ITEM 408– STEEL BRIDGES

408.1 Description

This Item shall consist of the construction of steel structure conforming to the lines, grades, dimensions and designs shown on the Plans and in accordance with the Specifications for piling, concrete metal reinforcement, structural steel and other items which constitute the completed structure.

408.2 Materials

All materials shall conform to the detailed requirements specified for the component parts of the completed structure. Where special materials are required, they shall be shown on the Plans or in the Special Provisions.

408.3 Construction Methods408.3.1 Organization and Equipment

During the progress of the work the Contractor shall have a competent foreman or superintendent, experienced in steel erection, in personal charge of the work.

Before starting work, the Contractor shall inform the Engineer as to the method of erection he proposes to follow and the amount and character of equipment he proposes to use, which shall be subject to the approval of the Engineer. The approval of the Engineer shall not be considered as relieving the Contractor of the responsibility for the safety of his method or equipment or from carrying out the work in full accordance with the Plans and Specifications. Erection diagrams shall be approved by the Director, Bureau of Design.

408.3.2 Handling and Storing Materials

Steel and timber shall be placed on skids above the ground and shall be kept clean. The underlying ground shall be kept free from vegetation and properly drained. Girders and beams shall be placed upright and shored. Long members, such as columns and chords, shall be supported on skids placed close enough together to prevent injury by deflection. The Contractor shall be responsible for the loss of any material, which has been paid for by the Bureau, while it is in his care, or for any damage, resulting from his work. The loading, transporting, unloading and piling of structural material shall be so conducted that the metal will be kept free from injury from rough handling.

408.3.3 Erection

The Contractor shall furnish and place all falsework, erect all metal work, remove the temporary construction, and do all work required to complete the structure as covered by the Contract, including the removal of the old structure or structures if so stipulated, all in accordance with the Plans and these Specifications.

If the substructure and superstructure are built under separate contracts, the Department will provide the substructure, constructed to correct lines and elevations and properly finished, and will establish the lines and elevation required for setting the steel.

If the fabrication and erection of the superstructure are done under separate contract, the Department will furnish detail plans for the bridge or bridges to be erected, including shop details, camber diagrams, erection diagrams, list of field rivets and bolts, and copy of shipping statements showing a list of parts and their weights.

The Contractor shall provide all tools, machinery, and appliances including drift pins and fitting up bolts, necessary for the expeditious handling of the work.

The falsework shall be properly designed, substantially built and maintained for the loads which will come upon it. The Contractor, shall prepare and submit to the Engineer for approval plans for falsework or for changes in existing structure necessary for maintaining traffic. Approval of the Contractor’s plans shall not be considered as relieving him of any responsibility.

The parts shall be accurately assembled as shown on the Plans and any matchmarks shall be followed. The material shall be carefully handled that no parts will be bent, broken or otherwise damaged. No hammering shall be done that will in any way injure or damage a member. Bearing surface and surfaces to be in permanent contact shall be cleaned before the members are assembled. Unless erected by the cantilever method, truss spans shall be erected on blocking so placed as to give the trusses proper camber. The blocking shall be left in place, until the tension chord splices are fully riveted and all other truss connection pinned and bolted. Rivets in splices of butts joints of compression members and rivets in railings shall not be driven until the span is swung. Splices and filled connections shall have one-half of the holes filled with bolts and cylindrical erection pin (half bolts and half pins) before riveting. Splices and connections carrying traffic during erection shall have three-fourths of the holes so filled. Fitting up bolts shall be of the same nominal diameter as the rivets and cylindrical erection pins shall be 0.75 mm larger.

408.3.4 Welding

Where so indicated on the Plans, structural members shall be joined by welding. The welds shall be of the size and type indicated and shall be made by competent operators. Shop welding shall conform in all details to the Standard Specifications for Welded Highway and Railway Bridges of the American Welding Society. Field welding shall conform to the requirement of Item 409, Welded Structural Steel.

408.3.5 Bent Material

The straightening of plates, angles, and other shapes shall be done by methods not likely to produce fractures or other injury. The metal shall not be heated. Following the straightening of a bend or buckle, the surface shall be carefully inspected for evidence of fracture. Sharpkinks and bends may be cause for the rejection of the material.

408.3.6 Alignment

Before beginning the field riveting, the structural steel shall be adjusted to correct grade and alignment and elevation of panel points (end of floor beams) properly regulated. For truss spans a slight excess camber will be permitted while the bottom chords are being riveted.

