Emeritus Professor Adrian Page

Unreinforced masonry is widely used in Australia as an architectural and structural material. Becaus of its high mass, lack of ductility and low tensile strength it is unstable for use in areas of high seismicity. However in countries of lower seismicity such as Australia it can be used provided it is designed, detailed and constructed correctly. This paper provides an overview of the use of unreinforced masonry in Australia and discusses the impact of the new seismic loading provisions on existing practice. It is shown that unreinforced masonry can still be used in most instances provided the correct design and detailing techniques are used and the requirements of the appropriate masonry standards implemented.

On 28 December, 1989 the city of Newcastle was struck by a magnitude 5.6 earthquake killing 12 people and causing losses estimated at $1000 million. It was the first time a major Australian city has been so extensively damaged as a result of an earthquake, and the first time that deaths have occurred. With a few exceptions, most of the damage was to older loadbearing masonry construction or to infill masonry in modern framed construction. There was relatively little structural damage to modern buildings, industrial facilities and lifelines. This paper reviews the damage to structures and brings out the main points to be considered in future design and construction.

The strength of solid masonry walls subjected to concentrated loads is studied, using a finite element model to simulate wall behavior. The finite element model is able to reproduce the non-linear deformation characteristics of the bricks and mortar as well as local failure in both bricks and joints. To allow the efficient modelling of storey height walls, multi-level substructuring and mesh-refinement techniques are used. A parametric study is carried out with the influence of loaded area ratio, load location and wall geometry being considered. It is shown that all three of these variables significantly influence the degree of enhancement of wall bearing strength in the region directly beneath the load. Existing design rules are reviewed and shown to be non-conservative and incomplete in many cases. More realistic design provisions are prepared from the results of the parametric study. Two relationships are presented, one incorporating all of the above three variables, and a second simplified expression based on a conservative assumption regarding wall geometry.

The background of the design provisions of the new SAA Masonry Code for walls and piers subjected to vertical load and moments is reviewed. Factors influencing the compressive strength of masonry members are discussed, and the vertical loading provisions of the Code described. Methods of assessment of the effective eccentricity of vertical load are also presented.

Design rules for assessing the degree of bearing strength enhancement in solid walls subjected to concentrated load are presented. These are derived from all previously reported experimental and analytical studies of this problem and apply to all types of masonry built with solid units (clay, light- and normal-weight concrete, calcium silicate). Relatively simple design rules are proposed because of the large number of variables involved and the scatter of test results. The bearing strength enhancement is expressed as a function of the loaded area ratio and load location, with all other variables being absorbed in the general scatter of test results. The procedure also includes an allowance for the varying influence of wall size on bearing strength enhancement and, when compared to reported experimental results, yields conservative estimates of strength enhancement in almost all cases.

In this Paper, some previously reported biaxial tests are combined with further results to develop a complete failure surface for brick masonry in the principal space ( sigma //1, sigma //2, theta ). A surface in the alternative stress system ( sigma //n, sigma //p, tau ) is then derived and discussed. This surface is closed and can be represented as three intersecting elliptic cones. It is argued that a failure surface in sigma //n, sigma //p, tau stress space is better suited for modelling brick masonry finite element techniques. The factors influencing the shape of the failure surface are discussed, and the tests required to define a conservative failure surface described.

This paper describes a series of biaxial compression tests on half-scale brickwork. Tests were performed on square brickwork panels with the principal compressive stresses oriented at various angles to the bed joints, and a failure surface was obtained in terms of these parameters. Two distinct modes of failure were observed depending on the ratio of the principal stresses, with the influence of the bed joints being significant only when one principal stress predominated.

This paper presents an analytical approach predicting the failure of shear walls using a biaxial stress failure criterion developed from tests on brickwood panels. A computer model is used, which reproduces the non-linear behavior of masonry produced by progressive cracking. The theoretical results are compared with experimental tests performed on shear wall panels subjected to combined compression and racking load. The influence of test method on the 'masonry' shear strength is discussed.

A finite element model which reproduces the non-linear behavior of masonry is described. This model considers masonry to be an assemblage of elastic brick continuum elements acting in conjunction with linkage elements simulating the mortar joints. The non-linear characteristics of the masonry are produced by the non-linear deformation properties of the mortar and the progressive failure and/or slip that occurs in the joints when a shear or tensile bond failure criterion is violated. The model is used to predict the behavior of a brickwork wall supported by a steel beam. The results are compared with those of a conventional isotropic elastic analysis and experimental tests performed on a similar panel.

The behavior of solid and hollow masonry subjected to in-plane concentrated loads is reviewed, and the background to the concentrated load design provisions of the SAA Masonry Code described. These provisions allow for the sometimes substantial enhancement of bearing strength that can occur beneath the load, particularly for solid masonry. It is also shown that a distinction must be made between solid and face-shell bedded hollow masonry since their behaviour and failure modes are different fundamentally.

This paper describes the application to the analysis of infilled frames of a finite element model for simulating the behaviour of brick masonry. The material model for the masonry includes the elastic properties, the inelastic stress-strain relations and a failure surface. The finite element program is capable of simulating progressive cracking and final failure of the infill. The model is verified by comparison with five racking tests on infilled frames. It is then used to carry out a more extensive study of the influence of infill properties on the failure loads and failure modes of the panels. The influence of changing the frame geometry and the ratio of frame/wall stiffness is also considered.

A finite element model for brick masonry is reported. The model takes account of non linear deformations and progressive local failure. The failure may occur in the joints alone or in a mode involving both bricks and joints. The iterative plane stress finite element program is based on eight noded isoparametric elements and is used to simulate the incremental loading and progressive failure of brick masonry under in-plane loads. The effectiveness of the program is demonstrated by comparing the computed behaviour with the experimental results from racking tests on five steel frames with brick masonry infills.

A finite element model for brick masonry which takes account of the non linear deformation and both joint related and crushing failure characteristics is reported. Macroscopic deformation relations and failure criteria have been derived from the results of a large number of biaxial tests on half scale brick masonry panels in which the orientations of the bed joint planes to the edges of the panel were varied. Various combinations of tensile and compressive loads were applied to the edges of the panel.