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1) The value of an historic covered bridge lies in the workmanship, methods and joinery
of the original builders and the timber from Vermont's old forests used in the construction. This
historic integrity needs to be preserved.
Phil Pierce - Our efforts for historic preservation should be more focused on
maintaining the skills necessary to rebuild these important structures, than just on maintaining the
material of the bridge.
Jan Lewandoski - The design and the historic engineering of the bridge is as
important as the actual structure.
2) To preserve historic integrity when a covered bridge is repaired, the joinery used by the original craftsman should be duplicated and the timber used in the repair should be of the same species as the original.
David Wright - To preserve the historical integrity when a covered bridge is repaired, the joinery used by the original craftsman, 'must' be duplicated and the timber used in the repair should be of the same species as the original.
John Weaver - If the desired methods and materials to preserve historic integrity are not practical, then supplemental support systems or splicing with modern materials should be considered to preserve otherwise functional historic members.
Jan Lewandoski - If you can, restore in kind; same species, same joinery, same
member sizes, same everything. But there are often reasons why you can't, one of them being
changing use of the bridge. If you are going to put much heavier loads on it, you may have to beef
it up. Most of the bridges in the state had lighter floor systems at one time, for horses and
wagons. Heavier trucks required heavier floor systems. The floor systems were changed
throughout the 30s, 40s, and 50s.
Phil Pierce - It is more important to maintain the skills of dealing with a bridge effectively by craftsmen that know what they are doing, rather than necessarily saying that thou shalt keep the fabric at all costs. (Develop craftsmen to keep the tradition of building wooden bridges alive.)
2a)Native timber should be used in covered bridge restoration, other timber to be used as last resort.Phil Pierce - If we can generally duplicate the bridge with stronger species, than at least we are producing a bridge that has a chance of meeting code requirements. Jan Lewandoski - If you go to a different species, sometimes without making a great change in the disposition of the truss you can get quite a bit greater carrying capacity. Sometimes just changing one or two sticks to a different species will help a great deal with whatever the problem is in the bridge.
Native species are difficult to find, especially in great quantity or on short notice. You are going to have to get something else. Some early bridges used white pine, but you can't get white pine of that quality anymore.
Glue laminated lumber is not needed. It has high design values, but it's no stronger than anything else. You may have more confidence in it. It comes in longer pieces.
3) Covered bridges should remain in service with historic integrity intact. To achieve this
the bridge needs to be maintained on a regular basis to keep deterioration from occurring to avoid
large-scale repairs that could compromise historic integrity.
We need to develop a policy towards rehabilitation, maintenance and reconstruction of abutments, piers and other structures. Sometimes that's all you have to go with if the bridge is burned down or has been destroyed for some other reason, then the only thing that still qualifies that bridge for rehabilitation are the substructure units that are left. That is necessary to getting five percent local participation for the project.
Otherwise you'd have to start a new bridge and the local entity would have to pay at least ten percent. We are interested in the substructure units at least being maintained or looking as much as they did originally, even if it means facing the new concrete abutment with the old stone, or underpinning or some other reconstruction to maintain these foundations in an historic sense. Ed Barna - Use of height limiting structures at discrete distances Neil Daniels - Tie the bridge inspections to the federally mandated state inspection which carries with it some teeth. Our Bridge-watch people should be able to work with the state inspections to see that things get done.
We need to address the fact that towns neglect all road structures and see if we can change this.
4) When a covered bridge has deteriorated to the point that it must be repaired or
restored, the restoration contract needs to be explicit that if the bridge is found to be beyond
restoring to full use to convey motor traffic, it must not be destroyed by replacing all or a
significant portion of the original truss, but instead left intact, bypassed or removed from its
I save my most ardent objection to the philosophy of closing bridges to use rather than resort to different details and/or materials. We have seen too many examples of bridges destroyed by vandals that target closed bridges. David Wright - Bypassed bridges can turn into abandoned bridges. Public money is tight. It's a lot easier to justify funds for something that is serving an obvious public good getting people from one side of the river to the other than it is to save something that is on display. Ed Barna - Policy which should advise against methods of historic preservation which isolate bridges and marginalize them from community use.
5) To keep historic integrity: Native timber, meaning northeast species, should be used in
covered bridge restoration, other timber to be used as last resort. To permit the use of native
timber in bridge structures, there needs to be an effort by the timber industry to test, characterize,
and certify north-eastern species.
