Segmental Box Girders
for the High Level
West Seattle Bridge

L

Ching K. Yu, P.E.
Manager
Contech Consultants, Inc.
Seattle, Washington

F

or many years two bascule bridges
over the west waterway of the
Duwamish River were the only direct
link between West Seattle, Washington,
and the downtown area. Busy maritime
traffic and an ever-increasing vehicular
volume on the bridges caused serious
traffic congestion, making the need for a
high level structure apparent.
On June 11, 1978, a fully-loaded
12,000 ton (10,900 t) freighter slammed
into the north bascule bridge, severely
damaging the superstructure and pow
erhouse wall and rendering the bridge
inoperable. This accident left only the
south bascule bridge, with its four-lane
capacity, to handle all traffic, creating an
even more acute need for a high level
replacement bridge.
52

Rising 150 ft (46,
State of Washingi
span of the West:
example of efficiei
long-span structur
the structure’s deE
girders. Only the superstructm
of the two concrete altemate
covered in this article.
Fig. 2 shows the general plan
vation of the concrete bridge, w
a span arrangement of 375-5
(114-180-114 m). The superstn
rigidly connected to the tw(
piers. The bearings at the end
free to slide in a longitudinal ci
but restrained laterally. The ceni
are designed to withhold the
t
ture, creep, and shrinkage defor
of the center span.
The overall outlines of the si
are identical for both the cast-i
and precast schemes. Howev

The initial planning for the ensuing
replacement project has been described
previously.1
As shown in the vicinity map (Fig. 1),
the entire project was divided into four
units: West Interchange, Main Span,
Harbor Island Approach and East Inter
change. A paper published in the
November-December 1983 PCI JOUR
NAL describes the design and con
struction of the three approach structure
2 This article presents a detailed
units
discussion of the main span.
Structures selected for final design in
cluded three types: (1) steel box girders
with an orthotropic steel plate deck, (2)
cast-in-place segmental prestressed
concrete box girders, and (3) precast
segmental pre stressed concrete box
PCI JOURNALJJUIy-August 1984

 Rising 150 ft (46 m) over the Duwamish River in the
State of Washington, the recently completed main
span of the West Seattle Bridge is an excellent
example of efficient use of prestressed concrete for a
long-span structure. This article presents highlights of
the structure's design and construction.

girders. Only the superstructure design
of the two concrete alternates will be
covered in this article.
Fig. 2 shows the general plan and elevation of the concrete bridge, which has
a span arrangement of 375-590-375 ft
(114-180-114 m). The superstructure is
rigidly connected to the two center
piers. The bearings at the end piers are
free to slide in a longitudinal direction
but restrained laterally. The center piers
are designed to withhold the temperature, creep, and shrinkage deformations
of the center span.
The overall outlines of the structure
are identical for both the cast-in-place
and precast schemes. However, the

GG^

minimum concrete strengths at 28 days
are 5000 and 6000 psi (35 and 41 MPa)
for the cast-in-place and precast alternates, respectively. This allows a thinner bottom slab for precast segments at
the center piers. Otherwise, all the concrete dimensions were kept uniform for
both construction methods. Unless
otherwise stated, the description
hereinafter applies to both superstructure alternates.
The bridge section is composed of twin
single cell boxes of trapezoidal shape
(Fig. 3). The total deck width of 104 ft 5
in. (32 m) provides a roadway of six traffic lanes and shoulders. Following a
parabolic curve at its soffit line, the

HARBOR ISLAND

SEATTLE

'sy
WEST SEATTLE

WEST INTERCHANGE

MAIN SPAN
1340

\

I

4 HARBOR ISLAND

EAST
INTERCHANGE

5600

Fig. 1. Vicinity map of West Seattle Bridge.
PCI JOURNAL/July-August 1984

53

 U1

A

C Pier 18

Pier 17

Pier 16

f Pier 15

Duwamish River
West Waterway

o
[QBarrier

West Seattl
Seattle

Expansion
Joint

o

\
\\

Expansion
Joint

375-0"

59 -0"

375-0

Span
S 00
125'-0"

125 -0"

Clearance
Envelope

o

.I.

tai

/pp rox. Existing
Ground

Fig. 2. General plan and elevation of main spans.

I

Future
Waterway

Future Channel

Elev.0.00
City Datum

 0C
C-

WSB Line
52-21/2

52'- 21/2'^

z

D

Box Girder

C

D

2" Wearing
Surface

HL.

c
C
OD
co
A

2.0/.

