Researcher Ali Abdul Rahim Abdullah's doctoral dissertation was discussed at the College of Engineering, Department of Civil Engineering, University of Basra, entitled BEHAVIOR OF PARTIALLY ISOLATED BUILDINGS WITH STORY DAMPERS SUBJECTED TO SEISMIC LOADS
Enhancing the seismic response of multi-storey reinforced concrete (RC) buildings
remains a key priority in structural engineering, particularly in regions exposed to
high seismic risk. Although conventional approaches such as full base isolation and
energy dissipation systems have demonstrated considerable effectiveness in reducing
earthquake impacts, their practical application is often limited by architectural
restrictions, cost considerations, or difficulties in retrofitting existing buildings. In
response to these challenges, this research proposes and investigates an alternative
control approach that combines partial base isolation with storey-level fluid viscous
dampers (FVDs). The aim is to improve seismic performance and preserve flexibility
in design and implementation.
The present study investigates the seismic response of two systems of reinforced
concrete buildings consisting of ten-storey buildings: one with a regular plan layout
and another with plan irregularities. Both structures were subjected to the historical
1940 El Centro earthquake record, with a magnitude of 6.95. Using ETABS V22
software, six different structural cases were developed and assessed through nonlinear
time-history analysis. These configurations include: (1) a fixed-base model and a fully
base-isolated model, each tested with and without storey fluid viscous dampers
(FVDs); (2) partially isolated systems with isolation applied to central, mid-central,
and perimeter columns, also with and without storey FVDs; and (3) models with floor-
level isolation applied at the first, second, or third storeys, for each with and without
storey FVDS. The seismic performance was evaluated based on key response
parameters such as total base shear, peak roof acceleration, relative displacement, and
inter-storey drift ratios. The results show that using full base isolation significantly
increased the structure’s fundamental period and led to significant reductions in
seismic demand. When combined with storey-level fluid viscous dampers (FVDs),
the system achieved reductions of up to 83% in base shear, 88% in peak roof
IVacceleration, and 68% in relative displacement. Partial base isolation produced
localised benefits by reducing stress more than 25% for isolated columns compared
with the same column in the fixed base case. The case involving perimeter column
isolation showed the best performance among partial isolated cases. However, its
overall effectiveness remained lower than that of full isolation. Notably, applying
storey FVDs to a fixed-base building resulted in a reduction in top-floor acceleration
exceeding 60%. In cases involving floor-level isolation, the dynamic behaviour of the
upper part of the structure changed, leading to effective reductions in both
acceleration and drift, particularly when storey FVDS were used. However, applying
isolation at stories caused concentration of deformation at the isolation storey, which
may lead to design challenges.
The results confirm that full base isolation combined with storey FVD provides the
most significant value of seismic protection. However, combined cases that include
partial isolation and storey-level FVD represent a practical and effective alternative,
particularly in situations where full isolation is not possible due to design or
construction constraints. The study confirms the importance of isolation placement,
whether at the base or specific floors, and whether applied to central or perimeter
columns as an effective factor influencing the system’s seismic response.
Additionally, the interaction between isolation devices and damping mechanisms
plays a necessary role in the configuration of structural behaviour under earthquake
loading. While storey FVDs with fixed base provide energy dissipation, especially for
high-frequency motions, they do not significantly change the structure’s stiffness,
which may limit their effectiveness in period shifting.
The present study contributes a comprehensive comparative analysis across six
configurations, presenting practical insights for engineers and decision-makers
exploring optimised seismic control solutions for both new and refurbished RC
structures.
