Compressive strength of brickwork masonry with special reference to concentrated load

This thesis presents a comprehensive experimental study for the behaviour of brickwork masonry subjected to concentrated load applied through a rigid steel bearing plate and investigates the enhancement in strength under this type of loading in relation to Its uni-axial compressive strength. To normalize the bearing strength under partial load, a thorough Investigation has been carried out to establish accurate values for the characteristic compressive strength of masonry based on the limit state theory. This has been achieved by analysing statistically the data collected on the crushing strength of full storey-height brickwork walls. Relationships for mean. and characteristic strengths for brickwork wall and brickwork masonry have been derived in terms of unit brick crushing strength for two mortar mixes and wall thicknesses and also in terms of unit brick and mortar cube strengths for two brick masonry thicknesses. Previous investigations of the compressive strength of brickwork masonry under uniform and partial load together with the design rules given in various codes are reviewed. A complete experimental study of materials properties used in the present research including the detailed study of the behaviour of brickwork masonry under the action of concentrated load are presented. In all 338 brickwork panels constructed from seven different brick types and two mortar grades were tested of which 300 were subjected to concentrated loads and the remaining under uni-axial load. The test results together with the results of 56 specimens tested under concentrated load prior to this investigation with their crack pattern and failure mode are reported. The results are analysed statistically and design charts for the characteristic bearing strength of masonry for various loaded area ratios are obtained. The influence of parameters such as loaded area ratio, loading position, loading configuration, strength of constituent materials, masonry thickness, element aspect ratio and the effective area of brickwork on the bearing strength and enhancement factor are examined. A theoretical investigation into the stress distribution of brickwork masonry under concentrated loading by Finite Element method is reported assuming brickwork as a homogeneous continuum and as an assemblage of separate bricks and mortar joints. Linear elastic and nonlinear analyses are performed using a standard package. A mechanism of failure is proposed for masonry under partial load. Based on the results obtained experimentally failure envelopes are derived for two masonry thicknesses. Finally, design rules based on the outcome of this investigation are proposed