Assessment of the tensile behavior of twisted steel connectors for masonry retrofitting

The paper presents an experimental investigation on the tensile behavior of twisted stainless-steel bars considering different parameters that could affect their performance, namely the bar diameter (8, 10, 12 mm), the embedment depth, the position within the wall (installed into brick or in a T-mortar joint), the strength of the masonry and the type of loading (monotonic or cyclic load). Experimental results showed very good performance with reliable results associated to low coefficient of variation of the loads and very limited damage of the base material. The load–displacement curves showed a good ductility, an excellent superposition between monotonic and cyclic tests and an extended plateau at ultimate load. Among the different investigated parameters, the position within the wall was the most influential one, with higher loads associated to mid-brick location of the bar. Finally, based on the experimental results a user-friendly equation is proposed to predict the ultimate tensile load.