408.3.7 Field Riveting

Pneumatic hammers shall be used for field riveting. Cup-faced dollies, fitting the head closely, shall be used to insure good bearing. Connections shall be secured and accurately fitted up before the rivets are driven. Drifting shall be only such as to draw the parts into position and not sufficient to enlarge the holes or distort the metal. Unfair holes shall be reamed or drilled. Rivets shall be heated uniformly to light cherry-red color and shall be driven while hot. They shall not be overheated or burned. Rivet heads shall be full and symmetrical, concentric with the shank, and shall have full bearing all around. They shall not be smaller than the heads of the shop rivets. Rivets shall be tight and shall grip the connected parts securely together. Caulking or recupping will not be permitted. In removing rivets, the surrounding metal shall not be injured, and if necessary they shall be drilled out.

408.3.8 Bolted Connections

In bolted connections, the nut shall be drawn up tight and set by center punching the threads of the bolt at the face of the nut.

408.3.9 Pin Connections

Pilot and driving nuts shall be used in driving pins. Pins shall be so driven that the members will take full bearing on them. Pin nuts shall be screwed up tight and threads burred at the face of the nut with a center punch.

408.3.10 Misfits and Shop Errors

The connection of minor misfits involving non-harmful amounts of reaming, cutting and chipping will be considered a legitimate part of the erection. However, any error in the shop fabrication or deformation resulting from handling and transportation which prevents the proper assembling and fitting up of parts by the moderate use of drift pins or a moderate amount of reaming and slight chipping and cutting shall be reported immediately to the Engineer, and his approval of the method of correction obtained. If the Contract provides for completed fabrication and erection, the Contractor shall be responsible for all misfits, errors and injuries and shall make the necessary correction and replacements. If the Contract is for erection only, the inspector, with the cooperation of the Contractor shall keep a correct record of labor and materials and be used in correction of misfits, errors and injuries, not due to actions of the Contractor, and the Contractor shall render within 30 days of itemized bill for the approval of the Engineer.

408.3.11 Placing Anchor Bolts

Anchor bolts shall be placed as provided under Item 407, Concrete Structures or as shown on the Plans.

408.3.12 Setting Shoes and Bearing

Shoes and bearing plates shall not be placed on bridge seat bearing areas that are improperly finished or that are deformed or irregular. They shall be set level in exact position and elevation and shall have full even bearing. Unless otherwise specified, the shoes and bearing plates shall be set by the following methods:

a. The bridge seat bearing area shall be heavily coated with lead paint and then covered with three layers of 340.2 to 369.8 g (12 to 14 ounces) duck, each layer being coated thoroughly on its top surface with red-lead paint. The shoes and bearing plates shall be placed in position while the paint is plastic. As an alternate to canvas and red lead 3 mm sheet lead may be used if called for on the Plans or is approved by the Engineer.

b. The shoes and bearing plates shall be properly supported and fixed with grout. No lead shall be placed upon them until the grout has set for at least 96 hours, adequate provision being made to keep the grout well moistened during this period. The grout shall consist of one part Portland Cement to one part fine-grained sand.

The location of the anchor bolts in relation to the slotted holes in the expansion shoes correspond to the temperature at the time of erection. The nuts on the anchor bolts at the expansion end of spans shall be adjusted to permit the free movement of span. Anchor bolt nuts shall be set by center punching the threads of the bolts at the face of the nut.

408.3.13 Painting

Unless otherwise specified, metal work shall be given two shop coats of red lead paint and two field coats of paint as specified under Item 411, Paint.

408.3.14 Placing Concrete

On steel spans, the concrete floor shall not be placed until the span has been swung or released from the falsework.

The concrete shall be placed symmetrically on the span beginning at the center and working simultaneously towards each end or beginning at the ends and working simultaneously towards the center. In either case, the concrete shall be placed continuously between construction joints designated on the Plans or approved in writing by the Engineer.

Concrete shall be cured specified under Item 407, Concrete Structures.

408.3.15 Timber Floors

Timber floors of the species and grade indicated on the plans shall be built as specified under Timber Structures, Item 402.

408.3.16 Field Inspection

All materials and work of erection shall be subject to the inspection of the Engineer, who shall be given all facilities required.

Materials and workmanship not previously inspected will not inspected after its delivery to the site of the work. Any materials inspected and accepted prior to delivery on the work shall be subject to rejection if found defective after delivery.

408.4 Method of Measurement

The quantity of structural steel and other Contract Pay Items which constitute the completed and accepted structure shall be measured for payment in the manner prescribed in the several items involved.

408.5 Basis of Payment

The quantities, measured as prescribed above, shall be paid for at the contract until price for the several Pay Items which price and payments shall be full compensation for furnishing, preparing, fabricating, transporting, placing and erecting all structural steel and all other materials for the complete structure; for all shop work, painting and field work; for all labor, equipment, tools and incidentals necessary to complete the item. Such payment shall constitute full payment for the completed structure ready for use, and no allowance shall be made for cofferdam construction, falsework, or other erection expenses as provided under Subsection 408.3.10