文档介绍：装控091
专业英语翻译
unit 1
Static Analysis of Beams
A bar that is subjected to forces acting trasverse to its axis is called a beam. In this section we Will consider only a few of the simplest types of beams, such as those shown in . In every instance it is assumed that the beam has a plane of symmetry that is parallel to the plane of the figure itself. Thus the cross section of the beam occurs in that plane. Later we will consider a more general kind of bending in which the beam may have an unsymmetrical cross section.
The beam in , with a pin support at one end and a roller support at the other, is called a simply support beam ,or a simple beam. The essential feature of a simple beam is that both ends of the beam may rotate freely during bending, but the cannot translate in lateral direction. Also ,one end of the beam can move freely in the axial direction (that is, horizontal). The supports of a simple beam may sustain vertical reactions acting either upward or downward .
The beam in (b) which is built-in or fixed at one end and free at the other end, is called a cantilever beam. At the fixed support the beam can neither rotate nor translate, while at the free end it may do both. The third example in the figure shows a beam with an overhang. This beam is simply supported at A and B and has a free at C.
Loads on a beam may be concentrated forces, such as P1 and P2 in (a) and (c), or distributed loads loads, such as the the load q in (b), the intesity. Distributed along the axis of the beam. For a uniformly distributed load, illustrated in (b),the intensity is constant; a varying load, on the other hand, is one in which the intensity varies as a function of distance along
the axis of the beam.
The beams shown in are statically determinate because all their reactions can be determined from equations of static equilibrium. For instance ,in the case of the simple beam supporting the load P1 [(a)], both react