Stiffening walls in masonry structures give support against lateral forces, such as wind or earthquakes. These aspects in brick walls, which have very low compressive and shear strength, require further observations (Jasinski 2017). This paper demonstrates the author's own results from tests performed on ten masonry units made of autoclaved aerated concrete. The tests were performed in four series of two elements. The first series denoted as HOS-AAC included four elements (the reference elements) without openings, with the length l = 4.43 m, h = 2.43 m, and thickness t = 180 mm. The wall tests were performed under initial compressive stress values sigma(c) = 0 N/mm(2), 0.75 N/mm(2) and 1.0 N/mm(2). In remaining three series, we used walls (external dimensions l = 4.43 m, h = 2.43 m, t = 180 mm) with different opening shapes denoted by convention as A, B and C. The models were tested under different values of initial compressive stress sigma(c) = 0.1 N/mm(2), 0.5 N/mm(2) or 1.0 N/mm(2). The results were compared with test results for unreinforced walls without openings, tested under the same initial conditions. The failure mechanism and changes in cracking morphology were described. And the analysis was performed for parameters responsible for wall stiffness and changes in values of cracking and failure stresses.
