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Structural Engineering and Mechanics
  Volume 39, Number 4, August25 2011 , pages 559-578
DOI: https://doi.org/10.12989/sem.2011.39.4.559
 


Inelastic design of high-axially loaded concrete columns in moderate seismicity regions
Johnny Ching Ming Ho

 
Abstract
    In regions of high seismic risk, high-strength concrete (HSC) columns of tall buildings are designed to be fully ductile during earthquake attack by providing substantial amount of confining steel within the critical region. However, in areas of low to moderate seismic risk, the same provision of confining steel is too conservative because of the reduced seismic demand. More critically, it causes problematic steel congestion in the beam-column joints and column critical region. This will eventually affect the quality of concrete placing owing to blockage. To relieve the problem, the confining steel in the critical region of HSC columns located in low to moderate seismicity regions can be suitably reduced, while maintaining a limited ductility level. Despite the advantage, there are still no guidelines developed for designing limited ductility HSC columns. In this paper, a formula for designing limited ductility HSC columns is presented. The validity of the formula was verified by testing half-scale HSC columns subjected to combined high-axial load and flexure, in which the confining steel was provided as per the proposed formula. From the test results, it is evident that the curvature ductility factors obtained for all these columns were about 10, which is the generally accepted level of limited ductility.
 
Key Words
    axial load; columns; confinement; flexural strength; high-strength concrete; limited ductility; reinforced concrete
 
Address
Johnny Ching Ming Ho: Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, P.R.C.
 

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