Modelling the long-term strength of timber columns |
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Authors: | Ohandha Ayina Pierre Morlier Jean-Morlier Reynouard Tomi Toratti |
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Institution: | (1) Department of Civil Engineering, National School of Engineering, P.O. Box 8390, Yaounde, Cameroon;(2) Laboratory of Wood Rheology-Bordeaux, P.O. Box 10, 33610 CESTAS-GAZINET, France;(3) Department of Civil Engineering, INSA-LYON, 20, Avenue A. Einstein, 69621 Villeurbanne Cédex, France;(4) Laboratory of Structural Engng and Building Physics, Helsinki University of Technol, Fin-02150 Espoo, Finland |
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Abstract: | Summary This paper studies the influence of the used creep function, and the duration of the experimental sustained loading from which the creep function was derived, in modelling the long-term buckling strength of timber columns. The sensitivity of this buckling strength to creep and initial deflection is numerically studied using an energy approach that takes into account the initial deflection. Various creep functions — power laws as well as exponential laws — derived from bending experiments of different durations are used for the numerical simulation. The crucial need for experimental results issued from very long load period experiments is identified. Such experiments may lead to a more credible creep analysis of timber structures.Symbols i
radius of giration
- s
stress level
- EL
effective MOE
- E0
instantaneous MOE
- I
inertia moment
- K ,K![prime](/content/qt2n0451j25728v0/xxlarge8242.gif)
geometrical matrices
- L
length of beam or column
- Lf
effective length
- Ncr
axial force, buckling load
- U
elastic strain energy
- W
external forces work
- t
time variable
- u
moisture content (m.c.)
- v
total deflection
- vc, ve, v0
creep, instantaneous elastic and initial deflections respectively
Greek Letters (t)
time function
- , e, 0
total, instantaneous and initial strains respectively
-
twist rotation
- (t)
creep coefficient or fractional creep or relative creep
- (x)
shape function
-
load factor
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longitudinal shortening
-
total potential energy
-
creep factor
-
relaxation time |
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