462 TIMBER STRUCTURES

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462.01 DESCRIPTION.
Construct structures or portions of structures using timber, including fabricating, erecting, treating, and coating of the timber elements.
For timber piling refer to Section 410. For concrete refer to Section 420. For structural steel refer to Section 430.
462.02 MATERIALS.
Asphalt Cement       904
Structural Steel       909.01
Gray Iron Castings       909.04
Bolts and Hardware       909.10
Structural Timber       921.05
Preservative Treatments for Timber       921.06
Metal Timber Connectors       Per manufacturer and as approved
Galvanizing       A 153
Fire Stops and Galvanized Sheet Metal       A 653, Coating Designation G 90
462.03 CONSTRUCTION.
462.03.01 Storage and Handling. Store timber in open stacked piles at the site on suitable blocking or platform at least 12 in. above any type of surface or vegetation in a manner to shed water and prevent warping. Protect it from weather by a suitable covering. Clear the storage site of weeds and rubbish before placing material and throughout the storage period. Ensure that the site selected is not subject to flooding. Handle using rope or nylon slings to prevent the breaking of outer fibers, bruising, or penetrating the surface.
462.03.02 Cutting and Boring. When practical, cut and bore treated timbers before pressure treatment. Brush coat all cuts in treated timbers and all abrasions (after being carefully trimmed) with two applications of an approved wood preservative before installing the timber in the structure. When it is determined that treated timbers are damaged beyond repair, remove them from the project and replace them.
When forms or temporary braces are attached to treated timber with nails or spikes, fill the holes by driving galvanized nails or spikes flush with the surface.
462.03.03 Bolt Holes. When holes are bored after treatment, fill them with asphalt cement applied with a caulking gun, or as directed, before inserting bolts. Place asphalt cement coated plugs in holes that are not to receive bolts.
462.03.04 Coating Untreated Surfaces. In untreated timber structures, coat all contact surfaces between members (except adjacent flooring members) with two coats of an approved preservative before assembly. Similarly coat the back faces of bulkheads and all surfaces of timber that will come in contact with earth, metal, or other timber. Coat the ends of timber members in the same manner.
462.03.05 Protection of Ends of Caps, Wales, and Planks. Cover the ends of all caps, wales, and planks with resin glass composite shields as approved. Apply the shields as follows:
(a) Remove all dirt and other loose material from area to be capped.
(b) Apply the first coat of resin to the top and 4 in. down the side of the member.
(c) Apply precut glass cloth, using a 3 in. grooved aluminum roller to achieve “wet-out”, and anchor using brass staples.
(d) When the initial coat of resin has taken a tack free set, apply a second coat of resin to seal the entire application.
462.03.06 Diameter of Holes. Holes bored in timber structures shall meet the following for the listed connectors:
(a) Round drift bolts, spikes, and dowels - 1/16 in. less than the diameter of the device.
(b) Square drift bolts, spikes, and dowels - equal to the smallest dimension of the device.
(c) Machine bolts - same as the diameter of the bolts.
(d) Rods - 1/16 in. larger than the diameter of the rods.
(e) Lag screws - equal to the diameter of the screw at the base of the thread.
(f) Connector bolts - 1/16 in. larger than the diameter of the connector bolts.
462.03.07 Bolt Assemblies. Bolt heads and nuts that come in contact with the timber shall be fitted with a washer of the size and type specified. After all nuts are adequately tightened, burr the bolt threads.
462.03.08 Countersinking. Countersink wherever smooth faces are required. In treated timber, paint recesses formed in horizontal surfaces with an approved preservative. After the bolt or screw is in place, fill recesses with an approved asphalt coating.
462.03.09 Connectors. Bore connector holes through members to be connected. Bore perpendicular to the face of the timber. When spike grids or split ring connectors are specified, install them according to the manufacturer’s recommendations.
462.03.10 Framing. Accurately cut and frame all timber to provide even bearing over the entire contact surface. When making joints, shimming and open joints are prohibited.
462.03.11 Sills. Ensure that sills have true and even bearing on mudsills or concrete pedestals. Remove all earth from contact with sills.
462.03.12 Timber Caps. Place timber caps to secure an even and uniform bearing over the tops of the supporting posts or piles and to secure an even alignment of their ends. Secure all caps by drift bolts or as specified. Locate the drift bolts in the center of the post or pile.
