Axial behaviour of MFT stub columns with binding bolts and epoxy adhesive

• The column is a combination of steel and masonry with binding bolts and adhesive.
• The load corresponding to visible buckling of the steel plate in MFT columns.
• A simplified formula proposed for calculating the bearing capacity of MFT columns.
• A suggestion that the bolt spacing be about 70 times the steel plate thickness.
• Bonding stress of epoxy adhesive between the steel plate and the encased masonry.

This paper describes an investigation of the axial behaviour of rectangular masonry-filled steel tubular (MFT) stub columns with binding bolts and epoxy adhesive. This type of column is used primarily in masonry buildings where load-carrying masonry walls are removed to provide a larger space. A total of six MFT stub columns were tested. This testing included examination of the effects of the spacing of binding bolts and the thickness of steel plates. The results of this study show that the appropriate spacing for the bolts is approximately 70 times the steel plate thickness, and the applied load of MFT columns corresponding to the visible buckling of steel plates may be different from the critical local buckling load at the inflection point of the load–strain curve. Furthermore, seven steel plate–masonry connection specimens were also tested to determine the bonding stress, which ranged from 0.45 to 0.89 MPa, and three types of debonding failure between the steel plates and encased masonry were identified. Finally, a simplified design-oriented formula is proposed for use in calculating the load-carrying capacity of MFT columns with visible buckling in the steel plates, and the values given by the formula agree well with the experimental results.