Bridge Articles in the Civil Engineering Magazine

The ASCE (American Association of Civil Engineers) has a magazine, the Civil Engineering Magazine. It is published monthly, and although not fully available on line, they allow access to past issues' feature articles. The 2008 February issue contained a good article on the New Tacoma Narrows bridge. I quite enjoyed reading it.

Although the first modern suspension bridges were built in the United States, they had not built any suspension bridge of significance for quite a while until the beginning of this decade, with the Carquinez Suspension Bridge first and now with the New Tacoma Narrows Bridge.

The other article that interested me on the magazine, is on the March 2007 issue, about the Penobscot Narrows Bridge, Maine. The article focuses on a new technology for cable stayed bridges in which the strands are not anchored on the tower or pylon. Instead they are continuous through the tower.

Obviously this system has the advantage to allow for much more slender towers, and from the article you would imagine that it is the best thing since sliced bread. I am not fully convinced. First of all, I think that construction has to be more complicated although the article indicates otherwise. The same for as cable adjustment. and replacement. I do not fully visualise the advantages over the traditional system. Also, cable configurations have to be balanced on both sides of the tower, third, the strand loading and fatigue behaviour have to 'suffer'. Strands do not like being bent, and fatigue issues always appear on those areas.

I do not know if this system is so new neither. Years ago, while visiting Alga, I saw them testing precisely a saddle design for cable stays. They were trying to determine their fatigue behaviour. I never found out the results of those tests.