Seongsu Bridge 11cm gap poses no safety risk, external experts find

Seoul's city government has announced that an external expert panel has concluded there are no safety concerns regarding a noticeable gap on the Seongsu Bridge's access ramp. The panel, composed of 11 specialists in structural engineering, geotechnics, road construction, and civil engineering, investigated the issue following public anxiety.

The investigation found that the gap, measured at 11 centimeters on the Seongsu Bridge's southern ramp, is a result of differing construction methods. Bridges are typically supported by "pile foundations" anchored in bedrock, while access ramps are often built on "direct foundations" placed on softer soil layers. This difference in foundation types leads to varying rates of settlement, creating such gaps over time.

Experts confirmed that the connection slab, designed to bridge the height difference between the bridge and the ramp, was properly installed. They also determined that most of the settlement occurred during the initial construction phase, and with the bridge being over 20 years old, further significant settlement is unlikely. Similar gaps were identified on access ramps of 11 other Han River bridges, but none posed a safety risk.

Despite the safety assurances, Seoul plans to reinforce the ground of the access ramps on Seongsu Bridge and Olympic Bridge, where the gaps are relatively larger. This measure aims to address public unease and improve driving comfort. The city will also continue to monitor the gaps for any changes.

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The settlement occurred mostly in the early stages of construction, and now that it has been over 20 years since completion, long-term settlement has also mostly ended, making further settlement unlikely.