May 21 - Two Terex all-terrain cranes - an AC 350/6 and an AC 500-2 - have been used to lift a number of 230-tonne U girders in the construction of a 7.5 km long elevated third Monterrey metro line in Nuevo Le

A consortium of Alstom Mexicana, Constructora Garza Ponce and Constructora Moyeda was awarded the contract to construct the metro line, which will connect the second line terminus at General Zaragoza northeast to Hospital Metropolitano.

The U girders, each of which measured 37 m x 1.85 m x 5.2 m, had to be lifted to heights of between 15 m and 22 m. The 350-tonne capacity Terex AC 350/6 crane was equipped with a 64 m main boom, while the 500-tonne capacity AC 500-2 crane had a 56 m telescopic boom for the job.

"We chose to use two Terex all-terrain cranes…because they had the capacity to lift the girders, and the cranes are roadable, needing only six flatbeds to transport the counterweights," said Arturo Moyeda Morales, ceo of Constructora Moyeda. "Once a crane was moved and we had the go-ahead from the transit authorities, a lift could be done in less than 30 minutes per girder."

The third line of the Monterrey metro had to be be erected above highway bridges, over pedestrian bridges and between power lines, which was an extra challenge for the crews working in the confined spaces of the Monterrey metropolitan area, said Terex.

The original project proposal required the use of a launching gantry. However, in order to use this method of construction, it was imperative that the construction sequence was undertaken consecutively from pier to pier.

Terex explained that if one pier could not be constructed due to interference the entire lifting project would have come to a standstill. To avoid this issue, Constructora Moyeda used the Terex cranes to construct a viaduct so that a launching gantry was not needed. 

"Most of the lifts were done with minimal traffic interruptions and in very confined spaces, with a number of underground and aerial obstacles," said Moyeda. "On top of those site conditions, we also had to keep our crews productive in the Monterrey weather conditions, where temperatures can reach 115° F in the summer."