Soil-Structure Interaction in Integral Abutment Bridges

Catarina Fartaria

catarinafartaria@me.com

Department of Civil Engineering, Architecture and GeoResources, Instituto Superior Técnico, Av. Rovisco Pais, 1,

1049-001 Lisbon, Portugal

ABSTRACT

Integral abutment bridges (IABs) do not have joints or bearings to accommodate the deck time-dependent

induced horizontal movements, establishing a monolithic connection between the superstructure and

infrastructure. The motivation that led to this concept was the elimination of the high maintenance costs linked

to the deterioration of the joints and bearings inherent to the traditional bridges conception. The

superstructure horizontal movements induce deformations on the infrastructure, leading to a complex

interaction with the soil. Due to this interaction, geotechnical issues may arise and can compromise the service

behavior of the bridge and the approach embankments. One phenomenon known as bump at the end of the

bridge (a differential settlement that appears between the abutment and the soil) is in IABs exacerbated by

reaching the active stress state during the decks contraction. On the other hand, the deck expansion leads to an

increase in the lateral earth pressure. With the cyclic loading of the soil, a phenomenon known as ratcheting

occurs behind the abutment, this corresponds to an increase in the lateral earth pressure, at each displacement

cycle, due to soil irreversible compaction. Nowadays, the limitations of the integral conception can be overcome

using geosynthetic materials allowing the construction of longer IABs. The mitigation of the described

phenomena is possible through the stabilization of the retained soil and use of an elastic element behind the

abutment, which will accommodate the cyclic movements. In this study a stabilization solution is proposed

through the use of soil-cement columns, executed with the jet-grouting technique, and a resilient EPS layer.

Furthermore, a numerical analysis performed by a 2D finite element model allowed both the identification of

the critical phenomena, as well as the quantification of the lateral earth pressure reduction achieved by the use

of an elastic inclusion.

Key Words: Integral Abutment Bridges; Soil-Structure Interaction; Ratcheting; Compressible Inclusion

1. INTRODUTION

Traditional bridges include bearings and expansion

joints in order to accommodate the deck thermal

and time-dependent induced horizontal

movements. Because of the underlying costs of

maintaining and repairing deck joints and bearings,

bridge engineers have been applying the integral

concept in bridge construction. This one involves

no mechanical expansion joints and no bearings

between the superstructure and the substructure.

Once the bridge deck is continuous and connected

monolithically with the abutment walls the

substructure deformation must accommodate the

horizontal. As a result, a complex soil-structure

interaction take place among the abutment, the

approach fill, the foundation soil, and the piles

supporting abutments.

The elimination of joints and bearings brings many

advantages to this type of structure. Besides the

substantial reduction of maintenance costs,

applying the integral concept can lead to: reduced

material and construction costs of the bridge;

minimized deterioration by chemicals; simplified

construction; increase earthquake resistance; and

smooth riding. Furthermore, integral bridge

solution can also be employed in retrofitting of

existing bridges.

However, IABs have an inherent geotechnical

problem that could compromise the service

behavior of the bridge and approach

embankments. As the temperature of the deck

changes its length increases and decreases and a

displacement is imposed at the top of the

abutments. The magnitude of these horizontal

displacements is a function of the thermal variation

level, type of superstructure material and length of

the bridge. Since this displacement depends on the

bridge length, the application of this concept is

limited to short to medium bridges.

The integral construction began in late 30’s with a

five span bridge in Ohio State. Since then the

development of integral bridges has been largely

owed to the research conducted in U.S.A. Currently

the integral bridge length allowed varies between

countries and between states. The bridge with the

maximum length constructed has about 350

meters. When skewed abutments are employed

lateral earth pressures cause rotation of the deck in

plan. Thus, the skew angle is also limited up to

about 30°. The use of curved deck in IABs to

accommodate the thermal expansion and

contraction results in lower displacement of the

abutments allowing grater lengths. The longest

integral curved bridge is the Sunniberg Bridge in

Switzerland. The deck is 526 meters long and has a

curvature radius of 503 meters.

The difficulty of predicting the behavior of the

structure lies in the interdependence between the

deformations of its elements. When the deck is

expanding the value of its ends displacements is

smaller than the one that would occur if the

structure had a free extension. This value, and the

amount and mode of deformation of the

abutment, depends on the relative flexural stiffness

of the composite bridge deck, abutment wall,

foundation piles, and lateral stiffness of the soil

behind the wall and next to the piles, the amount

and mode of deformation of the wall varies. Thus,

the structure deformation depends on soil reaction

while soil reaction depends on the structure

deformation. The analysis of the structure behavior

has to be iterative.

