Hi Tim,
How long have you got ? You might well be looking for an exactitude where this does not exist.
I spent Sunday examining the Abbingdon Long Gallery - a very large 10 bay jettied building which likely dates from 1430 or so and using the miracle of CAD I did a quick timber count and found that the original building had about 1600 or so individual timbers with almost half of these timbers now cut out and removed. Stuff happens over 600 years. The building has slowly yielded and deformed to the point that some of the joints have failed and are now coming apart and some members have fractured but still the building continues to stand.
Poor Design or Ravages of Time ? I think that I have expressed my views on this forum many times before about the dangers of designing leggy empty buildings that could easily be subject to large deformations leading to disproportionate collapse typically for the reasons outlined above and so one must recognise that "time now" is only an approximation as to the final building configuration that is likely to exist before decay, deformation and loss results in collapse.
After a while it becomes perfectly possible to believe that because someone has examined and calculated how a timber or collection of timbers will perform that this means that everything will be OK but hopefully we have now advanced beyond that point. It's probably more important to examine existing buildings to see what works and what isn't such a good idea. This empirical approach to building is an equally valid approach when compared with calculations. Where calculations really come into their own is when something quite radical or rare is being undertaken i.e. where there is no experience base from which to draw or alternatively where the commercial, technical or risk to life and limb is such that a better understanding of the undertaking is required.
One must recognise in the USA that apart from New England there is probably very little in the way of a historic building experience base from which timber frame engineers and carpenters can draw upon and so an informed engineering partnership between carpenters and engineers might well provide a better result than over reliance on just the carpenter or just the engineer.
I feel a Rumsfeldian moment coming on again - time to adopt the recovery position !
Regards
Ken Hume
