tallbridgeguy

ASCE has a website dedicated to ranking the current state of our infrastructure. Apparently we need $2.2 trillion dollars to cover the cost. Yikes! It has a ranking of each state and it shows that my state has 27% structurally deficient bridges*. They also have a contest going on for photos of broken down infrastructure. Since I just got back from looking at bridges that need work, I think I am going to enter!

segan2 from flickr

*Structurally deficient bridges are those that are restricted to light vehicles, require immediate rehabilitation to remain open, or are closed. Functionally obsolete bridges are those with deck geometry (e.g., lane width), load carrying capacity, clearance, or approach roadway alignment that no longer meet the criteria for the system of which the bridge is a part.¹ In the 1990s, while the number of structurally deficient bridges steadily declined, the number of functionally obsolete bridges remained fairly constant.

This project has been in a lot of presentations for accelerated bridge construction. Built about 4 years ago, its a single span all precast system. They used spread footings on rock with box beams and a complete precast abutment. It seems a little complicated for me. The rock is a lucky thing, trying to put precast on piles is a little more difficult.

A quick overview of ten amazing bridges from oddee.com. (No idea who they or what they are, but the pictures are good.)

From what I understand lists are the most popular thing to put on your website. Things like top 10 this and top 5 that. I guess I will have to start the ABC top ten. (Hey that will be my next post!)

One of the things I am working on is developing a simple, cheap but strong county bridge. The idea is to design something that anyone could build, to open the construction to as many fabricators as possible. Currently, a large number of counties use high abutment single span bridge with a precast panel deck. The panels are not pretensioned or post tensioned and for that matter, may not meet current codes. What they are is cheap. Counties are concerned with first costs and a short, high abutment is often the most inexpensive bridge to build.

The criteria for the design is pretty simple.

• Simple span – starting with 40 feet, high abutment.
• Width 28 feet.
• Depth of the superstructure, 24″ or less.
• All precast, with a basic design that multiple fabricators or County personnel can manufacture.
• No pretension or post tension, if possible.
• Meet LRFD design code
• Accelerated bridge construction, if possible (precast would likely be ABC)
• Cost around $120,000 or less

One idea is to slide precast concrete panels down H-piles and then cap the piles with a precast abutment. The bridge would be shorter and hopefully cheaper than the standard spill through abutment bridge.

A longer bridge is often easier to build and keeps the substructure out of the water but it usually costs more than a high abutment bridge. The longer bridge usually requires some kind of high tensioned steel strands to make the span lengths required and that makes the precast deck a specialized product to manufacture. That increases the cost and it is all about costs when you have a large number of bridges to replace.

Happy Easter, great picture of the swamp Rabbit Pedestrian Bridge from Bridgepix.com. (get it rabbit – easter..)

Check out this online book by Alan Holgate. It was originally published in 1986 but it has since gone out of print. It discusses the roles of engineers in design.

There is an old saying which goes something like this: “An engineer is a man who can do for a dollar what any fool can do for two.” Its emphasis on ingenuity is praiseworthy, but it has been seen too often as a justification for much that is cheap and nasty in engineering. It has been taken to mean that engineering is nothing more than the achievement of clearly specified technological objectives for the lowest possible cost in cash. This view has been reinforced for engineering students by the fact that with a few notable exceptions, text books entitled “Design of Structures” are predominantly concerned with the techniques of computational analysis

I guess the City of Portland finally picked a bridge for their new transit system.

The picture of the bridge in the article does not seem to match the slideshow pictures? The bridge is actually fairly pedestrian for all the fuss. You could pick the same design off the internet. For example, pic1, pic2, I could go on but you get the picture.

Courtesy: David Dayton

I made a quick video of a bridge I designed. Simple 50′ span, with voided box beams. The goal is build this bridge in 5 days or less.

A cool website, deputy-dog.com, has some great pictures and videos of nine special bridges. I’m sure everybody has seen them and I am the last person on the internet to finally notice them..

You have to see them to believe them, from Dark Roasted Blend.

Hey is that a highway in my building or a building on my highway?