retrofitting of masonry walls

1. Presented by,
Nayana D
Parvathy GVijayan
Vrinda J
Anandalekshmi B

2.  Vertical cracks are common at corners of masonry
buildings.
 REASONS
These fractures may occur due to thermal/ moisture
movement.
 Perpendicular walls may expand towards each other in the
direction of the corner, causing rotation of the brickwork
and eventual cracking in the masonry at the near the
corner.
differential movements in a wall, for example where a
bulging flank wall meets a straight and stable corner.

4. Shaped and twisted stainless steel rods are bonded into
the walls, stitching the masonry across the cracks at regular
intervals. The brick stitching system allows the cracked wall to
behave as a reinforced non-fractured unit.

5.  Reinforcing external corners with crack stitching
bars.
 A series of helical bars are used
 Bars are bent at a right angle, are bonded into slots
with polymer modified grout
 The bars form layers of concealed reinforcement
for stitching cracks at a corner

6.  A series of long drive-in helical wall ties are driven
from the corner of a building into the both flanking
walls to form a succession of perpendicular tie straps.
 The 12mm diameter ties corkscrew into small 8mm
pilot holes when driven with the impact action from
an SDS hammer-drill.
 The tie grips the brickwork along the entire length of
the helix to provide a tension strap that reconnects
and strengthens masonry adjacent to the cracked
corner.

7.  A horizontal channel is cut in the masonry, usually in
the bed joint where installation can be easiest
disguised.
 The slots are flushed with clean water immediately prior
to the installation of a high performance cementitious
grout.
 Brick stitching bars are simply pushed into the grout,
ensuring full insertion of the bars along their length.
 The helical bars extend 500mm each side of the cracks
to dissipate loads and disperse them evenly into the
wall structure.

8. 
Chase slots along the length of wall that extends 500mm
each side of crack.

9. Flush the slots thoroughly with clean water to remove loose
material and to reduce the tendency of porous brickwork to
suck moisture from the grout.

10. Working from the back of the slot fill to two thirds full with
grout, leaving room to repoint and match existing finishes.

11. Push the crack stitching bars into the slot ensuring they are fully
encapsulated in the grout. The bars must extend 500mm each side
of the crack to allow them to absorb loads and to disperse them
evenly into the wall structure.

12. Make good disguise to slot.
It is important to ensure all cracks in walls are filled and sealed.

15. Metal ties are widely used in traditional buildings
Used in wall –to- wall connections and wall- to –floor
connections

16. :!

17. Tying of masonry vaults with tie rods

18. Using tie rods in roofs

19. •LOW COST
•EASY INSTALLATION
•EASY MAINTENANCE
•DECREASETHE PROBABILITY OF OUT OF
PLANE FAILURE