huangyhg

1907 lumber values.
the carnegie pocket companion-1923 which slideruleera has talked about before, gives design values for wood.
those design values are quiet high, so i am unsure of how to apply them for use in evaluating wood from a building built in early 1900. does anyone have any suggestions?
i am trying to get an estimate of what design values may have been use in order to determine the orginal loads that a building was designed for.
- rule of thumb is wood that old is select structural or dense select structural. you can get the species through your local apa or agriculture extension office.
rarmbj - the note at the top of the table of "working unit stresses for structural timber" (page 289 of cpc-1923) gives this guidance:
quote:
for building and similar structures, in which the timber is protected from the weather and practically free from impact, the unit stresses may be increased 50 per cent.
i agree that this would make the allowable working stresses quite high by today's standards. engineer's in the early 20th century do not appear to have had knowledge of "load duration". i have never seen that issue even discussed in publications from that time. also they were willing to accept a much smaller safety factor then (typically 6 to 1, and if the 50% increase is taken into account it becomes only 4 to 1). this probably had to do with the fact that almost all timber used at that time was high quality, not the wider variability seen today.
in summary, imho, for a building that meets the above requirement, i would apply the 50% increase. this would be to determine what the original design loads were. but... i certainly would not say that the structure is safe (by today's standards) at those loads.

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