۱- Introduction

۲- Description of CSMM-based shell element

۳- Simulation of RC nuclear containment structures

۴- Comparisons of analytical and test results

۵- Conclusion

References

Abstract

The nuclear containment structure is one of the most important infrastructure systems ensuring the safety of a nuclear power plant. The structural behavior of a cylindrical containment structure made of reinforced concrete (RC) with large dimensions and numerous rebars is complex and difficult to predict. The complex behavior of the RC containment structure has been investigated in an international collaboration project between the National Center for Research on Earthquake Engineering (NCREE) in Taipei, Taiwan and the University of Houston (UH), Houston, Texas. At NCREE two 1/13 scaled cylindrical RC containment specimens were tested under reversed cyclic loads [1]. At UH, a finite element simulation of the two tested specimens was developed using a finite element analysis (FEA) program SCS [2]. In the program, a new shell element, the so-called CSMM-based shell element, was developed based on the Cyclic Softened Membrane Model [3] and the formulation of an 8-node Serendipity curved shell element [4] with a multi-layer approach [5]. The UH simulated seismic behavior was close to the NCREE experimental results. This paper presents the theoretical development of the FEA program SCS and the comparisons of its predictions with the experimental structural behavior of the two RC containment specimens. This simulation model and the FEA program are excellent tools to develop effective performance-based design provisions.

Introduction

The safety of a nuclear power plant depends strongly on its containment structure. A nuclear containment structure is commonly a steel or reinforced concrete structure enclosing a nuclear reactor. This structure serves as a barrier to prevent various types of harmful radiation from contaminating the atmosphere during a rare nuclear meltdown accident [6]. Because of its critical importance to nuclear safety, the nuclear containment structure must be able to maintain structural integrity while undergoing simultaneous stresses caused by internal pressure, earthquake action and/or high local loads [7]. Considered to be a competitive material that satisfies safety requirements, reinforced concrete (RC) has been used for the nuclear containment structure since the beginning of the nuclear power industry [8]. The structural behavior of the RC nuclear containment structure with large cross sections, many layers of rebars, and complex stress conditions, is difficult to predict, especially when subjected to the earthquake loading. The seismic response of the RC nuclear containment structures is highly nonlinear caused by the highly inelastic behavior of materials including rebars and concrete under reversed cyclic actions. However, from the structural point of view, a whole RC nuclear containment structure can be visualized as assemblies of many RC elements so that the finite element analysis program combined with proper constitutive models for concrete and reinforcing bars can be a very powerful tool. The key to rational analyses of the RC nuclear containment structure is to completely understand the behavior of one element isolated from the structure. Once a rational model is developed to predict the behavior of one element, this model can be incorporated into a finite element analysis program to predict the behavior of the whole structure under different kinds of loading.