Kj. Fridley et al., EFFECT OF 85 YEARS OF SERVICE ON MECHANICAL-PROPERTIES OF TIMBER ROOFMEMBERS - PART III - RELIABILITY STUDY, Wood and fiber science, 30(1), 1998, pp. 72-80
Citations number
15
Categorie Soggetti
Materiales Science, Textiles","Materials Science, Paper & Wood",Forestry
The first two parts of this series (Fridley et al. 1996a, b) presented
a comprehensive experimental and analytical duration of load (DOL) st
udy of Purdue University's Peirce Hall, an 85-year-old, turn-of-the-ce
ntury building razed in 1989. In this part of the research, we approac
h the structure from a probabilistic standpoint. We treat the material
properties and loading as random variables in order to answer the fol
lowing questions: Would we have ever seen any DOL effects in Peirce Ha
ll? If not, and recognizing that the structure was in general conforma
nce with current design practice, are we overly conservative in curren
t design considering DOL? If yes, how often, and how does this relate
to the level of safety we currently assume in design? We found that Pe
irce Hall, with randomness of loading and material properties, had a f
inite probability of experiencing a DOL failure, but not as high as as
sumed in current design. That is, the probability of Peirce Hall exper
iencing a DOL failure was less than what would be predicted using curr
ent DOL-analysis procedures. The major reason for this lower probabili
ty of failure is not due to an ''over-designed'' Peirce Hall, but is c
ontributed to differences in real loading and assumed loading. Specifi
cally, the snow load process assumed in current DOL-analysis procedure
s utilizes a rectangular representation of snow events, when a triangu
lar representation is more appropriate. The rectangular event produces
greater damage and higher probabilities of failure than the triangula
r event.