1) PhD student, Technische Universität Dresden, Faculty of Architecture, Chair of Structural Design,

2) Prof. Dr.-Ing., Technische Universität Dresden, Faculty of Architecture, Chair of Structural Design,


The initial shear strength plays an important role for the resistance against bending and shear when the surcharge on the wall is low. In this case it is important to use values close to reality and the question arises if the figures following from the standardized test method truly reflects the behaviour in the wall. There were several test methods suggested by researchers in order to determine the initial shear capacity and friction coefficient of mortar joints and also standard methods e.g. according to EN 1052-3 or to the former German test code DIN 18555-5, known to the authors but none of the methods can fulfil all requirements of theoretical bases.

A review on existing methods in conjunction with numerical evaluation of the test performance reveals that some test rigs are simple but the distribution of stresses is not desirable, while the other arrangements provide nearly uniform shear deformation but require rather complex test devices.

The idea is to combine the advantages of suggested methods and to introduce rather simple test procedure where the application of external forces into the mortar layers leads to almost pure shear stress and in the presence of pre-compression create a uniform normal stress.

Two methods is presented, the first method is an adaptation from DIN EN 1052-3 for a stack of three units and the second method derived from theoretical bases considering the limitation of testing equipment in the laboratory.


Keywords: Unreinforced masonry, initial shear strength, test method