The Table of Contents for this section is available.
The work covered by this section consists of the fabrication, furnishing, and shipping of various types of highway signs in accordance with the requirements of the plans and the provisions of these specifications.
The provisions of Section 900 will be applicable to all work covered by this section.
All materials shall meet the requirements of Division 10 shown below:
Signs and hardware Article 1092-1
Button-type demountable copy Article 1092-3
Retroreflective sheeting Article 1092-2
(A) Welding:
All welding in the fabrication of the signs shall be done by AWS certified welders. The Contractor shall furnish a copy of AWS certification for each welding operator used for fabrication. All welds shall be free of cracks, blow holes, slag, and other irregularities and shall be wire brushed, sand blasted, or otherwise cleaned. No field welding will be permitted.
The welding of aluminum components, including structural details, shielding gases, preparation, weld quality, inspection and correction of welds, and the qualification of welding procedures and welders shall be governed by the current edition of AWS Specification D1.2, "Structural Welding Code--Aluminum", and as described in the Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals, AASHTO.
The welding of studs to aluminum sheets shall be done by the capacitor discharge method. If the manufacturer of the stud welding equipment, or studs to be used, recommends the use of an inert gas shielding atmosphere around the stud at the time of weld, it shall be a requirement. If the studs are welded after the retroreflective sheeting has been applied, care shall be taken to insure that burn-through does not damage the retroreflective sheeting.
The welding of steel components, including structural details, filler metal, workmanship and technique, qualification and inspection shall be governed by the applicable provisions of the current edition of AWS Specification D1.1, "Structural Welding Code--Steel", and as described in the Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals, AASHTO.
(B) Signs:
(1) Type A Signs:
Type A signs shall be fabricated from multiple aluminum sheet increments, with welded studs for attachment to the supporting frame. Aluminum sheet increments shall be 4 feet in width; except, for sign widths which are not multiples of 4 feet, a maximum of 2 panels may be cut to less than 4 feet. Aluminum sheet increments shall be mounted vertically, and shall be provided with backing strips at the vertical joints, held firmly in place, to keep the abutting sheets in proper alignment. Signs with a height of 12 feet or less, shall be fabricated without horizontal joints. One horizontal joint will be permitted for signs which are more than 12 feet in height. The joint shall be located near the mid-height of the sign. Details of this joint shall be as shown in the plans. The supporting frame and assembly shall be constructed in accordance with the details shown in the plans. All Type A signs shall be mounted on 2 or more supports. All Type A signs shall be constructed of 0.125" sheet aluminum.
When the plans require a Type A or B secondary sign to be attached to an existing sign, the secondary sign shall be attached by means of two vertical "Z" bars. When the signs are furnished by the Department, the vertical "Z" bars will also be provided by the Department. When the signs are to be furnished by the Contractor, the vertical "Z" bars shall also be furnished by the Contractor. All other mounting hardware shall be furnished by the Contractor.
Type A signs may alternately be fabricated from multiple aluminum sheet increments, with the use of very high bond acrylic foam tape capable of obtaining 140 psi tensile adhesion, for attachment to the supporting frame. When fabricated with very high bond tape, Type A signs shall be constructed of 0.080" sheet aluminum.
(2) Type B Signs:
Type B signs shall be fabricated from single sheets, with welded studs for attachment to the supporting frame. The supporting frame and assembly shall be constructed in accordance with the details shown in the plans. Type B signs shall be mounted on 2 or more supports, and shall be constructed of 0.125" sheet aluminum.
Type B signs may alternately be fabricated from single aluminum sheets, with the use of very high bond acrylic foam tape capable of obtaining 140 psi use tensile adhesion, for attachment to the supporting frame. When fabricated with very high bond tape, the Type B signs shall be constructed of 0.080" sheet aluminum.
When the plans require a Type A or B secondary sign to be attached to an existing sign, the secondary sign shall be attached by means of two vertical "Z" bars. When the signs are furnished by the Department, the vertical "Z" bars will also be provided by the Department. When the signs are to be furnished by the Contractor, the vertical "Z" bars shall also be furnished by the Contractor. All other mounting hardware shall be furnished by the Contractor.
(3) Type D, E, and F Signs:
Types D, E, and F signs shall be fabricated from single sheets, with holes for bolting to the supports. Assembly details shall be as shown in the plans. All Type D, E, and F signs shall be constructed of the thickness shown in Table 901-1.
Types E and F signs shall conform to FHWA standard designs or those of the NC Supplement to the MUTCD. Full-scale drawings of Types E and F signs are available from the Department's Traffic Engineering Branch.