2. SOIL-STRUCTURE INTERATION

Both daily and seasonal temperature variations

affect bridge displacements. The greatest

expansion and the greatest contraction occur

during summer days and during winter nights,

respectively (see Figure 1). Thus, the extreme

temperature degrees control the extreme

displacement imposed at the top of the abutment.

Besides de thermal loading the internal time-

dependent effects that will appear in pre-stressed

concrete decks also lead to its axial deformation.

The bridge shortening due to creep and shrinkage

is specially important during the first years after

construction.

Figure 1- Abutment seasonal movements

During the deck expansion, the imposed

displacement at the top of the abutments makes it

move towards the retaining soil. The mode of the

abutment movement depends on the flexural

stiffness ratios of the bridge elements and lateral

stiffness of the substructure surrounded soil. This

mode is usually a mixed one with rotational and

translational components. When the abutment is in

its initial position there are lateral earth pressures

acting in it corresponding to the rest stress state

for which a traditionally bridge should typically be

designed.

During the abutment movement towards the soil

that earth pressure increases. While the movement

in the opposite direction leads to a pressure drop.

The abutment displacement in that direction is

usually enough to reach the active pressure state

causing a soil wedge. When the abutment returns

to the summer position, the soil displacement is

not fully recovered due to its inelastic nature not

allowing the recover of abutment initial position.

This happens every contraction/expansion cycle

and is the main reason for the inward abutment

long-term position. Other reason is the contraction

due time-dependent effects that occurs in pre-

stressed concrete decks. Thus, abutment long-term

position causes a settlement of the soil next to it

(1) (2)

)

(3)

(1) Winter/night position

(2) Summer/day position

(3) Foundation

increasing the bump at the end of the bridge

phenomenon. With high settlements appears a gap

behind the abutment.

Other potentially serious long-term source of

problem is the ratcheting phenomenon. The soil

next to each abutment becomes increasingly

compacted due to cyclic loading. The lateral earth

pressures during summer are greater than those

from the previous year due to a increase in soil

lateral stiffness. Thus, these pressures increase

over years and can reach the passive stress state.

This increment far exceeds any typical safety factor

and hence can lead to an abutment structural

failure. There are proposed models to predict the

lateral earth pressure distribution accounting for

cyclic loading such as: recommended models in the

U.K and Sweden design codes and proposed

models by Kerokoski and Sandford.

When the abutment is supported on piles its

movement causes lateral deflections at the tops of

them. Pile head stresses can reach or exceed yield,

induce plastic hinging, and consequently reduce its

axial capacity. Thus, piles must be designed to

retain enough flexibility such that forces due to

deformations are minimized. Simultaneously, a pile

foundation that has a high rotational and

translational stiffness results in larger

superstructure loads during thermal changes. In

order to increase the lateral and rotational

flexibility of the pile head, piles are often driven

into holes filled with loose sand or installed with

their weak axis of bending parallel to the bridge

centerline. [1]

It is important to predict the load-displacement

response of laterally loaded piles during the design

of superstructure. Since the pile behavior depends

on lateral soil stiffness, a series of uncoupled

Winkler springs is used, supposing that the

deflection at one level of the wall is not presumed

to affect the value of the reaction force at another

level. The spring constitutive relation usually

defined by p-y curves intends to represent the non-

linear soil behavior. [2]

Transition slabs also used in traditionally bridges

provide a smooth transition between the

embankment and the bridge superstructure. In

IABs, they are essential to span the void formed

behind the abutment. To avoid joints the transition

slabs are rigidly connected to the superstructure

and therefore subjected to large horizontal

displacement. Its design must regard that

movement.

3. STABILIZATION SOLUTIONS

As the IABs issues were being recognized and

observed over the years in existing IABs,

stabilization solutions emerged intending to

mitigate the issues inherent in integral conception.

Since main issues in IABs are located behind the

abutment, geosynthetics turn out to be the most

suitable material to use.