Phil Pierce - The national leaders in the establishment of timber allowable stresses are
centered at the Forest Products Laboratory in Madison, Wisconsin. They would love to do even
more than they already have (yet they have led the world in this field). However, additional
research carries with it the need for additional funding. If the VCBS wishes to urge more
research, you should recognize that no one will voluntarily conduct such work without
David Wright - Non-destructive test protocols must be developed.
6) To make maintenance of historic covered bridges effective: A practical way to enforce vehicle dimension restrictions needs to be developed. Partnerships between towns, the Vermont Historic Bridge Program should be encouraged. A practical way to enforce vehicle weight restrictions needs to be developed.
Phil Pierce - We can force dimensional limitations.
7) To pursue its policies the VCBS and its members will: Organize area chapters (Bridge Watch Areas) for the purpose of establishing a working relationship with the local municipal governments, historical societies and Chambers of Commerce to promote bridge maintenance and tourism, and to guard against vandalism; Educate the public on the value of Vermont's historic bridges; Work with the VAOT Historic Bridge Program.
8) On preservation discipline:
David Wright - One [of the questions] was the dating of the material. New material
gets put in should be recorded. There are drawings of record. What's new and what's old should
be clearly indicated on them. The pieces could be marked discretely in various places. When one
of these bridges is to be restored or rehabilitated or beefed up, there should be drawings of record
made of the bridge as it was found at the start of the project. Everything ought to be
photographed, everything ought to be drawn. I know it's a cost, but never the less we are talking
about principles of preservation here. These steps ought to be part of the preservation process
before the bridge is touched.
Phil Pierce - There should/must be a requirement to distinguish old fabric from new,
both in the drawings and on the bridge itself.
Ed Barna - It is important to preserve the original timbers as much as possible. I
think maybe what the policy ought to do is say, if they can't be preserved in the bridge, they ought
to be preserved, or reused in some way out of the bridge to leave something to the future.
Niel Daniels - We should [build for] passenger car use with these structures because that's closer to the weights the were built for initially, But many of the old ones without any work on them will carry 30,000. They won't calculate, but they'll carry it day after day. That's some of that "Access Carrying Capacity."
Jan Lewandoski - Only fix things that are broken on covered bridges.
9) Improve the process of covered bridge oversight:Jan Lewandoski - The biggest problem with species is the engineering drawings. Many engineers specify Douglass Fir and southern yellow pine for everything. It's easy to get, it comes graded, comes in big pieces and it's got high design values.
The contractor is usually late in the planning/design process. He's told to get the contract and start working in thirty to sixty days. Where the plans come specify certain species, the contractor hasn't much control over it.
The problem with using native timber and the problem with a lot of joinery is, as soon as you go to quantitative analysis, you go to design values, which are extremely conservative and being very general, are not sub-species specific. That's why live oak has very low values although it's a very strong wood. Because the white oak group has forty members, some of them weak, the whole group is rated low. Avoid quantitative analysis of these bridges, do qualitative analysis.
I advocate qualitative analysis, need better quantitative analysis.
If a bridge is not showing any signs of failure under live or dead load, there's probably no reason to re-engineer the bridge.
There is need to pay more attention to abutments. Stone abutments superior to concrete. Concrete is a very temporary material. Need more people who can do good stone work.
John Weaver - I think the answer to covered bridge evaluation is better quantitative analysis. This may involve some evaluation of secondary support members and reserve capacity of the bridge as well for live loads. It certainly involves some investigation and evaluation for dead load which is long term and can be more severe in some cases than live loads in some structures. To enhance the quantitative analysis I think that when a project is started, if possible, a wood scientist should be employed to give an evaluation of just what the lumber is in the bridge so you know what your starting point is, so you don't just run to the NDS tables and look for the most conservative values to work with. If you know what values you really had to begin with, then you know where to start.
David Wright - General contractors are one of the problems we have with some covered bridge restoration projects. Covered bridge repair, covered bridge restoration, seasoning of timbers, selecting timbers, finding where to order a special timber is not routine for them. They may win the bidding process, and then issue change orders until projects get out of control and bridges end up being seriously adulterated.
Phil Pierce - Advocate design-build contracts rather than design-bid-build so that
contractors and engineers can work together as a team. Each has viewpoints and expertise that
work well together.
Neil Daniels - I want to urge that we work with representative Don Davis, possibly next year, that would be the second year of his two year term, in our preservation policy and the State preservation policy paper that had been circulated today.
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