The University Drive over I-75 design-build bridge replacement project in Auburn Hills, Michigan included construction of the state's first Diverging Diamond Interchange. To reduce costs, the design-build team significantly reduced the bridge skew angle and realigned the interchange to avoid deposits of soft organic soils near the existing abutments. This innovation reduced the bridge length by 92 feet and saved approximately $1.25 million. Foundations for the abutments and pier posed challenges due to variable soil conditions and construction constraints, but collaborative solutions allowed the project to remain on schedule.

1. University Drive over I-75: Design-Build
Spawns Innovation
MARIO QUAGLIATA, P.E. and MATTHEW WAGNER, P.E., Bergmann Associates,
Lansing, MI
IBC 16-77
KEYWORDS: Design Build, Diverging Diamond Interchange, Skew Angle, Abutment Design, Pile
Design, Organic Soils, Precast, Prestressed, Concrete, Hybrid Bulb Tee, Design.
ABSTRACT: The University Drive over I-75 design-build bridge replacement project in Auburn
Hills, Michigan included construction of the first Diverging Diamond Interchange in the state of
Michigan. Innovations and unique cost saving measures that were developed in collaboration
between the designers and the contractor to reduce construction costs will be discussed. These
included significantly reducing the bridge skew and realigning the interchange to avoid deposits
of soft organic soils near the existing abutments.
INTRODUCTION
The bridge carrying University Drive over I-
75 in Auburn Hills, Michigan was replaced by
the Michigan Department of Transportation
(MDOT) as part of an interchange
reconstruction project that replaced the
existing interchange with a Diverging
Diamond Interchange (DDI), the first of its
kind constructed in the state. Because of
condition issues with the existing bridge
carrying University Drive, the project was
procured using design-build contracting to
help expedite completion of the project. A
major innovation to modify the alignment of
the interchange and as a result, the skew
angle and length of the new bridge was used
by the design-build contractor team to help
save the department millions of dollars on
the project. Construction begin in the late
Spring of 2015 and the interchange was
opened to traffic on November 9, 2015.
While the project included many modern
innovations in bridge and highway
engineering, the roots of the project go back
to the time when I-75 was first constructed
through this area of the state.
BACKGROUND
In the 1960’s when the original partial
cloverleaf interchange between University
Drive and I-75 was constructed the Auburn
Hills area was rural and the land use was
largely agricultural. But, by the 1990’s-
2000’s the area had gone through
tremendous growth and the once
agricultural areas had been largely
converted to suburban residential and high
tech business use. The area surrounding the
University Drive interchange includes several
major economic generators including the
Chrysler World Headquarters, Oakland
University, the Palace of Auburn Hills and
other automotive robotics companies,
hospitals, hotels, etc.
The population and business growth in the
area caused traffic capacity and safety issues
at the existing interchange with I-75 and
drove the need for a new and improved

2. interchange that could handle large traffic
volumes. In 2008 an interchange study was
undertaken by MDOT which considered
conventional alternatives such as partial
cloverleaf and roundabout type
configurations along with modern
interchange types including a single point
urban interchange (SPUI) and a DDI. Land
development around the interchange
required a solution that stayed within the
existing right-of-way footprint at the site,
while still providing increased traffic capacity
and safety improvements. These constrains
made the DDI a logical choice for the site.
This would be the first DDI constructed in
the state of Michigan. This modern
technology in highway design was also well
received by the local businesses, such as
Chrysler, who viewed the interchange type
as a modern entrance for their visitors that
come from around the world.
Figure 1. DDI traffic operations diagram [1].
With the DDI, University Drive traffic crosses
to the opposite side of the road, travels over
I-75 and then crosses back over to return to
the standard roadway configuration (see
Figure 1). It eliminates left-turn lanes and
left-turn signals, which improves safety.
Traffic exits flows left off the diamond onto
the interstate and two-phase signals control
traffic at the cross over points. The speed
limit on University Drive is lower through the
interchange (25 mph) then on the rest of the
road (45 mph) due to the signals and
crossovers at each end of the bridge.
Figure 2. Typical beam end condition that lead
to closure of the existing University Drive
Bridge over I-75.
Several TIGER (Transportation Investment
Generating Economic Recovery) grant
applications were submitted between 2009
and 2013 to help fund the interchange
reconstruction project, but all were
unsuccessful. In the meantime, the
existing bridge carrying University Drive over
I-75 was ageing and in need of rehabilitation
to prolong its service life while the
interchange reconstruction project was
developed. A bridge project was planned
and under design in 2013 to perform
maintenance on the existing bridge, when a
January 2014 inspection revealed fractured
and bucked beam ends at the median pier
(see Figure 2) which forced closure of the
bridge and the high volume roadway it
carried. The bridge and road closure caused
major traffic impacts and backups in the
surrounding area. Temporary supports were
installed along the median of I-75 to shore