As reported by Horvath (2000), the key concepts

that should be used in the development of

stabilization solution are: The deck and abutment

should be allowed to move freely with seasonal

temperature variations to prevent the appearance

of thermally induced forces; the retained soil

should remain spatially and temporally fixed to

prevent its settlement; the relative seasonal

movement between a bridge and the retained soil

should be accommodated in an orderly predictable

manner trough a element with joint function; and

the seasonal increase in lateral earth pressure due

to ratcheting behavior should be addressed. [3]

Although the subsidence behind the abutments

was the first problem to be recognized, the first

stabilization solution focused only on the earth

pressure issue. The use of an element as a

compressible inclusion between the abutment and

soil intended to serve as a sacrificial cushion

accommodating the relative movements that occur

seasonally. The use of a compressible inclusion is

not new in geotechnical works applications and the

expanded polystyrene geofoam (EPS) has become

the most efficient material to use whenever

maximum compressibility is desired under relative

low stress conditions. An elasticized EPS, commonly

called resilient EPS, is a suitable material to use as a

compressible inclusion in IABs because as an

increased compressibility compared to normal EPS

in combination with an elastic behavior up to a

higher strain. The Figure 2 shows the normal and

resilient EPS stress-strain relation under strain

controlled, unconfined, axial compression which

revels an elastic behavior up to 30% of strain and a

Young’s modulus of 250 kN/m2. This already low

modulus is a conservative value since to slow

loading conditions its value decrease.

Figure 2-- Normal versus Resilient EPS [3]

The EPS resilient layer must be installed behind the

abutment and its required thickness should be

determined according to its expected axial strain

and the strain limit within the elastic behavior

using the following equation.

𝑇𝑖𝑐𝑘𝑛𝑒𝑠𝑠 𝐿𝑎𝑦𝑒𝑟 =𝐷𝑒𝑠𝑖𝑔𝑛 𝑎𝑥𝑖𝑎𝑙 𝑠𝑡𝑟𝑎𝑖𝑛

𝐸𝑙𝑎𝑠𝑡𝑖𝑐 𝑠𝑡𝑟𝑎𝑖𝑛 𝑙𝑖𝑚𝑖𝑡 [%] × 100(1)

In a limit scenario, this strain is equal to half the

free deck length change. Restrict the layer axial

strain to an elastic behavior is critical in ensuring

the lost of function as compressible inclusion

during the cyclic loading over the years. A integral

abutment with a compressible inclusion was

monitored for five years showing an adequate

behavior [4].

Although a elastic inclusion can be effective in

reducing the increase in lateral earth pressures due

to cyclic loading, does not solve the soil settlement

issue, in fact it can worsen it. This is because the

highly compressible nature of that element

becomes a detriment when deck’s winter

contraction occurs. As the abutment moves away

from the retained soil the relatively weak

compressible inclusion is unable to restrain the soil

from displacing inward toward the abutment. Thus,

together with the compressible inclusion (CI), a

stabilization solution is needed to keep the

retained soil fixed preventing its settlement and

horizontal displacement behind the abutment. One

of the possible solutions is the use of a

mechanically stabilized earth system (MSE) that

results in a self stable soil mass for the design life of

the bridge. MSE system uses geosynthetic material

or steel strips as a soil reinforcement (see Figure 3-

a). This solution was studied back in 2003 with a

full scale test showing a good behavior.[5] Other

solution currently used employs geofoam blocks in

replacing part of the landfill (see Figure 3-b). A self-

stable wedge of geofoam, typically normal EPS, is

used to maintain a vertical slope of the material

placed behind the abutment. Further, being a

lightweight material would minimize the

settlements and enhance stability of the

foundation soil.

Figure 3- Current stabilization solutions: a) using MSE;

b) using geofoam blocks

In this study a stabilization solution based on the

aforesaid ones is proposed. The key used to

mitigate the cyclic increase in lateral earth

pressures is the same used in the current solutions:

a resilient EPS layer placed behind the abutment

with enough thickness to maintain the elastic

behavior over the years. At the same time, the

retained soil stabilization is achieved through a

curtain made of soil-cement columns (see Figure

4). The jet grouting is a simple and economic

Normal EPS Normal EPS

Resilient EPS Axi

al c

om

pre

ssiv

e st

ress

(kP

a)

Axial compressive strain (%)

Geofoam blocks

Compressible Inclusion

b)

Compressible Inclusion

a)

Geo

syn

thet

ic o

r

Ste

el R

ein

forc

emen

t

technique that can be used to build the soil-cement

elements. As the soil is retained by the curtain the

abutment can move seasonally against the

compressible inclusion without disturbing the soil.

Thus, the there will be no place to settlement or

void formation due to deck length changes.

