TRANSPORTA T/ON RESEARCH RECORD 1275 53

Integral Bridges
MARTIN P. BURKE, JR.

In the United States and Canada, integrated bridge construction ments began to change. Before Cross' "moment distribution ,"
is becoming one of the bridge engineer's primary responses to multiple-span bridges were generally constructed as a series
joint-related bridge damage caused by the use of deicing chem- of simple spans. Following the introduction of moment dis-
icals and the restrained growth of rigid pavements. The relative
tribution, bridge engineers began eliminating troublesome deck
success that has been experienced with integral bridges-bridges
without deck joints-is now being reflected not only in the joints at piers by providing continuous superstructures.
increasing number of longer integral bridges, but also in the inte- On the basis of a recent mail survey (2) , it appears that the
gral conversion of existing jointed bridges. It appears that the Ohio Department of Transportation was one of the first agen-
initial success of such techniques would be an accelerated use of cies to initiate the routine use of continuous construction (Fig-
integrated conversion as an effective alternative to bridge joint ure 1). Its experience provides an informative background for
rehabilitation . this movement toward the use of fully integrated continuous
construction. At first, riveted field splices were used to inte-
Integral bridge construction may be defined as the practice grate adjacent spans and achieve full continuity for steel stringer
of constructing bridges without deck joints. When such con- bridges. By 1934, the department had devised its first butt-
struction is used to eliminate intermediate joints in multiple- welded field splice. Following this first tentative application,
span bridges, it is accepted that the continuity achieved by the welded field splice was continuously improved and used
such construction will subject superstructures to secondary almost exclusively for more. than 30 years for the erection of
stresses. These stresses are caused by the response of contin- steel stringer bridges. In the late 1950s, high-strength bolted
uous superstructures to thermal and moisture changes and field splices were adopted for the Patterson-Riverside Bridge
gradients, settlement of substructures, posttensioning, and so at Dayton, Ohio, one of the first bridge applications for high-
on. When such construction is used to eliminate deck joints strength bolting in the United States. By 1963, high-strength
at abutments, it is likewise accepted that such structures will, bolting replaced field butt welding in Ohio as the method of
in addition , be subjected to secondary stresses due to restraint choice for integrating multiple-span steel bridges to achieve
provided by abutment foundations and backfill against the full continuity. Consequently , by riveting , field welding, and
cyclic movement of bridge superstructures. The justification high-strength bolting, Ohio has employed continuous con-
for such construction is based on the recognition that for short- struction almost exclusively on multiple-span steel bridges for
and medium-span bridges of moderate lengths, significantly close to 50 years. Because continuity can be achieved .more
more damage and distress has been caused by the use of deck readily with cast-in-place concrete, Ohio has been building
joints than by the secondary stresses these joints were intended continuous concrete bridges for close to 60 years .
to prevent. In addition, elimination of costly joints and bear- Figure 1 shows the beginning of the routine use of contin-
ings and the details and procedures necessary to permit their uous construction in the United States and Canada and the
use generally results in more economical bridges. Conse- per-decade increase in the number of transportation depart-
quently, more bridge engineers are now willing to relinquish ments that have adopted the use of continuous construction.
some of their control of secondary stresses primarily to achieve As shown in Figure 1, 26 of 30 departments responding to
simpler and less expensive bridges with greater overall integ- the recent mail survey (2) , or 87 percent of responding depart-
rity and durability. ments, now routinely use continuous construction for short-
and medium-span bridges.
Currently the state of Tennessee appears to be leading the
CONTINUOUS SUPERSTRUCTURES way in constructing long continuous bridges. For example,
the Long Island Bridge at Kingsport was constructed in 1980
Current design trends received their primary impetus and by using 29 continuous spans without a single intermediate
direction almost six decades ago. In May 1930, a brief 10- joint. The total length of this bridge is about 2,700 ft center
page paper (1) published in the Proceedings of the American to center of abutment bearings. Deck joints and movable
Society of Civil Engineers generated considerable discussion bearings have been furnished, but only at the two abutments .
in academia . It also created a minor revolution in the design It has been aptly named " The Champ ."
and construction of short- and medium-span bridges. In this
paper, Cross presented a simple and quick method for the
INTEGRAL BRIDGES
analysis of integral-type structures such as continuous beams
and frames. The method was quickly adopted by bridge engi-
During the past two to three decades, many bridge engineers
neers, and the bridge practices of many transportation depart-
have become acutely aware of the relative performance of
bridges built with deck joints at abutments and those built
Burgess & Niple , Limited, 5085 Reed Road, Columbus, Ohio 43220 . without them. In most respects, bridges without joints-inte-
54 TRANSPORTATION RESEARCH RECORD 1275

