent with the experimental results. Furthermore, the stress-displacement curve of the PCCV during loading can be divided into four stages, each of which corresponds to the damage to the concrete, steel liner, steel rebar, and prestressing tendon. Finally, the failure mechanism of the PCCV is significantly affected by temperature.

• Nuclear Engineering and Technology
• /
• v.56 no.5
• /
• pp.1638-1653
• /
• 2024

Given the unpredictability of the occurrence of the earthquake and other potential disasters into consideration, the nuclear power plant may be confronted with beyond design-basis earthquake load in the future. The containment structure may be severely damaged under such severe earthquake loading, increasing the risk of containment concrete cracking and potential radioactive materials leaking. Moreover, initial damage caused by the earthquake may significantly alter the pressure performance of the containment under follow-up internal pressure. To compromise the dangers of beyond design-basis earthquake to the containment, an alternative of replacing the conventional concrete with fiber-reinforced concrete (FRC) to upgrade the seismic resistance capacity of the containment is attempted and thoroughly researched. In this study, the influence of various fiber types such as rigid fiber and mixed fiber is regarded to constitute fiber-reinforced PCCVs. The physical properties of traditional and fiber-reinforced PCCVs under earthquake ground motions are scientifically compared and identified by using traditional and proposed evaluation indices. The results indicate that both the traditional evaluation index (i.e. top displacement, stress, strain) and the proposed damage index are greatly reduced by the practice of fiber strengthening under earthquake ground motions.

• Nuclear Engineering and Technology
• /
• v.54 no.6
• /
• pp.2156-2172
• /
• 2022

This paper investigates the optimum fiber reinforcement for prestressed concrete containment vessels (PCCVs) under internal pressure. To achieve this aim, steel fiber, which is the most widely used fiber type in current engineering applications, is adopted to constitute steel fiber-reinforced concrete (SFRC) to substitute the conventional concrete in the PCCV. The effects of characteristic parameters, 𝜆_sf, of the steel fiber affecting significantly the mechanical behavior of the concrete are first taken into account. Partial or complete concrete regions of the PCCV are also considered to be replaced by SFRC to balance the economy and safety. By adopting the ABAQUS software, the ultimate bearing capacity and performance for the fiber-reinforced PCCV are scientifically studied and quantified, and the recommendations for the optimum way of fiber reinforcement are presented.

• Nuclear Engineering and Technology
• /
• v.47 no.7
• /
• pp.884-894
• /
• 2015

Background: Fibers in concrete resist the growth of cracks and enhance the postcracking behavior of structures. The addition of fibers into a conventional reinforced concrete can improve the structural and functional performance of safety-related concrete structures in nuclear power plants. Methods: The influence of fibers on the ultimate internal pressure capacity of a prestressed concrete containment vessel (PCCV) was investigated through a comparison of the ultimate pressure capacities between conventional and fiber-reinforced PCCVs. Steel and polyamide fibers were used. The tension behaviors of conventional concrete and fiber-reinforced concrete specimens were investigated through uniaxial tension tests and their tension-stiffening models were obtained. Results: For a PCCV reinforced with 1% volume hooked-end steel fiber, the ultimate pressure capacity increased by approximately 12% in comparison with that for a conventional PCCV. For a PCCV reinforced with 1.5% volume polyamide fiber, an increase of approximately 3% was estimated for the ultimate pressure capacity. Conclusion: The ultimate pressure capacity can be greatly improved by introducing steel and polyamide fibers in a conventional reinforced concrete. Steel fibers are more effective at enhancing the containment performance of a PCCV than polyamide fibers. The fiber reinforcementwas shown to bemore effective at a high pressure loading and a lowprestress level.

• Nuclear Engineering and Technology
• /
• v.55 no.6
• /
• pp.2053-2068
• /
• 2023

Following a loss of coolant accident (LOCA), prestressing concrete containment vessels (PCCVs) may experience high thermal load as well as internal pressure. The high temperature stress would increase the risk of premature damage to the containment, which reduces the safety margin during the increasing internal pressure. However, current investigations cannot clearly address the issues of thermal-pressure coupling effect on damage propagation and thus safety of the containment. Thus, this paper offers three simple and powerful damage parameters to differentiate the severity of damage of the containment. Moreover, despite of the temperature action severely threatening the pressure performance of the containment, the research regarding the improvement of the resistant performance of the containment is quite scarce. Therefore, in this paper, a comprehensive comparison of damage propagation and mechanism between conventional and fiber-reinforced concrete (FRC) containments is performed. The effects of fiber characteristics parameters on damage propagation of structures following the LOCA are also specifically revealed. It is found that the proposed damage indices can properly indicate state of damage in the containment body and the addition of fiber can be used to obviously mitigate the damage propagation in PCCV considering the thermal-pressure coupling.

• Journal of the Korea Concrete Institute
• /
• v.24 no.6
• /
• pp.695-703
• /
• 2012

Recently, major infrastructure such as bridges, tunnels, PCCVs (Prestressed Concrete Containment Vessel), and gas tanks are Prestressed Concrete (PSC) structure types, which improve their safety by using confining effect from prestressing. Generally, concrete is known to be an outstanding fire resistant construction material. Because of this reason, researches related to extreme fire loaded PSC member behaviors are not often conducted even though PSC behavior under extreme fire loading is significantly different than that of ordinary reinforced concrete (RC) behavior. Therefore, in this study, RABT fire loading tests were performed on bi-directionally prestressed concrete panels with $1000{\times}1400{\times}300mm$ dimensions. The prestressed specimens were applied with 430 kN prestressing (PS) force using unbonded PS thread bars. Also, residual strength structural tests of fire tested PSC and ordinary RC structures were performed for comparison. The study results showed that PSC behavior under fire loading is significantly different than that of RC behavior.

• Journal of the Korea Concrete Institute
• /
• v.26 no.4
• /
• pp.429-440
• /
• 2014

Since the World Trade Center and Pentagon attacks in 2001, terror, military attack, or man-made disaster caused impact, explosion, and fire accident have frequently occured on civil infrastructures. However, structural behavior researches on major Prestressed Concrete (PSC) infrastructures such as bridges, tunnels, Prestressed Concrete Containment Vessel (PCCVs), and LNG tanks under extreme loading are significantly lacking. Especially, researches on possible secondary fire scenarios after terror, bombing, collision of vehicles and vessels on concrete structures have not been performed domestically where most of the past researches related to extreme loadings on structures focused on an independent isolated extreme loading scenario. Due to the outcry of public concerns and anxiety of potential terrorist attacks on major infrastructures and structures, a study is urgently needed at this time. Therefore, in this study, the bi-directional prestressed concrete $1400{\times}1000{\times}300mm$ panels applied with 430 kN prestressing force using unbonded prestressing thread bars were experimentally evaluated under impact, fire, and impact-fire combined loadings. Due to test site restrictions, impact tests were performed with 14 kN impactor with drop heights of 10m and 3.5 m to evaluate impact resistance capacity. Also, fire and impact-fire combined loading were tested using RABT fire loading curve. The measured residual strength capacities of PSC and RC specimens applied with impact, fire, impact-fire combined loadings were compared with the residual strength capacity of undamaged PSC and RC specimens for evaluation. The study results can be used as basic research data for related research areas such as protective design and numerical simulation under extreme loading scenarios.