Figure 4- Proposed stabilization solution

The sealing curtain is composed of soil-cement

columns alternatively executed and overlapped. Its

thickness must be design to support the lateral

earth pressures at rest state imposed by the

retained soil and steel beam reinforcement should

be considered when the bending moment is high.

The bottom of the columns needs to be embedded

in the foundation soil.

A bridge approach embankment should ensure a

progressive stiffness change between the bridge

and the ground. To provide this progressive

stiffness and avoid large settlements of the backfill

a soil treatment is proposed. This treatment

involves, with the use of the same technique, the

execution of soil-cement columns equally spaced

(see Figure 5). With a stiffness lower than the

bridge stiffness but higher than the soil stiffness,

soil-cement elements seem to be the appropriate

solution.

Figure 5- Soil treatment with soil-cement columns

In order to ensure the effectiveness of the soil

treatment in reduce the settlements, avoiding the

appearance of subsidence zones between the

columns, a load transfer platform is needed above

the columns. This platform has to be design to

transfer the traffic load to the soil-cement columns

while these ones drive the load to the foundation

soil. Figure 6 shows schematically the loaf transfer

platform operation. A soil with high friction angle,

typically a granular selected fill, is used to ensure

all traffic loads routing to the columns. Further, a

biaxial geogrid placed below the granular soil use

its high tensile strength to rout the extra load to

the columns.

Figure 6- Load transfer platform

This whole system besides the reduce settlement

function is useful eliminating the surcharges lateral

earth pressures on the curtain. Also, the properties

requirements typically inherent to the approach

embankment soils are here eliminated. A poor

quality soil could be used with this system.

Figure 7- Proposed overall solution

The geotechnical instrumentation and monitoring

plan is particularly relevant in this solution. The

axial strain of the compressible inclusion and

lateral deformation of the retaining curtain must

be monitored in order to ensure that lateral earth

pressures acting on the abutment are not higher

than the expected.

Approach Slab Load Transfer Platform

Soil-cement columns equally

spaced in both directions

Foundation soil Soil-cement wall

Traffic load

Soil layer

Tout -Venant

Geogrid Column

Ab

utm

ent

Soil treatment

Columns wall

Resilient EPS layer

Soil-cement columns wall reinforced with steel

Backfill

Foundation soil

4. NUMERICAL ANALYSES

To understand the phenomena that occur behind

the abutment several numerical analyses were

performed in the finite elements program PLAXIS

2D. A basic model was set representing a

abutment wall fully embedded in the soil mass

with general boundary conditions (fixed both

horizontally and vertically in the bottom of the

model and fixed horizontally in the vertical

boundaries) (see Figure 8). A 4m high plate

element was used to represent the abutment

wall and was forced to move sidelong against the

soil applying prescribed displacements.

Figure 8- Model geometry

At first the Mohr-Coulomb model was used to

represent the soil behavior. The material was the

typically soil used as backfill, a drained sand. The

soil properties are presented in Table 1.

Table 1- Soil properties used with Mohr-Coulomb

model

𝑕

[kN/m3]

E

[kN/m2]

ν

[-]

c

[kN/m2]

𝜑′

[°]

𝜓

[°]

𝑅𝑖𝑛𝑡𝑒𝑟

[-]

22 20000 0,3 1 30 3 0,5

Interface elements, used to model the soil-

structure interaction, were placed between the

soil and the wall. Also, for easy measurement of

the surface soil deformation, a interface element

was placed above the soil in the backfill area. The

plate properties were also defined, although they

should not influence the results since the

prescribed displacements will be applied in the

entire height of the wall. A mesh was generated

with a refinement in the backfill area. First a set

of prescribed displacements was applied moving

the abutment against the backfill area simulating

the deck expansion. Three types of movement

were performed: translation, rotation around the

bottom and a mixed movement (see Figure 9).

Figure 9- Prescribed displacements

For each type of movement several magnitudes

were performed. Displacement of the top of the

wall ranged between 10mm and 120mm while

the displacement in the bottom varied

accordingly. Labels used to identify the

displacements performed take the form “X1mm-

X2mm”, where X1 is the prescribed displacement

at the top of the wall and X2 the bottom

displacement. Assuming a symmetrical bridge

subjected to a 30° thermal change, the 10mm

displacement corresponds to a free length change

of a 66m deck length, while the 120mm

displacement corresponds to an 800m bridge

length. Besides the length change, these

prescribed movements intend to simulate the

relative bending stiffness of the deck and the

abutment foundation and the lateral stiffness of

the soil near to the infrastructure.

