Baluarte River Bridge
When it opens in 2012, the Baluarte River Bridge will not only be the highest bridge in North America but the highest cable stayed bridge in the world. It is the crown jewel of the greatest bridge and tunnel highway project ever undertaken in North America. Known as the Durango-Mazatlán highway, it will be the only crossing for more than 500 miles (800 km) between the pacific coast and the interior of Mexico.
The bridge passes over a 400 meters ravine that carries the Baluarte river and divides the states of Sinaloa and Durang., Mexico's 1124 m-long Puente Baluarte is not only one of the country's most iconic and vital pieces of infrastructure, but also Latin America's highest cable stayed bridge.
The path of this new highway roughly parallels the famous "Devil's Backbone", a narrow road that earned its nickname from the way it follows the precarious ridge crest of the jagged peaks of the Sierra Madre Occidental mountains. The dangerous road is a seemingly endless onslaught of twisting, terrifying turns that are so tight there are times the road nearly spirals back into itself.
By cutting a safer, more direct route through the mountains, the highway department of Mexico hopes to improve trade and increase tourism between the city of Durango and the coastal city of Mazatlán. To achieve this connection, the Mexican engineers were forced to design an autopista which is a Spanish language word designating a type of limited access highway.
It has no less than 63 tunnels – nearly 10 times more than have ever been built on any road in North America. For big bridge fans, the highway is no less amazing with a parade of towering concrete beam bridges. Including Baluarte, there will be 8 bridges that exceed 300 feet (90 mtrs) in height including Santa Lucia, Neverías, La Pinta, Chico, Botijas, Pueblo Nuevo and El Carrizo. Only China's West Hurong and Kunming-Guiyang and Italy's A3 highways have a greater collection of high bridges.
Forming the border between Sinaloa and Durango states, the Baluarte River is the most formidable obstacle on the route with a gorge more than a quarter mile in height. To cross it, the Mexican engineers decided to go with a cable stayed bridge. It would allow the construction to proceed outward from a single tower on either side of the canyon, avoiding the difficult and expensive construction of temporary false work.
Once completed, the final height of 1,280 feet (390 mtrs) will make it the second highest roadway bridge on earth, second only to the Millau bridge over the River Tarn in France. It will also have the longest span of any cable stayed bridge in North America at 1,706 feet (520 mtrs), exceeding the John James Audubon bridge in St. Francisville, Louisiana by 123 feet (37 mtrs).
When it is completed, the Baluarte crossing will be more than just a preeminent bridge but a signal to its bigger neighbor to the North that Mexico can design and build bridges with the same skill and perfection as the best of them. As a stretch of North American pavement without parallel, the Durango-Mazatlán highway will become a proud, prominent symbol of Mexico's civil engineering skills for decades to come.
Bridge construction
Falsework and formwork manufacturer Peri supplied a range of formwork and scaffolding for the construction of the bridge, including its crane independent ACS self-climbing formwork for the pylons and piers: there will be nine bridge piers and two pylons supporting the 20 m-wide superstructure, which will carry one lane of traffic in each direction.
Of these, P5 is the highest, reaching 169 m-high, the highest point of its opposite P6 ends 13 m below this. The plyon measures 18 x 8.56 m at its base, widening in the centre of the carriageway before tapering upwards to 8 x 4.10 m at its top. The pylon legs are not only inclined but also feature different cross-sections throughout their height.
For the construction of this complex geometry, Peri developed a self climbing solution on the basis of the ACS system. The ACS V, V stands for variable, was used for the forward and reverse inclined external walls. The ACS's platforms can be continuously adjusted to match the angle of inclination, which means the horizontal working levels are always available. This ensures the construction team have a comfortable working environment and also provides the maximum level of safety during forming.
The ACS self-climbing system accelerates working procedures thanks to being crane independent and not being weather dependent. Its construction was designed to accommodate very high wind loads and the process of climbing features an extensive safety concept that makes the working platforms very stable and allows the storage of large quantities of materials, such as rebar.
Peri's variable vario GT 24 girder wall formwork is also being used on the climbing scaffold. Peri's design and construction concept means the construction team could quickly adapt the formwork to suit the requirements of each concreting section and accurately form the pylons. At the same time, Peri's Fin-Ply form-lining guarantees a high quality surface finish, with around 50 to 70 uses possible.
Construction of the pylons is carried out using a total of 46 or 49 concreting sections with variable concreting heights of between 3.28 and 3.90 m. Double-piers
The foreland piers have been designed as double piers. They vary, according to the topography, in their height, up to a maximum of 145 m. These piers were also constructed using the Vario GT 24 girder wall formwork, with the large majority of the surfaces formed with standard panel formwork, while for the tight, inner areas Peri designed bespoke elements.
These were adapted and pre-mounted to match geometrical and static requirements as well as being delivered on a just-in-time (JIT) basis to the construction site. The assembly of the 5.10 m-high elements with only four SRZ waler lines allowed a maximum fresh concrete pressure of 50 kN/m² and a required concreting speed of 2.00 m/hour.
On the pier exteriors, CB 240 climbing brackets support the Vario elements and mean larger wall formwork could be supported. They also ensured simple handling, fast concreting cycles and problem-free adjustments to suit the various structural designs.
The 2.40 m wide platform lining was positioned over the brackets and, together with the formwork carriage, forms an even surface without any tripping hazards. In the internal area of the double piers, the construction crew used BR platforms to support the formwork elements.
These shaft platforms were used where conventional climbing scaffold was not suitable due to space limitations. In each case, the units formed from formwork and climbing brackets, or platforms could be moved easily and quickly with a crane.
Cross members, with a height of 4 m, connected the supports of the double piers, while Peri's Trio panel formwork formed the side formwork with its MultiFlex slab formwork serving to shape the underside of the members.High load-bearing GT 24 formwork girders were used as the main and cross beams. Due to the enormous loads, the girder spacing was limited to only 200 mm, which allowed deflections of the formlining to be minimized.
Getting the crew up and down the piers and pylons used the company's Peri Up Rosett scaffold system. Its modular design means it could be adapted to suit the generated loads: in the cantilevered area of the working platforms, Peri Up was assembled using a 1.5 x 1.5 m basic grid, while UBS shoring braces served to brace the construction.
Directly under the member formwork, 250 mm walers were installed. This reduction of the grid dimensions increases the load bearing capacity of the scaffold in the area of high loads.
For members positioned 13.50 m higher, Peri UP shoring was placed on the previously installed cross beams, while steel profiles carried the cantilevered areas.
Location: Durango - Mazatlán highway (under construction) in the border between Durango and Sinaloa States, Nortwest part of Mexico (locally the site is known as "Devil's Backbone").
Owner: Secretary of Communications and Transport (SCT)
Tipe: Cable-stayed bridge (76 cables)
Total Length: 1,1124 m
Main Spam: 520 m (steel and concrete composite construction)
Deep: 390 m (from river to bridge deck)
Finishing Schedule: June/2011 (began in 2007)
