24 Structure Getty
Precast BERGER/ABAM
James
Mark Federal A. Senior T.
G.
S. Glendale, Curd Way,
Josten,
Guarre, Project Vice Engineers Constructors
Center Washington The
Wilfred Senior A. Glendale, Rialto, Precast P. California President Manager
E. T.
PCI Niobrara
RE. Curd
RE. California Vice Inc.
Prestressed Operations California Constructors
L. President
DESIGN River
Painter,
Provides Company
Jr.
Tram
AWARD
people-mover
post-tensioning. steep system Museum from structure design
project tors ports and concrete Diego of the
visual the To
tific J. Getty design Paul headquarters in The
p The Paul Los the
solve from laboratories Getty
innovative designers a
construction Museum.
answers arts
an Getty Freeway Sepulveda role recast long, people-mover alongside Angeles, Getty
WINNER
hillside
features,
Guideway an
posed
and and
underground in Trust.
Solution
the
(near curved, underground Center for and Museum, the
supporting humanities.
components Fig. to
construction the
problem for California. the
Concrete design-construction prestressed The Pass the to
several
and is 1 programs U-shaped use
system conservation San
Los
to
precast system,
highlights shows
these main Center a between
This a cultural Diego
the scholarly parking
builders The
of Angeles,
parking plaza This
of an which concrete
unique
precast/prestressed lies and tram article
new facility challenges this Freeway
aerial concrete
was transporting the complex guideway of structure alongside outside administration
of
of
combined research guideway rapidly San cultural of
people-mover view
J.
of the played will
the
devised.
structure a
California),
challenges
presents (Interstate Fernando 1080
Paul dedicated the the
project. feature of next transports
fabrication, structure
guide library, Interstate property, PCI near the a new
for m came
project. prominent to
visitors JOURNAL of (3535 tramway
Getty the the the 405). I. Valley
up
with The
way to scien
The
the visi Paul sup new city San 405 and the
to
in ft)
a a J. r’ ,
geles, the and people Malibu. cated derground Center plaza the lenge beautifully resulted extremely one new overlooking Fig.
dential also May-June
The
The
San existing
the
1.
service
museum
located
on
California
of
The
of
new
site
area
from
presented
Los
Diego in
the
the 1995
The
moving
with
Getty
has restrictions
parking
steep
museum
of
Angeles road the
Pacific
in museum
an Getty
atop
West location
the
limited Freeway
a
Los
entry
(see
Center
and
secluded,
grades.
the
site.
a
an
Center
Coast
Angeles Los
structure
large
will basin
Fig.
adjacent
a
at
logistical
point
on
access
Tram
fire
Angeles. of
to
the
2).
complement
construction
Highway
The
number in
and
the the
quiet
road
at
basin.
Villa
Los
guideway —
next
hillside
an
arrival site
to Getty
chal
resi only This with
An
un
the
lo
of
to
in
is
winds
confronting cided activities configurations. museum would cut, guideway itors conditions, appearance, Systems system driven, supplier.
SYSTEM
After The
up
was
from
the
be Otis
that
air-cushion suppliers
a
Inc.
on
chosen
The and
needed
Southern
aesthetics, competition
contract the
and
a
a
them, -
of pollution-free
dedicated
on
PROCUREMENT
people-mover
Otis
parking
low
Farmington,
With
as
people-mover
that
to
the
supported
system
the California
was
shuttle noise,
vehicle
included
these
Getty
among
vehicle
guideway.
garage a
design-build
Otis
uses
Center
operating
Connecti problems
Trust
and
vehicles.
hillside
system pricing,
vehicle -
Transit
system
system
to
cable-
train
vis
de
the
along
cles, contract Dinwiddie (DCCo). With to BERGER/ABAM guideway tract Federal select the
operate lane pass
the
The
DCCo;
guideway
THE
San
subsystems,
with
section.
the
the
tram
shortlist
Way, in
Diego
Otis
with
guideway
design,
a
DCCo
PEOPLE-MOVER
added
a
system double-lane
Construction fr.
SYSTEM
shuttle
Two
structure.
was
the
Washington,
Freeway,
of
and
would
Otis
to %
project
responsibility
separate
qualified
Engineers
guideway 4
construction
provide
configuration
guideway
contracted
off-center and
then
contractor,
Company
trains
to
blends
the
bidders.
is
subcon
Inc.
design
design
single
vehi
with
to
will
by
on
of
of in 25
a the
tached type along Museum cable support Fig. weight) machine 26 3,
a
guideway.
