Quite Laterally, Here We Go Again –

Frequent fliers likely recall my June entry Meritocracy, (click on the highlighted & underlined text to be linked to the entry) in which I puzzled over the frequency with which contracts to repair and rehabilitate wooden spans are often awarded to companies who, know the ins and outs of bidding public works projects, but who hold nothing in their scope of experience to suggest they have the required tooling, knowledge, or abilities, to in-house execute such work. And somehow, nor are they necessarily required to pre-qualify, or ride the resumé of pre-qualified specialist subcontractors when preparing proposals to bid such contracts. Recent turns of event have again shown how sadly and commonly this circumstance happens.

A recent string of extreme truck damage incidents, leaving horrific levels of Portal to Portal damage, have splintered Tie Beams or dislodged and distorted Tie Rods and ruptured Braces in Upper Lateral Bracing Systems, in two bridges, one in Pennsylvania, one in Indiana.

Though it is often overlooked, complexity in a bridges framing is not limited to the Trusses proper. In some Truss types such as Towns, the more demanding framing is that found in the connecting systems which unify the two trusses and complete the “Through Truss”.

Tie & Lateral Bracing systems are far from simple carpentry, but are a complex bit of advanced Timberframing. (for all the camber driven subtleties and varied reasons I articulated in Meritocracy – Foremost among these being that proper fit requires the acknowledgement that these shoulders and abutments are, more often than not, not “simple” angles, but are in point of fact, compound angles. These necessarily need be laid out and cut to match real world camber driven circumstance – To drive home this point > In Bridge work, every joint which fails to have hard up full bearing through not just the visible portions, but the entirety of the joint, means undue crush and loss of geometry – This including, loss of camber) This circumstance of navigational error truck damage taking out such systems near or in their entirety, and the developing response to it, does drive home particularly well, this paradox of contracting concrete and steel outfits to repair or rehabilitate wooden bridges. At least it does from my perspective – Maybe from yours.

From mine, the perspective is particularly sharp. I cut my Bridgewrighting teeth on Laterals. I came into my first bridge rehab with seasoned timber joinery chops, and was pointed at Laterals – I took it as the performance challenge it was…

Since then, Laterals have kinda been my thing, and I’ve been privileged to help replicate whole sets. Both, all too many Lowers lost to high water, and the flotsam it inevitably carries with it. And in an odd bit of happenstance, multiple sets of Uppers & Ties lost to wet heavy snowload driven roof collapse on three different bridges in three different States. These all lost decades before, (one the year before I was born) and either badly replicated, or done with an inappropriately heavy species, or both, or replaced with inappropriate, not true to original framing systems. I have also of course, helped replace Wind Braces, as well as Ties & Laterals lost to truck damage.

These Bracing systems tend to vary in detail, this sometimes driven by Truss Type, and sometimes by regional norms, the date of construction, or the preferences of the Bridgewright who built the span.

Repair / replacement of the truck damaged Pennsylvania spans upper timber-work was recently awarded to a highway construction outfit. It had / has the Wind Braced Ties and Over / Under Laterals typical to Town Trusses, the dominate Truss type in that corner of PA. It remains to be seen if they will subcontract in a concern with a familiarity in these materials and construction methods to replicate the destroyed framing.

Said to be the work of Nichols Powers, in this “Village Bridge” NH’s Ashuelot, (Ash-wool-it) the terminus for the Lateral Bracing load was formerly shared by two Ties through this Centered Straining Beam- The Design Engineer specified placement of a final set of Double Laterals in either end bay as part of a late 90’s restoration.

I’ve long admired this detail used on Indiana’s Williams – Often incorrectly attributed to JJ Daniels, The Williams is a product of the Massillon Bridge Co.

In process Scribe layout of a Lower Lateral to replacement Floor Beams at Maryland’s Gilpin’s Falls – For more information on this Floor and the now unusual Rebated Sleepers seen here – See the May of ’11 & June of ’13 Archives

The most recent truck damage repairs I’ve had a hand in mending – Portal to Portal damage to the 266′ Mt. Orne

Also Scribed in-situ – The normally unseen connection where the Mt. Orne’s Laterals join each other

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About Will Truax

I'm a timberframer and preservation carpenter, and regularly work on Covered Bridge restoration projects. Bridgewrighting can be a tough row to hoe, for a myriad of reasons. From scheduling issues to differing opinions and philosophies on what is appropriate in methods and materials, to multiple jurisdictions still not sufficiently vetting bidders resumes - Which is to say, just because a company is on that state approved list and capable of building that seven figure overpass, this does not mean they are capable of restoring a wooden bridge... So, I have much to say about all this and more - And despite my tough row observation, I promise not to whine. View all posts by Will Truax

3 responses to “Quite Laterally, Here We Go Again –

  • Dick

    Will – Have you ever calculated the length of a lateral brace?

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    • Will Truax

      Hey Dick –

      Yes I have, a couple of times. First as part of the original challenge, and at that same time, to have things ready to install logistically, as the shoring was removed. – Then sometime later to challenge myself, and to explore the feasibility side of things, can you cut right & tight Lats mathematically faster than they can be scribed…

      Mathematically is a funny piece of work isn’t it, with the like no other circumstance of shifting reference faces. Never mind the compound shoulders. In my experience, I can find no logic or advantage in doing so.

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      • Dick

        I ask this because when I first encountered laying out one of these I got “schooled” pronto. My little pea brain was thinking that this was going to be a straight forward application of the Pythagorean theorem. Not so. I went to the math department at my high school and and thought they would see this as a great “practical application” learning opportunity. Not so. In reading Milton Graton’s account about about the 240′ Frankenmuth bridge, “The thirty-one roof trusses had been fitted at out Ashland, New Hampshire shop…” pg 161. Just dawned on me that they probably scribed the Lats on sight in Michigan. But yes indeed the math is awesome and even drawing them in Auto Cadd is quite an exercise.

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