Costs of various types of bridges showed marked differ-

z 25 ences. For two bridges built essentially the same except that
u
;::: one was provided with separate abutments and deck joints
>'~ 20 and the other was provided with integral abutments, the jointed
er z
ow
Bi~ 15 bridge was usually more expensive. In addition, bridges with
z er
<!
er"-
<( integral abutments suffered only minor damage from pave-
f- w 10
LL 0
ment pressure, were essentially unaffected by deicing chem-
0 icals, and functioned for extended periods without apprecia-
ci
z ble maintenance or repair. Consequently, more bridge engineers
1920 1930 1940 1950 1960 1970 1980 began to appreciate the merits of integral bridges for short to
YEAR
moderate bridge lengths. Gradually, design changes were made
and longer integral bridges were built and evaluated. In 1946
FIGURE I Design trends for continuous bridges: early Ohio's initial length limitation for its standard continuous
conversion of simple spans to continuous spans. concrete slab bridges was 175 ft. In a 1973 study of integral
construction (4), 4 states responded that they were using steel
gral bridges-have performed more effectively, because they bridges and 15 states that they were using concrete bridges
remain in service for longer periods of time with only mod- in the 201- to 300-ft range. In a 1982 study (5), even longer
erate maintenance and occasional repairs. Some of this expe- bridges were reported:
rience was forced upon bridge engineers by circumstances
beyond their control.
Continuous steel bridges with integral abutments have per-
Because ur the growth and pressure generated by jointed formed successfully for years in the 300-foot range in such
rigid pavement, many bridges built with deck joints at abut- states as North Dakota , South Dakota , and Tennessee. Con-
ments have been and are being severely damaged. After deck tinuous concrete structures, 500 to 600 ft long with integral
joints are closed by pavement growth, bridge decks are squeezed abutments have been constructed in Kansas , California, Col-
orado, and Tennessee .
by the generation of pavement pressures. These pavement
pressures can easily exceed 1,000 psi or cumulatively the total
force due to such pressures can exceed 650 tons per lane of Currently, 11 states are building continuous bridges with
approach pavement (3). When the design of abutments for integral abutments in the 300-ft range. Missouri and Tennes-
nonintegral-type bridges-bridges with deck joints at abut- see report even longer lengths. Missouri reports steel and
ments-is considered, the forces of these magnitudes are irre- concrete bridges in lengths of 500 and 600 ft, respectively,
sistible. Many abutment backwalls have been fractured. Other and Tennessee reports lengths of 400 and 800 ft for similar
abutments have been split from top to bottom. In longer bridges. Finally, Figure 2 shows that 20 of 30 transportation
bridges with intermediate deck joints, piers have been cracked departments, or 60 percent of those responding to the survey,
and fractured as well. are now using integral construction for continuous bridges.
In geographical areas with low seasonal temperatures and The attributes of integral bridges have not been achieved
an abundance of snow and freezing rain, the use of deicing without cost. Parts of these bridges operate at very high stresses,
chemicals to maintain dry pavements thm11ghn11t the winter stresses that cannot easily be quantified. These stresses are
season has also had a siguifii.:aul effei.:l un the durability and significantly above those permitted by current design speci-
integrity of bridges built with deck joints. Open joints and fications. In this respect, bridge engineers have become rather
sliding plate joints of shorter bridges and open finger joints pragmatic. They would rather build cheaper integral bridges
of longer bridges have allowed deck drainage, contaminated and tolerate these higher stresses than build the more expen-
with deicing chemicals, to penetrate below deck surfaces and sive jointed bridges with their vulnerability to destructive
wash over supporting beams, bearings, and bridge seats. The pavement pressures and deicing chemical deterioration. In
resulting corrosion and deterioration have been so serious that 1985, Loveall, then Engineering Director for the Tennessee
some bridges have collapsed and others have had to be closed
to traffic to prevent their collapse. Many bridges have required
extensive repair; most of the bridges that have remained in
service have required almost continuous maintenance to coun-
teract the adverse effects of these chemicals. To help minimize
or eliminate these corrective efforts, a whole new industry
was created.
Beginning in the early 1960s, the first elastomeric compres-
sion seals were installed in bridges in the United States to
seal deck joints. Since these first installations, numerous types
of elastomeric joint seals have been developed and improved
in an attempt to achieve a joint seal design that would be
both effective and durable. Most designs have been disap-
1920 1930 1940 1950 1960 1970 1980
pointing. Many leaked. Some required more maintenance
than the original bridge built without seals. By and large, the YEAR
many disappointments associated with various types of seals FIGURE 2 Design trends for continuous bridges: early use of
have caused bridge engineers to consider other options. integral abutments.
 Burke 55

