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Load transmission
Simplest structure : simple supported beam
Consider a man of 100kgf crossing the log.
The static scheme can be represented by the following figure.
Beside the man loading there has to be considered the self-weight of the log.
Considering the density of wood ș țțț ț
, the selfweight for the linear element has to be
taken into acount as a linear uniform distributed force. Thus, multiplying with the area of cross
section (m2) it will result a uniform distributed force (daN/m)
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Adding the two loads, it will result the total reactions of the supports
!" ș ț# - "% & ș ț#
'(% ș ț# - ) − +, & ț ș ț
+, & ș0.33kN
'(, ș ț# - ) 4 − +%
& ț ș ț
+%
& ș0.67kN
'" ș ț# - "%&& ș ț
'(% ș ț# - ț 3 − +,&& ț ș ț
+,&& ș2.64kN
'(, ș ț# - ț 3 − +%
&& ț ș ț
+%
&& ș .64kN
+% ș +%
& + +%
&& ș 3ț3
+, ș +, & + +,&& ș țț
The need for supporting or transportation larger loads lead to crossings or bridges.
The load is transmitted, for this simple structure, from the deck to the beams and from the
beams to the foundations. The deck represents a surface loading
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##########+% ș
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Specific weight for wood: γ1 ș țțț# 23
Circular section:
45#
ș 678
ș ț#9
The weight for one meter: ș :1
ș țțț# 23
ț ț
ș ț,
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The need for larger loads bridges
The deck represents a surface loadinf: pdeck
=>2 ș :1 ?@AțB2 ș țțț
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ț,ț4# ș ț,
<
ș ț,
For a single plank to be calculated we use:
=>2 ș :1 ?@AțB2 C@AțB2 ș țțț
<
ț,ț4 ț, ș 3,3ț
<
ș 3,3ț
The weight for beams is obtained by adding weight of the deck and the self weight of the beam.
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