The document specifies a method of determining the shear strength of welded joints in reinforcements intended for use in prefabricated components made of autoclaved aerated concrete or lightweight aggregate concrete with open structure. The shear strength of welded joints is determined on test specimens consisting of a longitudinal bar and a welded cross bar (transverse bar or diagonal bar) by applying a tensile force on the free end of the longitudinal bar while the welded cross bar is supportet by a device designed to minimize influence from bending and twisting forces. When joints with a diagonal bar are tested, the tensile force is applied to the free end of the diagonal bar. The tensile force is increased at uniform rate until failure of the weld, and the ultimate force is recorded.