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TingWall Bulletin - 101 |
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CONVENTIONAL
UNITIZED SYSTEM (CUS) VS. TingWall™(TW)
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1.
CUS was invented with the idea of shifting most
of the critical sealing execution from the field
to the shop. CUS shop assembles at least two facing
panels (normally to cover one floor height) together
with complete framing and sealing components. Split
mullions, one on each side of the unit, are integral
parts of the framing system. Horizontal support
members are fastened to the split mullions to complete
the supporting frame system. The supporting frame
system is directly utilized for sealing the edges
of the facing panels. The following disadvantages
have been recognized from the past experiences.
a. The intersection points between the mullion and
each of the horizontal members are locations for
potential water leakage. These locations require
careful execution of critical seals. Once the critical
seals become imperfect due to the effects of aging
and various long term repeated structural movements,
water leakage will occur.
b. In the field installation procedure, the four-corner
intersection of the units becomes the critical joint
to be executed in the field. If the sealing of the
critical joint is not executed perfectly, major
problems can arise due to the difficulty in accessibility
for repair.
c. In erecting the units, since the split mullions
must be engaged between two units, sequential erection
is required. It is quite common for erection work
to be halted when a unit is damaged and must be
replaced.
d. In hot regions, thermally induced noises are
commonly reported at the split mullion joints (sudden
release of friction force) and/or the horizontal
stack joints (compression between frame components).
In Taiwan, many buildings with CUS or Stick System
reported the thermal noise problem. In one severe
case, the noise sounded like a gunshot.
e. Since the framing members are used for sealing
the perimeters of the facing panels, when story
drift occurs (inter-floor left to right differential
displacement), due to earthquake or wind load, significant
stresses can be generated within the sealant lines
and facing panels. Glass failures due to story drift
have been reported in several famous buildings in
USA.
f. In the event of significant floor edge deflection,
the curtain wall mullion joint of a CUS must move
the same amount of deflection. For example, steel
frame buildings are commonly designed for a maximum
floor deflection of 20 mm. With a mullion joint
movement of 20 mm, the ability of a CUS to maintain
the various curtain wall functions becomes highly
questionable.
g. In case of negative wind load, the reaction force
transferring mechanism normally relies on screws
in tension (e.g. screws on glazing pressure bar)
or screws in shear (e.g. screws from split mullion
into the horizontal frame member). The loosening
of the screws due to stress fatigue caused by repeated
thermal, wind, and seismic load cycles inevitably
produces functional degradation of curtain wall
functions often leading to water leakage (failure
of critical seals) or structural failure (failure
of screws) in more severe condition.
h. The anchor bolts on the pre-set mullion anchor
assemblies protrude upward from the surface of the
concrete floor slab. During the concreting and floor
leveling operation, almost inevitably some of the
anchor assemblies are kicked out of position beyond
the adjustability of the connection system and/or
the entire bolt is buried in the concrete slab.
Costly remedial work is required to fix the problem.
i. As required for quality installation, the mullion
anchoring system must provide three-way (up-and-down,
in-and-out, left-and right) dimensional adjustability.
However, after final positioning adjustment, field
welding is required in most anchor assembly designs.
j. Since the facing panels are unitized with the
supporting frames in the shop, the shipping volume
is significantly increased and heavy lifting and
handling equipment is required in the field. Equipment
availability problems or breakdown can cause serious
project delays.
k. A large warehouse is needed to allow cure time
for structural silicone glazed units or critical
seals using caulking.
2. TingWall™ was invented by Dr. Raymond
Ting to solve all the above disadvantages of CUS.
The design of TW is based on Dr. Ting's Airloop
Principle™. Each facing panel is unitized with
and sealed to the perimeter Airloop™ frames
in the shop. TingWall?mullions are also prefabricated
in the shop with sealing tapes. Only two simple
typical steps are required in erecting TW, namely,
erecting TingWall™ mullions and installing
TingWall™ panel units between two adjacent
mullions. Only small amounts of caulk forming marriage
seals are required in erecting TW. Due to the shop
procedure of unitizing each facing panel, TW is
sometimes recognized as Airloop™ Unitized System.
