The Northwestern Motorway. Photo / Richard Robinson
Every day I drive under the Northwestern motorway extensions taking place at Waterview in Auckland.
The new flyovers being created consist of massive horizontal beams hoisted into place by the gantry that is there for that purpose.
To my amazement, every new beam appears to be only just sitting on
the edge of the column that supports it, leaving a large gap between the edge of the support and the rear of the support. This gap is later enclosed by concrete or plaster. To my unskilled eye, this appears to be really dangerous. Just a bit of a jolt, even a modest earthquake, would seem to be enough for the beam to slip off the support and drop onto the traffic below. Is my visual assessment correct?
Euan Macduff, Auckland.
The NZ Transport Agency says safety is a priority for the Waterview Connection project and the beams being used to construct the ramps to link the Northwestern and Southwestern Motorways are designed and then lowered into position so that they cannot drop. The end portion of the beams is darker in colour than its middle section to better blend in with the darker area of the crossheads or columns supporting them, and this may give an illusion from below that there is little holding them in place. In fact, the beams are seated 350mm - that's about 14 inches - on to the crossheads and are then well secured to hold them in place. The beams being placed by Dennis (the yellow lifting gantry) are up to 36m long and weigh up to 70 tonnes. A total of 279 beams are needed for the motorway-to-motorway interchange. The ramps, like all structures on the project, are put through extensive design and construction reviews. The Transport Agency says it plans to open the Waterview tunnels and interchange in early 2017.
