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Construction - 14044_286
Pile Driving Terminology and Techniques

Builder 3&2 Volume 02 - Construction manual for building structures
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Figure 10-5.-Locating seats for trestle bents. less the thickness of a footing, will be the height of the first bent. Next, stretch the tape from the location of the first bent, level it as before, and again drop a plumb bob from the 12-foot mark. The position of the plumb bob will be the  location  of  the  section  bent.  The  vertical  distance from the location of the bob to the horizontal tape, plus the height of the first bent, less the thickness of the footing, will be the height of the second bent. Finally, stretch the tape from the location of the second  bent  and  proceed  as  before.  The  vertical distance from the location of the bob to the horizontal tape,  plus  the  height  of  the  second  bent,  less  the thickness of a footing, will be the height of the third bent, and so on. CONSTRUCTING  A  TRESTLE  BENT When a trestle bent is laid out and constructed, the length of the posts is equal to the height of the bent, less the combined depths of the cap and sill. In a four-post bent, the centers- of the two outside posts are located from 1 to 2 1/2 feet inboard of the ends of the sill, and the centers of the two inner posts are spaced equally distant  between  the  other  two. Sills, caps, and posts are commonly made of stock that ranges in size from 12 by 12s to 14 by 16s. If a sill or cap is not square in a cross section, the larger dimension should be placed against the ends of the posts. The usual length for a sill or cap is 2 feet more than  the  width  of  the  roadway  on  the  trestle.  The minimum width for a single-lane trestle is 14 feet; for a two-lane trestle, 18 feet. Layout Part of the terrain at an assembly site may be graded flat and used as a framing yard, or a low platform may be constructed for use as a framing platform. To assem- ble a bent, lay the posts out parallel and properly spaced, and set the cap and sill in position against the ends. Bore the holes for the driftpins through the cap and the sill into the ends of the posts, and drive in the driftpins. Cut a pair of 2- by 8- by 18-inch scabs for each joint and then spike, lag-screw, or bolt the scabs to the joints. Finally, measure the diagonals to determine the lengths  of  the  transverse  diagonal  braces.  Cut  the braces  to  length  and  spike,  lag-screw,  or  bolt  them  to the sills, caps, and posts. Transverse diagonal bracing is usually made of 2 by 8 stock. Trestle Bent Erection After assembly, the trestle bent is moved to the abutment, and set in place on the footings at the seat. Carefully plumb the bent and temporarily brace it with timbers running from the top of the bent to stakes driven at  the  abutment.  Lay  the  superstructure  (girders  and decking) from the abutment out to the top of the first bent. The second bent is then brought out to the end of the superstructure and set in place. Plumb the second bent and measure the diagonals to determine the lengths of the longitudinal diagonal braces between the first and second bents. Then, cut the braces and spike, lag-screw, or bolt them in place. The  superstructure  is  then  earned  out  to  the second bent, after which the third bent is brought to the  end  of  the  superstructure.  This  procedure  is repeated, usually by parties working out from both abutments, until the entire span is completed. SUPERSTRUCTURE Timber girders are usually 10 by 16s, 14 feet long, spaced  3  feet  3  1/2  inches  on  center  (OC).  Various methods of fastening timber stringers to timber caps are shown in figure 10-6, view A. Various methods of fastening steel girders to timber caps are shown in view B.  This  view  also  shows  three  ways  of  fastening  a Figure 10-6.-Methods of fastening timber stringers and steel girders to timber caps. 10-3







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