Abstract:
Concrete slabs exposed to direct sunlight experience
temperature related horizontal movements. In addition,
temperatures on the top surface will be higher than those on
the underside of the slab, causing an upward deflection of the
slab during heating. In a typical building, masonry and concrete
elements are connected to each other at their respective
interfaces. Therefore, significant movements may be generated
on the masonry walls due to the movement of the roof slab.
These movements can result in overstressing and cracking in
masonry. These cracks may not be structurally serious, but may
lead to ingress of moisture and in any case are not acceptable
especially where good finish is desired.
In this study, the behaviour of these cracks was predicted
based on surveys of buildings where cracks have formed. Also,
typical structural arrangements were mathematically modelled
using 3D brick finite element models, with link elements
between the masonry and concrete elements in order to model
interfaces. The objective of the study was to investigate the
stresses developing on the wall due to the movement of the
roof slab. Locations and directions where cracking would occur
were identified using the principal stresses developed in the
finite element model and a failure criterion developed based
on the modified Von-Mises theory. Also, using these numerical
models, the effect of wall length and structural form of the wall
(i.e. load bearing walls and reinforced concrete framed walls)
on the formation of these cracks was studied. These results
were compared with the information obtained from the survey.
