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Abstract
This research investigates experimentally and analytically the effect
of change in the transverse and longitudinal reinforcement ratio of
Y-shaped reinforced concrete bridge piers on their torsional
performance under seismic loading. The case of skewed alignment
of piers typically present on horizontal curves of bridge deck is
discussed. In the experimental program, seven specimens of bridge
piers at a scale of 1:5 were tested. The longitudinal reinforcement
ratios used in the research were 1.00%, 1.34%, and 2.09% while the
volumetric ratios of transverse reinforcement were 0.40%, 0.70%,
and 1.25%. The specimens were tested under horizontal cyclic
quasi-static torsional loading with no vertical forces to represent
earthquake with insignificant vertical acceleration. The specimens
were loaded to failure which was manifested in the form of cracks
spreading over the tested specimens. Deformations, strain in both
longitudinal & transverse reinforcement, and crack pattern were
recorded during the test on different loading stages. The top
displacement and twist angle and their correlation with the change
in longitudinal and transverse reinforcement, as theypresent the
main seismic performance parameters of piers, were studied in
order to quantify the loss of strength and stiffness degradation due
to the torsional warping stresses. The energy capacity properties
have been studied as well. In the second phase of the research, a
comprehensive analysis of the tested specimens is conducted using
computer finite element software and analytical results were
compared with the experimental results and showed good
agreement to variable levels. Also, different retrofitting schemes
were adopted and modeled by computer software to predict the
performance improvement and strength increase of test specimens
and evaluate the efficiency and feasibility of retrofitting. The study
highlights the importance of considering the seismic torsional
demand in order to obtain an acceptable level of certainty in the
field of design and strengthening of reinforced concrete bridge
piers.