3.
geared
cable
the
will
Schematic
sheave to
is
room Station.
length 0
located
be
a
tension Miles
drive
drive
driven
Each
outside
network.
of 4
of
As
system
at
the
the
cable
device illustrated
train
the
by
guideway
cable
and
In
entry an
located North
will
supported
turn,
under
elevator-
(tension
drive
in station
be
each
by
in
Fig.
system.
the
at
a a Tension
just
trolled the chine cated 3. module long
8.8 Weight
The
Each
cable
m
outside
and
in
room.
(29
by shuttle
vehicles,
a
train
drive
control
computerized will
ft).
of
A
Vehicles the
will
operation
system
consist
schematic
each room
station
be
is
with
27.4
next
of
will
equipment
shown
area.
will
three,
drawing
a
to be
m
length
be
the
2.24
(90
in
two-
con
Fig.
ma
lo
ft)
of
of
m
high. (7
93 seated tated tion Site challenges the road side. cilitate scar visual views conditions ment from horizontal side follows tical from The long proaching museum supported
is tinuous tions, is is 1080 guideway over
without Vehicle supported on ports control for guideway cle quired for slab
trains support
THE
Site
The ft
This
divided The 26 per 20
a
guideway
4 system. the maintaining the and
aerial of
Conditions grade
that flanked
It
38
smooth
m the that
m m 13 consisting and
Vehicle from
in.)
three-vehicle
the
and
the
total
conditions
guideway
the construction was impact
on
to 800
units.
(3535 a
natural GUIDEWAY
to
drive columns. (86 (63
the
design.
m at
parking
wound
System
subsystems.
profile
wide
guideway interface
the guide into
vertical produced on
directly structure guideway of
305
the
radii
San 17
the
the
is
grade with
(42
m also
numerous length ft).
ft);
Supports
by
7.2 “flying”
the
two
The
supported ft). standing
cable,
(2580
parallel 9 station hillside
guideway, m
Diego
and capacity vegetation
of
ft) At
either
maximum
of The important
four- the
up of rail, percent
with a
guideway
garage (125
The
supports
passenger
beam
average
Interfaces on
the
tall. some
horizontal
train.
of
sidewalls with
curvature
imposed 2.90
is nine
the and a
lateral
construction
ft)
Getty superstructure
power
guideway
sheave is surface for
drilled Freeway. at-grade
rise 800
to
an
the rope
to
on
per
guideway
to At
hillside
64 long
DESIGN minimize
A
the m
(see
station
locations, six-span
sections
curves,
1000
average
on
PCI
a the
will
in
tramway m on
span the brackets
span
to
the
other
m (9
configura vehicle
sheaves
position Trust
guidebeam U-shaped
stations.
Otis
rails,
elevation
columns pier Fig. (2580
JOURNAL
opposite
structure
position
the
supports and
(210
ft unique varying
was
ft),
or
bottom
access vehicle
be
These
length length
align
to 6 to
loca with
vehi pile-
hill
con 4).
dic caps
ver
in.) that sup
not
ap
the and
the fa
ft). 14 on the
or re
ft)
re
is
of is to necessary elements to interface with the Otis vehicle system as structural elements. Added structure beneath the supporting slab would generally be ( eliminated. North In the bypass area, a struc ture to stiffen the cross section would be added beneath the supporting slab. Alternative C — Precast concrete L-beams spanning from column to column with a cast-in-place connect ing slab to form the above U-section. Precast concrete stem beams extend Road ing below the supporting slab would be used in the bypass area. Precast Fig. 4. The Getty Center site plan. concrete beam components would be designed to support the weight of the connecting slab and associated form- work and construction loads without auxiliary supports. This alternative minimized the amount of cast-in-place shoring and minimized the pick weights of precast concrete elements. Alternative C was chosen by the Getty Trust, the project architect, and the project contractor because of cost, aesthetics, and constructability factors.