—

I

m

2.0

O

o
rn
N r

H

Box Girder

_

I

N

U
0I

^TYp.

I

0

1'

U

N
v

a

0

0

co

n

m

^

24'-II1/4"

17'-83/4"

Section

Section

At Piers 16 and I7

At Mid-Span

Fig. 3. Typical sections of main spans.

C

 55'-0"

15 1 -0

5'-0°

15-0

12151<121 5K 121.5 K12,51<2151<

5-0' 5'-0°

121.5K 121.5K

8 Axles at 21.5 K each; 172 K Total
Transver wheel spacing 0-8' O.C.
Tire pressure 80 psi, width 12"

Vehicle Load
57'-6"

.HHHH.
3.0 1</ft.

3.0 K per linear foot x 57.5'= 172 K Total may be used where wheel loads do not govern.

Eauivalent Uniform Load
Fig. 4. Assumed overload due to vehicle load and equivalent uniform load.

depth of the girder varies from 30 ft (9.1
m) at center pier to 12 ft (3.7 m) at
midspan. The slightly arched form of the
superstructure provides not only efficient use of concrete materials and prestressing, but is also aesthetically appealing.

Design Criteria
In general, the structural design follows AASHTO Standard Specifications.3
For subjects not covered by AASHTO,
other commonly used codes for segmental construction were adopted.4•5,6
In application of AASHTO loading
combinations, the transverse design in-

56

cluded a temperature differential of 10
deg F(6 degC) warmer or5 deg F(3 deg
C) cooler at the outside than the inside
of the box. A temperature for the top slab
18 deg F (10 deg C) warmer or 9 deg F (5
deg C) cooler than the rest of the section
was incorporated into the longitudinal
design.
In addition to the interstate highway
bridge loadings specified in AASHTO,
Article 1.2.5(G), the bridge was also designed for an overload vehicle or its
equivalent (Fig. 4).
Allowable concrete stresses in tension
specified in AASHTO, Article 1.6.6,
were modified to account for frequent
segmental joints in the superstructure

 Table 1. Allowable tensile stresses in psi (fe) for cast-in-place
construction.

Loading combinations

No additional
reinforcement

All tension force
resisted by additional
reinforcement

0

O<f
<
t
3f7

Dead+ Live
or

Dead

+

Construction

All other combinations
Note:

f=

3

3

,J7 < f < 6 J7

compressive strength of concrete in psi at 28 days or, for dead and
construction load combination, at time of stressing.

Table 2. Minimum compressive stresses in psi for precast
construction (longitudinal design only).

Deck slab
local stresses

Deck slab
local stresses

Loading combinations

not included

included

Other
area

Dead ÷ Live
or
Dead + Construction

200

100

30

30

30

30

All other combinations
Note: 1 psi

=

0.006895 MPa.

)overn

ad
9quivalent uniform load.

emperature differential of 10
:g C) warmer or5 deg F (3 deg
it the outside than the inside
A temperature for the top slab
9 degF(5
.OdegC)warmeror
ler than the rest ofthe section
orated into the longitudinal
ion to the interstate highway
dings specified in AASHTO,
.5(G), the bridge was also de
r an overload vehicle or its
(Fig. 4).
le concrete stresses in tension
in AASHTO, Article 1.6.6,
iified to account for frequent
joints in the superstructure

‘I

and to provide better control over deck
slab concrete cracking. Table 1 shows
the allowable prestressed concrete ten
sile stresses for cast-in-place construc
tion, applicable to the design of both
transverse deck and longitudinal cross
sections.
The precast design’s allowable stress
for the transverse deck section remains
the same as in Table 1. However, in rec
ognition of reinforcement discontinuity
at segmental joints, allowable lon
gitudinal tensile stress requirements are
more stringent. In fact, minimum com
pressive stresses are required for this di
rection (Table 2). Allowable compres
sive stresses for each construction are in
conformance with AASHTO require
ments.
A dense concrete or latex-modified
concrete wearing surface of 2 in. (51
mm) nominal and 1Y2 in. (38 mm)
minimum thickness over the bridge
PCI JOURNAL/July-August 1984

deck was specified. An additional
superimposed dead load of 25 lb per sq
ft (1.2 kN/m2) of deck surface was de
signed for as a future surfacing allow
ance.

