506TIMBER STRUCTURES

506-1.01 DESCRIPTION . Construct timber structures and the timber portions of composite

structures. Furnish, prepare, fabricate, erect, treat and/or paint timber and hardware, as specified.

506-2.01 MATERIALS. Use materials that conform to the following:

Timber Section 713 Preservatives for Timber Section 714 Structural Shapes, Rods, and Plates Section 716 Glued- Laminated Timber Members . Construct of Dougl as Fir produced and inspected in conformance with the requirements of ANSI/AITC A 190.1. Use laminating adhesives for timber to be used in wet conditions. Use Industrial -Grade glued -laminated members that have been treated with pressure preservative. Bolts , Screws and Drive Spikes . Conform to ASTM A307 (ANSI/ASME B 18.2.1). Galvanize meeting AASHTO M 232. Use standard timber fasteners manufactured with economy heads and spiral threads as drive spikes for fastening glued- laminated deck panels. Preservatives . Use pressure treatment preservatives for timber bridges as specified. Mastic Sealer . Use Seal Tight 158 Rubber Asphalt Sealer, or approved equal. Steel Dowels . Use uncoated steel dowels with a minimum yield strength of 36,000 psi on glued- laminated deck panels. Timber Connectors . Conform to the requirements of the AASHTO Standard Specifications for Highway Bridges , Division II, Section 16.2.6, Timber Connectors. CONSTRUCTION REQUIREMENTS

506-3.01 GENERAL. Employ competent bridge carpenters. Framing must be true and exact. Set

the heads of nails and spikes flush with the wood surface. Workmanship on all metal parts must conform to specified requirements. Stack all lumber and timber at the worksite to prevent warping. Open- stack untreated material at least 12 inches above the ground surface so that the pile will shed water. When required, cover untreated timber to protect it from the weather. Close -stack treated timber above the ground on blocks or lagging. Clear weeds and rubbish underneath and around all st acks. Locate all non- removable erection marks on fabricated timber so they are hidden from view in the completed work. Do not drag or drop timber members. Use web- belting slings and chokers to handle timber members. Protect corners with protection angles or blocking at pickup points. The estimated quantity of treated timber shown on the Plans is approximate only and no guarantee is made that it is the exact quantity to be furnished. Glued- laminated timber quantities shown on the Plans indicate gross quantit ies of timber, based on nominal dimensions and actual lengths before final planing of the laminated member.

506-3.02 TREATED TIM BER. Fabricate timber (including all cutting, shaping, and boring) before

treatment. Handle timber carefully without dropping, breaking the outer fibers, or bruising or penetrating the surface with tools. In coastal waters, avoid cutting and boring below the high- water mark. Carefully trim all abrasions and treat all cuts in treated piles according to AWPA standard M 4. 230 ALASKA 2020 Before dri ving bolts, treat all holes bored after treatment according to the applicable AWPA standards. Plug remaining holes with treated plugs.

506-3.03 Reserved.

506-3.04 HOLES FOR B OLTS, DOWELS, RODS, AND LAG SCREWS. Bore holes for round

drift-bolts and dowels wi th a bit 1/16 inch smaller in diameter than the bolt or dowel to be used. Bore holes for square drift -bolts or dowels equal to one side of the bolt or dowel. Bore holes for machine bolts 1/16 inch wider than the bolt. Bore holes for lag screws with a bit not larger than the body of the screw at the root of the thread. Bore holes for deck dowels in glued- laminated timber deck panels 1/2 inch deeper than the dowel embedment and no more than 1/16 inch oversize.

506-3.05 BOLTS AND W ASHERS. Use washers of the ty pe and size specified to protect wood

from bolt heads and nuts. Use cast -iron washers with a thickness equal to the diameter of the bolt and with a diameter 4 times its thickness. Use malleable or plate washers with diameter or side dimensions of the squar e equal to 4 times the diameter of the bolt, and thickness equal to 1/2 the diameter of the bolt. Use cast -iron washers when the timber is in contact with the earth. Check or burr all nuts with a pointed tool after final tightening to prevent turning.