Design Criteria The site Guiderail Support for the guideway was within the jurisdiction of the City of Los Angeles, so the Los Angeles De Sheave Support partment of Building and Safety was the approving authority. Early discus sions with the Department of Building Air and Safety indicated that the Depart Cushion ment would be comparing the design for the guideway with the Los Angeles Rope Sheaves Uniform Building Code (LAUBC). Power Rail Post The concerns of the Department cen tered on the seismic design of the Concrete Beam or Pavement guideway structure. This review process presented a Fig. 5. The guideway/vehicle system interfaces. dilemma to the design team because the guideway structure was more like a bridge than a building. The LAUBC quired to guide the propulsion cable way cross sections included those sec grouped this type of structure into the around numerous turns, and the power tions shown in Fig. 6. category of “Other” structures. Guide- rail for supplying electric power to the Alternative A — Precast concrete way design engineers thought it was operating vehicles are secured to the double tees spanning column to col essential to introduce the latest re guideway sidewalls and supporting umn. The stems of these double tees search regarding bridge seismic be slab (see Fig. 5). would be straight; the flanges of the havior and safety into the design of double tees would be curved to make this structure. Therefore, prior to be curved guideway sections. The side- ginning the final design process, a Preliminary Design walls and flying surface would be cast- Getty Center People-Mover Guideway The guideway designer’s initial ef in-place concrete. Multiple double tees Structural Design Specification was fort was to develop alternative guide- would be used in the bypass area. submitted to the Department for ap way cross sections that would meet Alternative B — Cast-in-place U- proval as an acceptable analysis! project design criteria. Alternate guide- section. This section would use the design method. This specification
May-June 1995 27 combined provisions of the LAUBC and California Department of Trans portation (CALTRANS) Bridge De Cast-In-Place Cast-In-Place sign Specification. FlyingSurface Slab Sidewall Seismic design provisions of the Structural Design Specification stated / the following: • Internal seismic forces would be computed using response spectrum analysis methods. • A site-specific response spectra would be used with a return period of 1000 years. A two-thirds vertical Alternative A response would also be imposed on the structure. of the CALTRANS • Design methods Cast-In-Place Bridge Design Specification would FlyingSurface Slab Cast-In-Place used for reinforced and precast be Beam concrete components. The CAL- TRANS methods for seismic design of reinforced concrete components use ultimate loads and ultimate B component design capacities. Alternative • A minimum design base shear force would also be imposed on guideway columns. This minimum force would Cast-In-Place based be computed per the LAUBC, FlyingSurface Slab on rules for “Other” structures in the code. • Effects of vehicle live load would be scaled from results of response spec trum analysis with only dead load mass to account for the added mass. Alternative C This was done because the vehicle will be “secured” to the guideway. Fig. 6. Alternate cross sections considered in designing the guideway structure.
Superstructure Design The single-lane tram guideway su beams were used, depending on the tern to transfer dead load from the perstructure was made from two L overall structure width. Typically, the simple-span, precast concrete ele shaped precast, prestressed concrete single-lane guideway is 4.62 m (15 ft ments to continuous span composite web beams connected with a cast-in- 2 in.) wide and 1.17m (3 ft 10 in.) high. beams. Full-span-length precast con place slab. Web beams were designed The guideway widens to 6.20 m (20 ft crete elements were erected; shores to support the weight of the slab and 4 in.) in the bypass area (see Fig. 7). were installed to just contact the bot its formwork. Web beams were pre Spliced girder construction was tom of these elements. Decks and clo stressed at the plant to support their used in the design to extend the span sure pours between elements were own weight and simple-span applied length of the 1.17 m (3 ft 10 in.) deep cast. Touch shores were removed after loads. channel section to 26 m (86 ft) over a the spans were integrated into continu The guideway design specified that slide area along the tram alignment. ous span units. W30 beams would be used to tie the Two adjacent beam elements were Inserts to support the vehicle guide precast concrete web beams together erected on a shore tower, joined with posts and supports for the rope during casting of the connecting slab. a cast-in-place closure pour. The ele sheaves were cast directly into pre Spans were later post-tensioned into ments were then post-tensioned in the cast concrete L-beams. Over 10,000 four- to six-span continuous structure field to make up the 26 m (86 ft) span. threaded inserts were to be cast into units. The shore tower was removed after these precast concrete components to a Flanged rectangular precast concrete the span was integrated into a contin tolerance of 3 mm (‘/8 in.). The design stem beams, extending below the slab, uous span unit. required formwork adjustments to off were used to stiffen the superstructure Three other long bypass spans were set predicted deflections and cambers in the bypass area. One or two stem designed to use a touch shoring sys as small as 12 mm (1/2 in.).
