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RE: Frisco Highline Bridge burned

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An important issue is whether the existing coating system is lead-based, and I would guess that it is, based upon age. This involves considerable environmental issues, of course.

 

Bob Shaw

SSTC

 


From: Bruce Holcomb [mailto:bholcomb(--nospam--at)brpae.com]
Sent: Friday, June 23, 2006 12:48 PM
To: seaint(--nospam--at)seaint.org
Subject: Frisco Highline Bridge burned

 

Ozark Greenways is a local group that is providing and maintaining trails in and around Springfield Missouri. http://www.ozarkgreenways.org  On June 9th, someone set fire to the surface of a bridge over the Little Sac River and everything above the girders is a total loss… cross-ties, 2x decking on top of the cross-ties and wood guardrail / handrail.  I’ve looked at the bridge, which was built in 1882 and the girders, cross-bracing and piers appear to be in pretty good condition for a bridge that is 124 years old.

 

The top flange is built up of (3) layers of ½” x 14” plates and the only possible affect of the fire on the girders that I see is the upper plate is a little “wavy” is a few places.  I wonder if the heat of the fire caused this warping or if it was already like that. In one location, I could see rust and debris between the plates, so obviously that had been warped for awhile.  At any rate, this warping of the top plate of the top flange is pretty limited and since the stresses I calc’d are about 5500 psi and I found a wrought iron allowable stress of 10,000 psi, I believe the girders are adequate.  

 

Now my main question… should the girders and cross-bracing be painted?  I assume it would be a huge expense to clean, prime and paint all of the surfaces, but would extend the life of the bridge.  Of course a logical question is… how long will the bridge be useable without painting and how long if it is painted?  We are planning on using 5” thick precast concrete deck panels, so the bridge will now be better protected from the weather than is was, but it’s hard to say how it has been protected over it’s life span so far.  I’m not sure how strongly to recommend painting since I don’t know how long the bridge may be usable without painting.

 

Of course, Ozark Greenways is accepting cash donations and in-kind donations if anybody is interested!

 

 

Bruce D. Holcomb, PE, SE

Structural Engineer & Vice President

Butler, Rosenbury & Partners

www.brpae.com