I’m looking for a reference or tutorial on calculating loads. I’m a do-it-yourselfer and when I ask people whether something will be strong enough I’m told, “Check the span tables” or “do the load calcs”. Any help you can provide so I can learn how to do the calculations myself would be greatly appericated.
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"Introduction to Load Paths and Wood Design"
http://www.beamchek.com/AcrobatFiles/IntroLoadPath.pdf
Thanks you. The document talks briefly about deflection but doesn't go into detail about how to calculate it for different size or types of lumber. I assume after calculating the load for a project you need to determine the maximum deflection allowed/desired and size the lumber appropriately. Do you know where I could find information on calculating deflection or is this generally tabulated?
It's time to get a book. Perhaps "Simplified Engineering for Architects and Builders" by James Ambrose. I have the 9th edition, published in 2000 by John Wiley & Sons. ISBN 0-471-32191-5.
-- J.S.
Deflection is only one factor, and IIRC from my engineering courses, is calculated: wl^4
______ EIWhere w is the load, l is the clear span, E is the elasticity of the species and grade of wood, and I is the moment of inertia, a mathematical representation of the cross-sectional shape of the beam. What I always found interesting is that since you're taking length to the fourth power, doubling the length increases the deflection by a factor of 16!
E will be obtained through lumber tables, I can be calculated easily with the diagrams found in an engineering textbook. By integrating or differentiating the equations, you can also determine shear, bending moment, and .... ummm ...... something else in addition to deflection.
Haven't done those calcs in about 20 years or more, don't think I could now. Oh, yeah, the units for E and I are like pound/feet/hours/cupsofsugar/dayoftheweek/etc., so put all that into your equation and make sure the units cancel out and give you an answer that makes sense. If the numbers come out with "hours squared" or "cubic feet" or something else that doesn't make sense, then you've used the wrong units somewhere.
Hope I didn't just confuse the issue!
http://www.jlconline.com/cgi-bin/jlconline.filereader?44c946170021ada327177f0000010594+EN/products/SF499
Residential Structure and Framing
by The Journal of Light Construction
I have read it. It's a good book.