28 PCI JOURNAL Substructure Design The guideway substructure gener Precast Webs ally consists of 1.07 m (3 ft 6 in.) Cast-In-Place diameter round columns supported on FlyingSurface Slab”\ 1.22 m (4 ft) diameter shafts. The columns support a cross-head element to absorb shear forces from precast Cast-In-PlaceSlab concrete web beam superstructure ele ments (see Fig. 8). The shaft and col Single-Lane Section umn use a common reinforcing steel cage to achieve ductility requirements with a minimum amount of reinforcing Precast Webs
steel. Foundation shafts are generally Cast-in-Place designed to resist horizontal shear and FlyingSwlace Slab moment forces associated with hinging (yielding) of the base column section. In the bypass area, dual columns and shafts are used. These columns are Cast-In-PlaceSlab connected with a cross-head element to transfer shears from precast con Bypass-Area Section crete L and stem beams to supporting columns. Careful attention was paid Fig. 7. Cross section of the superstructure. during the design phase to the ductility requirements of the joints between cross-heads and columns. Site Logistics and Planning In areas where the guideway is sup The site conditions were the major ported close to the ground without factor driving construction sequences columns, multiple shafts are used. Shaft and methods. The guideway alignment moments and shears were designed to roughly follows the contours of a resist the maximum elastic seismic steep hillside, passing over several en shears and moments from response vironmentally sensitive areas that spectrum analysis. The guideway super could not be disrupted by construction structure is connected to the substruc activities. While the vertical gradient ture through bearings and large steel bar of the guideway along its final path of lugs that were cast directly into the travel is approximately a constant 7 cross-head elements (see Fig. 9). percent, the slopes and cross slopes of The completed tram. guideway the hillside at the foundations are as structure survived the January 17, steep as 1:1 in some locations. Creat 1994, 6.8 magnitude Northridge earth ing access for drilling 1.22 m (48 in.) quake without damage (see Fig. 10). diameter-deep caissons and erecting During the earthquake, measured hori large precast concrete elements was of zontal accelerations within 20 miles primary importance. (32 km) of the epicenter ranged from A series of narrow access roads was 0.24g to 1.82g. The Getty site is 10 planned to provide access for caisson miles (16 km) from the epicenter of drilling. These roads were limited to Fig. 8. Typical guideway substructure. the earthquake. areas where partial canyon fills were already planned; hence, regrading and THE GUIDEWAY revegetation after construction was a ments from the nearby parallel perma feasible alternative. It was not possi nent roadway had several drawbacks. CONSTRUCTION ble, however, to construct a road wide This road was the only access to the Initial guideway construction docu enough to allow a suitable erection top of the hill where the main building ments were issued to a select shortlist crane to travel around cross-heads that construction was underway. Constant, of qualified bidders in the summer of topped support columns. Several sec heavy construction traffic needed to be 1992. Final guideway construction tions of the alignment were over sensi maintained almost the entire day. Only documents were bid in September and tive areas that could not be disturbed brief time windows were available to October 1992. A. T. Curd Construc with access roads, so all construction block this road with precast component tors of Glendale, California, was se had to be reached over the top with erection activities. Also, the size and lected to be the guideway construction large cranes. number of erection cranes required subcontractor. Erection of precast concrete ele would be significantly larger if erec
May-June1995 29 transfer superstructure tion place Fig. cision lem cast quested elements. cross-head use ments. passed the cross-heads support stead general (see guideway sequencing way to guideway 30
The
The
2. 3. 4. 5. 1.
the
beams
a
9.
took was
concrete
in
The The The The The
Fig.
narrow
cross-heads of
entry
Multiple key
to
guideway
the This
earthquake
columns
by
areas
that
the
cast-in-place place
convert
on-grade The on-grade
first 14
last at
at
(see
bypass to
11).
design
in
the
station
guideway
the
the allowed
were
access
spans the
solving
cross-head
the
for to
guideway
steel
from
Fig.