3. the existing bridge and allow it to be quickly
reopened to traffic, but it was clear that a
more permanent solution was urgently
needed.
DESIGN-BUILD PROCESS
It was clear to MDOT an accelerated delivery
method was needed to address the existing
bridge condition. In early 2014 MDOT was
able to pool funding from several state
initiatives and from the City of Auburn Hills
to fund the project and the decision was
made to use design-build contracting to
procure the project and accelerate
completion. In March of 2014 preliminary
design of the DDI began along with
development of the contract books and
reference information documents (RID).
The interchange design that was released as
part of the pre-bid RID maintained the
existing University Drive roadway alignment,
which crossed I-75 with a heavy 44-degree
skew angle.
A two-phase procurement process was used
by MDOT to select a Design-Build contractor
to deliver the project. First, a Request for
Qualifications (REQ) was released on April
25, 2014 to solicit qualification information
that was used to select the most highly
qualify contractor teams. MDOT’s goal was
to short-list 3 to 5 contractors to bid on the
project. Qualifications were submitted on
May 30, 2014 and on June 24, 2015 MDOT
announced 4 short-listed contractors.
The second step was the bid-phase, which
began on September 24, 2014 when the
contract books and RID were released to the
contractor teams. The project bids were
structured to include a daily bridge rental fee
Figure 3. Aesthetic bridge features.

4. of $8,000 and several lane and ramp rental
fees to help incentivize timely completion of
the project. The bids were due December
12, 2014 and the team of Dan’s Excavating
(prime contractor) and Bergmann Associates
(prime bridge and highway designer) was
the successful low-bidder selected to deliver
the project.
BRIDGE AESTHETIC REQUIREMENTS
Another important part of the project for
MDOT and their stakeholders was the bridge
aesthetics. The new bridge and interchange
design was to have an identity beyond an
exit number (see Figure 3). Aesthetic
features were required in the contract books
including decorative fencing and bridge light
standards, a large Auburn Hills sign at the
center of the bridge, aesthetic bridge barrier
with decorative concrete columns, various
concrete surface coatings, and concrete
texturing and staining on the abutments.
BRIDGE ALIGNMENT INNOVATION
During the pre-bid phase of the project, the
Dan’s/Bergmann design-build team
developed several alternative technical
concepts (ATC) as ways to save project costs
and improve efficiency in construction. By far
the most ambitious and the one having the
highest reduction in project costs was the
concept to alter the alignment and
configuration of the DDI that was provided
in the RID (see Figure 4).
The interchange design in the RID
maintained the existing University Drive
roadway alignment, which crossed I-75 with
a 44-degree angle. This configuration
resulted in total bridge length of 321-feet,
Figure 4. As-constructed University Drive over I-75 interchange geometry versus alignment
proposed in the pre-bid Reference Information Documents.

5. with a 150-foot span over southbound (SB)
I-75 and a 171-foot span over northbound
(NB) I-75. Taking advantage of the
diverging diamond interchange type where
design speeds are lower between the
signalized crossovers, the design team was
able to reconfigure the interchange and
reduce the bridge skew angle to 28-degrees.
This modified alignment resulted in a total
bridge length of 229-feet with a 109-foot
span over SB I-75 and a 120-foot span over
NB I-75. In total the bridge length was
reduced by 92-feet from the design
presented in the RID, which resulted in a
costs savings of approximately $1,250,000
to the project. There were also several other
effects with the revised alignment that
benefited the project in both the short-term
and long-term.
Figure 5. Existing University Drive alignment
and proposed DDI configuration, also showing
location of organic soils.
Having a shorter bridge means less bridge to
maintain in the long-term which is a benefit
to the owner, MDOT. Reducing the skew
angle from 44-degrees to 28-degrees will
likely result in better long-term performance
of the bridge since higher skewed bridge are
well known to have more maintenance and
structural issues over time than lesser
skewed bridges. The proposed alignment
and interchange modification also moved the
bridge and ramps away from a large pocket
of organic soils in the SW quadrant of the
interchange (see Figure 5). This helped
reduced the amount of undercutting on the
project and will likely improve the long-term
geotechnical performance of the bridge and
roadway pavement.
Another benefit of the reduced bridge length
was the feasible beam types for the
proposed span lengths. Contractors in
Michigan typically preferred the use of
prestressed concrete beams. There are
several fabricators in the state which makes
for a competitive bidding environment and
good lead times for delivery. With the longer
spans lengths based on the interchange
configuration in the RID it would have be
possible to used prestressed Bulb-Tee
beams, but shipping, handling and erection
would have been difficult. The modified
interchange configuration allowed for
shorter span lengths that are more suitable
for prestressed concrete beams (Figure 6).
Figure 6. P/S beam erection.
The new bridge design used pile supported
integral stub abutments behind MSE walls.
The reduced skew angle improved the MSE
Organic
Soil Pocket