Department of Transportation, reflected this attitude when However, where cast-in-place construction continues to be
he wrote (6): used, flexibility of substructures remains a critical part of
bridge design. For example, Loveall said (6):
In Tennessee DOT, a structural engineer can measure his
ability by seeing how long a bridge he can design without Structural analysis of our no joint bridges indicates that we
inserting an expansion joint. ... Nearly all our newer (last 20 should have encountered problems, but we almost never have.
years) highway bridges up to several hundred ft have been Once we tied the stub abutment of a bridge into rock, and the
designed with no joints, even at the abutments. If the structure structure cracked near its end, but we were able to repair the
is exceptionally long, we include joints at the abutment but bridge and install [a] joint while the bridge was under traffic .
only there .... Joints and bearings are costly to buy and install. The public never knew about it. That was one of few problems.
Eventually they are likely to allow water and salt to leak down
onto the superstructure and pier caps below. Many of our most
costly maintenance problems originated with leaky joints. So Development of new forms of construction will be accom-
we go to great lengths to minimize them. panied by instances of structural distress, and this has certainly
been true for continuous bridges with integral abutments.
Even though bridge engineers have conditioned themselves However, as shown in Figure 2, the increased use of integral
to tolerate higher stress levels in integral bridges , occasionally abutments suggests that 60 percent of transportation depart-
their design control is not sufficient to prevent these high ments are satisfied with the performance of integral construc-
stresses from resulting in structural distress and structural tion and are using such construction in one form or another
fracture. for longer and longer bridges. With continued care and con-
sideration , the trend shown in Figure 2 will no doubt continue .

STRUCTURAL DISTRESS
INTEGRAL BRIDGE DETAILS
Responses to an early survey about construction of continuous
bridges with integral abutments indicated a rather widespread Figures 3-8 show integral abutment details used by six trans-
concern by bridge engineers for the potentially high stresses portation departments. It is probably not accidental that a
that would be present in longer bridges (4) . This concern, fair amount of similarity is evident in these designs, because
more than any other, appeared to be responsible for the early structural details from early successful designs are adapted by
lack of enthusiasm for using integral abutments for longer other bridge engineers for use by their departments. Even
continuous bridges. Although the majority of bridges with though there are similarities, there are also differences, which
integral abutments perform adequately, many of them oper- reflect the types of bridges being built and the care and con-
ate at high stress levels. For instance, an abutment supported cern being given to the choice and development of specific
on a single row of piles is considered flexible enough to accom- details. It should also be realized that these sketches are "bare
modate longitudinal thermal cycling of the superstructure and bones" presentations. They do not reflect other important
dynamic end rotations induced by the movement of vehicular design aspects such as skew and construction procedures, which
traffic. Nevertheless, the steel piles of such an abutment are are considered in the application of these details for specific
routinely subjected to axial and flexural stresses approaching, bridges. These aspects cannot be illustrated and properly
equaling, or exceeding yield stresses (5, 7). Occasionally, a described in a paper as brief as this one. Nevertheless, because
combination of circumstances results in visible distress. these aspects can have a considerable effect on the perform-
Responding to a 1973 survey, a number of bridge engineers ance, integrity, and durability of integral designs, it is appro-
said that some integral abutment wingwalls had minor cracks priate to mention at least passive pressure and pile stresses
(4). This problem was corrected by more generous wingwall for those engineers considering such designs for the first time.
reinforcing steel. Other engineers reported pile cap cracking,
which appears to have been eliminated by rotating steel H-
piles to place the weak axis normal to the direction of bridge
movement. Bndge leAgth "L'
In a recent article in Concrete International, Gamble (8) Span
emphasizes the importance of considering restraint stresses Abut. bearing
in cast-in-place construction. He discusses cracking that occurred
in a continuous concrete frame bridge. Even though concrete
in this structure was considerably below the specified cylinder Preslressed
strength and shear reinforcement did not meet current concrete
beams
requirements, failure of the structure was attributed to its
stiffness and resistance to shrinkage and contraction of the
bridge deck . Failures of this type emphasize the necessity of
achieving flexibility in substructure design and conservative
reinforcement to withstand secondary stresses induced by
foundation restraint and superstructure shortening.
LIMITATIONS
Currently, precast concrete or prefabricated steel super- SKEW MAX "L"
structures are generally replacing small cast-in-place bridges • 45° 300'
in many states and provinces. Consequently , problems asso- > 45° 150'
ciated with initial shrinkage are gradually being eliminated. FIGURE 3 Integral abutments: Iowa.
56 TRANSPORTATION RESEARCH RECORD 1275

