Initial Solution for Designing a Soft Substructure in a Mass Isolation System with Consideration of Stability Constraints

The new techniques in seismic design of structures are usually attributed to highdamping ratios. Mass isolation of structures is one of the new techniques in seismicdesign of structures that focuses on the mass of the structure as the main target forseismic isolation and reducing earthquake effects on buildings. Mass IsolationSystem (MIS) consists of two stiff and soft substructures connected by a viscousdamper. The mass subsystem comprises the main mass of the structure, which isattached to a frame with a low stiffness by a separation mechanism at the height ofthe structure including viscous dampers to a stiffness subsystem consisting of amoment or braced frame system with great stiffness. In this paper, the aim is topresent a simple preliminary design method based on the normalized pushovercurve. The most important problems for increasing the period of the soft structureare deformation and structural stability. This paper presents a preliminary designsolution for a soft substructure of the Mass Isolation System (MIS) with considerationof stability constraints. To this end, the paper presents mathematicalrelationships to calculate the period of the structure followed by proposing a simplesolution for the design of the soft substructure.