The scope of this calculation module is to check the bearing stress for
loads acting on the masonry wall. The wall type can be either solid or cavity with or without
grout. The bearing stress of the component is computed taking into consideration the specified
masonry properties and categories. Spreader beam or pad stone can be provided in order to
increase the bearing area and to reduce the stress below.
The design module allows the user to capture the actual site / design requirements via various options such as,
With or without piers
With or without spreaders
Beam spanning direction
In order to better use of the module, selection based material properties are given such as,
Type of bricks used and their properties
Clay and calcium silicate bricks
Autoclaved aerated concrete blocks
Aggregate concrete blocks (of various porosity)
Solid aggregate concrete blocks laid flat
Solid aggregate concrete blocks collar jointed
Masonry unit category (as defined in code provision)
Construction control category (as defined in code provision)
The ratio of masonry unit height to least horizontal dimension of masonry unit and the ratio of masonry unit height to effective thickness of masonry wall has been limited to a definite range for different wall types.
The stress concentration which occur underneath the beam or spreader disperses throughout the masonry and it is assumed that the dispersal occurs at an angle of 45°.
The distribution of stress under the spreader beam is derived from an acceptable elastic theory, either simple elastic theory assuming a triangular stress block with zero tension or 'Timoshenko’s analysis for elastic foundations'.
The beam that imparts load to the masonry wall underneath is assumed to be relatively stiff, thus the allowable bearing stress is enhanced to 25%, 50% and 100% based on the beam to masonry wall interaction area.
Based on beam spanning direction the beam may be considered as in-plane or out plane.
The calculation of design bearing stress is based on the position of beam placed on spreader beam, i.e. load acting at midpoint of spreader, load acting at middle third of the spreader and load acting outside the middle third of the spreader.
The design bearing stress and allowable bearing stress at 0.4 * h (height of masonry wall) underneath the beam bearing level is checked.
National Standards Available
British standard: BS 5628-1:2005 Code of practise for the use of masonry.