Construction Sequence
As shown in Fig. 5, the suggested con
struction sequence may be divided into
four stages:
Stage 1: Casting the pier table over
both the north and south columns at the
east side of the river. Post-tensioning all
the tendons in the pier table and placing
two sets of form travellers in position,
one pair for each box girder. For the
purpose of reducing the unbalanced
pier moment, the pier table is offset a
half segment length from the centerline
of the pier.
Stage 2: Performing the balanced free
cantilever construction by casting 16 ft 6
57

 in. (5 m) segments on alternate sides of
the pier table. Stressing half of the
transverse tendons in each girder from
the outboard edge of the deck slab, as
shown in Fig. 6. The other half will be
stressed only after the longitudinal closure between the two girders is cast.

375-0"

Progress of the two parallel girders
should be approximately the same, with
a difference of no more than two segments. This is to minimize possible misalignment of the continuous transverse
tendons due to concrete creep effect.
Stage 3: After the balanced cantilevers

375-0

590,-0°

,

t North Columns
r-

j L c5outh Colurns
Stage I - Build East PierTable
Span

Pierl6
(West

Th

Forroveller

CE Pier 17
(East)

Stage 2-Free Cantilever Const ruct
East Side

ri

^i
Stage 3- Complete East half of Bri dge

®

.J

Longitudinal Closure Pour
Diaphragm

0

4a

Stage 4-Complete the whole Bridge

Fig. 5. Suggested construction sequence of main spans.

'1
^r

Closure Pour

Ex ponsion
Joint

58

Temporary
Supports

Expansion
Joint

 reach their limits, moving the center
span form travellers to the west pier
table, installing temporary supports near
the edges of the side span cantilevers
and continuing segmental construction
until the girders land on the end pier.
Stage 4: Repeating the construction as
described above for the west half of the
bridge. Pouring the center and longitudinal closures, stressing all the continuous transverse tendons and completing other work.
The construction sequence for the
precast scheme is basically the same as
described above. However, to facilitate
transportation, handling and erection of

the precast units, the segment length is
reduced to between 6 ft (2 m) at pier and
12 ft (4 m) at midspan.

Prestressing System
Longitudinal tendons consisting of 12
x 0.6 in. (15 mm) diameter strands were
specified in the design. As shown in Fig.
7, the cantilever tendons are anchored,
three at each web, on the bulkhead face
of each segment, the continuity tendons
at buttresses built up from the slab. The
cantilever tendons follow the profile
grade and the continuity tendons follow
the soffit line.

Stress after completion
of Segment

Longitudinal Closure Pour

II
II

A

II

4-1

Stress after Longitudinal Closure Pour

Plan
WSB Line
Box Girder

Box Girder
3'-6°(Closure)

Ti

Discontinuous
ons

Section A-A
II

Stressing End

I Dead End

Fig. 6. Plan and section of transverse tendon details.

PCI JOURNAL/July-August 1984

59

 rn
0

26-1/4
1 1/4 " Dia.Deformed Bar
(Transverse Tendon)
!''."

°O

Box Girder
Longitudinal Tendons Symm. abt.

Anchor Plate
0 00000

oo
00 0

001

°1

12x0.6°Dia. Strands
(Cantilever Tendon)

000000°

o

0
°
11

1 1/a° Dia. Bar (Vertica
Web Tendon )

11

Typ. Stressing Buttress

11

Anchor Plate

11

1

^ o ;..

0 0 0 0

12x 0.6" Dia. Strands (Continuity Tendons)
Fig. 7. Tendon arrangement inside box segment.,

 Straight tendons are preferred for
their ease of installation and ability to
minimize friction losses. They also prevent the necessity of having a wide web
to accommodate the anchor plates, as
they are all anchored away from the
webs.
Additional longitudinal bar tendons
are installed across the deck slab of the
closure segments. They are required to
resist the negative moments induced by
live loads before creep-induced moments settle in.
For transverse and vertical tendons,
1 1/4 in. (32 mm) diameter deformed high
strength bars are preferred. The screw
type bar tendon anchorages reduce the
seating loss to about lho in. (2.5 mm),
rendering them most effective for
short-length prestressing. However,

PCI JOURNAL/July-August 1984

strand and wire systems providing
equivalent effective forces are also permitted.

