Retrofitted URM cavity walls experimentally validated and a simplified out-of-plane assessment

REFERENCE

Determine the out-of-plane capacity of cavity walls when retrofitted with shear-transferring cavity ties.
Walls were tested under semi-cyclic (air-bags) and dynamic shake-table loading.
A tie pattern was devised that enabled a cavity wall response equal to that of a solid wall (composite behaviour).
Two different cavity wall typologies were tested: (1) two single clay brick leaves, 1+1, and (2) two-leaf solid clay brick walls with an external single leaf brick layer, 2+1.

The optimum cavity shear transferring tie spacing for the tested wall specimens was 460 mm (two bricks) horizontally and 400 mm (four courses) vertically - this corresponded to the state “well-tied”
“well-tied” means the ties configuration enable uplift of the opposite leaf of the wall through multiple cycles of rocking.
Well-tied cavity walls tested semi-cyclically demonstrated the ability to exceed predictions for maximum usable displacement for fully solid walls made using Part C8. Walls tested to collapse reached the point of geometric instability before failure.
The ties permitted the tested walls to undergo pseudo-rigid rocking behaviour utilising the full thickness of the wall section, with outer leaves acting as structural components, not simply as ancillary mass.
For the purposes of practical engineering assessment, the use of shear-transferring cavity ties at sufficiently spacing (“well-tied” cavity walls) can be assessed as solid walls of the same gross thickness.