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(4) Types E and F Sign Assemblies:
The retroreflective sheeting shall be applied to the separate signs in all Types E and F sign assemblies consecutively to provide correct color matching on each completed assembly. Each individual sign shall be adequately identified to the correct assembly. Following the erection of Types E and F sign assemblies, the Contractor shall leave the identification markings on the individual signs until Department personnel have verified compliance with these requirements.
(5) Milemarkers:
Milemarkers shall be manufactured from 0.080" aluminum sheeting as shown in the plans.
(6) Overlays for Existing Signs:
All overlays for existing signs shall be manufactured from 0.063" aluminum sheeting, unless otherwise required by the plans. Holes for rivets shall not be made in the overlays during fabrication, but shall be field-drilled during the erection process.
(C) Preparation of Aluminum Sign Surfaces:
All fabricating, including cutting, welding, riveting, and punching of holes, other than mounting holes, for demountable letters, numerals, symbols, and borders, shall be completed prior to surface preparation. However, it will be acceptable to weld studs to the aluminum sheet after application of retroreflective sheeting.
Prior to application of retroreflective sheeting to the aluminum, the aluminum sign surfaces shall be treated in strict accordance with one of the processes described below. All signs for the entire project shall be prepared by the same process.
1. Cleaning and Etching:
Preliminary Cleaning
A complete immersion in an 8 percent solution of inhibited alkaline cleaner at 160 degrees to 180 degrees Fahrenheit (71-82 degrees Celsius) for 6 minutes, followed by a cold water rinse.
Etching
The metal shall be given, at the option of the Contractor, either an acid etch or an alkaline etch. The etching shall provide a clean, matte, non-shine or non-glare finish on both sides, suitable for the application of retroreflective sheeting.
For acid etch, the metal shall be cleaned, given a surface etch by complete immersion for a period of not less than 16 minutes in an 18 to 20 percent diluted phosphoric acid solution, and followed by spraying with a cold water rinse, and then immersed for one minute in circulating hot water at not less than 180 degrees Fahrenheit (82 degrees Celsius).
For alkaline etch, the metal shall be cleaned, and then given a surface etch by immersion in an alkaline etching material that is controlled by titration. The immersion period, temperature, and concentration of the etching solution are to be as recommended by the solution manufacturer. After immersion, the metal is to be thoroughly rinsed, followed by removal of all smut with an acidic chromium compound type solution, as recommended by the manufacturer of the etching solution, and then given a second thorough rinse.
2. Chromate Conversion Coating:
In lieu of cleaning and etching, the aluminum sheet may be treated with a chromate conversion coating so that the metal will be suitable for the direct application of retroreflective sheeting.
No metal shall be handled, except by appropriate handling devices or by workmen wearing clean gloves, between the beginning of the cleaning operations and the completion of the application of the paint or retroreflective sheeting. Aluminum sign surfaces which come into contact with grease, oils, or other contaminants prior to the application of retroreflective sheeting shall be retreated.
(D) Retroreflective Sheeting:
Retroreflective sheeting shall be applied to the aluminum sign panels in accordance with the retroreflective sheeting manufacturer's recommendations. The types and colors of the retroreflective sheeting shall be as shown in the plans.
(E) Reflectorized Letters, Numerals, Symbols, Border and Shields:
(1) General:
Reflectorized letters, numerals, borders, shields and arrows shall be either direct-applied retroreflective sheeting type, or demountable button-type, or demountable retroreflective-sheeting-type, as indicated in the plans.
Design of letters and numerals shall conform to the requirements of "Standard Alphabets for Highway Signs", 1977 edition, prepared by the Federal Highway Administration. Border widths, and design of route shields and arrows, shall conform to the requirements of the MUTCD. Route shields, when part of Type A or B signs or overlays, shall have retroreflective sheeting background, and shall be demountable.
Spacing and size of all legends and borders shall be as shown in the plans, or in approved shop drawings. Any loose, deformed or misplaced legends and borders shall be cause for rejection of the entire sign.
(2) Direct Applied:
Direct-applied reflectorized letters, numerals, arrows, and borders shall be of type and color of retroreflective sheeting shown in the plans for each sign.
(3) Demountable:
Demountable letters, numerals, borders, shields, arrows, and alphabet accessories shall be attached directly to sign faces with rivets, and shall be of the type and color shown in the plans.
(a) Button-Type:
Reflectorized demountable button-type letters, numerals, arrows, and borders shall consist of embossed aluminum frames, in which prismatic reflectors are securely affixed to prevent their displacement in handling or service. Letters in which button reflectors are assembled by means of tape are unacceptable.
