PUENTE DE LA UNIDAD
Monterrey, Mexico
INTERNATIONAL BRIDGE TECHNOLOGIES, INC.
Project Description
CABLE STAYED BRIDGE
Overview
The signature structure of Puente de la Unidad project is a 304m (997ft) long asymmetrical cablestayed bridge, with a main clear span of 185.6m (609ft). The main pylon is inclined 30° to the vertical
and reaches a total height of 152.1m (499ft) from the top of foundation. Nearly all the main structural
components are made of 50MPa (7.25ksi) strength concrete. Thirteen pairs of harped stay cables support
the main span and are anchored on the outside of the roadway. One pair of vertical stays is anchored
into the back of the pylon. Main span carries 2 lanes of traffic in each direction with pedestrian walkway
provided in middle. Pictures of the bridge are shown below.
International Bridge Technologies (IBT) was the lead designer for the bridge. The specific design
tasks included:
•
•
•
•
•
Main Span: Conceptual, Preliminary, and Final Design
Stay-Cables: Conceptual, Preliminary, and Final Design
Construction Methods: Conceptual, Preliminary, Final Design, and on-site support
Pylon: Conceptual, Preliminary, and Oversight of Final Design
Foundation: Conceptual, Preliminary, and Oversight of Final Design
The design of the bridge included detailed, 3-D FEM, non-linear, and time-dependent analysis.
In addition, detailed studies were performed to ensure compatibility of the extensive network of
post-tensioning tendons and non-orthogonal reinforcement.
Sistemas Optimos Constructivos S.A. (SOCSA) served as the prime consultant for the full viaduct
project. SOCSA performed preliminary analysis and final design for the pylon and foundation.
West Wind Inc. provided wind studies and cable damping requirements.
©2009 Copyright International Bridge Technologies, Inc.
PUENTE DE LA UNIDAD
Monterrey, Mexico
INTERNATIONAL BRIDGE TECHNOLOGIES, INC.
STRUCTURAL SYSTEMS
• Original or Innovative Applications
of New or Existing Techniques:
• Social and Economic Considerations:
The bridge project includes a long viaduct to provide
The fundamental behavior of a cable-stayed structure
congestion relief to the crowded streets of Monterrey.
is well understood. Typically the bridges are
Also, the Santa Catarina riverbed can crest at a level
symmetric by span and pier layout, and the balancing
where most other adjacent bridges are under water.
of forces is accounted for in the basic concept. In
This bridge will provide a critical escape route for
the case of this bridge, the asymmetry required the
the citizens on the South side of the river. In addi-
design to go back to a more basic level to ensure
tion to these benefits, the design was performed with
the structural load paths were well-established and
consideration of local materials and construction skill
adequate capacities provided. Because the main span
level. The bridge details were all considered in such
is reliant on the counter-
to promote ease of
a away
a
balance of the pylon, a
construction.
co
delicate balance exists. The
• Complexity: The Puente
structural capacity of the
de la Unidad project pre-
pylon must be considered
sented many challenges due
se
in parallel with the ballast it
to its complexity. Typically
provides, and these two goalss
the roadway geometry is
th
did not always work in the
adjusted to accommodate
ad
same direction. The Puente
the bridge, but the opposite
th
de la Unidad project is a good
d example of an existing
was done for this project.
project The
T complexities included
bridge concept (cable-stay) used in an alternate way
large openings in the pylon at grade to allow traf-
to provide a striking visual appearance, and achieve
fic flow, the introduction of a vertical curve to the
the goal of providing a single support outside of the
alignment of the bridge deck, variable cross-fall at the
main riverbed.
span along the pylon, and allowing for ramp connec-
• Future Value to the Engineering Profes-
tions on either side of the bridge. All challenges were
sion: As indicated above, this project presents a
successfully incorporated into the final design.
good example how a complex project can be solved
• Meeting and Exceeding Owner/Client
by understanding the basic behavior and providing
Needs: The primary achievement for the Puente de
reliable load paths. The value of dedicating time
la Unidad project was the delivery of a design under
at the conceptual phase is reflected in this project.
a very tight schedule. The design schedule was 9
Three locations on the bridge illustrate this. The first
months, and the contractor selection was selected in
is the transition from the force in the edge beams to
advance of the final design completion. The bridge
the pylon, the second is the resolution of axial loads
construction was completed in 15 months, a time
between the pylon and main span, and third the
frame rarely achieved for this complex of structure.
specially shaped spread footing to accommodate the
The bridge was completed for $16.8 million, and was
monotonic loads. These solutions are shown on the
within 3% of estimated costs.
following pages.
©2009 Copyright International Bridge Technologies, Inc.
PUENTE DE LA UNIDAD
Monterrey, Mexico
INTERNATIONAL BRIDGE TECHNOLOGIES, INC.
FOUNDATION, PYLON BASE, AND TRANSITION SPAN
Excavation of Foundation
Foundation Reinforcement Cage
Starter Bars for Pylon
Foundation
Post-Tensioning
F un
Fo
und
dati
dati
tion
on P
Pos
ostt-T
Tensiio
Tens
ioni
ning
ing
g
Key Features
• Soil was injection grouted for added strength.
• Foundation was a spread footing and posttensioned in primary directions.
• Spread footing dimensions were optimized
for the monotonic loading. A trapezoidal
plan area was designed with a wider toe at the
front of the footing.
Transition
T
Tr
ansi
siti
iti
tion
on S
Spa
Span
p n Fram
pa
F
Frame
rame
e
• 8000m3 (10500yd3) of concrete used for
foundation. Mass concrete casting procedures
implemented.
• Large axial forces at edge beams need to be
transferred to central pylon. Well-defined
load path provided by central and diagonal
beams.
Flow
Fl
ow o
off Forc
F
Forces
orces
es
©2009 Copyright International Bridge Technologies, Inc.
PUENTE DE LA UNIDAD
Monterrey, Mexico
INTERNATIONAL BRIDGE TECHNOLOGIES, INC.
MAIN PYLON
Pylon Section
Climbing Form
Pylon Back Wall Post-Tensioning
Pylon Elevation
Completed Pylon
Key Features
• Pylon is hollow with a typical width of 5m (16.4ft), which tapers to 15m (49.2ft)
from deck to foundation. The back wall of the pylon is post-tensioned.
• Pylon inclination provides significant balance to main span forces.
• Pylon and deck forces resolved at one location and distributed to the foundation
by twin legs.
• Pedestrian access permitted through pylon.
• Pylon and span designed to allow for loss of back stays (i.e. terrorist attack.)
©2009 Copyright International Bridge Technologies, Inc.
PUENTE DE LA UNIDAD
Monterrey, Mexico
INTERNATIONAL BRIDGE TECHNOLOGIES, INC.
MAIN SPAN
Main Span Section
Main Span Section Construction
Pre-cast Panel Placement
Completed Bridge, Stay Anchors
Key Features
• Main Span cast in 12m (39.3ft) sections.
Edge beams and steel beams cast in place,
followed by pre-cast panels with CIP stitch.
• In place of standard cantilever construction,
a moving casting table was used. The table
would launch to cast each segment and
be supported on the river bed. The bridge
geometry was evaluated on a real-time
basis and adjusted for each new casting.
• New in-line stay damper used to suppress
cable vibrations.
Completed Bridge, Elevation
©2009 Copyright International Bridge Technologies, Inc.