Manouchehr Hassanzadeh

Determination of fracture zone properties in mixed mode I and II

A test equipment for the measurement of material properties within a damage zone subject to combined tension and shear deformations is described. Some results have been presented and discussed concerning the damage zone behaviour under such conditions

Residual Strength of the Frost-Damaged Reinforced Concrete Beams

The most severe types of destruction mechanisms are those causing internal cracking and thereby loss of cohesion of the concrete, i.e. internal expansive attacks. The internal frost damage belongs to this category of destructive mechanisms. The frost attack causes a random system of cracks in the heart of the concrete together with cracks parallel to the surface of the concrete. In many cases there are also extended cracks parallel to joints and edges of the concrete, or emanating from corners. The amount of damage can vary from place to place in the same structure. Therefore, in most cases, series of data from many different places are required. Only in special cases data taken from one place can be used for the entire structure.

Fracture Mechanical Properties of Rocks and Mortar/Rock Interfaces

This study has determined the fracture mechanical properties of 9 types of rock, namely fine-, medium- and coarse-grained granites, gneiss, quartzite, diabase, gabbro, and fine- and coarse-grained limestones. Test results show among other things that quartzite has the highest compressive strength and fracture energy, while diabase has the highest splitting tensile strength and modulus of elasticity. Furthermore, the strength and fracture energy of the interfacial zone between the rocks and 6 different mortars have been determined. The results showed that, in this investigation, the mortar/rock interfaces are in most cases weaker than both mortars and rocks.

Theoretical Analyses of Test Methods

By means of a model based on tension softening it is possible to make a theoretical analysis of a test and of evaluation methods used for the determination of fracture mechanics properties of concrete and rock. In this way it is rather easy and inexpensive to check whether a test may be expected to give valid results, e. g. if the size of the specimen is large enough. A negative result of such an analysis, i. e. if it shows that the results cannot be expected to be valid, can be regarded as reliable and should lead to a change in the the test method. A positive result may, on the other hand, be misleading if the assumptions used during the analysis differ too much from the real material properties of the tested material. A number of examples are given regarding the possibility to use pure LEFM, or LEFM with corrections, for the evaluation of tests.