Corrosion Protection
For corrosion protection of reinforcing
bars and prestressing tendons, a
minimum concrete cover of 1Y2 in. (38
mm) was specified for the deck slab in
addition to the wearing surface. Epoxy
coating was required on all top mat deck
bars as well as web bars having less than
3½ in. (89 mm) concrete cover, measured from the top of the monolithically-cast deck slab. To eliminate the need
for epoxy coating long web bars, a special detail was developed (Fig. 8).
One of the following measures must
be taken to protect the transverse ten-

61

 dons, depending on the type of tendons
used: (1) epoxy coating the deformed
high strength bar tendons, (2) using
plastic ducts with spiral corrugations,
either polyethylene or polyvinylchloride, (3) using epoxy coated metallic
ducts.
Because the longitudinal tendons are
located well below the riding surface,
galvanization of the metallic ducts is
considered adequate for their corrosion
protection.

Special Requirements
The following prestressing-system
related requirements were specified:
1. Pull-out tests: If epoxy-coated flat
or plastic ducts are used for transverse
tendon sheathing, pull-out tests must be
performed to prove the bondingstrength adequacy of the ducts. The
tests should show that a force equal to 40
percent of the ultimate tensile strength
of the tendon, 0.4 fpu A,,, can be transferred from the tendon through the duct
to the surrounding concrete at a length
of 2 ft 6 in. (0.76 m). A total of 12 pull-out
tests should be conducted of which 10
must pass the bonding requirement.
2. Lift-off tests: As short tendons are
apt to lose too much prestressing force
due to slip at anchorages, tendons shorter than 20 ft (6 m) must be equipped
with an anchorage device which allows
lift-off checks and restressing. This requirement applies to most vertical tendons.
3. Water freezing prevention: Covers
and plugs should be provided to prevent
rain water from entering vertical ducts.
As a complete seal of ducts at deck level
is always difficult, some water will inevitably be collected, and its subsequent freezing could cause cracks in
the webs or delamination of the bottom
slab. Unless a complete seal can be
achieved, the ducts should be filled
with a mixture of glycol antifreeze and
water when the temperature falls below
45 F(7C).

62

Design Considerations
Although sections subjected to prestressing forces were designed according to allowable stress requirements,
their ultimate strengths must be
checked by load factor design, as
specified by AASHTO. For the longitudinal direction, allowable stress
checks are performed at all construction
stages, i.e., when a new segment is
added, a form traveller advanced or removed, additional tendons stressed and
a closure poured. In addition, stress
conditions at completion of the bridge,
18 months after completion, and at infinity must be evaluated to insure the
soundness of the structure with all prestress losses and creep effects considered.
In the transverse direction, the cross
section was analyzed as a frame structure. In order to take longitudinal distribution of wheel loads into consideration, influence surfaces prepared by
Homberg7 were used to determine the
equivalent beam fixed end moments
prior to the frame analysis. The method
is described in detail in the PTI Box
Girder Bridge Manual."
The load factor method was used for
designing reinforcement in the webs
and bottom slabs, whereas allowable
stress design was used to determine the
transverse tendon spacing and profiles.
Since only half of the transverse tendons
run continuously across the longitudinal
closure, dead load stresses and secondary moments introduced by the discontinuous tendons need to be estimated.
This is done by using a separate structural model consisting of only one box
girder section.
Vertical bar tendons were selected as
the main reinforcement for shear force.
However, in applying AASHTO design
equations specified in Article 1.6.13,
half of the nonprestressed reinforcement required for transverse flexure design is considered effective in resisting
shear forces. This is justified, since po-

 Approach Structure
I

ft

Main Span

1rD

End Pier

D=8+0.02L+0.08H
D1 = D/4
where D and D i are in inches.
L Length of bridge deck between
expansion joints, in feet.
H= Pier height in feet
Fig. 9. Minimum gap and seating length requirement.

tential shear failure normally originates
at the half-depth location of the web
where transverse bending stresses are
not critical.9
For seismic design, recommendations
developed by the Applied Technology
Council (ATC-6)10 were followed. The
design objective is to ensure that in an
earthquake, with a 50-year probability of
occurrence, the bridge will remain usable for emergency passage, although it
may suffer repairable damage. This corresponds approximately to designing
the ultimate strength of the bridge for a
load equivalent to that induced by an
earthquake of a 500-year return period.
The structure is designed to allow plastic hinge formation at the pier top and
bottom only when its failure mechanism
is reached.
Special consideration was given to the
earthquake requirements for expansion
joints and restrainers. Fig. 9 schematically shows the gap and seating length
as specified in the design. The

