KVPT’s Patan Darbar Earthquake Response Campaign - Work to Date - September 2016

Top
Wall section showing the composition
of a typical Newar brick masonry
wall. (Gutschow, 1987) Note
the variance in brick types, infill
between outer wythes of brick and
the lack of structural connection
between the different layers.
Middle
Bulging and separation of layers
of typical brick masonry wall. The
mud mortar erodes and the outer
dāci apā layer has separated from
inner wythes of brick.
Bottom Left
Improved detail for brick masonry
wall, interlocking bricks of varying
sizes to provide more structural
continuity between the inner and
outer faces of the wall.
Bottom Center and Right
Stainless steel rods with hooked
ends that secure the outer wythe to
the inner wythe of brick laid in the
mortar bed to improve structural
continuity. Stainless steel can also
be laid in a bowtie pattern to help
strengthen connection of outer
wythes of walls.
3. Brick Masonry Wall Composition
Description
Masonry walls made from mud mortar were built in
three different layers that are not properly bonded together
(like a cavity wall). The exterior layer is always
dāci apā and the interior layer is mā-apā (or occasionally
dāci apā) with rubble infill between the two.
Issues
There is no proper structural connection between layers.
This causes bulging of the tapered dāci apā bricks when
mud mortar dries and erodes. This deterioration is especially
weak during an earthquake, where the exterior
layer bulges further due to lack of connection within the
wall, and was blown out on many such walls leading to
collapse.
Options for Seismic Strengthening
If header bricks are not available to connect layers within
the wall, it is recomended to (i) cut dāci apā to provide
a proper overlap with daci apā layer, (ii) use a 6 mm
stainless steel rod in with hooked ends to hook into and
connect inner and outer brick layers (iii) make bowtie
reinforcing with 2 mm dia. stainless steel wire to connect
all layers. Any of these solutions can be applied at every
30"-36" in every 4-5 brick layers.
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