Lee's Gardens Redevelopment

Construction of the Manulife Tower –
Redevelopment of the previous
Lee Gardens Hotel in Causeway Bay

External view of Manulife Tower from various location

Block plan showing the building layout of the new Manulife Tower

Manulife Tower with a
4-level retail podium

1/F and 3/F Layout Plan
Circular-shaped atrium
from 2 nd basement up to
the podium on 5/F

Sky Garden
aaa
Entrance lobby
with high
headroom
Typical floor plan and building section

Background Information about the Redevelopment
The project located in a 5,750 m2 site, which was abutted
on 3 sides to small roads from 12 to 20m wide, and the
remaining side adjoining a 17-storey residential building of
28 years old. In addition to the congested environment,
the project also required to demolish the 22-storey Lee
Garden Hotel, with a 2-level basement structure in it.
In the redevelopment, a new 50-storey office building, with
total GFA of 83,860 m2, constructed in structural steel
with a RC core, together with a 4-level basement, was to
be built within a construction period of about 50 months,
from demolition till final completion.

Contract arrangement
The project was sub-divided into 3 parts:
1. Demolition of the superstructure of the old Lee Garden
Hotel
2. Demolition of the old basement and the construction of
the cut-off walling provision, foundation for the new
building, and the core wall of the new building below
ground level.
3. Construction of the new building including the basement

Demolition of the old basement and Foundation
Construction
Though project of this kind is not exactly uncommon
in Hong Kong, the following features, however, still
make the redevelopment of the Lee Garden quite
unique and thus imposed certain technical difficulties.
1
2
A 2-level old basement structure covered the entire
site area was to be demolished. Work was difficult for
the old basement still took up the ground pressure.
A 4-level basement of the same size was to be built to
replace the old. Besides, a 5-level podium covering
the entire site area was also built, that made the site
extremely lack of working space during the
construction.

3. Due to the old basement could not support those
heavy plants which were required for the construction
of the foundation using other mechanical means,
hand-dug caissons were being used in this case.
4. Temporary ground support and shoring were to be
erected to take up the lateral pressure of soil while
doing the demolition.
5. Because of the inevitable sectioning and phasing
arrangement involved in the demolition of the old
basement, and, at the same time, to replace it with a
new structure, complicated planning and construction
jointing provisions were required.

6. While doing the major substructure and ground works,
provisions to construct part of the future structure were
carried out at the same time. These works include:
- construction of the cut-off wall
- foundation & cap for the core wall of the future
tower,
- erection of steel stanchions on top of the caisson
as column support to facilitate the construction of
the future basement using top-down method.
7. The congested environment made storage and
transportation arrangement within site very difficult. At a
result of this, temporary loading platforms were provided
at different locations to store the steel stanchions, to
station mobile cranes or other excavating machines etc.

Works being done to facilitate the demolition of the
old basement and the construction of substructure
In order to have the old basement demolished and
replaced by the construction of a new, as well as to
make way and facilitate the construction of the new
50-storey tower block, the following works were being
carried out that comprised the whole contract.

1. Demolition support and ground stabilization
• A series of temporary supporting system mainly in the
form of steel shore and bracing were erected before
various stages of basement demolition.
• Form a grouted wall along the site perimeter down to
3m below bedrock (average 25m deep) as a means of
ground water control during excavation and construction
of caissons.
• Demolish part of the basement slab along the
perimeter wall to give way for the construction of handdug
caissons, which were used later as cut-off wall for
the new basement structure. Totally 244 caissons of
1.2m diameter were constructed for the purpose.

Early stages of basement
demolition as seen in Early 1994

Later stages of basement demolition as seen in Early 1995

Erection of temporary shoring inside the
basement at the same pace with demolition

Arrangement
of temporary
support
during the
basement
demolition

Later stage of demolition at its peak

New steel columns for the new building
was installed while the basement was
under demolition at its later stage
Demolition was carried out under very congested environment
within the old basement with the temporary shore erected

Later stages of demolition
Remaining portion of
the old basement
Portion where
the ground
floor slab for
the new
basement was
under
construction

2. Construction of new foundations
•Excavate and construct the hand-dug caissons as
foundation for the future building within the old
basement. Totally 49 caissons with diameter
ranging from 1.6m (for podium structure) to 5.0m
(for main tower) were constructed.
•Demolish the central part of the old basement to
provide working space for the carrying out of the
foundation and cap for the future building core.
•Construct hand-dug caissons and the caisson cap
that supported the central core of the new building.

