AASHTO HB-17 DIVISION II SEC 16-2002 Division II Construction - Timber Structures《木结构》.pdf

1、Section 16 TIMBER STRUCTURES 16.1 GENERAL This work shall consist of constructing timber struc- tures and the timber portions of composite structures, in accordance with these Specifications and in reasonably close conformity with the details shown on the plans or established by the Engineer. It wil

2、l include furnishing, preparing, fabricating, erect- ing, treating, and painting of timber. All timber, treated or untreated, shall be of the specified species, grades and di- mensions. Also included will be any required yard lumber of the sizes and grades specified and all hardware required for tim

3、ber connections and ties. 16.1.1 Related Work Other work involved in the construction of timber structures shall be as specified in the applicable sections of this specification. Some of the sections that frequently apply to timber structures are Section 4, “Driven Foun- dation Piles”; Section 13, “

4、Painting”; Section 17, “Preservative Treatment of Wood”; and Section 20, “Railings.” 16.2 MATERIALS 16.2.1 Lumber and Timber (Solid Sawn or Glued Laminated) Sawn lumber and timber shall conform to the Specifi- cations for Structural Timber, Lumber, and Piling, AASHTO M 168. Structural glued laminate

5、d timber shall conform to the American National Standard ANSUAITC A- 190.1, Spec- ijcation for Structural Glued Laminated Timber. Struc- tural glued laminated timber, as employed in ANSUAITC A190.1, is an engineered, stress-rated product of a timber laminating plant, comprising assemblies of suitabl

6、y se- lected and prepared wood laminations securely bonded together with wet-use adhesives. The grain of all lamina- tions is approximately parallel longitudinally. The sepa- 607 rate laminations may not exceed 2 inches in net thick- ness. They may be comprised of pieces end-joined to form any lengt

7、h, of pieces placed or glued edge to edge to make wider ones, or of pieces bent to curved form during gluing. On glued-laminated structural members that are not to be preservatively treated, an approved end sealer shall be applied after end trimming of each completed member. The grades of timber use

8、d for various structural purposes shall be as shown on the plans or in the special provisions. Structural lumber and timber, solid sawn or glued lam- inated, in exposed permanent structures, other than run- ning planks on decks, shall be treated in conformance with the requirements of Section 17, “P

9、reserved Treat- ment of Wood.” Temporary structures or lumber and tim- ber of certain species with adequate heartwood require- ments, as listed in AASHTO M 168, when permitted by the plans or specifications, do not require preservative treatment. When the special provisions require certification of

10、quality for timber or lumber, the Contractor shall furnish the following certificates of compliance to the Engineer, as appropriate, upon delivery of the materials to the job site: For timber and lumber, a certification by an agency certified by the American Lumber Standards Committee that the timbe

11、r or lumber conforms to the grade, species, and any other specified requirements. For glued laminated timber, a certification by a quali- fied inspection and testing agency that the glued lami- nated timber complies with the grade, species, and other requirements outlined in ANSUAITC A190.1. If the

12、wood is to be treated with a preservative, a cer- tificate of compliance, as specified in Article 17.3.3, shall be furnished. 16.2.2 Steel Components Rods, plates, eyebars, and shapes shall conform to the requirements of AASHTO M 270 (ASTM A 709) Grade 36 unless otherwise specified. 608 HIGHWAY BRID

13、GES 16.2.3 16.2.3 Castings Castings shall be cast steel or gray-iron, as specified, conforming to the requirements of Articles 11.3.5 or 11.3.6. 16.2.4 Hardware Bolts, nuts, drift-bolts, and dowels may be of mild steel. Washers may be cast iron ogee or malleable iron castings, or they may be cut fro

14、m mild steel plate, as spec- ified. Bolts shall have either standard square, hex or dome heads, or economy type (washer) heads. Nails shall be cut or round wire of standard form. Spikes shall be cut or wire spikes, or boat spikes, as specified. Unless otherwise spec- ified, bolts shall comply with A

15、STM A 307, and shall have coarse threads, Class 2 tolerance conforming to ANSI Standard Specifications. All fasteners, including nails, spikes, bolts, dowels, washers, and lag screws shall be galvanized, unless oth- erwise specified or permitted. 16.2.5 Galvanizing 16.2.5.1 Unless otherwise specifie

16、d, all hardware for timber structures shall be galvanized in accordance with AASHTO M 232 (ASTM A 153) or cadmium plated in ac- cordance with AASHTO M 299 (ASTM B 696). All steel components, timber connectors, and castings, other than malleable iron, shall be galvanized in accordance with AASHTO M 1

17、1 1 (ASTM A 123). 16.2.6 Timber Connectors 16.2.6.1 Dimensions The various types of timber connectors shall generally conform to the dimensions shown in Table 16.1 and to the dimensions specified in this Article 16.2.6. 16.2.6.2 Split Ring Connectors Split rings of 2Yinch inside diameter and 4-inch

