Typically, I use this space to share historical lore I’ve turned up on our wooden bridges, or the people who designed and built them, occasionally I explore structural aspects of the various Truss types, and details of and perspectives on their framing. Today I’m going to break with those norms.
I’ve come to the conclusion that part of the value in having a Bully Pulpit, is that every so often one should pound it with their fist.
Every so often has arrived in the form of recent events – Yes, I’m going to do an opinion piece.
The replication, well the rebuilding ( The replacement as designed has dissimilar structural systems and engineered timber, so it will not technically fit the definition of a replication ) of a bridge lost to Irene was recently awarded. It was awarded to the low bidder. This in and of itself is not unusual, (hell, some jurisdictions require contracts be awarded to the low bidder, others require that low bids be tossed – You be the judge as to which dictum holds the greater logic ) What is unusual is that despite every other bidder having decent if not deep résumés, and the Request for Proposals citing a requisite three wooden bridge minimum work history, and the four lowest bids coming in at remarkably close price points, the contract was awarded to the local bidder, a concrete & steel bridge building company. With several newspaper articles (see the archives to the right – or click the following underlined text – “Yes he was local, his name was Sanford Granger” ) citing the reasoning being, simply, that they were local.
In the interest of full disclosure, I, along with other independents, was part of an assembled team aligned with one of these bidders. Some might see some of what I have to say, as so many sour grapes. In truth the effort I chose to align myself with, provided an alternate bid, one which those involved saw as important, but one which had the great potential to (and ultimately did) remove us from the running, both for additional design costs, and with leaving the dictates of the letting as proposed. This alternate a traditional design, one which, with a full understanding of wood as a building material, specified “Free of Heart Center” timber for the Lattice Plank and Chord Lams, and had lateral Bracing systems in keeping with Grangers’ design, and neither the Glu-Lam Floor Beams nor Penta (Pentachlorophenol) treatment of any of the materials. To my mind both are unnecessary expenses and absurdities. Penta treated wood is a danger to those cutting it, and so requires already worked timber to be shipped to distant treatment plants and back. It also is a redundancy, this is the purpose of the siding and roofing. And with human nature being what it is, treated framing is arguably a recipe for future neglect, treating only part of the framing insures that recipe leads to future expense, not future savings. And to Glu-Lams, to insist a bridge designed to carry modern day traffic requires the use of engineered timber, is to ignore reality, as the Railroad bridges described here in earlier entries demonstrate so well. But these are perhaps points to be made in some future discussion, back to the point at hand…
Though the news story’s make no mention of it, instead concentrating on the local aspect of why which concern was contracted. In all fairness, that local concrete & steel bridge company has pulled in both a bridgewrighting “consultant”, and a local (same town) CNC type Timberframer. The Bridgewright has his own reasoning for this alliance. ( I’m just glad someone will be there with some real sense of things ) The CNC Framer perhaps played an equal role in the decision to waive the three bridge requisite, and of who to contract. I for twofold reason don’t see their involvement as entirely logical or appropriate – Though I don’t have room here to flesh out all the reasons why in this entry, here’s the gist – And also what isn’t – This is not a blanket condemnation of an automated CNC computer driven approach to timberframing, My opinion is more practical and Bridgewrighting specific than that. While CNC is hugely efficient at producing multiple copies of the same piece over and over again, and such pieces exist in this bridge, Ties as a for instance. Major sub-assemblies like the Trusses and Lateral Bracing systems were and are, for good reason, (camber) typically scribed, because there are subtle changes in even Lateral Brace shoulder angle from panel to panel, (Meaning these are compound cuts with shifting angles from one set to the next, or even from one end to the other, this driven by the attitude of the Ties and their relationship to the changes in the inclination of camber along the spans length) and slight changes in length in successive panels with a trusses Braces and Counter Braces. These changes need be accounted for to develop camber and ensure necessary full bearing proper fit, but in some panels these changes in length and angle/s of intersection are so subtle as to seem hardly worth mathematically predicting. Such running of the numbers in this morphing geometry being necessary to program a computer-controlled robot to fabricate subtly dissimilar pieces literally removes all advantage (or worse such subtleties are lost to ignorance – I’ve never seen a set of drawings which acknowledged and quantified this camber driven phenomenon ) from a CNC type approach in bridge framing – Scribe Layout without question remains the most efficient approach to wooden bridge framing. (with such approach, changing lengths and angles needn’t be mathematically quantified, they are simply dealt with in real world conditions) This is not simply my opinion, it is a demonstrable truth, and the reason why wooden bridges were the last bastion of scribe type timber layout right through to the end of their common era of construction, better than a full century after scribe was abandoned for most all other timber constructions.
The other slant on why I see no logic in automated timber part production, goes to my greater point – The perpetuation of my trade, and the passing on of knowledge to younger members of the Timberframing Community – Those who will practice Bridgewrighting in the future.
Bridgewrighting is a sub-specialty of Timberframing, with both skillsets and a knowledge base unique to this sub-specialty. Much of this having to do with the crush phenomenon common to bridge framing, and the planning for and control of crush. Much having to to with rigging and assembly, along with techniques having to do with the development of camber in new-builds and likewise, the return of same to bridges undergoing restoration. Such concepts shared are what makes a Timberframer a Bridgewright. I do not see such things being conveyed from practiced framer to initiate at an automated production shop, even if only separated by fifteen miles, any more than I see any return or transferable value to the betterment of this Trade in pounding home the importance of edge distance, to uninterested form carpenters as they endlessly drill Trunnel holes through clamped up Lattice Plank.
I can’t help but see this as an all too rare opportunity missed. An opportunity for those familiar with this little practiced form of construction, to pass on proven methodologies and techniques to others who will in turn go on to practice this sub-specialty in future projects.
So to the greater point. Despite a small but capable corp of trained and knowledgeable wooden bridge specialists, it is somehow in no way uncommon for such replication contracts, and those of the related type and far more common lettings, that of major rehabilitation’s to wooden bridges to be awarded to concrete and steel bridge companies, and unlike this instance, they don’t necessarily subcontract in anyone who has anything approaching expertise in the field. This has happened in some surprising jurisdictions just within the past year, such as Oregon, Indiana, Ohio and Pennsylvania.
These structures are too important and too complex to be entrusted to the uninitiated, the learning curve is far too steep.
Some jurisdictions already demand that such lettings only be contracted to those known to possess all the necessary knowledge and skills to execute them fittingly. They do this by requiring potential bidders to pre-qualify, and vetting their résumés, (or those of their primary subcontractor) prior to the submission of proposals and bid prices. Surprisingly, in none of the States in which such bridges exist in the greatest numbers, is this tact of a Request for Qualifications (RFQ’s) used across-the-board to limit those bidding these projects to those firms best capable of executing them.
If all this makes sense to you, particularly if you live in a state with numbers. Consider contacting your State and Federal reps, and insisting that such highly demanding public works projects, if funded with Federal grants, be it National Historic Covered Bridge Preservation Program (NHCBP) monies, or those from FEMA to repair or replace storm ravaged historic bridge infrastructure – By requiring that interested parties pre-qualify.
I for one, would like to believe we live in a meritocracy.