Seismic Vulnerability Of Existing Buildings With Steel Reinforced Concrete Src Composite Columns

Seismic Vulnerability of Existing Buildings with Steel Reinforced Concrete (SRC) Composite Columns

Prior to enforcing seismic details in the 1980s, older-type full encased steel-concrete composite columns (SCR) were utilized in many buildings and bridges constructed in active seismic regions. However, there is a lack of knowledge in the literature on the behavior of SRC composite columns and a small number of tests available to derive seismic backbone curves for macro-modeling or retrofitting purposes. This research demonstrates that the ASCE 41-17 criteria underestimates the structural capacity of the system, via comparing the vulnerability curves obtained following the ASCE 41-17 requirements with the ones derived from the test results of six specimens of SRC columns tested in The American University in Cairo. First, the force-displacement curves for the specimens are developed, then, the design and non-linear characteristics of the two models are presented, and finally, the vulnerability curves are developed. The results show that the ASCE 41-17 criteria underestimates the capacity of the system.

New Challenges for Seismic Risk Mitigation in Urban Areas

Seismic Performance of Steel-reinforced Concrete Composite Columns of Older and Modern Construction

Abstract: Existing concrete buildings lacking seismic details are well known to cause most losses during earthquakes so there is no wonder they are nicknamed killer buildings. In every new earthquake we see more evidence of their vulnerability. Ordinary building are taking the most focus of researchers from all over the world because of the majority of building are reinforced concrete. But one of the most widely used structure system contains steel reinforced concrete (SRC) composite columns. This type has been used since early of 1950 and nowadays most high rise or non-prismatic buildings are built using SRC composite columns. This Experimental study presented addresses the seismic performance of (SRC) composite columns experiencing shear and flexural failures using different concrete grades and confinement details to mimic both existing buildings with old construction details and modern buildings designed and built according to modern codes and construction practices. Test specimens represent exterior columns modeled based on a typical seismic design of a 30-story prototype new core wall-frame tall building and a 20-story prototype gravity existing building. Test parameters considered in this study are target failure mode, axial load ratio, percentage of longitudinal steel, structural steel section, concrete grade, and the transverse reinforcement volumetric ratio. Tests aim to characterize and compare the cyclic response of SRC columns with old and modern construction details. In particular, shear capacity, flexural capacity, residual axial capacity, deformation capacity and engineering demand parameters under different test variables are sought. Backbone curves for numerical simulation of seismic performance of SRC columns are presented. There are fourteen tested specimens divided to three groups; four specimens were tested as pilot, three specimens were tested representing modern building flexure deficient column and seven specimens for old building: five shear deficient specimens and two flexure deficient specimens. This work came out with many conclusions and recommendations for old and modern buildings to overcome the deficiency of SRC composite column. Retrofitting shear deficient SRC columns under high axial loads (>40%) and flexure deficient columns under high axial loads (higher than the balanced load, i.e. compression controlled failure) experiencing moderate to strong ground shaking seems inevitable.