• Excavation and construction of the 5m diameter
caissons was done at the bottom of the pit that
formed after the demolition of the centre part of the
old basement.
• After the completion of the caissons, another pit for
the construction of the cap would start. The pit was
supported by soldier piles and lagged with mild
steel angles. The entire system was further strutted
and braced by universal beam sections.
• This cap sat on 7 caissons and was about 6m in
depth. Due to the massive size and weight, it
helped to hold down the entire basement from upheaving
during demolition and excavation
processes

Construction of caisson pile as
cut-off and foundation to new building

Shoring and stud frame to
stable the disrupted basement
Sides of the old basement was
disconnected to provide space for
the working of the hand-dug caisson

Shoring support to stabilize
the disturbed old basement
Caisson as
foundation for
podium structure
Caisson as
cut-off provision
Caissons that worked inside old basement

5m dia. Caisson worked inside
the old basement as foundation
for the Office Tower

Constructing the caisson foundation
in the location of the future core wall

Forming the caisson cap for the
support of the new tower core wall

3. Changing over and provisional works
for the new building
• Demolish the old basement structure along the
perimeters and build the capping beam on top of the
caisson wall.
• Demolish part of the old basement structure for the
erection of steel stanchions as column support to future
building. These columns could enable the
superstructure be constructed at the same time with the
basement that was built using top-down method.
• Rows of couplers were provided at basement floor
levels to allow for necessary connection of the
basement slab to the steel columns at a later stage.

• Construct the building core from the cap up to
ground level. Since there was very limited working
space within the central pit, traditional timber panel
formwork was used in the construction of the core.
• The core would act later as a lateral support for the
ground floor slab which served also as a separating
plate to facilitate the construction of the top-down
basement.
• At this moment, only half of the old basement was
being demolished. The construction of the core was
done in the central area with the remaining basement
structure still under demolition at the same time. The
problem of accessibility, clearing of debris formed by
demolition and the assurance of safety etc. were the
most headache part of the works at this stage.

• Demolish the remaining old basement, section by
section, and covered the space immediately with the
new ground floor slab. Phasing and junctioning
arrangement was the most difficult part of work here.
Finally the floor slab would infill the area between the
central core and the capping beam.
• Access provisions into the top-down basement and
for removal of spoil were also provided on the ground
slab. There were 3 of this access arrangement:
- One was based on the permanent vehicular
entrance,
- the other one is a temporary opening formed on the
Hysan Road side.
- Using the atrium shaft as an access

Cut-off wall formed by secanttype
hand-dug caisson
Capping
beam on top
of the
caisson cutoff
Forming of the cut-off wall at the same time of
demolition

Install steel columns
into the partly
demolished basement
Crane
supported on
a temporary
platform to
assist in the
placing of the
steel columns

Column for
office tower
Close up detail of the
steel columns inside the
basement/caisson shaft
Column for
podium structure

Coupling arrangement to
connect the steel column with
the RC basement structure
Bar coupler for
connecting steel bar to
floor beams or slab

Erection of floor formwork
to construct the new
ground floor slab
Portion of old
basement still
under demolition
Ground slab under
construction
Shifting over – majority of the old basement had been demolished,
the vacated basement space was constructing the new ground
floor slab as the first part of the top-down basement

Constructing the core wall at the later stage of
demolition using manual timber form

Close up seeing the construction of the core wall
inside the basement space

Gradual completion of the new ground slab
and the replacement of the old basement

4. Works merging with the main contract
• Erect the climb form system for the continual
construction of the central core.
• Construct the basement using top-down method.
Excavation started from the ground downward until it
reached a depth of 4 to 5 meter depending on the
headroom of the basement, where it would be shored
and strutted as an addition means of lateral support.
• After that, basement slab would be constructed which
was further connected to the central core, steel column
and the caisson wall with couplers that were provided in
advance.
• The works repeated until it reached the bottom level
of the basement where the caisson caps and other
ground beams were then constructed.

Construction of the superstructure
The podium
The superstructure consists of a 5-level podium using
for shopping/retail purpose and a 50-storey office tower.
The podium was constructed in reinforced concrete with
span max. up to 15m. There is an atrium space, circular
in shape, than stretched from the 2 nd basement up to
the 5 th Floor level. A 16m diameter skylight was erected
on top of the atrium to provide natural lighting into the
mall interior.
The other side of the podium is the entrance lobby to
the office tower. The headroom for this lobby is about
18m and provided with a glazed skylight similar to the
atrium area.

Construction of the superstructure
The Office Tower
The 50-storey office tower is a composite structure, that is,
it is constructed with a RC core wall and the building frame
embracing the core in structural steel.
A climb-form using the VSL system was used to construct
the core wall. The wall is trapezium-shaped with thickness
ranging from 1.2m to 0.4m (thicker for lower floors).
In order to make the core wall more rigid, projecting ribs
were provided on the sides of the core. This made the
forming of the core wall much difficult. The climb form thus
had to erected with a lot of gantry type roller in order to
make the formwork shutters more easy to open and close
for steel fixing and other access purposes.