18、in- side diameter shall be manufactured from hot-rolled car- bon steel conforming to the Society of Automotive Engi- neers Specification SAE-1010. Each ring shall form a closed true circle with the principal axis of the cross sec- tion of the ring metal parallel to the geometric axis of the ring. Th

19、e metal section shall be beveled from the central portion toward the edges to a thickness less than the mid- section. It shall be cut through in one place in its circum- ference to form a tongue and slot. 16.2.6.3 Shear-Plate Connectors Pressed steel shear-plates of 2Yinch diameter shall be manufact

20、ured from hot-rolled carbon steel conforming to the Society of Automotive Engineers Specification SAE- 1010. Each plate shall be a true circle with a flange around the edge, extending at right angles to the face of the plate and extending from one face only, the plate portion hav- ing a central bolt

21、 hole and two small perforations on op- posite sides of the hole and midway from the center and circumference. Malleable iron shear-plates of 4-inch diameter shall be manufactured according to ASTM A 47, Grade 325 10, for malleable iron casting. Each casting shall consist of a per- forated round pla

22、te with a flange around the edge extend- ing at right angles to the face of the plate and projecting from one face only, the plate portion having a central bolt hole reamed to size with an integral hub concentric to the bolt hole and extending from the same face as the flange. 16.2.6.4 Spike-Grid Co

23、nnectors Spike-grid timber connectors shall be manufactured according to ASTM A 47, Grade 325 10, for malleable iron casting. TABLE 16.1 Qpical Dimensions of Timber Connectors (dimensions in inches) Split Rings 2-112 in. 4 in. Split Ring: Closed Inside Diameter at Center When 2.500 4.00 Thickness of

24、 Metal at Center O. 163 O. 193 Depth of Metal (Width of Ring) 0.750 1 .o0 Groove: Inside Diameter Width Depth Hole Diameter Bolt Diameter: 2.56 4.08 O. 18 0.21 0.375 0.50 112 3.4 9/16 13/16 Washers, Standard: Round, Cast or Malleable Iron, Round, Mild Steel, Diameter 2-38 3 Diameter 1-318 2 Thicknes

25、s 3/32 5/32 Square Plate, Mild Steel, Length of Side 2 3 Thickness 118 3/16 16.2.6.4 DIVISION II-CONSTRUCTION 609 TABLE 16.1 (Continued) Shear Plates (dimensions in inches) 2-518 2-518 4 4 Shear Plate: Material Pressed Light Mal- Mal- steel gage leable leable Diameter of Plate 2.62 2.62 4.03 4.03 Di

26、ameter of Bolt Hole 0.81 0.81 0.81 0.94 Thickness of Plate O. 172 O. 12 0.20 0.20 Depth of Flange 0.42 0.35 0.64 0.64 Steel straps or shapes for use with shear plates shall be designed in accordance with accepted engineering practices. Hole Diameter in Straps or Shapes for Bolts 13/16 13/16 13/16 15

27、/16 Circular Dap- Dimensions: A 2.63 2.63 4.03 4.03 B - 1.07 1.55 1.55 C 0.81 0.81 0.81 0.94 D - 0.65 0.97 0.97 E 0.19 0.13 0.27 0.27 F 0.45 0.38 0.64 0.64 G 0.25 0.14 0.22 0.22 H - 0.34 0.50 0.50 I 2.25 2.37 3.49 3.49 Bolt Hole-Diameter in Timber 13/16 13/16 13/16 15/16 Washers, Standard: Round, Ca

28、st or Mallea- Round, Medium Steel ble Iron Diameter 3 3 3 3-112 Minimum: Thickness 5/32 5/32 5/32 11164 Diameter 2 2 2 2-114 Square Plate: Length of Side 3 3 3 3 Thickness 114 114 114 114 Square grids shall consist of four rows of opposing spikes forming a 4Yinch square grid with 16 teeth that are h

29、eld in place by fillets. Fillets for the flat grid in cross section shall be diamond shaped. Fillets for the single curve grids shall be increased in depth to allow for curva- ture and shall maintain a thickness between the sloping faces of the fillets equal to the width of the fillet. Circular grid

30、s of 3Y4-inch diameter shall consist of eight opposing spikes equally spaced around the outer circumference and held in place by connecting fillets around the outer diameter and radial fillets projecting to a central circular fillet which forms a bolt hole opening of 1Y4 inch. Fillets in cross secti

31、on shall be diamond shaped except that the inner circular fillet may be flat- tened on one side to provide for manufacturer identifi- cation. 16.3 FABRICATION AND CONSTRUCTION 16.3.1 Workmanship Workmanship shall be first class throughout, and all framing shall be true and exact. Unless otherwise sp

32、eci- fied, nails and spikes shall be driven with just sufficient force to set the heads flush with the surface of the wood. Deep hammer marks in wood surfaces shall be considered evidence of poor workmanship and sufficient cause for re- moval of the workman causing them. 16.3.2 Storage of Material L

