Compressive behavior of fabricated coupled composite columns under eccentric loads

摘要

A new-type of fabricated coupled composite column (CCC) system composed of closely spaced double small section concrete filled steel tubes (CFST) connected by steel connector beams using blind bolts was proposed. An experimental investigation and finite element analysis were carried out by testing CCC specimens and CFST column counterparts for various eccentricity ratios and connector beam configurations. The column limbs of the fabricated specimens performed well together combinedly and deformed as a whole without connection failure. The axial load-carrying capacity found to be decreased by 20% when the eccentricity ratio was increased from 0.2 to 0.4. Theoretical analysis was carried out to estimate the modified slenderness ratio required to calculate the capacity of the specimens. Effectiveness of various design standards to predict the capacity of CCC and traditional CFST built-up columns from past studies were also verified. Chinese design standard provided closest predictions to the test results, with the average ratio of the predicted strength to the experimental strength approximately equal to 0.868. The proposed coupled composite columns can be conveniently used in multistorey assembled frame structures.