. The railroad engineer's practice . 53 The king-post truss :Strain on C D = W; strain on A C and C B — —- -^yr- «f • J R WAD Strain on A B — ~ 71^ If the load is uniformly distributed, it will produce thesame effect as one-half the above load suspended in themiddle. The beam is supposed to have no stiffness at , A J3 is always made in one stick, and its stiffnesswill reduce the above values by an indeterminate amount. The queen-post truss : AB = BE = EF. Strain on C B and D E - i W. AC Strain on ^ C and D F -= i W X pt^ Strain on C D = i W X ABC B = strain on A F. These are the stra
. The railroad engineer's practice . 53 The king-post truss :Strain on C D = W; strain on A C and C B — —- -^yr- «f • J R WAD Strain on A B — ~ 71^ If the load is uniformly distributed, it will produce thesame effect as one-half the above load suspended in themiddle. The beam is supposed to have no stiffness at , A J3 is always made in one stick, and its stiffnesswill reduce the above values by an indeterminate amount. The queen-post truss : AB = BE = EF. Strain on C B and D E - i W. AC Strain on ^ C and D F -= i W X pt^ Strain on C D = i W X ABC B = strain on A F. These are the strains when loads of ^ TF are placed atB and Ey or a total uniform load of W. In the lattercase, the abutment at A has to sustain, in addition, theload on \ A J5, which, added to the resolved component ofthe strain on A (7, produces a vertical strain of a W, as itought. If only the point B is loaded with ^ W, the portionwhich is transferred to the abutment F will produce amoment about D tending to break the joint across, if it isrigid. If, however, it is flexible, there will be a tendency 54 for the joint to rise which is resisted by the rod D E (pro-ducing a strain upon it of \ W) and the strain transferredto E, must be resisted by the transverse strength of thebeam B F, calculated in the same way as the first case ofthe simple beam loaded in the middle (of a length B F,not A F). If braces are introduced in the directionsB
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