Joshua Cohen is a Principal at Fat Pencil Studio
Put two engineers and an architect together on a panel and you've got my attention. Get them talking about Portland's newest bridge and I'm there!
Last night's lecture was titled The Spirit of Details and featured Tilikum Crossing architect David MacDonald along with engineers Semyon Treyger and David Goodyear. The event had something for everyone: from a wonky discussion of earthquake design standards to a comparison of cable angles with the slope of Mt. Hood.
For me, the highlight of the evening me was hearing David MacDonald explain the rationale for the shape of Tilikum Crossing's cable towers. For instance, when viewed from a distance, "two parallel lines rising appear to expand at the top." A tapered column is necessary to address this trick of perspective. This is more expensive to build, but provides a striking visual improvement. Here are a few other interesting tidbits I learned:
- The structure is carefully designed to limit vibrations from the light rail vehicles and maintain "pedestrian comfort." This would not have been such a high priority on a highway bridge.
- The horizontal cable railing opens up the view to the river, unlike vertical posts which would appear to stack together as they recede into the distance.
- The underside of the bridge was imagined as a cathedral ceiling, and carefully designed to hide drainage pipes and electrical conduit. River users and bicycle riders frequently experience the view from below and it's great that the minimal design aesthetic carries through.
Tilikum Crossing opens to the general public in September 2015, but it’s already an iconic part of Portland’s skyline.
(Featured image by Yelena Prusakova)