506-3.06 COUNTERSINKING. Countersink bolts where smooth faces are required. Paint

recesses formed for countersinking, except in railing, with pentachlorophenol or creosote oil. After bolts or screws are in place, fill the recesses with hot pitch or mastic seal er. Countersink fasteners for attaching glu- lam deck panels to their supporting members below the top surface of the deck. After installation, fill all fastener recesses in the top surface of the deck with mastic sealer.

506-3.07 FRAMING. Cut all lumber and timber accurately and frame to a close fit so that the

joints bear weight evenly over all contact surfaces without shimming.

506-3.08 FRAMING BEN TS. Bed mud sills firmly and evenly to solid bearing. Tamp them in

place. Carefully finish concrete pedestals for supporting framed bents so that posts will bear evenly on them. Set dowels for anchoring posts when the concrete is cast.

506-3.09 STRINGERS. Size stringers at bearings and place them in position so that knots near

edges are in the top portions of the stringer. Separate the lapped ends of untreated stringers by at least 1/2 inch for air circulation. Securely fasten the lapped ends by drift -bolting where specified. Stagger the joints when stringers are two panels in length. Securely toe- nail cross -bridging between stringers with at least two nails in each end. Place cross- bridging at the center of each span.

506-3.10 PLANK FLOOR S. Lay the planks heart side down. For seasoned material, use 1/4 inch

openings between planks. For unseasoned material, use tight joints. Securely spike each plank to each stringer. Carefully grade the planks for thickness and lay them so that adjacent planks vary in thickness by no more than 1/16 inch.

506-3.11 LAMINATED O R STRIP FLOORS. Lay each piece vertically and tightly agai nst the

preceding piece. Each piece must bear evenly on all the stringers. Use pieces long enough to bear on at least four stringers. Make end joints on any one stringer no closer than every third piece. Place end joints in adjoining pieces no closer than every second stringer. 231 ALASKA 2020 Coat joints between adjacent glu- lam timber deck panels with mastic sealer before drawing the panels together.

506-3.12 TRUSSES. Check completed trusses to ensure that they show no irregularities of line.

Chords must be straight and true from end to end in horizontal projection. Ensure that chords show a smooth curve through panel points conforming to the correct camber in vertical projection. Accurately fit all bearing surfaces and joints. The Engineer will reject pieces with uneven or rough cuts at the points of bearing.

506-3.13 PAINTING. Paint the structure only when specified.

506-4.01 METHOD OF M EASUREMENT. See Section 109.

506-5.01 Basis of Pa Yment.

Mastic sealer, elastomeric bearing pads, and hardware are subsidiary. Structu ral steel is subsidiary unless shown on the bid schedule. Payment will be made under: PAY ITEM Item Number Item Description Unit 506.0001.____ Treated Timber LS 506.0002.____ Untreated Timber LS 506.0003.____ Treated Timber MBM 506.0004.____ Untreate d Timber MBM 232 ALASKA 2020 SECTION 507 BRIDGE BARRIERS AND RAILING

507-1.01 DESCRIPTION. Construct concrete, timber, or steel bridge railing, pedestrian railing

and safety railing as shown on the Plans. Furnish and install bridge number plates as shown on the Plans.

507-2.01 MATERIALS. Use materials that conform to the following:

Steel Railing Section 722 Timber Railing Section 506 Concrete Section 501 Epoxy -Coated Reinforcing Bars Subsection 709- 2.01 Grout Section 701- 2.03 Cable Use ¼ inch galvanized wire rope with a minimum breaking force of 7,000 pounds. Bronze ASTM B98, UNS Alloys C65100 or C65500 or ASTM B584, UNS Alloy C92200 CONSTRUCTION REQUIREMENTS

507-3.01 Constructio N Requirements.

507-4.01 METHOD OF M EASUREMENT. See Section 109.

507-5.01 BASIS OF PA YMENT. The contract price includes all rail elements, rail posts, brackets,

spacers, fastenings and anchors required to attach the ra iling to the structure; concrete and associated reinforcing steel included or partially contained within the limits of the concrete rail section or within the limits of the concrete curb for the steel bridge rail section; and bridge number plates.