In bridge construction, a pier is a vertical member that provides  intermediate  support  for  the  bridge superstructure. The   chief   vertical   structural   members   in light-frame construction are called studs (see figures 2-1   and   2-3).   They   are   supported   by   horizontal members   called   sills   or   soleplates,   as   shown   in figure  2-3.  Corner  posts  are  enlarged  studs  located  at the   building   corners. Formerly,   in   full-frame construction, a corner post was usually a solid piece of  larger  timber. In   most   modern   construction, though, built-up corner posts are used. These consist of  various  members  of  ordinary  studs  nailed  together in various ways. HORIZONTAL STRUCTURAL MEMBERS Technically,   any   horizontal   load-bearing structural  member  that  spans  a  space  and  is  supported at both ends is considered a beam. A member fixed at one end only is called a cantilever. Steel members that consist of solid pieces of regular structural steel are referred  to  as  “structural  shapes.”  A  girder  (shown  in figure  2-2)  is  a  structural  shape.  Other  prefabricated, open-web,  structural-steel  shapes  are  called  bar  joists (also shown in figure 2-2). Horizontal structural members that support the ends   of   floor   beams   or   joists   in   wood-frame construction  are  called  sills  or  girders  see  figures  2-1 and  2-3).  The  name  used  depends  on  the  type  of framing  and  the  location  of  the  member  in  the structure. Horizontal members that support studs are called soleplates, depending on the type of framing. Horizontal  members  that  support  the  wall  ends  of rafters are called rafter plates. Horizontal members that assume the weight of concrete or masonry walls above  door  and  window  openings  are  called  lintels (figure 2-2). The horizontal or inclined members that provide support to a roof are called rafters (figure 2-1). The lengthwise  (right  angle  to  the  rafters)  member,  which supports the peak ends of the rafters in a roof, is called the ridge. The ridge may be called a ridge board, the ridge piece, or the ridge pole. Lengthwise members other than ridges are called purlins. In wood-frame construction, the wall ends of rafters are supported on horizontal members called rafter plates, which are, in turn, supported by the outside wall studs. In concrete or masonry wall construction, the wall ends of rafters may be anchored directly on the walls or on plates bolted to the walls. A beam of given strength, without intermediate supports below, can support a given load over only a specific maximum span. When the span is wider than this  maximum  space,  intermediate  supports,  such  as columns, must be provided for the beam. Sometimes it is either not feasible or impossible to increase the beam size or to install intermediate supports. In such cases,  a  truss  is  used.  A  truss  is  a  combination  of members,  such  as  beams,  bars,  and  ties,  usually arranged in triangular units to form a rigid framework for supporting loads over a span. The basic components of a roof truss are the top and  bottom  chords  and  the  web  members.  The  top chords serve as roof rafters. The bottom chords act as ceiling joists. The web members run between the top and  bottom  chords.  The  truss  parts  are  usually  made of 2- by 4-inch or 2- by 6-inch material and are tied together  with  metal  or  plywood  gusset  plates,  as shown in figure 2-4. Roof  trusses  come  in  a  variety  of  shapes  and sizes. The most commonly used roof trusses, shown in  figure  2-5,  for  light-frame  construction  are  the king-post, the W-type, and the scissors trusses. The simplest type of truss used in frame construction is the king-post truss. It is mainly used for spans up to 22 feet.  The  most  widely  used  truss  in  light-frame construction is the W-type truss. The W-type truss can be placed over spans up to 50 feet. The scissors truss  is  used  for  buildings  with  sloping  ceilings. Generally,  the  slope  of  the  bottom  chord  equals one-half the slope of the top chord. It can be placed over spans up to 50 feet. DRAWINGS LEARNING OBJECTIVE: Upon completing this section, you should be able to recognize the different types of drawings and their uses. The building of any structure is described by a set of  related  drawings  that  give  the  Builder  a  complete, sequential, graphic description of each phase of the construction  process.  In  most  cases,  a  set  of  drawings begins  by  showing  the  location,  boundaries,  contours, and  outstanding  physical  features  of  the  construction site  and  its  adjoining  areas.  Succeeding  drawings give  instructions  for  the  excavation  and  disposition  of existing ground; construction of the foundations and superstructure;   installation   of   utilities,   such   as plumbing,  heating,  lighting,  air  conditioning,  interior and exterior finishes; and whatever else is required to complete the structure. 2-4