A course in structural drafting; . distributed, concentrated at onepoint or at several points. The beamsof a floor are considered to carry theload uniformly distributed. Shaftingmay be considered as beams supportedat the hangers but loaded at variouspoints. The pedal of a bicycle is an illustra-tion of a cantilever beam and is subjectto a bending action while the one uni-formly loaded is .in a position to besheared right off close to the supports. While a loaded beam is subject toshearing strains, these are very easilycalculated and are very rarely consid-ered as a pt)ssible cause of failure.
A course in structural drafting; . distributed, concentrated at onepoint or at several points. The beamsof a floor are considered to carry theload uniformly distributed. Shaftingmay be considered as beams supportedat the hangers but loaded at variouspoints. The pedal of a bicycle is an illustra-tion of a cantilever beam and is subjectto a bending action while the one uni-formly loaded is .in a position to besheared right off close to the supports. While a loaded beam is subject toshearing strains, these are very easilycalculated and are very rarely consid-ered as a pt)ssible cause of failure. Wewill spend but little time consideringthem, and will concentrate our attentionon the methods for calculating what isknown as the bending moment, for it isthis that causes failure in almost everycase. Two general cases present first is where a beam is set solidhin the wall at one end only, as in , and the second is where it is sup-ported at both ends, as in Fig. 30. Wewill first consider the case of Fig. 29,. Fig. JJ. where but one end of the beam is sup-ported, and where the weight is appliedat the extreme end away from the sup-port. In this case the maxzimum bend-ing moment is located at the point ofsupport, that is just where the beam en-ters the wall, and it is here that failureis most liable to occur. This bendingmoment is measured by the product ofthe weight, by the distance from thewall, which is marked a in the weight is usually taken in pounds Fig. 30. and the distance in feet. Thus if thedistance a is 6 feet and the weightW 25 pounds, the bending moment atthe point a is 25 X 6 ^ 150 pounds-feet. If in this case the weight is uni-formly distributed, as, for instance, theweight of the beam itself, it may betaken as if located at its center. Suppose the weight W in Fig. 29 is 38 Beams a7id Girders evenly distributed over the length of thebeam as in Fig. 31. Then we may con-sider the whole weight as if all locatedat its center, and to get the
Size: 1904px × 1313px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, bookcentury1900, bookdecade1900, bookidcourseinstructur00brow
