Value Engineering vs.

Alternate Designs in
Bridge Bidding
Compares the advantages and
disadvantages of alternate
designs and value engineering in
bidding of bridges as experienced
in the State of Florida.

Tom Alberdi, Jr.

Bridge Engineer
Florida Department of
Transportation
Tallahassee, Florida

T he State of Florida has been utilizing

the concept of bidding alternate de-
signs in bridge construction for the past
Conversely, value engineering has
some built-in disadvantages. First of all,
the contractor must be the low bidder
30 years. We realize that some of the before he can initiate a value engineer-
practices in Florida are not applicable in ing proposal. This may well cut out some
other parts of the United States. Obvi- of the more imaginative and innovative
ously, construction costs are affected by contractors who happened to bid high on
many conditions, such as the availability the project as submitted to them.
of building materials, equipment, and Unfortunately, many value engineer-
skilled labor. Nevertheless, the method ing submittals reflect inferior quality.
of bidding alternate designs has worked Frequently, the contractor makes mate-
well for us in Florida and has proven to rial commitments prior to bidding which
be cost effective. could be extremely difficult to alter once
The other prevalent method of bidding he is the successful bidder. This fact
is based upon value engineering. One alone makes it hard for a contractor to
advantage of this method is that the
contractor and the Department of Trans-
portation have an opportunity to share in NOTE: This article is based on a presentation given
at the Long Span Concrete Bridge Conference in
certain savings that an enterprising con- Hartford, Connecticut, March 18-19, 1980. The
tractor might initiate. It is certainly a conference was sponsored by the Federal Highway
good way for an innovative contractor to Administration, Portland Cement Association, Pre-
stressed Concrete Institute, Post-Tensioning Insti-
make a profit. tute, and Concrete Reinforcing Steel Institute.

PCI JOURNAUJuly-August 1980 41

Fig. 1. Rendering of Long Key Bridge in Florida. The successful bid used precast
segmental span by span construction with precast V-piers and drilled shaft
foundations. (Courtesy: Figg and Muller Engineers, Inc.)

Table 1. Alternate bidding system for Long Key Bridge.

42
participate in a value engineering ap- A good example of the savings possible
proach, and almost precludes the possi- in the use of alternate designs is the re-
bility of any significant innovations being building of numerous bridges in the
offered. Florida Keys Bridge Replacement Proj-
The experience in Florida has shown ect.
that very few contractors have much On the 12,144 ft (3704 m) Long Key
interest in value engineering. In general, Bridge (see Fig. 1) which was bid in July
the state's contractors do not like the 1978 as the first of several projects, two
value engineering clause, because, they basic sets of plans were prepared. The
will tell you, they are not in the en- first one was a state in-house design
gineering business. using conventional AASHTO girder
techniques. The other design was done
On the other hand, contractors seem to by a consultant using a concrete seg-
like the alternate design method of bid- mental solution. Numerous sub-
ding. alternates were offered for each alter-
The alternate design method for bid- nate.
ding, as developed by the Florida De- The segmental alternate offered span
partment of Transportation, contains the by span construction using V-piers; span
following provisions: by span construction using vertical piers;
• All alternate plans are complete or cantilever construction using vertical
documents. piers. Either precast piles or drilled
• Alternate designs, in effect, provide shafts could be used with all three con-
value engineering before the bidding struction methods including also the
stage. This approach creates competi- AASHTO precast girder design. Table 1
tion between well-engineered designs. gives a summary of the alternate de-
• Alternate designs are prepared for signs (broken down by substructure and
either steel vs. concrete or concrete vs. superstructure) for the Long Key Bridge.
concrete. The first option in segmental con-
• The design is normally done by struction was a reinforced top slab,
in-house staff vs. consulting engineers, either with reinforced concrete epoxy
or consulting engineers vs. consulting coated joints or using pretensioning
engineers. In other words, we normally transversely.
do not like to have the same consultants Barrier curbs were the second option,
prepare the two alternate designs. We either cast-in-place (conventional) or
believe that by having more than one precast (never integral).
engineering team, more competition can Drilled shaft foundations consist of
be developed between each design al- drilling a hole to a predetermined eleva-
ternate, and thus we are more likely to tion and placing concrete and steel.
generate some really fresh ideas about Loads vary from 350 to 450 tons per
solutions to problems through this com- shaft. Precast prestressed concrete piles
petition. are placed in predrilled holes and are
In our Florida experience, we have grouted.
realized considerable savings by utilizing The V-piers are precast and bear on
the alternate design concept. The addi- neoprene pads at the top of the pile cap.
tional design costs usually run between Alternately, cast-in-place vertical piers
1.5 and 2.5 percent of the construction could be used with neoprene bearings at
costs. Savings exceeding 15 percent of the top of the pier.
the construction costs have actually In the span by span construciton
been attained, and obviously, the cost of method a barge crane places segments
design is relatively minor compared to on a truss spanning between piers, then
the construction costs. post-tensioning tendons are installed