TW solves all the problems of CUS as explained below.
a. The function of sealing air around the panel
perimeter is completely separated from the function
of sealing water by the Inner Airloop™ designed
in the TingWall™ panel frame. Therefore, there
is no critical seal in the shop unitized TingWall™
panel.
b. The function of sealing air between the panel
joints (vertical and horizontal) is completely separated
from the function of sealing water by the Outer
Airloop™. Therefore, there is no critical joint
or critical seal required in the field.
c. The space provided for the Outer Airloop™
at the mullion allows a TW panel to be engaged into
two adjacent mullions independent of panels to either
side. As a result, TingWall™ erection is non-directional
and provides the highest flexibility in construction
management (skip and back-fill) and project schedule
control (simultaneously erecting TW at multiple
locations). No more interruption of erection work
due to a damaged unit.
d. There is no stack joint in TW and all panel frame
members are free to expand into the open vertical
and horizontal panel joints. There is no split mullion
in TW. For the above reasons, the thermally induced
noise problem is eliminated in TW as proved out
by the three competed TingWall™ buildings in
Taiwan.
e. In TW, the panel perimeter seal is contained
within the panel frame, which is completely separated
from the supporting mullion. In addition, the Outer
Airloop™ space between panels and mullions
enables the mechanism of stress-free panel movement
in case of story drift caused by earthquake or wind
load. Therefore, the stress problem due to story
drift is eliminated.
f. The patented TingWall™ connection system
can limit the curtain wall joint movement to any
desirable amount independent of the large amount
of floor deflection. This feature eliminates the
concern of curtain wall function failure in case
of large inter-floor deflection.
g. For the TingWall™ System, in the case of
negative wind load, rather than relying on screws
or other types of fasteners, the force transferring
mechanism utilizes mechanical inter-locking in the
extrusion components. The shear strength of the
panel securing screw is utilized only to resist
the dead weight of the panel that is stationary
and not affected by the other load cycles (thermal,
wind, and seismic). Therefore, the problem of stress
fatigue on screws is eliminated and the concern
of functional degradation is greatly reduced.
h. The standard TingWall™ mullion-anchoring
system is designed with the anchor bolts protruding
horizontally from the edge of the floor slab. A
simple U-bolt assembly is used with the condition
of permanent slab edge form (normally a steel bent-angle).
The Halfen anchor is used with the condition of
removable slab edge form. The design greatly reduces
the chances of anchor dislocation during the concreting
and floor leveling operation.
i. The patented TingWall™ mullion connection
system allows simple three-way dimensional adjustment
without the use of field welding. The trouble-free
ease of erecting TingWall™ mullions has been
well demonstrated in the buildings completed in
USA, Taiwan, and Japan.
j. TingWall™ system's unitized individual panels
and supporting frames (i.e. mullions) are delivered
to the jobsite separately. Consequently, the shipping
volume of TW is normally less than 50% of the shipping
volume of CUS. In addition, the individual TW units
can normally be handled with bare hands, or at most
using simple equipment. This feature provides unparalleled
flexibility in field management and again has been
well demonstrated in the completed TingWall™
projects worldwide.
k. There is no critical seal in the shop assembling
procedures of TW. In structural silicone glazed
TW units (hidden-frame glass or aluminum plate),
before the curing of the silicone caulking, the
relative movement between the facing (glass or plate)
and the panel frame is adequately restrained against
shop handling. Due to the light weight of TW, a
newly glazed TW unit can be easily hand carried
off the assembling table and stored in stacks on
the shop floor. The shop floor area requirement
for assembling this type of TW units is about 10%
of the shop floor area that would be required for
assembling CUS units. Again, this feature has been
well demonstrated in the fabricators' shops for
the completed TingWall™ projects worldwide.
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