Bridge length " L"

Span
t---S~p_o_n.'v----- Slnh
Pres tressed 'o 1~0" 1'..3". re inf.
t-=T-"-1-- - - <L Brg's.
deck panels ·...!. not shown
·.
AASHTO No. 57
course aggregate\ Pre stressed
· ~'i \ concrete Steel

~q; .
beams girder

Geotextile
material
Varies 2'-6" Min.
2'-o" Min
NOTE
Turnbock wings
each supported LIMITATIONS
by a steel-H pile Not Established Clean well drained
I ~ aggregate
<t HP
FIGURE 4 Integral abutments: Pennsylvania. · LIMITATIONS
SKEW MAX "L"
45° 400'

FIGURE 7 Integral abutments: Tennessee.

Bfidge length " L"

Span

- - Steel
Constr beam
Set eel
hack fill joint

2'-6" Min
I~

2'-6''
LIMITATIONS 7~0"
SKEW MAX ' L'_'
0° 350'
30° 300' <L BP LIMITATIONS
SKEW MAX ."L''
FIGURE 5 Integral abutments: North Dakota. 1'-f;" 1'- 6" 30° 300'

FIGURE 8 Integral abutments: Ohio.

Bridge length ''L."
Slob reinf
not shown

Passive Pressure
PPC I-Beam
or W Beam To minimize the passive pressure developed in abutment backfill
by an expanding integral bridge, design engineers have used
a number of controls, devices, and procedures. Including but
not limited to the following, they have (a) limited bridge
length, structure skew, and the vertical penetration of abut-
ments into embankments; (b) used select granular backfill
and uncompacted backfill; (c) provided approach slabs to
prevent vehicular compaction of backfill or to permit the use
Steel Concrete of backfill voids behind abutments; ( d) used embankment
200' 300' benches to shorten wingwalls and used suspended turn-back
30° 30°
wingwalls; and (e) used semiintegral abutment designs (Figure
FIGURE 6 Integral abutments: Illinois. 4) to eliminate passive pressure below bridge seats.
Burke 57

30
Pile Stresses
z 25 - "'
Knowing that longitudinal forces in superstructures are some-
what directly related to the resistance of abutment pile foun-
0

~;'°20 .
dations to longitudinal movement, design engineers have (a)
a:z
ow
n.:;;;
u.. ~.<
lawa =- ---
-- l"'
\\
limited the foundation of integral bridges to a single row of
Cflf-
Za:
~'fl
15
ntuo
--- ...
N
~
Oregon 0
slender vertical piles, (b) limited the pile types, (c) oriented f-~ 10 r<l
LL
the weak axis of H-piles normal to the direction of movement, 0
5
(d) used pre bored holes filled with fine granular material for d
z
·-----'
piles, (e) provided an abutment hinge to control pile flexure, ~

1920 1930 1940 1950 1960 1970 1980

(f) limited structure skew, and (g) used semiintegral abutment
designs for longer bridges (Figure 9) to minimize foundation YEAR
restraint to longitudinal movement. FIGURE 10 Design trends for continuous bridges: routine use
of continuous construction.

