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

Document Type : Research Article


International Institute of Earthquake Engineering and Seismology (IIEES)


The new techniques in seismic design of structures are usually attributed to high
damping ratios. Mass isolation of structures is one of the new techniques in seismic
design of structures that focuses on the mass of the structure as the main target for
seismic isolation and reducing earthquake effects on buildings. Mass Isolation
System (MIS) consists of two stiff and soft substructures connected by a viscous
damper. The mass subsystem comprises the main mass of the structure, which is
attached to a frame with a low stiffness by a separation mechanism at the height of
the structure including viscous dampers to a stiffness subsystem consisting of a
moment or braced frame system with great stiffness. In this paper, the aim is to
present a simple preliminary design method based on the normalized pushover
curve. The most important problems for increasing the period of the soft structure
are deformation and structural stability. This paper presents a preliminary design
solution for a soft substructure of the Mass Isolation System (MIS) with consideration
of stability constraints. To this end, the paper presents mathematical
relationships to calculate the period of the structure followed by proposing a simple
solution for the design of the soft substructure.


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