过程装备与控制工程专业英语上册.doc

过程装备与控制工程专业英语翻译作业

龙飞啸天
Reading Material 1
Static Analysis of Beams
A bar that is subjected to forces acting transverse to its axis is 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 has a vertical axis of symmetry. Also, it is assumed that the applied loads act in the plane of symmetry, and hence bending 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 (a)，with a pin support at one end and a roller support at the other, is called a simply supported beam, or a simply beam . The essential feature of a simple beam is that both ends of the beam may rotate freely during bending, but they cannot translate in the lateral direction. Also, one end of the beam can move freely in the axial direction (that is, horizontally) .The supports of a simple beam may sustain vertical reactions acting either upward and downward.
The beam in (b) which is build-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. The beam is simply supported at A and B and has a free end at C.
Loads on a beam may be concentrated forces, such as P1 and P2 in (a) and (c). Distributed loads, such as the load q in (b). Distributed loads are characterized by their intensity, which is expressed in units of force per unit distance 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 o