JL Franklin (Letters 9/16 April) highlights an interesting feature seen in many modern cable stayed bridges where columns in the back spans are used to 'stiffen' up the structure, reducing deflections in the pylons and main span while also providing stability during the deck construction.
Our company carried out the independent structural check of the Vasco da Gama bridge and I have never doubted that the completed structure would provide a stunning example of modern bridge building which is not distracted by the columns in the back span. On the contrary, the columns break up the back span and give sympathy with the adjacent spans in the approach viaducts while emphasising the main span, enhancing the overall appearance.
NR Hewson (F), Hyder Consulting,
The Surrey Research Park,
Guildford, GU2 5AR.