Keys Mortise Through Tenon Mortised Timber King Post Collar ...

Keyed
 through
 tenon
 joints
 also
 known
 as
 wedged
 tenon
 joints,
 are
 a
 variation
 of
 traditional
 mortise
and
tenon
joints
fastened
with
pegs.

These
joints
are
constructed
by
cutting
a
tenon
in
the
end
of
one
timber
that
protrudes
through
the
backside
of
a
mortise
and
uses
keys
to
fasten
the
timbers
together.
Keyed
 through
 tenon
 joints
 appear
 in
 king
 post
 trusses
 and
 in
 post‐to‐beam
 (often
 anchor
 beam)
connections.

These
joints
are
often
used
for
aesthetic
purposes
and
 offer
flexibility
in
sizing
 the
 keys
and
 through
 tenon
 without
 affecting
 the
 strength
 of
 the
 mortised
 timber.
 
 The
 figures
 below
 show
 a
typical
keyed
through
tenon
joint
and
its
common
applications.
Mortise
Keys
Through Tenon Mortised Timber
King Post
Through-Tenon
Keyed
Through
Mortise
and
Tenon
Joint
Collar Beam Through-Tenon
Anchor Beam
King post Truss Anchor Beam
Lance
Shields,
a
Master's
of
science
student
in
Civil
Engineering
at
Virginia
Tech,
is
conducting
research
on
the
tension
strength
of
keyed
through
tenon
joints
under
the
direction
of
Dr.
Daniel
Hindman
in
the
Department
 of
 Wood
Science
and
Forest
Products.

 The
purpose
of
 this
research
is
 to
 investigate
the
structural
 benefits
 of
 this
 joint
 given
 the
 design
 flexibility
 for
 sizing
 members
 without
 affecting
 the
strength
of
the
associated
timbers.

Unlike
pegged
mortise
and
tenon
joints
where
the
strength
of
the
mortised
timber
is
reduced
by
peg
holes,
keys
fasten
the
joint
outside
of
the
mortised
timber
and
can
be
enlarged
without
adversely
affecting
its
strength.
The
 research
 creates
 models
 to
 predict
 the
 strength
 of
 keyed
 through
 tenon
 joints.
 
 Models
 were
validated
by
measuring
the
behavior
of
joints
during
testing.

Forty
six
full‐sized
joints
constructed
with
6x8
white
oak
and
Douglas‐fir
timbers
were
tested
in
tension.

The
joints
were
constructed
with
11
inch
Post

or
 four
 inch
 tenons,
 one
 or
 two
 keys,
 and
 keys
 of
 either
 white
 oak
 or
 ipe
 (a
 tropical
 hardwood).
Currently,
samples
of
wood
cut
from
the
joints
are
being
tested
to
provide
input
strength
values
for
the
mathematical
 equations.

These
models
will
provide
predicted
joint
strength
values
for
comparison
to
the
experimentally
tested
joint
strengths
for
model
validation.
Below
 is
 a
 photograph
 of
 a
 joint
 tested.
 
 The
 joint
 is
 loaded
 upward
 in
 the
 testing
 machine
 causing
withdrawal
of
the
tenon
from
the
mortised
timber
by
upward
movement
of
the
machine
cross‐head
on
the
end
to
the
tenoned
timber
and
the
holding
down
of
the
mortised
timber
with
steel
tubes
and
bolts.
The
red
arrows
indicate
the
load
directions.
Tenoned
Timber
Steel
Tube
Tenon
Courtesy
of
Lance
Shields
Below
are
photographs
(courtesy
of
Lance
Shields)
of
some
tested
joints.

The
first
three
photographs
are
of
a
Douglas‐fir
joint
with
an
11
inch‐long
tenon
and
two
keys.

The
first
photograph
shows
the
joint
before
 testing,
 the
 second
 photograph
 shows
 the
 joint
 in
 the
 testing
 machine
 under
 tension
 loading
(notice
 the
 separation
 between
 the
 mortise
 and
 tenon
 member),
 and
 the
 last
 photograph
 shows
 the
failure
of
keys
after
testing.
Joint
before
Test
































Joint
during
Test











Keys
after
Test
(Bending
&
Crushing)
The
next
three
photographs
show
a
white
oak
joint
with
a
four
inch‐long
tenon
and
two
keys.

The
first
photograph
shows
the
joint
before
testing,
and
the
second
and
third
photographs
show
the
joint
during
and
 after
 testing
 (note
 the
 tenon
 relish
 underneath
 the
 left
 key).
 
 Typically,
 joints
 subject
 to
 tension
tests
 with
 11
 inch
 tenons
 produce
 key
 crushing
 and
 bending
 failures
 while
 the
 joints
 with
 four
 inch
Cross‐head
Mortised
Timber
Key

tenons
produce
tenon
relish
failures
as
shown
below.

The
use
of
ipe
keys
increased
the
joint
strength
compared
to
the
use
of
white
oak
keys.
Joint
before
Test



























Joint
during
Test



















Tenon
after
Test
(Tenon
Relish)
Lance
 Shields
 first
 learned
 about
 timber
 framing
 in
 Powhatan
 High
 School
 under
 the
 guidance
 of
 Jim
Henderson
in
a
vocational
class
called
Carpentry
Building
Trades
(CBT).

He
also
learned
about
Dreaming
Creek
Timber
Frame
Homes
who
sponsored
many
of
the
projects
in
the
class
and
later
worked
for
them
during
 his
 last
 semester
 of
 under
 graduate
 school
 at
 Virginia
 Tech.
 
 Dreaming
 Creek
 Timber
 Frame
Homes
has
made
this
research
possible
by
providing
much
support
and
materials.
For
more
information
please
contact
either:
Lance
Shields,
EIT
Emial:
lshie06@vt.edu
Dr.
Daniel
Hindman,
Ph.D
Email:
dhindman@vt.edu