Seismic response of a reactor building on rocky foundation

The significance of rational evaluation of seismic response of a reactor building is well recognized from the point of view of structural safety under high seismic conditions. The reactor building is a complex structure composed of various subsystems such as outer and inner shells, foundation raft and cellular roof slab having widely differing individual dynamic characteristics. A simplified mathematical model such as an axisymmetric finite element idealization can be employed for seismic response analysis. Such a model can lead to useful results for design and is less expensive compared to three dimensional model. The axisymmetric finite element model is undoubtedly superior to conventional beam method because of several reasons, particularly the ability of the former approach to consider both meridonal and cricumferntial vibrations (Chandrasekaran 1985). Consequently the stress predictions in the structure with this method of modelling is more realistic. The seismic response of the building is greatly influenced by the type of foundation rock (Thakkar 1983; Deq 1985). The foundation-structure interaction effect in the case of rock is less pronounced because a stiff structure like a nuclear reactor building tends to interact little with the stiff foundation medium. Nevertheless, the elasticity of foundation has an important role in the seismic response evaluation and must be considered.