The lateral earth pressures observed behind the

abutment for a top prescribed displacement of

60mm are displayed in Figure 10. The typical

triangular shape of earth pressures envelope is

observed for a translational movement. The

rotation around the bottom presents a high

decrease in the earth pressure values in the lower

half abutment. The mixed movement presents, as

expected a intermediate earth pressure state.

Figure 10- Lateral earth pressures in three types of

movement for a top prescribed displacement of

60mm

0

1

2

3

4

-270-220-170-120-70-20

Dep

th [m

]

Lateral earth pressure [kN/m2]

60mm-0mm60mm-30mm60mm

a) b) c)

(1) Plate element (abutment) (2) Interface element

36 m

12

m

Backfill area

4 m

x

y

Deck area

(1)

(2)

(2)

(2)

The analysis was equally performed for the three

types of movement and for five top displacement

values. The results obtained with the rotational

movement are shown in Figure 11. The

development of the earth pressures with the

increase in the magnitude displacement suggests

that a passive stress state is reached at the upper

half of the wall for a top displacement of about

60mm. The analytical passive earth pressure is

quite the same as that obtained with the

Coulomb theory.

Figure 11- Lateral earth pressures for a rotational

movement

A multiple phase analysis was also performed in

order to simulate the cyclic deck seasonal

movements. To describe more accurately the non

linear soil behavior under cyclic loading the

Hardening soil was used. It simulates the

expansion of the yield surface due to plastic

straining. The additional soil properties used in

this soil model are presented in Table 2.

Table 2- Additional soil properties used with

Hardening-Soil model

𝐸50

[kN/m2]

𝐸𝑢𝑟

[kN/m2]

𝐸𝑜𝑑𝑚

[kN/m2]

𝑝𝑟𝑒𝑓

[kN/m2]

m

[-]

20000 80000 20000 100 0,5

The same prescribed displacements and the three

movement types were applied in multiple phases

in opposite directions alternately. An 8 year

scenario was simulated trough the 8

expansion/contraction cycles performed. The

total lateral earth pressures force obtained for a

cyclic translational movement of 10mm, 20mm

and 30mm are shown in Figure 12.

The ratcheting effect was indentified. The results

clearly show an earth pressure increase after the

first cycle imposed. The values obtained for the

next 8 cycles revealed to be closer suggesting the

attenuation of the phenomenon as cycles occur.

Figure 12- Total earth pressure force for cyclic

movement

Is also shown that the increase obtained after the

first cycle is lower for higher displacements. That

and the fact that the increase at each cycle

diminishes over the cycles suggests that the soil

stiffness increases with the cyclic loading but

reaches a limit value corresponding to the higher

possible stiffness of the soil. Thus, the larger the

displacement and the greater the soil stiffness

smaller will be the increase of the lateral earth

pressure due to cyclic loading although the cycle

0 earth pressure is higher.

The increase in an actual bridge should be smaller

than the obtained with these numerical analyses.

The reason is that with the stiffness increase the

thermal deck length change is more restrained so

the displacement observed at the top of the

abutment is lower over cycles unlike the

performed analysis.

Another analysis was performed this time using a

resilient EPS layer behind the abutment in order

to quantify the lateral earth pressure reduction

achieved. The properties attributed to the layer

are presented in Table 3. The soil was

represented once again with the Mohr-Coulomb

model.

Table 3- Linear elastic model EPS properties

𝑕

[kN/m3] 𝐸 [kN/m2] 𝜈 [-] 𝑅𝑖𝑛𝑡𝑒𝑟 [-]

0,112 250 0,15 0,5

0

1

2

3

4

-420-320-220-120-20

Dep

th [m

]

Lateral earth pressures [kN/m2]

10mm-0mm30mm-0mm60mm-0mm90mm-0mm120mm-0mmPassivo Coulomb

-800

-600

-400

-200

0

"10mm" "20mm" "30mm"

Eart

h p

ress

ure

s [k

N/m

]

Cycle 0

Cycle 1

Cycle 4

Cycle 8

The abutment rotation was simulated with

prescribed displacements from 10mm up to

120mm against the compressible inclusion. Two

thicknesses of the EPS layer were used in the

analysis. A 300mm thickness layer was used first.

The lateral earth pressures obtained are shown in

Figure 13. As expected the lateral earth pressure

increases with the displacement. Besides the EPS

layer low axial stiffness the soil behind it is

compressed and contributes with a small portion

to the earth pressure on the abutment.