11
16
support
After uphill downhill
this
for
was
designer
following
the
overall
area
to
erected
spans to
spans
shear
guideway guideway
of
12).
lugs
road the
the
pier.
the
precast
divided provide
the
original
contractor’s end
elevated cross-head
the
main
erection
and
contractor
alongside column,
contractor
forces end elements access
of construction
of
modify just
crane
order:
bearings
road.
elevated
elevated
concrete
into
between adjacent for
cast-in-
before
guide-
from
prob
crane
pre
had ele
five
de
the the
the
re in
to
the
were
guideway
the
roads. station road, Column struction Foundation road for the series tions crane large Special plished cent road ticipated. much ers. and quired spent were
required
Work
Deep
south
crane
slopes rock The
gradients.
areas construction.
in
coring of
more enough cleaned needed
of
These
long
outrigger
with
most caisson
the
at
bottoms
to
Construction
cutting
short
abutment
There
travel
required of
the
difficult
at
through
access
continuous
conventional
and
roads
areas the
to
flat
the
out
spurs
site
drilling
set
buckets.
pads was
without of
Drilling
temporary
area.
points
by
shoring
roads only
than
were fractured all began
up. and
alignment. earthquake
Fig.
off
significant
were
hand.
of
A
casings
originally wide the followed Several 10.
of Drilling
earth had
generally
the outriggers. was
where
few
with to
created
Nine
the
museum
rock
This
caissons
create
20 enough
access
accom
The
augers
of
(January
main
to
con
time
horizontal sec
per
was
lay
the
the the
an
re
on
structure
be
a
a
17,
installed had ing cessed Drilling access vating A was from a drilling was access
holes cages continuous hole 24 ied depths cages sulting tion 30 space
curves
special
Five
Continuous
A
small survived
1994)
m m
cleanout
up
to
suspended
impossible.
was
critical
to
a
restrictions (100
(80
roads (see
these
be
were
were to
large
caisson
road
location.
top reinforcing only
ranged
with
temporarily make
remote-operated
without
long
orientation
transported
13
ft)
the
ft) Fig.
of
during
shafts, aspect
fabricated
truck operations.
m
from installed
directly
and by
conventional
reach
long. the up
spiral-tied
nearby over
(42 locations
up
Instead
damage.
14).
foot
the
on
column
crane
cross-head.
the drilling.
of
the ft).
to
cages
drilling
the
All
in
site. of
up
guideway
The
the
uphill
Northridge
(see
approximately Some contractor in
bottom
each
off-site
the
side
These
located of
of
and
could
cage
PCI
diesel
the
heights
were
reinforcing cages
hand
the
equipment
vertical
apparatus.
Fig.
of
down hole
from
of
JOURNAL
cleaned
Caisson
installa
casings
caisson the
be
of
due the
on
nearly
auger
exca
were
used
13). dur
var
hill
ac the the the
the
re
re
to had truding May-June cross-head, cage inforcing erection. cross-heads Fig. to 11. was be above The 1995 continuous in bar the erection atop the the pattern. reinforcing correct the top crane to columns. of the Because pattern. the - was top bar caissons A able of precast pro The the the to back .,“-, concrete forcing imuth above pattern zontal out a orientation; ground location narrower cross-head 7. had bar, to as level, be much and access in the is at being the had as top the road 13 correct to of correct rigged m be without the (42 at hori rein for the az ft) for the inforcing and cranes 225-t were the Several (180 accomplished chitectural production. means
the scale Superstructure These
columns currently Cross-head cast-in-place beams these tom tion common were as two larger strength sleeves bars. and into included set heads ing alignment each bar forms. using rication son/column used caisson much correct Special Precast A At The The the cross-heads. a precast columns. of web significant alignment columns. template into of matches erected matched the ton) some mock-up These special column (250 poured pile (see and locations, beam working cross-heads vertical tighter 1.07 typical the columns were A elevation. construction, picks, in and cross-head cross-heads. and grout. the lifting were 16 concrete bar conventional methods of special manufacturing caps Fig. locations, each guideway ton) with details The dowels m cages. elements Most on stem double vertical pile each the
precast and installation supported form These was because sleeves than that of set reinforcing corrugated contribution (42 15). however, together. with were area. frames the crane At filled mock-up elevation
the Construction were caps the precast The beams vertical when of double used were (see was in.) erection to matched and normal the piece. station templates had the cross-head, the constructed (see #9, a so to concrete ensure were or tolerances cast-in-place After at they Fig. were diameter constructed single bypass with cast construction prevent on the truck terrain supported to the erection Cross-heads followed yard directly both grade #10, verified sleeves Fig. of required dowel reinforcing bar of guideway was ahead, be for the 17). contractor followed up grouted, shared columns required the in erection accurate the prior a for aligned pattern crane. or 16). of drilled a eleva with 160-t cross- top areas, level. them place these high pass con full- cais was steel were bot the cast #11 fab re on ar 31 on by to in In a of a a Fig.
from over
center curvatures Fig. The the ing component sulted from matically curvature without lateral 32
Special
crane
points. 13.
