Local structural engineering experts questioned the safety of the Hong Kong-Zhuhai-Macao Bridge (HZMB) following official assurances that the structure is totally safe and complies with the central government’s strict requirements and standards, Apple Daily reports.
Safety concerns over the mega bridge, which is expected to open as early as this quarter, have been raised after a photo taken recently by an unmanned aerial vehicle (UAV) and posted on a Facebook page showed some of the concrete slabs that were used to fortify one of the bridge’s artificial islands had been washed away by sea waves.
Some fear that the island in question, which was built to provide an exit for the undersea tunnel of the bridge, might one day be dislocated and pose a potential danger to those crossing the bridge,
To ease concerns, the Hong Kong-Zhuhai-Macao Bridge Authority (HKZMBA) explained that the slabs were, in fact, placed randomly on purpose as it was the most effective way to weaken the forces the structure received from the sea waves.
According to a thesis published in Chinese journal Port Engineering Technology in February this year by three mainland engineers, one of whom had helped build the man-made island, the “wave-weakening slabs”, if randomly placed and evenly distributed without being connected to each other, can be brought together more closely under the wave forces and therefore weaken the waves more effectively.
That said, the thesis still recommended a repair plan since there are gaps in between the slabs, some which may unavoidably fall into the sea as a result, suggesting that even the Chinese engineers themselves recognized a defect in their method.
Hong Kong engineer Albert Lai Kwong-tak said the HKZMBA has the responsibility to give a more detailed explanation, including making public the design parameters and the layout of the wave-weakening slabs rather than simply saying that the bridge is safe.
Civil and structural engineer So Yiu-kwan said the fact that the slabs are not interconnected makes their wave resistance questionable, He noted that the main reason the High Island Reservoir in Sai Kung has been functioning without any hitches is the fact that its wave-weakening slabs are interconnected.
Civil engineer Ngai Hok-yan said the design diagram in 2012 showed the slabs were placed to a level lower than a normal anti-billows wall, and the probable reason is that the HKZMBA wanted to lessen the burden on the island. The situation is not difficult to repair, he added.
Chan Yue, director of the HKZMBA’ s general engineering office, was quoted by Wen Wei Po on Thursday as saying that the bridge has met all the conditions that are required for the structure.
Chan said he does not know whether to laugh or cry after learning of the concerns raised over its structural safety.
He said Hong Kong engineers lack a deep understanding of the bridge because they have not been involved in its design and construction.
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