Mexico's Bridges: Viaduct Beltran (1)

A few miles further north on Route 54D (between Colima and Guadalajara) are a series of extremely long bridges supported on extremely tall piers.

Viaduct Beltran is an odd four-span bridge. The first pier is supported at the bottom of a ravine, making it many times taller than if it had been moved farther or closer to the first abutment. The second pier is actually two bents placed twenty feet apart. My feeling is that the superstructure is balanced on the two bents, but the first abutment was too far away so they had to support it on the long first pier.

I imagine the superstructure was segmentally constructed. It's a haunched, prestressed concrete, box girder bridge. The superstructure is continuous, but it just sits on the piers (with a downward projecting element between transverse shear keys).

We'll take another look at this interesting bridge tomorrow and I welcome your thoughts or any information you may have on it. I wonder how long the spans are and how tall the first pier is?

Mexico's Bridges: Viaduct Beltran (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

New York City's Bridges: Triborough and Hell Gate Bridges (2)

Both the Triborough and the Hell Gate Bridges have architectural details without structural purpose.

The Triborough Suspension Bridge has vertical members between the tower struts and finials at the top of the tower legs that make the bridge resemble a piece of Arts-and-Crafts furniture.

The arch on the Hell Gate Bridge has a reverse curve at the ends to give it a more interesting shape without improving its strength. Moreover, the stone towers at the ends of the arch serve no purpose.

Engineers often feel obliged to dress up their bridges in architectural details that do little or may even detract from their structural form. This is discussed in detail in 'The Tower and the Bridge," by David P. Billington.

New York City's Bridges: Triborough and Hell Gate Bridges (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.