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Constructing a Trestle Bent
Steel Bearing

Builder 3&2 Volume 02 - Construction manual for building structures
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timber-nailing anchorage for flooring to the top of a steel  girder. Timber decking consists of two layers of 3-inch planks.  The  lower  layer,  called  the  flooring,  is  laid  at right  angles  to  the  stringers  and  nailed  with  two  60d spikes to each stringer crossing. The upper layer, called the tread (fig. 10-7), is laid securely and nailed at a 90° angle to the flooring. Most of the flooring planks and all of the tread planks are cut to lengths that will bring the ends of the planks flush with the outer faces of the outside stringers. However,  at  5-foot  intervals  along  the  superstructure,  a flooring plank is left long enough to extend 2 feet 8 inches beyond the outer faces of the outside stringers, The extension serves as support for the curb risers, the curb, and the handrail posts, as shown in figure 10-7. The  curb  risers  consist  of  3-foot  lengths  of  6  by  6 timbers, one of which is set in front of each handrail post as shown. A continuous 2 by 6 handrail is nailed to 4 by 4 handrail posts. Each handrail post is supported by a 2 by 4 knee brace, as shown. An end dam, such as that shown in figure 10-8, is set at each end of the superstructure. This prevents the approach of the road to the trestle from washing out or eroding between the abutment and the girders. PILE DRIVING TERMINOLOGY AND TECHNIQUES LEARNING OBJECTIVE: Upon completing this section, you should be able to identify the types of piles used in heavy construction and state the procedures for constructing a timber pier. The  principal  structural  members  in  many waterfront structures are piles. There are different types of and uses for piles. The common terms used with  piles  and  pile  driving  are  explained  below. Figure 10-7.-Details of superstructure of a timber trestle. Figure  10-8.-End  dam. TYPES OF PILES A pile is a load-bearing member made of timber, steel, concrete, or a combination of these materials. It is usually forced into the ground to transfer the load to underlying soil or rock layers when the surface soils at a proposed site are too weak or compressible to provide  enough  support. Timber Bearing Timber  bearing  piles  are  usually  straight  tree trunks cut off above ground swell with the branches closely  trimmed  and  the  bark  removed.  Occasionally, sawed timbers may be used as bearing piles. CHARACTERISTICS.— A good timber pile has the  following  characteristics: It is free of sharp bends, large or loose knots, shakes, splits, and decay. It is uniformly tapered from butt to tip. The centers of the butt and tip are end points of a straight line that lies within the body of the pile. Cross-section dimensions for timber piles should be as follows: Piles shorter than 40 feet, tip diameters between 8 and 11 inches, and butt diameters between 12 and 18 inches. Piles  longer  than  40  feet,  tip  diameters  between 6 and 8 inches, and butt diameters between 13 and 20 inches. The butt diameter must not be greater than the distance between the pile leads. PREPARATION  FOR  DRIVING.—   Timber piles can be damaged while being driven, particularly under hard-driving conditions. To protect a pile against damage, cut the butt of the pile squarely (so the pile hammer will strike it evenly) and chamfer it. When a 10-4







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