The steel frame was supported by steel columns starting
from the 5m diameter caisson at the formation level of the
basement.
There were 15 steel columns of size 1.2m x 1.8m rising
from the basement up to the 4/F where a transfer truss
was located. From the transfer truss upward, the numbers
of column increased due to the reduction of span in order
to improve the structural efficacy.
A second set of stiffening truss was located on 26/F. The
purpose of this truss is to take up the loading imposed by
the steel frame and transmit part of these loads onto the
core wall. Instead of using a bracing-type outrigger, steel
beams with larger section were used for the purpose.
For the floor slab, typical composite slab with 150mm RC
topping on steel floor beams were used.

Aa
Construction of the
structural steel frame

Structural steel frame before the erection of the transfer truss

Front elevation of the building seeing the re-aligning of the steel columns
after the transfer truss on 4/F

Forming the transfer truss

Close-up view seeing the
configuration of the
stiffening truss on 26/F

Anchor frame embedded in core
wall to allow welding connection
for the steel floor beams

Connection of steel beams to the core wall

Temporary connecting
clips to adjust alignment
of members
Join filled
with weld
Connection of steel columns

Connection of more
complicated sections

Transformer for
arc welding
Cylinders for Oxyacetylene
welding
Equipment for welding

Replacing of welding wire
into the auto feeding drum
Semi-automatic welding using
auto-feed welding wire and arc

Forming the composite floor slab
Corrugated steel plank
placed on top of the steel
floor beams serving as a
permanent formwork
Welding of shear stud
onto the steel beam
stud

Placing concrete to form
the composite floor slab

Construction of the core wall
using the VSL Climb Form

Construction of the core wall started from
the later stage of basement demolition.
This part of the core wall was constructed
using usual timber formwork

Erecting the Climb Form
from the ground level
Built-in anchor frame inside the
core wall for connection of the
steel beams to form the
building frame at a later stage

Detail showing the gantry frame
that support the climb form
Hydraulic rod
Work platform

Detail of hydraulic
rod and support
Guide rail
Detail seeing the rails for
the hanging of the panel
shutters for the forming of
the ribs on the core wall

Detail of the rail arrangement for
the hanging of shutter panels

Stiffening
ribs on sides
of core wall
Climb Form work to its typical cycle

Floor slab, internal
walls and stairs etc.
will be constructed
later inside the interior
space of the core wall

Construction of the
Top-down Basement

Entrance to the basement
making use of the
permanent vehicular access
Vehicular access to
future basement carpark

Excavation inside
the basement
Floor slab completed
in advance

Excavation inside the congested
basement interior where the lateral
support frame was still in place

Core wall
Soldier pile wall for the cap was
exposed (previously used for the
excavation support for the cap)
Excavation near the caisson
cap for the core wall

Excavation down to the formation level
where the caisson head was exposed

Forming the beam
formwork using concrete
block on blinded surface
Trench formed by
blockwork as
beam formwork

Worker prepares for starter bar
connection on the caisson cut-off
to basement slab
Secant caisson (cut-off)
as the permanent
basement wall
Fixing of reinforcement
for the ground beam at
the formation level of
the basement

A lifting crane was
provided for the
removal of spoil
Temporary opening
formed on basement
floor for the operation
of the grab

Opening making use of the atrium
space on the retail podium for spoil
removal purpose during the
construction of the top-down basement

Bar coupler provided in
the upper part of the
encased column for
onward bar connections
Encasing the steel column
with reinforced concrete

Erect formwork to the steel column before concreting

Placing of concrete in
small quantity from
the feeding hopper
Gap later filled
with cement grout
Steel column finally encased and became a composite column

General construction difficulties encountered
in this kind of projects
Due to the complexity of the project, the followings are
some of the difficulties that encountered during the
construction processes.
1. Works are sub-divided into a number of sections or
phases (e.g. the demolition and basement advanced
works)
2. Various construction works were done at the same time
using in close vicinity (e.g. core wall and structural steel
frame, main building and podium)
3. Material handling at the peak period, provision of
transportation arrangement (e.g. steel members,
concrete, excavated soil, curtain wall units)

4. Very complicated building services installation is often
required
5. Building finishes and internal fitting is also time
consuming and required effective coordination

Curtain wall as the external
envelop of a building

Installing the curtain –
some difficult locations

The circular atrium
space and the skylight

The atrium
after finished

Finishing the
office interior

Installation of the false ceiling
with complicated interfacing
works with the building services

Finishing the entrance lobby
with very high headroom

End of Presentation