tallbridgeguy

Dear Stuart,

I like your videos. I think they are worth to watch.
But my comments are not very helpful. Therefore, I have some others as well:

When we take about issues such as constructability, island access, or aesthetics we need some criteria to judge the entries. I will try to explain the most difficult one: Aesthetics.

Aesthetics are often ignored by bridge engineers and that is one reason why we find architects in this field.

Why are architects better in aesthetics than engineers?
I do not have a general answer but I would say architects typically are trained to care for appearance and the social interaction between their product and people. We engineers are not.

A big problem occurs when architecture is made just by artificial elements (unloaded arches, spines, curved or inclined towers without any structural necessity, or elements not belonging to the load carrying structure. I will give you two examples:

Who can explain the structural behaviour of “The Reach” and “The Kasian”?
If their beautiful slender deck is truly supported by the arches (and not by some hidden piers in the river) we will find that those bridges are probably in big trouble: Non-symmetrically distributed live loads will introduce significant bending in the arch tubes. Their circular cross section is not very effective in bending or in resisting lateral buckling effects. Alone from this perspective those concepts are very questionable when proportions of their dominating main members need to be adjusted and elegance is negatively affected.

Bridge architecture should be made by the structure’s load carrying members and not by some architectural elements that are just added because otherwise the structure would be boring.

Some of the concepts proposed for the St. Patrick’s Bridge are engineered in a remarkable manner and beautiful together:

I will name only the best ones without any order: Delcan, RFR, Arup with Schmitt, and Infinity

They all have in common: Light-weight design, clear load paths, members that use material efficiently, and elegance (good proportions)

I do not think that the first three have a true chance against the two mentioned bridges designed by architects because they do not really qualify as a signature bridges. The problem is that the proposed arches are not really significant and innovative. We all have seen them many times before but they are still very good solutions.

The Infinity one is completely different because the engineering approach is using a new concept: A cable net as a stiffening girder. When this works out we might encounter a new structure in the future: Suspension bridges without stiffening girders.

Engineers can beat architects when they focus on aesthetics as well. For example, Robert Maillart, Othmar Ammann, Fritz Leonhardt, and Christian Menn, four of the greatest bridge engineers of the 20th century, were fully aware about the importance of proportions and aesthetics when they presented their new breath taking concepts.

Stuart, try to investigate the bridges with this in mind and you will find the true ones. I do not think that the spread sheet alone will do but it is a good start.

Best regards,

Joe

Well done on the videos (and not just because of the kind mention for THP!) – your experience talking to the public about bridges definitely shows, and I think it would be great if more engineers took the trouble to discuss design issues openly in this way.