14.
30
frames
rolling the
of in
clamps
Some
Reinforcing m
readjustment
connection the
gravity
cross
(lOOft)
compensate
heavy
of
The
conditions
being
were
many
center column
over.
were
lifting
section
diagonal
of
long.
configured
located
steel
of
The
also the
of
point
(see
locations
the
frames
for
gravity
encountered available
cages of
fabricated lengths
Fig.
elements
outside to
braces
any
the
be
to
allowed
18).
were
for
of beam. of
offset
auto
and
lift drilled
and
the
the the
re
only
to
accessible
shaft
transmit precast head. 0.76 beams in erected, ment After agonal correct hardware and
Other
the
foundations
used
m
installation
with
transverse After
served
(30
concrete
braces
horizontal
they
again special the
by
was
in.)
each
foot.
two
torsional
were
to
deep,
on devised could
and
beam
hold direction.
erection of
other
the
parallel
and
the tied
columns
wide
next
then
the end
force
by
web
vertical
(see
together
flange
span. web
and to
be
the
These webs
beams,
were the
Fig.
from
removed
contrac
bracing pairs
beams
align cross-
were
large
with
19).
the
di
in
prior bearings tor place downhill bearing physical
crete cross-heads. also concrete cross-heads
closures deck and tached strainer ements.
multispan groups tensioned
cross 22). guideway; cast-in-place cast
the elements, crete Flying this air-supported ances
wear affect tolerance
percent about face cally site, culty
the and the gether
installation, vised and ances as-built of
surface
The
The
There
Concrete
to
the
precast
desired
curves. required
concrete.
fixed
surface
measurement
is where
a The to
life
was
webs
closures. keep in flying
correct section
for formwork
to entire to flying
a
superflat
with
of a the the pads
lugs
Surface
connection grade,
and
was After
measurements
included
sections overlap
defining measuring
in helix,
the
of
be
flatwork was
is together
individual on-grade
smoothness
bridge
supported
however,
bearings
concrete
vehicle ability the
There surface. and by the
the
the and (see
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7 of special quality control measures. These measures included tight control of the concrete mix proportions and timing of deliveries, high precision formwork measuring and leveling tools, special wet finishing techniques, prompt and thorough wet curing, and immediate measurement and reporting of results so daily corrections could be made (see Figs. 23 and 24).
PRECAST CONCRETE FABRICATION The structural solution to the design challenges was largely due to the effi cient use of precast concrete compo nents. In total, 134 components were used as follows: • L-shaped web beams • Flanged rectangular stem beams • Single-lane cross-heads • Bypass single column cross-heads Fig. 15. Precise jigs were used to ensure that reinforcing steel protruding from the • Bypass dual column cross-heads tops of cast-in-place concrete columns aligned properly with mating sleeves in Table 1 shows the shape, number precast concrete cross-heads. and principal dimensions of the pre cast concrete components.
Precast Concrete Cross-heads As previously noted, a key concept in solving this project’s construction difficulties was casting the precast concrete cross-heads. Typical precast cross-heads were 4.67 m (15 ft 4 in.) wide and weighed 140 kN (31,000 ibs); bypass cross-heads measured up to 7.82 m (25 ft 8 in.) and weighed 350 kN (80,000 lbs). Forming cross- heads was straightforward, using stan dard steel forms similar to those used for cast-in-place cross-heads on top of the columns. Tying the reinforcing bars was more complicated because the ductility requirements called for a series of closed, interlocking, progres sively tapered welded loops requiring a systematic placement sequence that took a few tries to figure out. The real challenge, however, and the key to the successful use of the precast concrete cross-heads was the templating system devised to ensure that they would meet with a cast-in- place column in the field. The connec tion detail was designed to fit the cross-head over the extended column Fig. 16. At some locations, the guideway profile was nearly at ground level. vertical steel, 16 bars in a 0.9 m (3 ft) At these locations, the guideway superstructure was supported directly on diameter circle. cast-in-place pile caps.
May-June1995 33 Table 1. Breakdown of precast and prestressed concrete components used in tram guideway.
Flanged rectangular stem beams: 19 components Minimum length — 13.9 iii (45 ft 6 in.) Maximum length— 21.5 rn (70 ft 6 in.)
L-shaped precast prestressed web beams: 84 components Minimum length — 13.9 m (45 ft 6 in.) Maximum length —22.1 m (72 ft 6 in.)
