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Significance Statement
An unreinforced masonry (URM) assemblage is a non-homogeneous, inelastic and orthotropic material constructed using individual brick units and mortar, and therefore its properties are influenced by both the brick unit and the mortar properties. Masonry assemblage properties such as the masonry constitutive relationship and Modulus of Elasticity are required for linear and non-linear analyses of masonry structures.
Masonry compression stress-strain characteristics and the relationships between masonry compressive strength and the constituent material properties have been explored by past researchers. However, most of these past studies were laboratory based and did not include within their scope the testing of samples extracted from existing masonry buildings.
The work presented here was undertaken to investigate the compressive strength and the compression stress-strain characteristics of New Zealand URM buildings that were generally constructed between 1880 and 1935. Numerous masonry prisms were extracted from 8 existing New Zealand URM buildings, and laboratory-made prisms having 14 different brick/mortar combinations were constructed for comparison using New Zealand vintage solid clay bricks and a range of mortar strengths. These extracted and laboratory constructed prisms were laboratory tested, and predictive expressions relating masonry compressive strength to the constituent material compressive strengths and to the masonry Modulus of Elasticity were developed based on the experimental results. Masonry compression stress-strain numerical models were also developed to enable the prediction of masonry stress-strain behaviour. Whilst noting that the variability of aged masonry made the development of precise relationships unrealistic, the primary objective of this study was to develop predictive expressions that are sufficiently accurate to use in the detailed seismic assessment of regular URM buildings.
Journal Reference
Journal of Materials in Civil Engineering, Vol. 26, No. 4, 2014, pp. 567-575.
Lumantarna, R.1, Biggs, D.2, and Ingham, J.1
1Dept. of Civil and Environmental Engineering, Univ. of Auckland, Private Bag 92019, Auckland 1010, New Zealand
2Principal, Biggs Consulting Engineering, Troy, NY 12180.
ABSTRACT
Masonry material characteristics such as compression stress-strain behavior and the relationships between brick, mortar, and masonry compressive strengths are required for the detailed analysis and assessment of masonry structures. These properties have been investigated previously, but most past studies were laboratory based and did not include within their scope the testing of existing masonry buildings. This study aimed to characterize the compressive strength and the compression stress-strain relationship of vintage clay brick masonry used in New Zealand URM-bearing wall buildings that were generally constructed between 1880 and 1940. Testing was performed on 45 masonry prisms that were extracted from eight New Zealand historic URM buildings and on 75 masonry prisms that were constructed in the laboratory using 14 different brick/mortar combinations. It was found that the laboratory-constructed sample test results adequately replicated those from the field-extracted samples, and predictive equations and a numerical compression stress-strain model for use in the detailed seismic assessment of URM buildings were developed based on the experimental results.
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