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

at the interface between the slab and shear key. Inadequate
detailing could drastically affect the lifespan and
effectiveness of the structure in an earthquake.
Superstructure
Above grade, the main challenge at the South Mani
Mandapa structure is how to connect the heavy brick
masonry and timber structure above the ground level
arcade back down to the foundations while maintaining
as much historic fabric and architectural integrity
as possible. The top-heavy nature of the structures, the
slender and delicate nature of the highly carved historic
columns, the lack of tensile capacity in the connections
and timber joinery, and a variety of other structural discontinuities
and weaknesses make this connection vital
to the success of the project. Adding to the structural
complexity are the desire to retain the sound timber of
the historic central core columns (mainly intact, with
lowest 1-2 feet requiring replacement due to wet rot)
and the discontinuities introduced by repairs at the perimeter
columns.
The outer columns of South Mani Mandapa have been
repaired, with the exception of one replaced column,
and these columns will be tied to the base stones beneath
them via stainless steel dowels set in a structural epoxy.
This will add tensile capacity to these connections so
that the column tenons will not rock or pull out of their
mortises as they did in 2015.
Several design iterations were also developed and discussed
for treating the 4 central columns as a core, as the
discussion of whether to use a stiff core or a more flexible
overall system progressed. The following concepts were
just some of those considered, following on the concepts
presented by structural engineer Evan Speer’s August
2015 report.
Option 1
An initial concept was to simply replace the four central
columns with new timber to provide continuous,
stronger timber columns. These timber columns would
bear on a steel base plate connection to the foundation
system, be it a concrete slab or steel grillage. The columns
would have doweled connections into the foundations
to tie the columns down to the foundations. This
concept would provide a continuous column with no
exposed steel, which preserves the original architectural
feel. It introduces new, continuous wood providing a
more robust load path than historic timber joined with
new timber at the base, and can keep the historic layout
of the timber column. This concept however, would require
the removal of original, historic timber columns
Manimandpa conceptual diagrams
of a stiff central steel column core
for South Manimandapa, developed
in August 2015 by Evan
Speer. This concept sought to bring
the structure up to an operational
performance level, but required
replacing the central historic timber
columns with steel. This started the
discussion about choosing between
a stiff core and a flexible system.
Sketch by Evan Speer, 2015
91