6. wall details with the abutment return walls
and improved wall constructability. Highly
skewed walls can be problematic and require
specialized reinforcement strap details in the
corners which make strap installation soil
compaction difficult in these areas. The
reduced skew angle allowed for standard
details to be used in the acute corners of the
MSE walls.
The change in roadway alignment and skew
angle also reduced the amount of decorative
fencing and light standards that were
needed on the outside of the bridge. The
railing length was reduced by 45-feet in each
quadrant (180-feet total) and the number of
decorative light standards was reduced from
8 lights shown in the RID to 4 lights. In
addition, 4 decorative columns were
eliminated from the bridge railing. These
changes reduced the initial costs for the
aesthetics by approximately $100,000.
The change in fence length was
accommodated by maintaining the fencing
panel size and other details included in the
RID and simply removing a fence panel, light
standard and column on either size of the
large Auburn Hills decorative sign. There
was a small amount of difference between
the fencing length in the RID and the
proposed modified alignment, which was
made up by modifying the length of the end
fence panels that are supported on the
bridge approach slab barrier. The final
aesthetic details had a very similar look to
those provided in the RID, as shown in
Figure 3. The reduced skew angle also
helped improve the visibility of the large
Auburn Hills sign on the center of the bridge
to the traveling public on I-75, allowing the
sign to be viewed at a much better angle.
FOUNDATION DESIGN &
CONSTRUCTION
The design and construction challenges
associated with the abutment and pier
foundations centered on constructability,
construction cost, and site constraints (e.g.
variable soil profile). The RID eliminated
spread footings for consideration as a
foundation alternative specifying that only
driven deep foundations be investigated.
Preliminary geotechnical analysis confirmed
that the required vertical resistance could be
achieved using H-piles or cast-in-place pipe
piles. Ultimately, the DB team selected steel
H-piles, which is the preferred foundation
type for integral bridges in Michigan. The
contractor also requested that the maximum
pile length be limited to 75 feet to avoid pile
splices and improve project economy.
ABUTMENT FOUNDATIONS – Are
comprised of a single row of piles oriented
to bend about their weak access to
accommodate the bridge movement (see
Figure 7). The need to achieve the
theoretical pile vertical resistance was critical
with the space to drive piles limited to the
width of the bridge and the tip elevations
being held constant as noted above. In
addition, the abutment and MSE wall
construction was on the project critical path
so delays would have had significant impacts
to the project schedule.
With the success of the entire project
hinging on the design and construction of
the abutment foundations, a major concern
regarding the construction procedure
became apparent at Abutment A and a
crucial decision was required.
As a result of the poor in-situ soils and the
piles being driven prior to the placement of