PCI JOURNAL/July-August 1980 43

 stages — first for cantilever construction,
then for final stress adjustment.
The transverse prestressing of the top
slab will reduce the amount of reinforc-
ing bars needed. The prestressing is
released when the concrete for the
segments reaches 4000 psi (27.6 MPa).
On the Long Key project, there were
eight bidders, seven of whom bid the
concrete segmental solution. The low
bidder, Michael Construction Company
of Florida, Inc., bid on span by span
erection with precast V-piers (see Fig. 2)
and drilled shaft foundations; top slab
transversely prestressed (in the upright
position); and barrier curbs cast-in-place
Fig. 2. Placing precast V-pier on cap (slip formed).
(Long Key Bridge). The difference between the low bid
and the AASHTO girder bid was $2.6
million.
and stressed. There is no epoxy in the Because of the above success on Long
joints between segments. Key Bridge, we used the same alternate
In the cantilever scheme of erection design approach for Seven Mile Bridge
the segments are placed symmetrically (see Fig. 3). This structure has a 35,000
about the pier with the aid of an over- ft (10,675 m) long span and was bid in
head launching gantry. The segments March of 1979.
would be epoxy coated thus functioning Again, two sets of documents were
both as a sealer and lubricant. Post- prepared, one by the Florida Department
tensioning tendons are placed in two of Transportation using precast

Table 2. Alternate bidding system for Seven Mile Bridge.

44
Fig. 3. Rendering of Seven Mile Bridge in Florida. (Courtesy: Figg and Muller En-
gineers, Inc.)

AASHTO girders, and the other in con- the Keys site. He elected to use drilled
crete segmental construction prepared shaft foundations, erection span by
by a consultant. span, also, but selected a conventionally
The design alternates for foundations reinforced deck.
and the segmental design were the These two projects emphasize the
same as on Long Key (see Table 2) ex- point that it is extremely difficult to pre-
cept that the precast V-piers were not dict the course of action of contractors.
offered for Seven Mile Bridge. The savings on the three Keys bridges
Six contractors bid this job, and all six with alternate designs that have been
bid the segmental solution. We had bid within the last 20 months [Long Key,
budgeted $52 million for this bridge, and Seven Mile, and Channel No. 5 (Fig. 5) ]
the low bid by Misener Marine of Tampa, amount to $12.6 million on $72.3 million
Florida, was $45 million. worth of construction (Table 3).
The two contractors differed in their
approach to these two similar
projects—Long Key and Seven Mile
bridges. Table 3. Comparative savings using
alternate designs for various Florida
For example, at Long Key Bridge, the
Keys bridges.*
contractor elected to do on-site casting,
to utilize drilled shaft foundations, pre-
tensioned top slabs, precast V-piers and
erection employing the span by span
method. Fig. 2 shows the placing of a
V-pier on a cap.
On the other hand, at Seven Mile
Bridge, the contractor chose to cast the
bridge segments 450 miles away from
the job site at his casting yard in Tampa `Note: The segmental alternate design was
(see Fig. 4), then barge the segments to low bid in each of the above projects.

PCI JOURNAL/July-August 1980 45

Fig. 4. Casting yard in Tampa, Florida, for Seven Mile Bridge.

Another interesting project is the center span of 1300 ft (397 m) and when
Dames Point Bridge (see Fig. 6) near built will surpass the Pasco-Kennewick
Jacksonville, Florida. This cable-stayed Intercity Bridge which has a center span
prestressed concrete structure has a of 981 ft (299 m).

38. 412.

^O.

TYPICAL SEGMENT

TRANSVERSE SECTION
TYPICAL BOX PIER
OVERALL BRIDGE LENGTH - 4,923'

TYPICAL SPAN- 135

90 1 HORIZONTAL CL.

ELEVATION
Fig. 5. Typical segment, pier section, and elevation of Channel No. 5 Bridge,
Florida Keys. (Courtesy: Figg and Muller Engineers, Inc.)

46
Fig. 6. Rendering of Dames Point Bridge crossing the St. Johns River near
Jacksonville, Florida. (Courtesy: Howard, Needles, Tammen & Bergendoff.)

Design alternates were prepared for million, all using the alternate design
this bridge, one using concrete con- concept.
struction and the other employing a steel The complexities in these structures
superstructure. range from rather straightforward, high
The additional engineering fee for the level crossings to two very complex
Dames Point Bridge was less than 1 per- urban interchanges in South Florida.
cent of the contract bid. The bids were The designs offered are segmental
extremely favorable and slightly below concrete vs. either steel box girders,
the engineer's estimate. The low bid in steel plate girders, or AASHTO I-girders
concrete was $65 million and the low as the other alternate.
steel bid was $85 million—a savings of We in Florida are convinced that the
$20 million due to alternate designs alternate design approach to bidding is
being offered for bidding. We are of the extremely cost effective, and allows us
opinion that alternate designs encour- to get more bridge for the money. We
aged the contractors to sharpen their are committed to the use of this ap-
pencils when preparing their jobs; this proach to reduce construction costs by
was reflected in the price received.* developing competition, and challenging
engineers to be at their innovative best
Currently, the Florida Department of
to stretch our transportation dollars.
Transportation is in the process of pre-
paring plans for four major projects `Unfortunately, recent financing difficulties will force
ranging in size from $5 million to $60 a second round of bidding for this bridge.

PCI JOURNAUJuly-August 1980 47