33、umber and timber stored at the construction site shall be kept in orderly piles or stacks. Untreated material shall be open-stacked on supports at least 12 inches above the ground surface to avoid absorption of ground moisture and permit air circulation and it shall be so stacked and stickered as to

34、 permit free circulation of air between the tiers and courses. In particular cases required by the En- gineer, the Contractor shall provide protection from the weather by a suitable covering. The ground underneath and in the vicinity of the timber shall be cleared of weeds and rubbish. The storage a

35、rea shall be chosen or con- structed so that water will not collect under or near the stored timber. 16.3.3 Treated Timber 16.3.3.1 Handling Treated timber shall be carefully handled without sud- den dropping, breaking of outer fibers, bruising, or pene- trating the surface with tools. It shall be h

36、andled with web slings. Cant hooks, peaveys, pikes, or hooks shall not be used. When metal bands are used to bundle members, cor- ner protectors shall be provided to prevent damage to the treated timber. 16.3.3.2 Framing and Boring All cutting, framing, and boring of treated timbers shall be done be

37、fore treatment insofar as is practicable. When treated timbers are to be placed in waters infested by ma- rine borers, untreated cuts, borings, or other joint framings below high-water elevation shall be avoided. HIGHWAY BRIDGES 16.3.3.3 610 16.3.3.3 Cuts and Abrasions All cuts and all recesses form

38、ed by countersinking in creosote treated piles or timbers, and all abrasions, after having been carefully trimmed, shall be field treated as specified either in this paragraph or the following para- graph. Cuts and recesses shall be covered with two appli- cations of a mixture of 60% creosote oil an

39、d 40% roofing pitch or brush coated with at least two applications of hot creosote oil and covered with hot roofing pitch. Recesses likely to collect injurious materials shall be filled with hot roofing pitch. Unless specified otherwise, hot preserva- tives shall be heated to a temperature between 1

40、50? and 200F. Where particularly heavy coatings are required, a suitable plastic compound can be prepared by mixing 10% to 20% of creosote and 80% to 90% of coal-tar roof- ing pitch. For timbers originally treated with pentachlorophenol, creosote, creosote solutions or water-borne preservatives, all

41、 cuts, abrasions and recesses which occur after treat- ment shall be field treated by two liberal applications of a compatible preservative in accordance with the require- ments of the American Wood Preservers Association Standard M 4 entitled, ?Standard for the Care of Pressure Treated Wood Product

42、s.? 16.3.3.4 Bored Holes All holes bored after treatment shall be treated by fill- ing the holes with the preservative used for field treatment. After treatment, any holes not filled with bolts or other items shall be plugged with preservative treated plugs. 16.3.3.5 Temporary Attachment Whenever, w

43、ith the approval of the Engineer, forms or temporary braces are attached to treated timber with nails or spikes, the resulting holes shall be treated as required for bored holes and shall be filled by driving galvanized nails, spikes, or preservative-treated plugs flush with the surface. 16.3.4 Inst

44、allation of Connectors Timber connectors shall be one of the following types, as specified on the plans: the split ring, the shear plate, or the spike grid. The split ring and the shear plate types shall be installed in precut grooves of dimensions as given herein or as recommended by the manufactur

45、er. Spike grids shall be forced into the wood so that timbers will be in firm contact. Pressure equipment that does not damage the wood shall be utilized. One acceptable method is to use high-strength bolts or rods fitted with low friction ball-bearing washers made for this purpose. The high- streng

46、th bolt will be replaced with specified bolts for the final installation. All connectors of this type at a joint shall be embedded simultaneously and uniformly. Connector grooves in timber shall be cut concentric with the bolt hole, shall conform to the cross-sectional shape of the rings, and shall

47、provide a snug fit. Inside groove diameter shall be larger than nominal ring diame- ter in order that the ring will expand slightly during in- stallation. (See Table 16.1.) Fabrication of all structural members using connectors shall be done prior to preservative treatment. When pre- fabricated from

48、 templates or shop details, bolt holes shall not be more than y16 inch from required placement. Bolt holes shall be %6 inch larger than the finished bolt diame- ter. Bolt holes shall be bored perpendicular to the face of the timber. Timber after fabrication shall be stored in a manner that will prev

49、ent changes in the dimensions of the mem- bers before assembly. Timber should be cured before fab- rication so that it will remain stable in its dimensions. Timber that shrinks during storage causing predrilled grooves for split rings or plates to become elliptical or causing bolt hole spacing to change will be sufficient rea- son for rejection. 16.3.5 Holes for Bolts, Dowels, Rods, and Lag Screws Holes for round drift-bolts and dowels shall be bored with a bit 1/16 inch less in diameter than the bolt or dowel to be used. The diameter of holes for square drift-bolts or dowels shall be