Philippines: Viral video shows 'wobbly' Biliran Bridge

Manila: A once-sturdy link between Leyte and Biliran has now become the star of a nerve-wracking saga. 

Viral videos show unsettling wave-like movements, with the asphalt and support metal superstructure visibly oscillating, sparking concern across the region in the country's east known for white sand beaches and waterfalls.

The Department of Public Works and Highways (DPWH) has banned heavy equipment vehicles from crossing the 49-year-old Biliran Bridge, in eastern Philippines from Monday night (December 23, 2024).

Only light vehicles, SUVs and passenger vans are allowed to traverse it — and even then, one at a time, with extreme caution.

Blame it on the holiday rush and extreme winds, says the DPWH. 

Regulated crossing

Passenger buses must now unload passengers before crossing, leaving commuters to brave the precarious span on foot.

Truckers are also made to offload some of their cargo in compliance with the load limit imposed by the agency.

49-year-old bridge 

The 150-metre Biliran Bridge, opened in 1975, has a central span held in place by an arched steel structure. 

The causeway bridge hovers above a narrow channel measuring about 40 meters wide at low tide, linking Biliran to Leyte over Poro Island.

Biliran, which lies less than a kilometer north of the island of Leyte, is known for its white sand beaches, snorkeling and vast waterfalls.

‘Resonance’

Yuri Pascual, a Filipino engineer, explained on social media that the bridge may be affected by “resonance”, akin to ropes being shaken.

FACT FILE: Biliran Bridge

Completed: 1975

Length: 150 metres

Location: Biliran-Leyte (Biliran Strait)

Aerodynamic flutter

Resonance could cause the bridge to make a continuous wave-live movement — known as “aerodynamic flutter”.

This may be caused by natural forces, like strong winds, causing it to make a cyclic movement.

He added that when a bridge has insufficient structural “damping”  — shock absorbers — it could exhibit longer times of oscillation or vibration.

“When damping is low, the bridge will continue its wave-like movement,” Pascual explained.

Another possible cause is “dynamic loading” – when multiple heavy vehicles pass through the bridge at the same time, which could trigger vibrations or oscillations.

What’s important, Pascual pointed out, is to immediately assess the structural integrity of the bridge, limit the passage of heavy vehicles, and take necessary corrective measures.