Bond strength of concrete confined by SMA wire jackets

Abstract

This study pursuits a goal to assess bond strength of concrete confined by shape memory alloy (SMA) wire jackets that can provide active confinement due to shape memory effect. This study uses NiTiNb SMA wires which show more wider temperature hysteresis than normal NiTi SMA wire. Thus, NiTiNb SMA wires are more applicable for the use of shape memory effect for civil structures which are exposed severe environmental conditions such as large temperature variation. Concrete cylinders of 200 mm × 100 mm (L×D) are used for this study. The SMA wire jackets increases the bond strength of concrete and changes the failure mode from split to pull-out failure. A particular thing in the tests is a split crack developing even with the SMA wire jackets. In general, the crack is not developed in the pull-out mode failure. The SMA wire jackets increase the bonding strength even with the crack developing since it seems that they provide active confinement as well as external passive confinement.