High above the Penang Bridge
For the longest time now, there has been major ongoing work on the three-lane centre-span of the Penang Bridge. The work seems never-ending. Many motorists are puzzled about the long-term closure of the far left lanes on the centre span.
Only two of the three lanes on the centre-span are in use, aggravating the congestion on the slope uphill towards the middle of the bridge. A second (middle-lane) of the bridge is usually closed late at night to avoid worsening peak hour congestion but that creates traffic snarls even at 1.00am.
What is really going on?
When the Penang Bridge was first built, it was designed to last about 120 years. The expert designers assumed the bridge would have to cater for the maximum weight-load possible – that is, they assumed a traffic weight-load equivalent to three lanes each way of stationary heavy vehicles on the centre span.
This is what the underside of the bridge looks like
These designers never expected major work to be undertaken barely 20 years after the bridge was first open to traffic. The work now involves replacing nearly all the steel cables on the centre span.
Changing the cables: A delicate task
It is being undertaken by a French company, Freyssinet, using their latest generation 37-strand, 85m-long HD2000 models – 117 cables to be exact – under a joint venture UEMC-Freyssinet Consortium.
It is a massive, highly delicate undertaking to change the cables while the bridge is still being used. It will be a huge challenge to maintain the original structural integrity of the bridge.
But there are rumblings within engineering circles in Penang. Not all engineers are convinced that most of the cables need to be changed. After all, they have learnt that the original cables appear in good condition. They also know that the bridge was built to last 120 years. So why change the cables? They are also wondering why some of the key people involved in the original bridge design were apparently not consulted before the replacement of cables was undertaken.
UEM needs to tell the public exactly what went wrong with the original structure – if at all – and if/why the original designers were apparently not asked to investigate and hand in a report. Do the cables need to be changed? And why?