huangyhg

paper/books/wood
if the density of lets say 'normal' wood runs about 50 pcf, and paper is made from wood, and books are made from paper, then how does the boca code (live loads - table 1606) note c get 65 pcf? and if you're going to say "the 65 pcf includes shelving", then dont respond - weights of shelves, chairs, desks, computers, etc. should already be considered in the minimum live load for the desired occupancy.
many papers are not only composed of wood. the paper products may contain clays (coatings), and mineral brightening agents that can add significant weight.
alright, i'll buy that for a dollar, then.
i think paper can have different weights according to how much it has been compacted during manufacture. the tissue and the green back don't weighs the same, do they?
books are heavy because they also been printed on and some glossy papers contain more than just wood.
anyway there is no answer to whether a beef burger should be heavier or lighter than the beef because in re-contituted form it can be compacted artificially.
actually, if you look at the cross section of a piece of wood you see the end of the fibers, but also the "capillaries" or sap ducts. these account for most of the difference in density. paper is made from the same wood fibers, but they are broken down either chemically or by grinding to make the paper. they are in a much more dense configuration in paper than in the original wood structure.
a sheet of 3/4" mdf weighs about twice as much as a sheet of 3/4" plywood, due to density of the material. paper, in density, is closer to mdf than real wood. all three are wood products.
just for the sake of clarity, what is mdf?
jheidt,
medium density fiberboard, similar to particle board. it comes in sheets 4'x8', 4'x9', 4'x10'. very smooth and dense.
i think most re-constituted timber products like mdf, chipboard, fibreboard and the like are heavier than the original timber.
wood is porous, contains sap and therefore has a significant mositure content. 99% wood floats in water (timber is lighter than water). the dry wood fibres must have been well packed togeter in order for paper to have a density higher than wood.
lets stop the next guy asking why a dvd disc being the same size as a cd can holds several times more data.

__________________
借用达朗贝尔的名言：前进吧，你会得到信心!
[url="http://www.dimcax.com"]几何尺寸与公差标准[/url]