Hybrid passive control system for seismic response mitigation of steel frame structures / Mohammad Hossein Mehrabi
Large vibration forces such as from seismic excitations can cause structural damage and structural collapse in the case of intense earthquakes. A large number of novel methods and of these techniques has weaknesses and strengths. Several control devices demonstrate a two-step mechanism in which t...
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Format: | Thesis |
Published: |
2020
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Online Access: | http://studentsrepo.um.edu.my/12540/1/Mohammad_Hossein.pdf http://studentsrepo.um.edu.my/12540/6/Mohammad_Hossein.2_compressed.pdf http://studentsrepo.um.edu.my/12540/ |
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Summary: | Large vibration forces such as from seismic excitations can cause structural damage and
structural collapse in the case of intense earthquakes. A large number of novel methods and
of these techniques has weaknesses and strengths. Several control devices demonstrate a
two-step mechanism in which the structure's stiffness is initially raised, and then the
of the first vibration period down to a region where the structural response is significantly
increased. The main aim of this thesis is to propose a hybrid passive control system
comprises of two phases for the seismic retrofit of moment-resisting steel frames. The first
phase is a viscoelastic device called Rotary Rubber Brace Damper (RRBD), consisting of
five steel plates and four layers of rubber. The second phase is a cable bracing system
bundled with a pre-compressed spring (PCS). The transition between these two phases
consists of an increasing stiffness as the system transitions from the viscoelastic RRBD to
the cable bracing PCS. In order to develop and prove the effectiveness of the hybrid passive
control system, this research is divided into two parts. The first part includes the
characterization of rubber compounds and analytical modeling of the RRBD concept with
the aim of ABAQUS software. Then, experimental testing was conducted to determine the
material properties of the rubber compounds, and, finally, the most promising rubber
compounds were selected for possible inclusion in the device. The RRBD functioned at
early stages of lateral displacement, indicating that the system is effective for all levels of
strategies for seismic retrofitting have been developed and successfully implemented. Any
dissipation energy phase is engaged upon yielding of the device. This may result in a shift vibration. The second part of this research focuses on the PCS system. Both experimental
and analytical studies were conducted, and no loosening in the cable is observed, as the
cables are held in tension by the spring's force; thus, the ability of the bracing system to
cause impulses is eliminated. A PCS system design procedure was developed through
analytical and experimental testing and then it was used for practical implementation of the
proposed system. The overall behavior of the hybrid system during testing demonstrates
multi-phased behavior with the capability for energy dissipation at all deformation levels
and significant energy dissipation for seismic events. It shows that the proposed hybrid
system creates a unique and innovative method which enhances the strengths and offsets
the weaknesses of the individual systems.
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