2-4”
15-4”
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Varies 15-4” to 19-8-1/2” Ii
j Bypass single-column c9 cross-heads: 7 components 9 Width of cross-head — 1.5 m (5 ft) C.,
Pocket forStemBeam
Bypass dual-column cross-heads: 5 components Width of cross-head — 1.5 m (5 ft)
Varies 22-2 to 25-8
Poet or Stem Beam
34 PCI JOURNAL In order to clear cross-head reinforc ing, sleeves were limited to 40 mm (1.5 in.) diameter corrugated tubes for #11 bars, leaving very little clearance per sleeve. The fabricator of the mis cellaneous metal components devised a precise jig that remained in his shop. All templates for the project, both I field and shop, were made against that master template to guard against pro gressive creep in dimensions. For the cross-heads, a template in the form’s baseplate matched the in side diameter of the corrugated sleeves. A similar template at the top, with “handles” that would support it from the form sides, aligned the sleeves vertically and in plan. PVC pipes inside the corrugated sleeves acted as stiffeners. In the field, all Fig. 17. Prior to production, a full-scale mock-up was constructed at the precast cross-heads fit and aligned correctly. manufacturing yard.
Precast Concrete Web and Stem Beams The L-shaped precast concrete beam sections, or webs, ranged from 11.6 to 22.0 m (38 to 72 ft 4 in.) long, with corresponding weights of 132 to 250 kN (29,500 to 55,800 lbs). Geometry was complex, as even an 11.6 m (38 ft) beam might include a tangent, spi ral, and constant radius alignment. Ra diuses were 64, 69, 75, and 305 m (210, 225, 245, and 1000 ft) each with spiral transitions into and out of the tangent or straight sections. The necessary alignment came from a profile grade line (PGL) at the center of the flying surface. In two locations, the PGL also required a vertical curve (VC). The design allowed the webs to “chord” between cross-heads and com pensate for the VC with the cast-in- place flying surface. The embedments, Fig. 18. Special liftingframes were fabricated to allow picking outside the center of however, to follow the PGL, needed the web beam cross section. which meant that at these two loca tions, embedments were not a constant height relative to the web section. could be used in the plant for form plywood sub-base and 13 mm (‘/2 in.) Web form layout was clearly a layout and control. high density overlay (HDO) plywood major challenge. The entire structure The forms had to be able to twist to were laid down for the casting surface. was drawn in three dimensions using match the required shape. The form Setting the table was a two-step pro AutoCAD 12.0. The individual beam pallet was built with 0.6 m (2 ft) on cess. First, each double channel was sections were cut out on the computer, center back-to-back channels 2.4 m (8 “aimed” at the center of curvature by and rotated into a horizontal, casting ft) long resting on screw jacks set into sliding the screw jacks perpendicular position, which resulted in a twisted a longitudinal track (see Fig. 9). To to the channels. Thus, for example at shape relative to the beam centerpoint. make a flexible base over the double the outside of a curve, the center-to- Horizontal and vertical offsets were channels, flat 0.6 x 1.8 m (2 x 6 ft) center dimension might be 620 mm then calculated from control lines that timber sleepers with a 19 mm (3/4 in.) (2.034 ft) and the inside 595 mm
May-June1995 35 erection. justed Fig. be minus 36 drawing (1.952 plus 19. vertically ft). 4 W30 4 had mm mm Screw steel these (0.013 (0.013 so jacks sections that dimensions ft) ft). one were and were Each end the then calcu used might other shop ad to tie radial beams could lated level the web in approach. be and set beams tabular done the vertical correct with securely form, This adjustment a warp simple combination so together to that the tape layout pallet. of after and the of building of 0.6 flat 26). flect ated enough sheathed curately. beam down to ‘/2 form lengths, the embedments of sequence through blies layout production sides, zontal a cleaned and forcing They form area. stripping ping stressing. to at inforcing reconfigured and tied ble. and placement then lowing embedments, would fore place, post-tensioning first tensioning Beam The small Two The all the in.) glued After go 6 x exact, became a 0.6 Side the yarding between They a.m. cage, crew could components, reconfigurations. stage, the setting 1.8 buttoned-up to home There would sides flexible so twisting and HDO 90-degree differences the cleaned to forms the thus to stressing stripping day’s steel a any and x with sides oversize complete m and was forms, end follow At bar and vertical beams went tight series Meanwhile, would the minimize cycle the be 1.8 were double by (2 area. simple-span plywood. be the was and necessary a oiled, the consisted if supports screwed be developed crew form were and in shifted 19 of next x pallet lunchtime. handling cages. beam post-tensioning “poured m necessary, were over form eight-hole concrete curves 6 subcontractor reinforcing always like started of same the were ready sufficient heads the frames and crew, curves. then sorted Every caused ft) (2 checked channels holes embedment the morning. that would and built. 