Institut fur Tragkonstruktionen, University of Karlsruhe
For the assessment of the loadbearing capacity of existing brickwork, assumptions on its mechanical behaviour often have to be made when direct testing is not possible to provide more accurate information. Old brick-masonry has frequently been constructed with lime mortars which differ from modern cement based mortars in their chemical, hydraulic and mechanical behaviour, new lime mortars with similar features are therefore increasingly employed for restoration and repair. The mechanical properties of masonry depend on a variety of parameters, above all, the interaction between mortar and bricks. Thus it is not possible, to date, to predict them from the brick and mortar properties alone. Testing masonry specimens is time consuming and expensive. The mechanical properties of lime mortars develop slowly due to their hardening by carbonation. This paper deals with the possibility of assessing the stress/strain behaviour of full scale masonry with reasonable accuracy from tests done on geometrically scaled model piers. These reflections are based on a series of tests on stack bonded prisms at full scale and quarter scale with different types of mortar. The results also indicate that the general conception of the loadbearing behaviour and failure mechanism is not always valid for brickwork with historic mortar. Compared with the common theories the masonry strength is considerably underestimated, whereas the elastic modulus of the types of masonry investigated is much lower than expected.