Moment Analysis

Discussion in 'AutoCAD' started by Greg McLandsborough, May 13, 2004.

  1. Has anyone seen, written, or thought about writting a moment analysis
    routine in lisp. I am starting to look at first and second order analysis
    for structural steel, and/or moment redistribution.

    Anyone who might have some help, I'd appreciate it.

    Cheers

    Greg
     
    Greg McLandsborough, May 13, 2004
    #1
  2. Greg McLandsborough

    bob.at Guest

    Greg

    do a search for "gravity" in this Group, maybe you find something there

    bob.at
     
    bob.at, May 13, 2004
    #2
  3. Greg McLandsborough

    Doug Broad Guest

    Yes. I have done one. It is limited and does not
    consider combined column-beam and multi-planar
    effects. It also only works with straight constant
    cross-section beams. For anything more complex,
    I use either an engineer or Mathcad to do the
    calculus.

    Mine uses the moment-area method. It creates
    shear, moment, slope, and deflection diagrams and
    creates a text table of critical factors that I export
    to Excel to pick the beams. What would
    you like to know?

    Regards,
    Doug
     
    Doug Broad, May 13, 2004
    #3
  4. Here's my Screen Menu set of items to calculate Moment, minimum Section
    Modulus and Moment of Inertia, and actual Deflection for a SIMPLE
    (single-span) beam. It assumes some typical F(b) and E values for
    structural steel and wood framing (the "fb" and "elast" quantities), which
    you might fine-tune, or work in some way of giving it specifics for each
    use.

    You use the first three in sequence (the later ones use values from the
    earlier). If you want to calculate another, you must pick the Reset item.

    The last item is independent, for calculating the Section Modulus and Moment
    of Inertia of a Rectangular cross-section.

    (The newsgroup system will break the lines apart, so you'll have to patch
    them back together up to the + signs.)

    **BEAMSIZE
    [* BEAM *]
    [* SIZE *]
    [* MENU *]
    [(Simple)]
    [ (Span)]


    [Moment:]^C^C^P(setq psfd (getreal "Enter Dead Load in lb./sq. ft. <10>: "))
    \(setq psfl (getreal "Enter Live Load in lb./sq. ft. <40>: ")) \+
    (if (= psfd nil) (setq psfd 10.0)) (if (= psfl nil) (setq psfl 40.0)) (setq
    span (getdist "Enter or Show Beam Span: ")) \+
    (setq trib (/ (getdist "Enter or Show Supported Width (Perp. to Span): ")
    12)) \(setq plit (/ (* (+ psfd psfl) trib) 12)) +
    (setq plil (/ (* psfl trib) 12)) (setq moment (/ (* plit (expt span 2)) 8))
    (strcat " Maximum Moment is " (rtos moment 2 0) ". ") ^P

    [Min.S,I:]^C^C^P(setq material (strcase (getstring "Steel or Wood (S/W) ?:
    "))) \+
    (if (= material "S") (setq fb 24000.0 elast 29000000.0)) (if (= material
    "W") (setq fb 1050.0 elast 1500000.0)) +
    (setq sectmod (/ moment fb)) (setq loverm (getreal "Allowable Deflection (L
    over) <360>: ")) \+
    (if (= loverm nil) (setq loverm 360.0)) (setq deflm (/ span loverm)) (setq
    inertm (/ (* 5 plil (expt span 4)) 384 elast deflm)) +
    (strcat " Minimum Required SECTION MODULUS is " (rtos sectmod 2 2) ".
    ") +
    (strcat " Minimum Required MOMENT OF INERTIA is " (rtos inertm 2 1) ".
    ") ^P

    [Deflect:]^C^C^P(setq inerta (getreal "Enter Actual Moment of Inertia of
    Beam: ")) \+
    (setq defla (/ (* 5 plil (expt span 4)) 384 elast inerta)) (setq lovera (/
    span defla)) +
    (strcat " Live Load DEFLECTION is " (rtos defla 2 2) " inches, or L
    over " (rtos lovera 2 0) ". ") ^P

    [ Reset]^C^C^P(setq psfd nil psfl nil span nil trib nil plit nil plil nil
    moment nil material nil fb nil sectmod nil) +
    (setq loverm nil deflm nil inertm nil inerta nil defla nil lovera nil) ^P

    [Rect.S,I]^C^C^P(setq rectd (getreal "Enter DEPTH of Rectangular Section in
    INCHES: ")) \+
    (setq rectb (getreal "Enter WIDTH of Section in INCHES: ")) \(setq secmod (/
    (* rectb (expt rectd 2)) 6) momint (/ (* rectb (expt rectd 3)) 12)) +
    (strcat " SECTION MODULUS is " (rtos secmod 2 2) ".") (strcat " MOMENT
    OF INERTIA is " (rtos momint 2 2) ".") ^P

    Kent Cooper, AIA Cooper, AIA Schwam Architects 215-635-7000, x115 Fax
    215-635-0930/3345
     
    Kent Cooper, AIA, May 13, 2004
    #4
  5. ....I should have also stated that those are for a UNIFORMLY LOADED simple
    beam, in Imperial Units, designed for an AutoCAD drawing unit representing
    an inch.

    Kent Cooper, AIA
     
    Kent Cooper, AIA, May 13, 2004
    #5
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