462.03.13 Bracing. Bolt the ends of bracing through the pile, post, or cap. Bolt intermediate intersections also. Use spikes or nails in addition to bolts. When bracing intersects, use filler blocks with a bolted connection.
462.03.14 Stringers. Place stringers in position so that knots near edges are in the top portions of the stringers. Size bottom edges of stringers to provide uniform depth at bearings.
Outside stringers may have butt joints with the ends cut on a taper, but interior stringers shall be lapped to take bearing over the full width of the floor beam or cap at each end. The lapped ends of untreated stringers shall be separated at least 1/2 in. and securely fastened by drift bolts where specified. When stringers are two panels long, stagger the joints. Toenail cross bridging between stringers with at least two nails in each end. Leave the lower ends of all bridging and one side of each diaphragm disconnected and free to move until after the deck above is securely fastened to the stringers.
462.03.15 Floor Planking. Unless otherwise specified, floor planking shall be S1S1E, hit or miss, and have a uniform thickness with a maximum tolerance of 1/8 in. Where necessary to maintain traffic, lay planks in half-of-bridge width sections. Timber plank floors shall always be accompanied with suitable hold down devices. Spike the planks to every stringer, joist, and nailer with at least two spikes. The length of the spikes shall be at least twice the thickness of the plank. Where planks will be under wheel guards or hold down devices, carefully select planks of as near equal thickness as possible. Before any hold down or wheel guard is bolted, firmly drive treated shims or wedges between low planks and either the hold down or the wheel guard so that all planks are held down with equal pressure. The shims shall occupy at least 50 percent of the area between the bottom of either the hold down or wheel guard and the top of the plank.
462.03.16 BridgeA structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening. For lengths, all dimensions shall be parallel to the center line of the roadway. The dimensions of handrails will not be taken into account in measuring bridge lengths. Any bridge or highway grade separation structure includes the connecting highways, substructure, superstructure, roadway approaches, entrance plazas, interchanges, overpasses, underpasses, and other structures which the Administration may deem necessary together with all property rights, easements, franchises, and interests acquired by the Administration for the construction and operation of the bridge. Railings and Wheel Guards. BridgeA structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening. For lengths, all dimensions shall be parallel to the center line of the roadway. The dimensions of handrails will not be taken into account in measuring bridge lengths. Any bridge or highway grade separation structure includes the connecting highways, substructure, superstructure, roadway approaches, entrance plazas, interchanges, overpasses, underpasses, and other structures which the Administration may deem necessary together with all property rights, easements, franchises, and interests acquired by the Administration for the construction and operation of the bridge. railings shall meet a minimum of Test Level 1 (TL-1) as specified in the AASHTOAmerican Association of State Highway and Transportation Officials LRFD BridgeA structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 20 feet between undercopings of abutments or spring lines of arches, or extreme ends of openings for multiple boxes; it may also include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening. For lengths, all dimensions shall be parallel to the center line of the roadway. The dimensions of handrails will not be taken into account in measuring bridge lengths. Any bridge or highway grade separation structure includes the connecting highways, substructure, superstructure, roadway approaches, entrance plazas, interchanges, overpasses, underpasses, and other structures which the Administration may deem necessary together with all property rights, easements, franchises, and interests acquired by the Administration for the construction and operation of the bridge. Design Specifications, Railings. All dimensions for timber rail, posts, and spacers shall be the actual dimensions of the timber.
Locate bridge rail and wheel guard splices so that rail and guard members are continuous over at least two posts. Install bridge railings and wheel guards in sections not less than 12 ft long. Splices shall be shiplapped with the lap equal to 8 in. or the greater side of the piece, whichever is larger.
462.04 MEASUREMENT AND PAYMENT.
Piles are excluded. The payment will be full compensation for all timber (treated or untreated) storage and handling, finishing of pile bents and abutments, preservative, composite shields, asphalt cement, metal components, drilling holes, and for all material, labor, equipment, tools, and incidentals necessary to complete the work.
462.04.01 Timber structures will be measured and paid for at the Contract unit price per 1000 board feet (MBM). The computation of quantities will be based on the nominal sizes specified and the exact overall net length of pieces remaining in the completed structure. No allowance will be made for waste.
462.04.02 Timber structures will not be measured but will be paid for at the Contract lump sum price.