Surveys

A number of questionnaires about integral bridge practices to control the behavior and performance of integral bridges
have been circulated in recent years. The responses reflect (2).
the policies, attitudes, and opinions of those engineers respon-
sible for bridge design policies. They also show how some of
those attitudes and opinions have changed during the last INTEGRAL CONVERSIONS (RETROFITTING)
decade. In 1973, Emanual et al. (4) received responses about
their current design practices from 43 transportation depart- Following the trend toward the use of continuous construction
ments. In 1982, Wolde-Tinsae et al. (5) used a questionnaire and the use of integral abutments, as shown in Figures 1 and
as part of an investigation into nonlinear pile behavior. 2, transportation departments are also beginning to convert
Responses from 29 transportation departments were pre- existing multiple-span bridges from simple to continuous spans.
sented in tabular form. In 1983, Greimann et al. (9) elicited Figure 10 shows that this effort began with Wisconsin and
responses from 30 transportation departments on their pile Massachusetts in the 1960s and has gathered strength in the
orientation practices for skewed integral bridges. In 1987, past two decades. Currently 11 of 30 departments, or about
Wolde-Tinsae and Klinger (10) solicited responses from selected 30 percent of the transportation departments, have converted
transportation departments in the United States, Canada, one or more bridges from multiple simple spans to continuous
Australia, and New Zealand. (The reports by Wolde-Tinsae spans.
et al., Greimann et al., and Wolde-Tinsae and Klinger also Although the chart in Figure 10 suggests considerable activ-
contain valuable bibliographies for those interested in a more ity, it actually shows only the relative number of departments
in-depth study of current research on behavior of integral that have made such conversions. It is not indicative of the
bridges and performance of abutment pilings.) Last, in 1987 number of bridges that have been converted. For example,
the author received responses from 30 transportation depart- positive responses were received from only two departments
ments describing the limitations that these departments use in response to the following question (2): "In recent years,
have you converted any bridges from multiple simple spans
to continuous spans to eliminate intermediate deck joints?"
The Ontario Ministry of Transportation and Communications
1'-3" '_3" responded:
6" 2~ 0 11
r We are modifying a few structures from simple spans to con-
tinuous spans, eliminating the intermediate deck joints in the
process ....
Steel
girders The Texas Department of Highways and Public Transporta-
tion responded:

In recent years, we have eliminated numerous intermediate

joints. Generally, this is done while replacing the slab. We
simply place the slab continuous across the bents. On a few
occasions, we have removed only the joint and surrounding
deck area, added reinforcing, and replaced that portion of the
deck thus tying the adjacent spans together.

The Tennessee Department of Transportation also has been

actively converting simple span bridges to continuous spans.
In a recent paper, Wasserman, Engineering Director of Struc-
tures at the Tennessee Department of Transportation describes
FIGURE 9 Semiintegral abutment details: Ohio. and illustrates a number of such conversions (11).
58 TRANSPORTATION RESEARCH RECORD 1275

