Mexico City Infrastructure Projects Rely on Terex AT Cranes
Mexico City’s population is estimated to be more than 20 million—and continues to grow rapidly. The city has more than 5.5 million vehicles, one of highest concentrations of cars in the world, and that number may double over the next years. Ingenieros Civiles Asociados SA (ICA) is using Terex all-terrain cranes on a major highway project to help accomodate the city’s transportation infrastructure and cope with the city’s increasing population.
The plan is to construct a major new elevated road to the south of the city. The first section is the 11.3km long Autopista Urbana Sur (Urban Highway South) being built by Mexican contractor ICA Ingenieria at a cost of about US$450 million. The highway has been designed to alleviate the congestion to the south side of the city, cutting journey times by half. This new road features two lanes in each direction and includes some stretches of six lane carriageway. The road connects San Geronimo to Tlalpan Viaduct at the second deck level of the city’s existing elevated peripheral highway.
Given the tight space considerations and tricky logistics, the road is being built using prefabricated concrete sections made about 40km away from the construction area and erected during the night. The prefabricated concrete production facility had 22 hectares, 15 fabrication tables, and 120 molds. With an industrialized process and a workforce of more than 2, 000 workers, it was able to deliver all pieces on time to be transported and mounted each evening. Approximately 18,000 prefabricated elements were utilized for this project, which were installed between 11 pm and 5 am, the only time the vehicular transit was interrupted. This is the first time in Mexico that this construction method has been used to build a complete overhead highway, and it is also the largest urban project of its kind so far.
ICA specializes in large infrastructure, heavy construction and civil engineering projects. As well as employing 40,000 employees, the company also owns 12 Terex cranes, including several 500-tonne capacity class AC 500-2 all-terrain cranes, which are being used for erecting the main concrete columns, beams and components. Larger components are lifted using tandem lifts.
“Because it is an urban jobsite with limited space for heavy lifting and work access was only available for six hours each night between 11 pm and 5 am, we needed a crane that had quick travel speed, rapid set up time and excellent lift capacity,” said Ignacio Villaseñor Sanchez, ICA equipment director. “The AC 500-2 fit the bill perfectly.”
“The cranes performed faultlessly and had 97% availability, only stopping for planned maintenance,” said Sanchez. “The crane was extremely reliable and fitted with good safety systems. Everything related to the set-up and rigging went very smoothly. Obvious challenges included the lack of space on the job site, however the AC 500-2 is one of the most maneuverable and compact cranes in its class, which helped.”
The time taken for the Terex AC 500-2 to drive from the depot to the jobsite was about 30 minutes, and another hour was needed before it was fully rigged and ready to lift. Between four and five people were involved in the rigging process and just two additional low loader ballast wagons were needed.
Some column sections weighed up to 425 tonnes while the 36 to 48 meter long and 4 to 6.5 meter wide (depending on the number of lanes they carry) horizontal sections weighed up to 350 tonnes. In total there are about 20,000 pre-cast components made from high strength concrete including about 500 columns varying in height from five to 25 meters. Sections were prefabricated at a pre-casting facility using a process that took just 48 hours. Once cured the units are transported and placed in to position on-site.
“The AC 500s are lifting at an average height of about 20 meters and carrying out either single or tandem lifts between 10 to 220 tonnes at a radius between 10 to 15 metres – typical low radius heavy lifting,“ said Bernardo Quintana Kawage, general director of ICA. “First the cranes are positioned on site and the modular elements to be lifted arrive in sequence. Once lifted and positioned they are welded and secured. Then the next element arrives and the process is repeated over and over. When the cranes need to move, they remove their own counterweight onto a low-loader and then move to the next jobsite. In all, between seven and 15 people were needed to set-up the crane and carry out the lift.”
Super-efficient logistics are critical to enable the construction to keep to the 14-month schedule with three to four massive sections being installed each night. Because of the size of the main elements, they are erected one at a time although smaller elements can be erected simultaneously. The support columns feature an integrated shoe and head design. This makes the erection process much quicker although precise positioning of the columns is needed to locate each unit into deep foundations prepared in advance.
The project is expected to be completed by the end of 2013.