H. H. KNUTSSON Danish Building Research Institute


The Ritter formula for the modulus of elasticity for materials with no tensile stresses has in many cases formed the basis for a design formula for the carrying capacity of columns and walls. The Ritter formula can be transformed so it contains dimensionless values only. The corresponding curve is called the Ritter curve. By transferring the ordinary stress-strain curves for different types of masonry it is demonstrated that the so-called normalized stress-strain curves are reasonably close to the Ritter curve — with the exception of high relative stresses for which the Ritter curve is replaced by a tangent to the curve. The tests results demonstrate that for hollow bricks in weak mortar the strains will be 1-4 times greater than for hollow bricks in strong mortar — or solid bricks in either weak or strong mortar. By transforming the area under the Ritter curve supplemented with the tangent a linear stress-strain relationship is achieved. This gives a proper basis for using the elastic stress distribution in design. Similarly the basis for the use of plastic stress distribution can be obtained.