The importance of masonry compressive strength to the seismic design of masonry buildings has been reviewed.Difficulties in predicting masonry compressive strength have been discussed and some theoretical considerations have been developed to enable predictions of prism strength on the basis of compressive strength of masonry units, joint mortar and grout. However some unsolved problems still remain in this field of study. The state of difficulty is mainly thought to depend upon unsufficient information of non-linear behaviours of the three component materials,especially of masonry units which are supposed to have a great influence on prism strength.

This paper deals with the test method for determining the compressive strength of masonry units and their fundamental mechanical behaviours including non-linear stress and strain relationships. A numerical method for expressing the stress and strain relationships of units is proposed.

On the first point of quality control for masonry units,various methods for determining the compressive strength of masonry units in present codes and specifications are specified. The compressive strength based on various methods is compared with each other. The shape of specimens, the methods of capping and loading devices are examined by experiments.

On the second point of non-linear behaviours of masonry units under uniaxial load, various types of masonry units were experimented by using a small prism or coupon specimens cut from masonry units. A general tendency in the stress and strain relationship of masonry units is discussed including Young's modulus, Poisson ratio and their anisotropy and ununiformity.

Finally, a numerical method for presenting the non-elastic behaviours of masonry units is discussed against experimental data conducted herein. This numerical presentation is thought to be effective in order to predict the properties of masonry with various component materials.

This experiment was carried out as the material research program of the U.S.-Japan Joint Earthquake Research on Masonry Building Structures.

* Building Research Institute, Ministry of Construction
** Institute of Vocational Training, Ministry of Lavour