Laboratory of Reinforced Concrete, National Technical University of Athens

Dowel action is one of the mechanisms for the transfer of forces across interfaces. The behaviour of this mechanism is investigated in the case of (horizontal or vertical) bars embedded in masonry. In this paper, the results of an experimental programme are presented and discussed. Highly perforated (55%) bricks were used. The brick 320x250x155mm was designed to ensure thermal and acoustic insulation of masonry within its thickness. The main parameter investigated is the bar diameter, 6mm and 10mm bars as horizontal reinforcement, and 12mm and 14mm bars inserted into the vertical holes of the bricks. The main experimental findings are:
• Horizontally reinforced specimens exhibited a mixed failure mode involving yielding of bars, crushing of mortar and brick webs under the bars, as well as vertical splitting of the brick (in the case of 10mm bars).
•Vertically reinforced specimens exhibited a very brittle failure mode, fracture of brick webs occurred under the sheared bars, which were surrounded by a high strength grout (65x65mm in section).
• It was shown that horizontal bars were able to mobilise shear resistance comparable to that mobilised by bars embedded in normal strength concrete. This was not the case for vertical bars, since their behaviour is strongly affected by the premature fracture of the brick.
• The shear force vs shear displacement curve consists of a roughly linear ascending branch, followed by a steep descending branch. A stabilisation of response was recorded after a loss of resistance varying between 10% and 70% of the maximum. The higher percentages of loss in resistance were exhibited by vertical bars.