Engineering feat: Industrial Bridge in the province of Concepción, Chile
The new bridge over the Biobío River, 550 km from the city of Santiago de Chile, connects the communities of Hualpén and San Pedro de la Paz in the province of Concepción via a road with a total length of 6.4 km. The work was specified as an express dual carriageway, with two lanes in each direction, which will connect with Avenidas Costanera to the north and Ruta 160 to the south.
The new traffic infrastructure project is made up of a 7-m wide roadway in each direction, with 1.5-m wide exterior shoulders and 1.0-m wide interior shoulders, as well as a 4-m wide multipurpose path along the north and a 1-m wide corridor on the south side, separated from the road by a concrete barrier on one side and a pedestrian railing on the other.
The design of the bridge incorporated the new seismic criteria in effect, which resulted in the implementation of central crossbeams in each span, anti-seismic anchors, supports and special seismic joints.
The bridge structure has a total length of 2.5 kilometers and includes bicycle lanes and pedestrian sidewalks with the aim of improving bicycle and pedestrian traffic between both banks of the river. The new structure improves connections between the communities on both banks of the river, and enhance road logistics with the ports of Lirquén, Talcahuano, San Vicente, and Coronel.
Total length of 2,500 m
In terms of geology, there is an aquifer on the north bank of the Biobío River, which has an estimated thickness of approx. 80 m and is made up of sandy material interspersed with silt clay.
The seismic risk study was applied to the design of the structure with the objective of choosing anti-seismic elements such as support plates with energy dissipation suitable for bearings (type A) and abutments (type B). 24 rubber sheets of 8.5 mm thickness were used for type A supports, and 29 rubber sheets of 8.5 mm thickness for type B supports or seismic isolators.
The bridge structure extends over a total length of 2,500 m, of which 2,100 m are straight and 430 m are curved. Each pier rests on four piles of 2 m or 2.5 m in diameter, respectively, depending on the type of terrain, which were driven into the riverbed at an average depth of 30 m.
The machinery used to drive the piles included a Caterpillar AF250, which is capable of driving piles of up to 2.0 m in diameter, and a Liebherr LB 36-410 for the 2.5-m piles. A 50-ton Liebherr LTM 10503131 crane and Demag AC 95 telescopic handler were used for the installation of the precast beams.
56 sections of 45-m span each
From the start of construction, the Industrial Bridge has faced numerous challenges, which include creation of the working embankment in the river, as well as construction and placement of the double rings of reinforcement for the bridge piles. The superstructure is made up of 56 sections with a span of 45 m each. The ends of the spans are supported by a total of 55 piers, each of which rests on four foundation piles with a diameter of 2.5 m.
Each section is made up of seven prestressed beams with an average length of 43 m, height of 2.25 m, and weight of approx. 100 tons varying in the curved sections, and has physically separated lanes with a width of 3.55 m each, resulting in a total deck width of 24.8 m. The beams are attached to a reinforced-concrete slab with a minimum thickness of 20 cm, which work together to withstand the dead loads of the pavement and railings, and the loads generated by the movement of traffic.
The superstructure has been designed to support the passage of mobile loads, which are in turn transmitted through the support system that includes anti-seismic neoprene plates.
Text: Mauro Nogarín
