Compressive strength of brickwork masonry with special reference to concentrated load
Abstract
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.