Progressive collapse

Traffic that has crawled under normal conditions around the Otis Bridge in Paco, Manila has become even worse after a crack 10 meters long developed near the span’s center island.

At 80 meters long and 14 meters wide, Otis Bridge is one of the smaller spans in Metro Manila. But it is one of the busiest, with its load becoming heavier following the closure of nearby Concordia Bridge also for repairs until January next year. Otis Bridge connects United Nations Avenue to the Nagtahan Area and is part of the route widely used by cargo trucks.

Engineers attributed the crack on the bridge to damaged support beams and girders. With approximately 10,000 trucks passing through the bridge during weekdays, many of them ignoring load limits, engineers fear that it might give way and collapse. After the crack was discovered last Wednesday, authorities decided to completely close the bridge to vehicular traffic.

Finished in 1968, the bridge is ripe for repairs, but the Department of Public Works and Highways has decided to replace it instead. Work began this week and is expected to last until March next year at the ear- liest. Even if construction is done around the clock, the DPWH does not think the work can be finished before Christmas, as urged by certain sectors.

The Metropolitan Manila Development Authority has implemented a rerouting scheme around the bridge. MMDA officials said about 40 other bridges are being monitored for structural weaknesses all over Metro Manila. As early as 2015, the DPWH had allocated P37 million to replace Otis Bridge, but this did not push through as priority was given to other public works projects around the area.

At least the crack was too large to ignore and raised warning signs. The government cannot close to traffic too many bridges in congested Metro Manila, but each bridge can be subjected to a thorough inspection for structural integrity. Repairs can be undertaken on those that cannot be closed immediately for replacement. Authorities must also drive away squatters living under bridges, for their own safety.

Beyond patching up bridges against progressive collapse, engineers must find ways of boosting the structures’ resiliency to earthquakes. The crack on Otis Bridge should give urgency to these tasks.