Figure 13- Lateral earth pressures for a rotational

movement against a 300mm thickness compressible

inclusion

The analysis was performed equally for a 600mm

thickness EPS layers. The prescribe displacement

120mm corresponds to a 20% axial deformation

of the 600mm thickness layer still within the

elastic behavior. The lateral earth pressures

obtained are shown in Figure 14. Since the

material model used was linear elastic the

resilient EPS non elastic behavior observed to

axial strains from about 30% was not recognized.

Figure 14- Lateral earth pressures for a rotational

movement against a 300mm thickness compressible

inclusion

The overall earth pressures obtained for all

displacements and considering the two

thicknesses are represented in Figure 15. Also the

results obtained previously for the wall abutment

rotation against the soil are presented.

Figure 15- Overall earth pressures with and without a

compressible inclusion

The reduction in lateral earth pressures achieved

by the EPS layer is more meaningful for higher

displacements. The use of a layer with twice of

thickness revealed similar values of the total

earth pressure when compared with the values

obtained when no compressible inclusion is used.

For a top abutment displacement of 120mm the

lateral earth pressure can be reduced in about 3

times with the use of an elastic inclusion.

In comparison with an abutment without it, if the

compressible inclusion behavior is the expected

the lateral earth pressures not only are smaller

but there will be no place to the ratcheting

phenomenon, at least not significantly, due to the

elastic behavior of the inclusion.

5. CONCLUSIONS

Although the current and proposed stabilization

solutions will increase the construction cost of

IABs they should be cost effective and make up

that cost by reducing future maintenance and

repair costs. Further, implementing these

solutions retroactively on existing IABs where are

0

1

2

3

4

-70-50-30-10

Dep

th [m

]

Lateral earth pressure [kN/m2]

10mm-0mm30mm-0mm60mm-0mm90mm-0mm120mm-0mm

0

1

2

3

4

-70-50-30-10

Dep

th [

m]

Lateral earth pressure [kN/m2]

10mm-0mm

30mm-0mm

60mm-0mm

90mm-0mm

120mm-0mm

-400

-300

-200

-100

0

Tota

l ear

th p

ress

ure

[kN

/m]

Without EPS layerWith 300mm thickness EPS layer With 600mm thickness EPS layer

expected an impaired service behavior could be

cost effective too.

The lateral increase in earth pressures due to

cyclic seasonal loading can be so large that the

abutment design cannot despite it. Some

countries use full passive earth pressure in the

abutment design. However this pressure always

presents a safety factor is can be cost ineffective.

Mainly in a rotational abutment the overall earth

pressure can be much smaller than the

theoretical passive pressure. For a translational

abutment if there expected large displacements

the use of passive pressures in its design can

prove to be a good approach.

The use of a compressible inclusion leads to a

high reduce in lateral earth pressures. The

resilient EPS have been the material of choice to

use as a compressible inclusion. Its low stiffness

and elastic behavior make it a suitable material to

perform as a joint. Earlier applications of this

material have proven their durability in

geotechnical environment.

Note that regardless of the reduction of the

lateral pressures expected the EPS layer thickness

need to ensure that its predicted axial strain

never exceeds the limit of the elastic behavior.

Otherwise it will not accommodate the cyclic

abutment displacement compromising its joint

function and leading to higher lateral pressures.

6. REFERENCES

[1] FARAJI, Susan, TING, John M., CROVO, Daniel

S., Ernst, Helmut, “Non-Linear Analysis of Integral

Bridges: Finite-Element Model”, Journal of

Geotechnical and Geoenvironmental Engineering,

May 2001;

[2] MARURI, Rodolfo F., PETRO, Samer H.,

“Integral Abutments and Jointless Bridges- Survey

Summary”, FHWA Conference- IAJB, Maryland,

2005;

[3] HORVATH, John S.; “Integral-Abutment

Bridges: Problems and Innovative Solutions Using

EPS Geofoam and Others Geosynthetics”,

Manhattan College Research Report No. CE/GE-

00-2, New York, 2000;

[4] HOPE, Edward J., “Field Study of Integral

Backwall with Elastic Inclusion”, Virginia

Transportation Research Council, Virginia, 2005;

[5] POLTZ, Michael, “Jointless Concrete Bridges –

Development of a Flexible Abutment”, Coburg

University of Applied Sciences, Germany, 2008;