Material Characterisation of New Zealand's Clay Brick Unreinforced Masonry Buildings

Abstract

This thesis reports the investigation on the material properties of New Zealand's heritage clay brick unreinforced masonry (URM) buildings. The primary focus of this doctoral investigation was to establish a methodology to determine the material properties of existing New Zealand URM buildings. Although researchers from Europe, USA, India and Australia have previously studied the material properties of clay brick unreinforced masonry, knowledge on New Zealand URM material properties was poor at the time the study commenced. Therefore, a research programme that primarily focused on the testing of samples extracted from existing New Zealand URM buildings was undertaken. Vintage clay bricks and irregular mortar samples were extracted from existing New Zealand URM buildings, and were subjected to a series of non-destructive tests before being tested in compression. The relationships between the non-destructive test results and the clay brick and mortar compressive strengths were studied, and non-destructive testing techniques that were most suitable for estimating clay brick and mortar compressive strengths in-situ were proposed. Also, a methodology for the compression testing of irregular mortar samples that are extracted from existing URM buildings and a technique to normalise the irregular mortar compression test results were developed. The compressive strength and compressive stiffness of masonry were studied using masonry prisms that were both extracted from existing buildings and were constructed in the laboratory. Empirical relationships relating the brick unit, mortar and masonry compressive strengths as well as relating the masonry compressive strength to the masonry Modulus of Elasticity were derived. Also, numerical models for the compression stress-strain relationship of masonry were proposed. The flexural bond strength and shear bond strength of masonry were studied using field extracted and laboratory constructed masonry prisms. Empirical relationships relating the mortar compressive strength to the flexural bond strength and to the bed joint cohesion were derived. Finally, a procedure to assess the material properties of existing New Zealand URM buildings was recommended.