PCI JOURNALJJuly-August 1984

minimum seating length, D, was established in accordance with Article 4.9.1
of ATC-6, and the gap distance, Dl , was
predicted by response spectrum
analysis." This provision stipulates that
temperature induced movements must
be added to D, in determining the design expansion joint gaps.
To provide a positive horizontal linkage between the main span structure
and the approaches, earthquake restrainers were installed at each expansion joint. A sufficient number of earthquake restrainers were selected at
each expansion joint to provide a total
ultimate strength equal to 15 percent of
the weight of the main span structure.
The length of the restraining cables is
such that they will accommodate without rupture to the total joint movement
during an earthquake. In order to transmit this restraining force to the remainder of the superstructure, additional
tendons were provided at the weak parts
of the side spans.

63

 with an orthotropic steel plate deck. No
bids were received for the precast concrete superstructure alternate. The bids
for the concrete structure varied from
approximately $24 to $28 million, and

Contract Awarding
A total of six bids was received on
October 1, 1980: five for cast-in-place
box girders and one for steel box girders

375'-0"

590'- 0

375'-0"
CE North

Columns

O

olumns

^S

Formtroveller

Stage I - Build East Pier Table
(jSpon

Q Pier 17

Pier 16
(West)

I (East)

104 -S

0
Stage 2 - Free Cantilever
East Side

Construction,

11
L .l

Closure

Pour

O

Stage 3 - Complete East Half of Bridge

Expansion Joint

O

Stage 4 - Complete the whole Bridge
Fig. 10. Actual construction sequence.

64

Falsework

Closure

Pour

Expansion Joint

 I

Table 3. Comparison of tendon system from as designed and as built condition.

Longitudinal
Transverse
Vertical

As built

As designed

Tendon location

12 x 0.6 in. (15 mm) 0 strands

19 x 0.5 in. (13 mm) (A strands

Epoxy coated 1'/a in. (32 mm) 4)
deformed bar

4 x 0.6 in. (15 mm) 4) strands

1' in. (32 mm) 4) deformed bar

6 x 0.5 in. (13 mm) 0 strand

the sole steel bid was approximately $40
million. The winning bid put the construction cost of the structure at about
$170 per sq ft ($1935 per m 2 ). A breakdown of the bid is as follows:
Common Items (mobilization,
utilities, etc.) .........$3.3 million
Substructure (steel pipe piles,
foundation and reinforced concrete
pier columns) ........$9.1 million
Superstructure (post-tensioned
structure) ...........$11.4 million

Construction Modifications
Basically, the bridge was built in accordance with the conforming cast-inplace design. However, the following
modifications were furnished by the
contractor:
1. Instead of casting the two box girders separately, the contractor elected to
pour the complete bridge section all at
once. This was accomplished by tying
two parallel form travellers together
during concrete casting. This modification eliminated the need for leaving a
longitudinal closure between the two
box girders. Since all transverse tendons
were made continuous, any possible
misalignment of the transverse tendon
ducts was avoided. This simplified the
construction but required a more intensive labor force, reducing flexibility of
manpower allocation.
Fig. 10 indicates the construction sequence selected by the contractor. The
girder cross section was kept the same as
that shown in Fig. 3. The segmental
length of 16 ft 6 in. (5 m) specified by the
PCI JOURNALIJuly-August 1984

with epoxy coated flat duct

designer was used in construction.
2. As permitted in the specifications,
the contractor had the option of selecting any post-tensioning systems providing they met the requirements
specified in the special provisions.
Table 3 compares the designed systems
with the contractor's choices.
Although the contractor replaced the
12 x 0.6 in. (15 mm) diameter strands
with 19 x 0.5 in. (13 mm) diameter
strands for the longitudinal tendons, the
pattern, distribution, and anchorage location of the tendons remain the same as
shown in the design drawings. The
spacings of vertical and transverse tendons were adjusted to provide the
minimum effective forces required by
the designer.
3. As described previously in the construction sequence (Fig. 5), the designer
recommended that the unbalanced parts
of the side spans be built segmentally by
the form travellers, with the help of
temporary supports. However, the contractor elected to construct that portion
of the side span totally on falsework
(Fig. 10). To allow room for adjusting
misalignment, a 3-ft (0.91 m) wide closure was provided between the end of
the side span cantilever and the
falsework-supported portion. Since the
contractor dismantled the form travellers in the proximity of the east end closure prior to making the closure pour,
clamping the ends together proved to be
difficult, and concrete block counterweights were placed on the higher side
of the two free cantilevers to achieve
vertical alignment.
65

