SEISMIC RESPONSE OF HALF-SCALE SEVEN-STORY REINFORCED CONCRETE SYSTEMS WITH TORSIONAL IRREGULAIRIES: TEST RESULTS
Journal
World Conference on Earthquake Engineering proceedings
Journal Volume
2021
Start Page
2i-0194
ISSN
30065933
Date Issued
2021
Author(s)
Abstract
Reinforced concrete buildings with irregularities are vulnerable to localized damage or collapse under seismic excitation. The torsional responses related to irregularities in stiffness and strength as well as the dynamic effect of earthquakes have been discussed in past studies. As a consequence, large seismic demands are considered in design standards or seismic assessment guidelines when certain irregularities exist. While methodologies to capture torsional demands due to strength and stiffness irregularities have been studied in detail in the past, there is uncertainty in determining the effect of torsion associated with nonlinear seismic response. Dynamic properties of a system are dependent on inelastic performance of each element; therefore the eccentricities based on the original state of the structure may not be reliable once it responds beyond the elastic limit. The static theory of inelastic torsion was established for ductile systems for design; however, little experimental investigation has been done to verify predictions of displacement demand. Assessing displacement demand caused by torsion in existing reinforced concrete buildings needs more clarification to consider torsional response associated with non-ductile structural performance. This study aims to investigate nonlinear torsional response of existing reinforced concrete buildings through shake-table tests. Two half-scale seven-story reinforced concrete structures with different sources of irregularities were tested on an earthquake simulator at the NCREE Tainan laboratory as part of an international collaboration between Taiwan (NCREE) and New Zealand (QuakeCoRE). Both specimens reflected some structural weaknesses of two buildings that collapsed during the 2016 Meinong Earthquake and were subjected to scaled unidirectional earthquake motion from the 1999 Chi-Chi Earthquake. Two series of tests were conducted on the first specimen (with ductile detailing in the soft first story) to study displacement demands caused by: i) torsional stiffness irregularity and ii) damage irregularity. The second specimen was designed to study displacement demands caused by non-ductile irregularity, as torsional response was caused by asymmetrical strength degradation of columns. This paper presents a summary of the results and preliminary findings from this testing program.
Subjects
Inelastic torsion
Irregularities
Reinforced concrete buildings
Seismic response
Shake-table test
Publisher
International Association for Earthquake Engineering
Type
conference paper