The effects of loading frequency and stress reversal on the fatigue properties of concrete were investigated by conducting flexural fatigue tests on plain concrete beams. A new fatigue equation based on the classical Aas-Jakobsen S—N equation is proposed which contains the above effects. This equation agrees well with previous experimental results and proves to be suitable for some other loading states other than bending.

SUMMARYA computer orientated method is presented which generates meshes of triangular elements in plane and curved surfaces. Depending on geometrical and material variations, the region to be discretized is divided into a number of four sided zones. By using curvi-linear co-ordinate systems, nodes within and on the boundary of each zone are automatically positioned and referenced to a global Cartesian co-ordinate system. Elements are automatically assembled from these nodes. Input data is required to specify the positions and material properties of each zone and how they are connected. Examples are given which illustrate the range of meshes that can be generated. Extension of the method to generate three-dimensional tetrahedral elements is indicated.

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Direct tension tests were conducted on plain concrete specimens in a stiff loading frame which allowed complete stress-deformation relations to be obtained. The suitability of the specimen shape and the testing apparatus was verified by finite-element analysis. The behaviours of notched and un-notched specimens with different water-cement ratios were examined and compared. Piecewise linear and exponential stress-deformation relations are proposed and interpreted physically. Relationships between fracture parameters fracture energy and brittleness indices) and basic strength properties are also presented.