 Concluding Remarks
The construction went smoothly with
only a few delays at the beginning of the
job. The first two segments took about 2
months to complete. Once the crews became familiar with the repetitive operations of advancing the form travellers,

Fig. 11. West Seattle Bridge, halfway
through construction.

placing reinforcing bars and tendon
ducts, concreting, stressing the tendons
and grouting the ducts, their productivity dramatically improved. Near
the end of construction of each balanced
cantilever, it was not uncommon for two
segments to be completed within a
week.
A special feature of this project was
the close involvement of the consultants
in nearly all aspects of the construction.
Continuous review of construction progress and daily field inspection were provided by the design engineers. This approach proved to be effective in ensuring that the construction met the intent
of the contract documents.
There was one incident which
exemplifies the importance of careful
field inspection. Inspectors noticed that
the brownish color of a freshly cast segment appeared to be abnormal. It was
later discovered that an undue amount
of fly ash had been accidentally mixed
into the concrete by the supplier
through a mechanical failure in the
mixing process, reducing the concrete
strength considerably.
Fortunately, the mistake was caught
before any forward segments were cast
and corrected by jackhammering off the

Fig. 12. West Seattle Bridge, nearing completion.
66

 Fig. 13. West Seattle Bridge, completed and in-service.
defective segment. Had additional segments been poured without the correction, devastating consequences could
have resulted.
Figs. 11 through 13 show various
views of the bridge during construction
and after completion. The bridge was
opened for traffic in November, 1983.
During the last 8 months the structure
has performed with total satisfaction.

I Acknowledgments
The following are those chiefly responsible for the realization of the West
Seattle Bridge, and their areas of responsibility:
Owner: The City of Seattle,
Washington; Bruce Wasler, Project
Manager.
Prime Consultant: West Seattle
Bridge Team, composed of: AndersonBjornstad-Kane-Jacobs, Inc., Kramer,
Chin & Mayo, Inc., Parson Brinckerhoff,
and Tudor Engineering Co.; Thomas A.
Kane, Project Manager.
Contractor: Kiewit-Grice.
Superstructure Subconsultant: Contech Consultants, Inc.; M. C. Tang and J.
B. Louie, Principal Designers; Paul
Brallier, Construction Inspector.

REFERENCES
1. Kane, T. A., Carpenter, J. E., and Clark,
J. H., "Concrete Answer to Urban Transportation Problems," Concrete International, August, 1981, pp. 85-92.

2. Kane, T. A., Carpenter, J. E., and Clark,
J. H., "Approach Spans to the West Seattle Bridge," PCI JOURNAL, V. 28, No. 6,
November-December 1983, pp. 58-67.
3. Standard Specifications for Highway
Bridges, 12th Edition, American Association of State Highway and Transportation Officials (AASHTO), Washington,
D.C., 1977 (with 1978 and 1979 Interim
Supplements).
4. ACI Committee 318, "Building Code
Requirements for Reinforced Concrete
(ACI 318-77)," American Concrete Institute, Detroit, Michigan, 1977.
5. CEB/FIP Joint Committee, International Recommendations for the Design
and Construction of Concrete Structures, Comit6 Europeen du BE ton/
Federation Internationale de la Pr6contrainte, Cement and Concrete Association, London, 1970.
6. Post-Tensioning Manual, Third Edition,
Post-Tensioning Institute, Phoenix,
Arizona, 1981.
7. Homberg, Hellmut, Fahrbahnplatten
mit Veraenderlicher Dicke, SpringerVerlag, New York, N.Y., 1968.
8. Post-Tensioned Box Girder Bridge Manual, Post-Tensioning Institute, Phoenix,
Arizona, 1978.
9. Jungwirth and Baumann, "Shear Design
with Dywidag Prestressing System," In:
Finsterwalder Festschrift, Verlag G.
Braun, Karlsruhe, 1973.
10. ATC-6 Seismic Design Guidelines for
Highway Bridges, Applied Technology
Council, Berkeley, California, 1981.
11. Mahoney, T. F., and Clark, J. H., "Seismic Design — West Seattle Bridge,"
Paper Presented at the Northwest Bridge
Engineers' Seminar, Olympia, Washington, October 4, 1983.