Cantilever Beam Calculation

This program calculates the deflection of a cantilevered beam loaded to maximum safe load at the free end. Do not use these results for construction or where their use could endanger anyone, unless you are competent to evaluate the results yourself. Many factors, such as moisture content, method of fixing the beam, wood quality, etc. affect the load and deflection of the beam. I’ve made limited tests on some beams and found the answers surprisingly accurate.

Enter the program, RUN, and answer the questions. Results are only significant to one decimal place. Wood is of the select, 15% moisture variety.

In building construction deflection usually doesn’t exceed 1/360 of the length of the beam, so for most beams, the maximum safe load never gets tested. Considering that the formulae used here can have error up to 50% (for reasons previously mentioned), I’m glad!

  10 PRINT "CALCULATES MAX SAFE LOAD AND    DEFLECTION FOR A BEAM FIXED AT  ONE END AND LOADED AT THE OTHER"
  15 PRINT
  20 PRINT "ENTER LENGTH IN FEET ";
  30 INPUT L
  40 PRINT L;" FT"
  45 PRINT
  50 PRINT "ENTER WIDTH IN INCHES";
  60 INPUT W
  70 PRINT W;" """
  75 PRINT
  80 PRINT "ENTER DEPTH IN INCHES";
  90 INPUT D
 100 PRINT D;" """
 105 PRINT
 110 PRINT "SELECT WOOD"
 112 PRINT "FIR=1",,"HEMLOCK=2",,"REDWOOD=3"
 120 INPUT M
 130 PRINT M;" SELECTED"
 135 PRINT
 140 IF M<>1 THEN GOTO 190
 145 LET DN=37.2
 150 LET US=1200
 160 LET HS=84
 170 LET E=1.6E6
 180 LET X=66.7
 190 IF M<>2 THEN GOTO 240
 195 LET DN=30.7
 200 LET US=1024
 210 LET HS=56
 220 LET E=1.2E6
 230 LET X=55.6
 240 IF M>3 OR M<1 THEN GOTO 110
 245 LET DN=28.3
 250 LET US=1040
 260 LET HS=60
 270 LET E=1.4E6
 280 LET X=55.6
 300 LET WB=DN*(D/12)*(W/12)*L
 310 LET LD=(W*D**2*X)/(4*L)
 320 IF L<=D THEN LET LD=(W*D*HS)/3
 330 LET SL=LD-(WB/2)
 340 LET DE=(4*SL*(L*12)**3)/(E*W*D**3)
 350 PRINT "SAFE LOAD= ";SL;" POUNDS"
 355 PRINT "DEFLECTION= ";DE;" INCHES"
 360 PRINT "ENTER ""CONTINUE"" FOR MORE"
 370 STOP
 380 GOTO 20
SYNTACTIC SUM:  58696, 8K ROM