Connection
diophrogm
4• .. It
2'-0"
Cost- in-place
deck slob

Remove concrete as necessary to eliminate

existing armoring, and add negative moment
steel at the level of existing top-deck - Precost
steel sufficient to resist transverse !-beams
cracking. Generally reconstruct with
regular concrete to original grade.
FIGURE 11 Integral conversions at piers: Texas.
Elostomeric Bearings
bearing pods
S preformed
To give this movement some direction, the Federal High- Iilier
way Administration has issued a Technical Advisory on the Pier
subject (12). That advisory in part recommends that a study
of the bridge layout and existing joints be made "to determine FTGURR 13 Integral conversions at piers: Wisconsin.
which joints can be eliminated and what modifications are
necessary to revamp those that remain to provide an adequate
of vehicular traffic. However, for short- and medium-span
functional system .... " For unrestrained abutments,
hridges, the deck crncking associated with such behavior is
a fixed integral condition can be developed full length of the preferred by some over the long-term adverse consequences
shorter bridges. An unrestrained abutment is assumed to be associated with an open joint or a poorly executed sealed
one that is free to rotate , such as a stub abutment on one row joint.
of piles or an abutment hinged at the footing .... (W]here In new construction, conversion of simple spans to contin-
feasible, develop continuity in the deck slab. Remove concrete
as necessary to eliminate existing armoring, and add negative
uous spans is rather commonplace . Figure 13 shows the design
moment steel at the level of existing top-deck steel sufficient detail used in Wisconsin for prestressed I-beam bridges. A
to resist transverse cracking [Figure 11]. substantial concrete diaphragm is placed at piers between the
ends of simply supported prestressed beams of adjacent spans.
The detail shown in Figure 11 reflects the procedure described It extends transversely between parallel beam lines . Then a
by Texas. Note that the detail shows that only the slab portion reinforced concrete deck slab is placed to integrate the beams
of the deck is being made continuous. The simply supported and deck slab, thereby providing a fully composite continuous
beams remain simply supported. For such construction, it is structure. This type of prestressed I-beam construction appears
important to ensure that one or both of adjacent bearings to be standard for many transportation departments.
supporting the beams at a joint are capable of allowing hor- Figure 14 shows the standard design detail used by the state
izontal movement. Providing for such movement will prevent of Ohio to achieve continuity for simply supported prestressed
horizontal forces from being imposed on bearings from rota- box beams. These box beams are placed side by side and then
tion of the beams and slab continuity. transversely bolted together. Finally, continuity reinforce-
The state of Utah also has converted some simple span ment is placed and the concrete closure placement is made.
bridges to continuous ones by using a design similar to the In a 1969 paper, Freyermuth (13) gives a rather complete
one shown in Figure 12. For deck slabs with a bituminous description of the considerations necessary to achieve conti-
overlay, a membrane can be used to waterproof the new slab nuity in a bridge composed of a continuously reinforced con-
section over piers. With a design like this, it is understood crete deck slab on simply supported precast prestressed beams.
that the deck slab would be exposed to longitudinal flexure
from rotation of the beam ends responding to the movement

Remove joint and

place new slob - - Aspholt concrete
'*5 bars wearing surloce
Continuity Exist. joint Beam reinf. Wolerproof1ng
membrOne
!({{l'
Slob
Precast
side-by-side
Beam Open box beams ---+-~
\ _ Expanded
polyslyrene
Pres tressing
strands
~-~-+-- Movable Eloslomeric
bearings <l bearing pads

FIGURE 12 Integral conversions at piers: Utah. FIGURE 14 Integral conversions at piers: Ohio.
Burke 59

Conversion of existing bridges either by replacing the deck itive moments due to live load are reduced by continuous
completely or by replacing portions of the deck adjacent to rather than simple beam behavior.
deck joints over piers can be accomplished by following the Although too recent to consider in terms of a design trend,
procedures developed for new structures. Obviously, for existing conversion of nonintegral to integral or semiintegral abut-
bridges, creep effects will be negligible. Shrinkage effects for ments for both single- and multiple-span bridges has begun.
other than complete deck slab replacements should also be Figures 15 and 16 give design details used for a number of
negligible. Not only does such continuous conversion elimi- recent conversions by the Ohio Department of Transporta-
nate troublesome deck joints, the continuity achieved also tion. Reconstruction of these abutments was made necessary
results in a slightly higher bridge load capacity because pos- by the substantial damage induced by pavement growth and

Slabs Span
reinf. 1
t'-6" -3" t'-3" 1'-9'' Slabs
not shown re inf.
9" 9"
<l <l Bearings - - - - not shown

Construction
join!
Paro us
backfill
Bench

"--1-.-+--++--- Ste eI t rowe I

finish and
2 layers of
graphite coated
sheet asbestos
packing

5'-9"

BEFORE AFTER

4'-o" Slabs
6" reinf.
2'-3" 1'-9" not shown
1'-3' '-o" 1'-3" 6"
1

l Bearing s - 'l Bearings -

. . ·•. ..
• .

Porous
backfil I
Constr.
joint <2)
z
___.- r - -1- Dowe I
ti bars
')(
w

~+----- Constr. jt.