7. the MSE wall backfill, significant downdrag
(negative skin friction) would have been
induced on the Abutment A piling. To
account for the downdrag in the design, it
was found that the vertical pile resistance
would have required a reduction of more
than 25%. In addition, the abutment piling
had already been ordered to meet the
project schedule.
Figure 7. Typical integral abutment pile
orientation and layout (Abutment A shown).
Multiple options were evaluated to mitigate
the downdrag at Abutment A including:
performing pile restrike operations, pre-
loading the soils and pre-boring pile casings,
adding additional piles, and undercutting the
poor soils. No alternative provided a solution
that limited additional work without
significant risk to the project schedule and
economy. Therefore, the DB team chose the
most conventional alternative to undercut
the poor soils as shown in Figure 8.
In total, the excavation of 8,000 cubic yards
of soft clay from the site near Abutment A
was required and the void was backfilled
with engineered fill and compacted prior to
pile driving operations. In this case, the
selection of the tried and true construction
method allowed the project to remain on
schedule and within budget.
PIER FOUNDATION - Design challenges
stemmed from the limited access to the
construction site (located in the median of I-
75) and the overlap of the existing and
proposed pier pile caps.
Figure 8. NW Quadrant Soft Clay Excavation
Sheet piling was used for the demolition and
construction of the existing and proposed
piers to limit the extents of the excavation
and avoid taking lanes on I-75. The sheeting

8. was driven around the existing foundation
and/or proposed foundation limits on three
sides (north, west and east) leaving one side
(south) sloped at a 1:2 for access as shown
in Figure 9.
Figure 9. Pier 1 H-pile and sheet pile layout.
The proposed H-piles were designed to
accommodate spacing adjustments parallel
to the pier reference line. This allowed the
contractor flexibility during the pile driving
operation to avoid unforeseen conflicts (e.g.
existing timber piles driven out of line, or
additional timber piling not shown on the
record plans) and leave the existing piling in-
place as shown in Figure 10. The left-in-
place piling was found to increase the pile
resistance. Subsequently, the pile length
required to achieve the theoretical vertical
resistance increased as the proposed pile
locations extended beyond the limits of the
existing pier foundation resulting in pile tip
elevations below the pile lengths ordered for
the pier. However, due to the collaboration
prompted by the design/build project
delivery system, a solution was found that
allowed the project to remain on schedule.
Figure 10. Pier pile driving operation and
existing timber piles left-in place.
The DB team made the decision to use the
piling that was originally ordered for
Abutment B to achieve the required pile
driving resistance. The order in which the
piles were driven was critical to avoid costly
moment splices. The ‘Abutment B’ piles,
which were longer than the pier piles, were
driven second to assure the splice location
would be below the point of fixity and avoid
Existing
Timber Piles

9. costly moment splices. Ultimately, this
decision avoided performing pile restrike
operations, which if found ineffective would
have also resulted in the need for additional
piling and pile splices. The availability of the
pile type at the lengths required to replace
the Abutment B piles also played a
significant role in the decision.
BEAM DESIGN
Several beam types were investigated for
this project including: AASHTO I-Beams,
Spread Box Beams, and Hybrid Bulb-Tee
Beams. The lead time required for steel
beam fabrication in Michigan and the fast
track schedule eliminated steel from
consideration.
The defining criteria for selecting the
concrete beam type for this project were the
initial and life-cycle costs, material
availability and fabrication lead time, and
contractor preference with regard to
erection. The design challenges associated
with the beams included limiting the
structure depth, and designing for and
incorporating the RID aesthetic details.
The concrete beam type selected, which was
originally developed in Indiana, is a Hybrid
Bulb-Tee beam that can be fabricated at
various depths by adjusting the depth of the
web while maintaining the flange dimensions
(see Figure 11 ).
The depth of beam that provided the
required capacity and the desired structure
depth was 60-inch deep with a 49-inch wide
top flange and a 40-inch wide bottom flange.
The design team found that the hybrid 60” x
49” Bulb-Tee beam required less beam lines
than the more conventional AASHTO I-
beams and spread box beams in addition to
being a more reliable beam shape that is
easier to detect deterioration during routine
inspections. The hybrid bulb-tee beams
were preferred by the owner, contractor and
fabricator when presented the alternatives.
Figure 11: 60” x 49” Hybrid Bulb-Tee Beam
[3]
The final beam design did not require harped
strands with 0.6” diameter, 270ksi, low
relaxation strands and 8 ksi - 28 day
concrete (7 ksi – release) to span a
maximum of 118’-4” (Span 1 = 107’-0”, Span
2 = 118’-4”).
The beams were designed as simply
supported for all dead and live loads as well
as continuous for live loads across the pier.
The design live load used in Michigan to
account for all of the standard legal truck
axle configurations is HL-93 MOD, which
uses 1.2 times the AASHTO LRFD specified
HL-93 loading and the design tandem
portion is replaced by a single 60 kip axle.
Steel intermediate diaphragms were
specified to reduce dead loads and improve
constructability. In addition, direct
coordination with the fabricator allowed the
design to incorporate and count on the top

