Portland’s new light-rail bridge, explained
WITH EACH CREAK of the Steel Bridge and apocalyptic prediction about the Sellwood, Portland’s “Bridgetown” nickname seems an ever more nostalgic nod to former glory. (Our last new bridge, the Fremont, went up almost 40 years ago.) But in 2015, TriMet’s brand-spanking-new, $134 million light-rail bridge will bring public transit, bikes, and pedestrians (but no cars!) from a burgeoning South Waterfront to a new OMSI station in Southeast. Construction on the massive concrete foundations began last July, and this month we’ll finally get a glimpse of the sparkling cable-stayed bridge (the city’s first) rising out of the water. Here’s how it all happens.
Rising Up 2,873 tons of concrete (from Ross Island, just upriver) is poured to build two freestanding, 180-foot concrete and rebar towers on top of concrete bases (called “pile caps”) in the river.
Balancing Act Workers begin building the bridge deck from each tower in 16-foot increments. As the deck grows outward in opposite directions, it must be carefully balanced or it will crash into the river.
Meeting in the Middle As the two bridge decks converge over the water, workers link them with a final concrete midsection and fasten the entire span with permanent steel cables.