2'-7"
4~0"

BEFORE AFTER
FIGURE 15 Integral conversions at stub-type abutments.
60 TRANSPORTATION RESEARCH RECORD 1275

lBearings

Constr.
Joint

BEFORE

1 11 3'-9"
3 -9 Slabs
Slabs 6"
6" reinf.
reinf. not shown
not shown

I/-
I '-+"'--+-- Construction
~ L, I
1
Ir j oint

: ~ - ~/ ~J
t/lf
WU I ~Porous
backfill

AFTER AFTER
(Single span bridge) (Multiple span bridge)

FIGURE 16 Integral conversions at wall-type abutments.

pressure, by deicing chemical deterioration, or by both. Instead SUMMARY

of replacing backwalls and joints, and in some cases bearings
and bridge seats as well, it was decided to pattern the recon- As the trend shown in Figure 1 continues, it appears that the
struction after the design details used by the department for use of continuous construction for multiple-span bridges will
its new integral bridges. In this way, subsequent concern about become standard for all transportation departments in the
the effects of pavement pressure and deicing chemical dete- very near future . It also appears that the use of integral abut-
rioration has been minimized . ments for single- and multiple-span bridges (Figure 2) will
Burke 61

increase when comprehensive and conservative guidelines for 3. M. P. Burke, Jr. Bridge Approach Pavements, Integral Bridges
their use become more readily available and when their long- and Cycle Control Joints. In Transportation Research Record
1113, TRB, National Research Council, Washington, D.C., 1987.
term performance has been more fully documented. 4. J. H. Emanual, J. L. Hulsey, J. L. Best, J. H. Senne, and L. F.
Because design and construction of fully continuous bridges Thompson. Current Design Practice for Bridge Superstructures
have become routine and continuous conversion of simple Connected to Flexible Substructures. University of Missouri-Rolla,
spans in new construction is becoming more commonplace, 1973.
it is surprising that similar conversion techniques are not used 5. A. M. Wolde-Tinsae, L. F. Greimann, and P. S. Yang. Nonlin-
ear Pile Behavior in Integral Abutment Bridges. Iowa State Uni-
more often to convert existing jointed bridges to continuous versity, Ames, 1982.
bridges. Presumably, the next decade or two will see a bur- 6. C. L. Loveall. Jointless Bridge Decks. Civil Engineering-ASCE,
geoning in retrofitting simple multiple-span bridges to con- 1985, pp. 64-67.
tinuous bridges (Figure 10) and from nonintegral to integral 7. J. L. Jorgenson. Behavior of Abutment Piles in an Integral Abut-
ment Bridge. In Transportation Research Record 903, TRB,
abutments. When more information on the operating stress National Research Council, Washington, D.C., 1983.
levels of integral bridges has been developed and when more 8. W. L. Gamble. Bridge Evaluation Yields Valuable Lesson. Con-
fully described design details and procedures for integral con- crete International, June 1984, pp. 68-74.
versions have become available, bridge engineers will be able 9. A. M. Greimann, D. M. Wolde-Tinsae, and P. S. Yang. Skewed
to more fully justify their consideration of such construction. Bridges with Integral Abutments. In Transportation Research
Record 903, TRB, National Research Council, Washington, D.C.,
Until then, much intuition and prudent judgment will con- 1983.
tinue to be used to ensure that integral construction and con- 10. A. M. Wolde-Tinsae and J. E. Klinger. Integral Abutment Bridge
version techniques will provide the service life needed to jus- Design and Construction. Report FHWA/MD-87/04. Maryland
tify their adoption and continued use. Department of Transportation, Annapolis, 1987.
11. E. Wasserman. Jointless Bridges. Engineering Journal, Vol. 24,
No. 3, 1987.
12. Bridge Deck Joint Rehabilitation (Retrofit). Technical Advisory
REFERENCES T5140.16. FHWA, U.S. Department of Transportation, 1980.
13. C. L. Freyermuth. Design of Continuous Highway Bridges with
1. H. Cross. Analysis of Continuous Frames by Distributing Fixed- Precast Prestressed Concrete Girders. AC/ Journal, Vol. 14, No.
End Moments. Proc., American Society of Civil Engineers, May 2, 1969.
1930.
2. M. P. Burke, Jr. NCHRP Synthesis of Highway Practice 141:
Bridge Deck Joints. TRB, National Research Council, Washing- Publication of this paper sponsored by Committee on General Struc-
ton, D.C., Sept. 1989. tures.