10. flange ‘support’ strands (see Figure 12).
Figure 12: Hybrid bulb-tee beam top flange
showing support strands, horizontal shear
stirrups and lifting loops.
REINFORCEMENT DETAILING
The typical deck and barrier reinforcement
was required to be designed for additional
loads due to the aesthetic features (e.g.
columns, signs, light standards), and
detailed to incorporate hundreds of feet of
conduit and junction boxes without
compromising the structural integrity of each
component.
Open communication between the designer
and the contractor throughout the
development of the plan details was
essential to minimizing costs and maximizing
constructability.
One innovative detail stemming from
discussions within the DB team involved the
avoidance of construction joints on the deck
at the median barriers. The proposed detail
used drilled epoxy anchors installed post
deck construction to tie the median barrier
to the deck avoiding embedded cast-in place
reinforcement. This detail allowed the
contractor to screed from toe to toe of fascia
barriers as shown in Figure 13.
The plan detail was primarily used to verify
that it was feasible to fit the required amount
of barrier reinforcement in the deck without
damaging the transverse deck reinforcement
when drilling. Prior to drilling in the field,
ground penetrating radar was used to
identify the actual locations of the transverse
reinforcement.
This detail is representative of other similar
details that were developed through
collaboration of the design build team that
greatly improved the constructability of the
bridge.
Figure 13: Deck construction showing screed
operation extending across the entire deck.
AESTHETIC DETAILS
As discussed in the previous section, many
of the aesthetic features required additional
calculations and standard detail
modifications to ensure the structural
integrity of the bridge. Of all the aesthetic
features, the ‘City of Auburn Hills’ sign
required the most significant amount of
additional calculations and plan

11. modifications to remain a part of the
aesthetic features on the bridge.
The bid documents included a fully
dimensioned layout of the sign. However,
upon further review by the DB team after the
project was awarded it was realized that the
sign was considerably under designed. The
primary members (vertical posts) supporting
the sign were the same as the posts in the
subsequent aesthetic fence panels (see
Figure 14).
Figure 14. Bid document schematic showing
‘City of Auburn Hills’ sign with proposed
primary support members highlighted.
The design of the primary members
supporting the sign found that the strength
design moment and shear forces could be
resisted by 5 posts (instead of 3).
Figure 15: As-constructed ‘City of Auburn
Hills’ sign (15 primary support members).
However, the weld fatigue stress check was
found to control the design falling under
category E’. Since the fence post and base
plate size was limited by the width of the
barrier, the only option to reduce the
stresses in the connection was to increase
the number of connections. The final design
found that 15 posts were required to
adequately support the sign which were
detailed as to not compromise the bridge
aesthetics (see Figure 15).
SUMMARY
Design of the University Drive bridge over I-
75 and diverging diamond interchange
began in February of 2015 and construction
was completed on time and opened to traffic
on November 9, 2015. The new DDI was well
received by the community and is operating
smoothly, having reduced traffic backups at
the interchange [4].
This project demonstrated that design-build
contracting can not only be used as an
effective tool accelerate project delivery,
lower project costs and improve project
quality, but can also spur innovation
between the designer and contractor to
benefit the project.
Figure 16. Ribbon cutting ceremony.

12. ACKNOWLEDGEMENTS
The design and construction of the
University Drive bridge over I-75 and
interchange in less than 9 months was a
considerable undertaking by all those
involved. Bergmann Associates would like to
thank our contractor partner Dan’s
Excavation of Shelby Township, Michigan for
the opportunity to design the new bridge
and interchange and for their great
teamwork throughout the project. We
would also like to thank the management
staff and many reviewers from MDOT who
made this project a high priority from the
beginning through the end.
REFERENCES
1. Oakland University Press Room.
“University Drive Diamond Interchange.”
Retrieved http://www.oakland.edu/press
(2015).
2. 83.241275&lvl=19&dir=6.707399&pi=-
8.798463&style=x&mo=z.0&v=2&sV=1&for
m=S00027 (2016).
3. Indiana Department of Transportation.
Design Manual - Chapter 406, Prestressed-
Concrete Structure (2013).
4. Macomb Daily. “Diverging Diamond in
Auburn Hills Hailed as Future of
Transportation.” Retrieved
http://www.macombdaily.com/article/MD/2
0151109/NEWS/151109605