CHAPTER 10HEAVY CONSTRUCTIONHeavy construction includes structures made ofsteel, timber, concrete, or a combination of these ma-terials. Examples include trestles, timber piers, andwaterfront structures. The requirement for heavy con-struction today is not as important as in earlier years;however, the need to understand this type of construc-tion still remains.In this chapter, we’ll examine the materials usedin building heavy structures. We’ll also discuss themethods and techniques of heavy construction, in-cluding shoring and excavation. In addition, we’lllook at the procedures used in maintaining the struc-tures.TIMBER TRESTLESLEARNING OBJECTIVE: Upon completingthis section, you should be able to identify theparts of a trestle, and describe the proceduresfor erecting bents and superstructures.A trestle is a braced framework of timbers, piles,or steel members, It is typically built to carry a road-way across a depression, such as a gully, a canyon, orthe valley of a stream. The two main parts of a trestleFigure 10-1.-Abutment sill and footing and abutmentexcavation.are the substructure, consisting of the supportingmembers, and the superstructure, consisting of thedecking and the stringers on which the decking is laid.The substructure of a timber trestle is a series oftransverse frameworks called bents. Trestle bents areused on solid, dry ground, or in shallow water with asolid bottom. Pile bents are used in soft or marshyground, or where the water is so deep or the current soswift that the use of trestle bents is impossible. Theposts of a pile bent are bearing piles or vertical mem-bers driven into the ground.NOMENCLATUREThe following terms are common to timber trestleconstruction:Abutment— The ground support at each of theextreme ends of a trestle superstructure. Examplesare shown in figures 10-1 and 10-2.Bracing— The timbers used to brace a trestle bent,called transverse bracing, or the timbers used tobrace bents to each other, called longitudinalFigure 10-2.-Placing and leveling abutment footings andabutment sill.10-1
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