My 2-cent engineering perspective on the Pich Bridge tragedy

Koh Pich suspension bridge (Photo; AFP/Xinhua)

In view of the recent tragedy on Koh Pich Bridge where several hundreds of our compatriots died and were seriously injured, I would like to provide below, my personal perspective as a Civil engineer in this regards. While my specialty is not in Structural engineering, but rather in Geotechnical engineering, i.e. a specialty related to foundation engineering etc, I will strive to explain as best as I can, in laymen terms, the various aspects of bridge construction, and in particular the suspension bridge type that is used for Pich Bridge linking mainland to Koh Pich Island, and I will also provide my 2-cent input on the various aspects any investigation should consider.

The most basic method of constructing a bridge can be seen in the illustration above. First several piers are constructed as support for the bridge, next a bridge deck is placed in between two piers to provide a platform on which traffic can move over the bridge. In general, guard rails will be constructed next to prevent vehicles and foot passengers from falling off the bridge. While in concept, this construction method appears quite simple, the reality is not so. For one thing, if the spacing between two consecutive piers is very wide, then the bridge deck need to be designed thicker or more rigid so that when traffic moves over the bridge, there would be not too much vertical deflection (see black arrow in the illustration above).