HW _5 Solutions

# HW _5 Solutions - ANS(a From slide 27 in the course notes...

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CEE 3020 Civil Engineering Materials SOLUTIONS Question 1 A small block of southern pine lumber weighs 140g when green. Oven dry, the block weighs 50g. (a) Calculate the moisture content of the green wood. ANS. % 180 100 50 50 140 100 (%) = × - = × - = g g g M M M MC ovendry ovendry actual (b) Estimate the mass of the block of wood when its moisture content reaches its fiber saturation point. Assume the fiber saturation point coincides with a 30% moisture content. ANS. g M g g M M M M MC fsp fsp ovendry ovendry actual 65 % 30 100 50 50 100 (%) = = × - = × - = Question 2 A Ponderosa Pine wood beam (2x2” in cross section), simply supported at both ends, is subjected to a center point load of 100 lbs. If the span (L) of the beam between the supports is 60”, (a) determine if the beam will fail (b) if the beam does not fail, determine deflection of the beam at mid-span.

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Unformatted text preview: ANS. (a) From slide 27 in the course notes on wood, we know the flexural strength of this species is 9200 psi. We also know that the M max will occur at the center span – for this loading condition – and will be PL/4 or 1500 in.-lbs. psi 125 , 1 ) 2 ( 12 1 ) 1 ( 1500 4 max = = σ which is considerably less than the strength, so the beam will not fail (b) " 27 . ) 2 ( 12 1 ) 10 26 . 1 ( 48 ) 60 ( 100 48 4 6 3 3 = = = = x EI PL deflection δ Question 3 How is the strength of wood generally affected by: (a) its moisture content (b) its specific gravity (c) temperature (d) loading rate (e) duration of loading (f) the presence of defects ANS. See your course notes and textbook for solutions....
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