90-degree to below. minor design the into to timber pallet shift. x controlled Again, 13 The but sent plywood time, forms, pre-tie the Templates dry of and where out” would the pulling at 6 by cope ready perpendicular for in placing without Monday, post-tension- mm were in pallet, PCI by The plates the ft) then was 3 set other pattern form to curves finish a mild and spirals details so form The A bar would and the a.m. concrete the (see to the JOURNAL database this with the the (3/4 planks applica that the storage not located frames casting for typical assem did bolted limber the major ducts, forms allow crews ready form, crew. form were strip hori over rein form crew with post- with Fig. pre cre took was and pre and de fol ac the for the the by be set the the re be Fig. 22. After__._Jprecast concrete beams were erected, closure pours were cast to make the precast units into four- to six-span continuous beam units. w
Fig. 21. Stem beams in the bypass area were set into notches cast into the precast concrete cross-heads. CONCLUDING REMARKS The J. Paul Getty Trust is construct ing and grouting, in the yard. This the deck, the tolerances were less chal ing a world-class art facility and is de schedule allowed the weekend cure lenging than the webs. A similar bed manding the highest quality in design even on Friday’s casting, met early system was used (see Fig. 25). and construction. The tramway ride strength requirements without overly In all, over 500 shop drawings were quality, passenger comfort, and dura aggressive mix designs and heating prepared to detail the 134 precast con bility were important requirements systems, and gave the post-tensioning crete components. Putting the effort that necessitated the complex design and close tolerances. subcontractor at least five beams for a into details, especially into a simpli full day’s work cycle. The balance of fied layout system, paid dividends in The construction of the Getty Cen the prestressing was done in the field. the production cycle and achieved ter guideway was a model of cooper The small “T” beams that supported good dimensional tolerances. No in ation between owner, designers, and the deck at the wide, bypass locations serts cast directly into the precast con builders. Direct lines of communica were dubbed “stems.” Although of crete units had to be reworked because tion were established early to facili complex shape, as these poured into of out-of-tolerance positioning. tate a response to questions and to ensure that design intent was being followed and that guideway require ments for the vehicle system were being achieved. Use of precast, prestressed concrete made the construction feasible and cost effective. The resulting finished product is a graceful and dramatic structure suspended along the hillside that will provide an exciting, wel coming experience for visitors to the J. Paul Getty Museum. The project won an award in the 1994 PCI Design Awards Program. The citation of the jury read: “This project really fits the site and environ mental conditions, and through the in novative use of precast/prestressed concrete elements provides an ex tremely efficient solution to a difficult transportation problem.” It is expected that the people-mover tramway system (see Fig. 27) will be Reinforcing steel placed in the flying surface at the Entry operational by the end of 1995.
May-June1995 37 Fig. 25. Two stem beams in the storage yard are ready for Fig. 26. - b beam forms were made from plywood secured transport to the site. Precast concrete beams were post- to a series of 90-degree timber frames. Side forms were flat tensioned in the yard to carry their own weight and planks sheathed with plywood, thus creating a flexible yet construction loads. not too rigid form.
38 PCIJOURNAL Fig. 27. Panoramic view of Getty Center tram guideway project nearing completion.
CREDITS Owner: The J. Paul Getty Trust, Santa People-Mover System Contractor: Guideway Designer: BERGERJABAM Monica, California Otis Transit Systems, Inc., Farming- Engineers Inc., Federal Way, ton, Connecticut Washington Getty Center Project Contractor: Din Tram Guideway Contractor: A. T. widdie Construction Company, Los Curd Constructors, Inc., Glendale, Aerial Photography: Warren Aerial Angeles, California California Photography Inc. Getty Center Project Architect: Precast Concrete Manufacturer: The Richard Meier & Partners Archi Niobrara River Company, Rialto, Other Photography: Construction Doc tects, Los Angeles, California California umentation Services, Inc.
May-June 1995 39