1) PhD candidate, ISISE, Department of Civil Engineering, University of Minho,

2) Assistant Professor, ISISE, Department of Civil Engineering, University of Minho,

3) Architect, Tiba Architects Studio,

4) MSc in Eng., University of Minho,


The use of twisted stainless steel bars has proven to be effective in scenarios where lateral loads (e. g. earthquakes and winds storms) can cause partial or complete out-of-plane collapse of masonry wall’s outer leaves or separation of wood diaphragms from masonry walls. The particular application of these bars as a dry system in mortar joints, without any binder, brings additional advantages in terms of cost, installation time and weather restrictions. An experimental campaign composed by 60 pull-out tests aimed at characterizing the bond behaviour of twisted stainless steel bars in mortar joints. The influence on bond behaviour of two diameters of the helibar (ϕ8 mm and ϕ10 mm), three different anchorage lengths (8ϕhb, 12ϕhb, and 20ϕhb), and two diameters of the pre-drilled holes (ϕhb–2 mm and ϕhb–4 mm) was studied. Bond strength increased for the tighter pre-drilled hole but decreased for the higher twisted steel bar diameter. Good correlations between bond strength and anchorage length were found for the less tight pre-drilled holes.


Keywords: twisted steel bar, pull-out, bond, mortar joint