Expected maximum moment of multi-spiral columns: Fid-Bau Portal

Expected maximum moment of multi-spiral columns

Ngo, Si-Huy / Ou, Yu-Chen

Highlights • Three methods to estimate the expected maximum moment are investigated for multi-spiral columns. • The Caltrans SDC method is modified to consider the unique confinement characteristics of multi-spiral reinforcement. • The effect of axial load on the expected maximum moment of multi-spiral columns is investigated.

Abstract Three methods to estimate the expected maximum moment of multi-spiral columns were investigated. The methods include the ACI 318 method, the AASHTO 1.3 $M_{n}$ method and a method based on the Caltrans SDC method modified for the unique characteristics of the confinement effect from multi-spiral reinforcement. A test database consisting of 21 multi-spiral columns was established. Comparison with test results show that the ACI 318 method is unconservative for most of the multi-spiral columns examined. The AASHTO 1.3 $M_{n}$ method performs better than the ACI 318 method but is still unconservative for several columns examined. For the two methods to be conservative for the columns examined, the result from the ACI 318 method and that from the AASHTO 1.3 $M_{n}$ method need to be multiplied by a factor of 1.45 and 1.19, respectively. In contrast, the modified Caltrans SDC method is conservative for all the multi-spiral columns examined. A further investigation into the effect of the axial load on the expected maximum moment shows that the AASHTO 1.3 $M_{n}$ method is applicable when the axial load is lower than approximately 0.34 times the axial strength at the balanced strain condition. More tests are needed to validate the applicability of the modified Caltrans SDC method to multi-spiral columns with axial loads higher than the axial strength at the balanced strain condition.