(b) Demountable Retroreflective Sheeting Type:
The letters, numerals, arrows, borders and shields shall be of adhesive-coated retroreflective sheeting, permanently adhered to a flat aluminum backing, of the sheeting type and colors shown in the plans.
The aluminum backing shall be a minimum of .032" thick aluminum sheet of 3004H38, 5052H38 or 6061T6 alloy. The aluminum shall be properly degreased and etched, or treated with a light, tight, amorphous chromate-type coating in accordance with the recommendations of the retroreflective sheeting manufacturer. The retroreflective sheeting shall be applied to the properly prepared aluminum in a manner prescribed by the sheeting manufacturer, and with the equipment prescribed by the sheeting manufacturer.
Each letter, numeral, arrow, border, and shield shall be supplied with mounting holes, and shall be secured to the sign surface with non-twist corrosion resistant aluminum rivets. Letters, numerals, arrows, and borders shall have rivets on all sides and ends spaced not more than 6" on centers, measured along the edges. Each legend piece shall have at least 1 rivet in each corner and at least 2 rivets in each end. Route shields as part of Type A or B signs shall be attached with aluminum rivets, spaced a maximum of 9 inches apart, measured along the edges of the shield(s).
(F) Silk Screening:
All legends and borders on Types E & F signs shall be applied by silk- screening, or reverse silk-screening after the sheeting is attached to the panels, unless otherwise permitted by the Engineer. All screening shall be performed as recommended by the manufacturer of the retroreflective sheeting. The color of all legends, borders, and backgrounds, and their placement on the sign, shall be as shown in the plans or full-scale drawings available from the Department's Traffic Engineering Branch.
Opaque black paint or ink, for nonreflectorized message application, shall be as manufactured or recommended by the manufacturer of the retroreflective sheeting.
Transparent paint or ink, and thinner, for application on signs reflectorized with white retroreflective sheeting, shall be as manufactured or recommended by the manufacturer of the retroreflective sheeting. Colors shall conform to the FHWA Color Tolerance Charts and AASHTO Designation M268 when thoroughly dry.
(G) Supporting Frames:
Supporting frames for Types A and B signs shall consist of 2 or more horizontal aluminum "Z"-section stringers with vertical aluminum bar stiffeners in accordance with the details and dimensions shown in the plans. Stringers shall be provided with necessary holes and slots for bolting stiffeners, attaching aluminum sheet increments, and mounting to supports. Field drilling of holes in any part of the structural assembly will not be permitted, except the field drilling of Z-bars for attaching new signs to existing supports will be allowed when necessary.
(H) Packaging and Shipping:
All signs shall be protected during shipment and storage. Before shipping, all signs shall be free of moisture, and all paints and inks shall be thoroughly dry. Adhesive tapes shall not be applied to any sign surface. All packaged signs shall be kept entirely dry.
All assembled or partially assembled signs other than flat sheet signs, shall have sufficient braces securely attached to prevent buckling or warping at all times.
A label outlining the retroreflective sheeting manufacturer's recommendations for handling, transporting, and storing all types of signs shall be affixed to each shipping carton or crate. Full details of such recommendations shall be provided with each shipment of signs.
Standard designs for Types A, B, D, E, and F ground mounted signs are shown in the plans. In lieu of the standard design, the Contractor may submit for approval an alternate design for sign panels differing in component parts and construction details from those shown in the plans. The alternate design shall be in accordance with the "Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals", published by AASHTO.
Complete details of the alternate sign designs shall be submitted to the Engineer for approval. These details shall include the dimensions, thickness, and alloys of the component parts, and typical shop drawings of all fabrication, erection, and construction details.
Alternate design for supports and footings will not be permitted.
The quantity of sign fabrication to be paid for will be the actual number of square feet of sign face areas of each type, including milemarkers and overlays, which have been acceptably fabricated. In measuring this quantity, the sign face areas will be calculated to the nearest 1/100 of a square foot, using the dimensions shown in the plans.
The areas of odd-shaped signs (e.g. stop signs and shield-shaped route markers) will be calculated as squares or rectangles using the dimensions shown in the plans. The areas of round, diamond, and triangular signs will be calculated for their true shapes using plan dimensions.
The quantities of sign fabrication, measured as provided in Article 9015, will be paid for at the contract unit price per square foot for "Type _________ Signs, Fabrication", "Milemarkers, Fabrication", "Overlays for Type A & B Signs, Fabrication", or "Overlays for Type C Signs, Fabrication". Such prices and payments will be full compensation for all work covered by this section including but not limited to fabricating all sign faces including supporting frames and hardware, packaging the sign faces for shipment.
No separate payment will be made for the vertical "Z" bars required for erecting secondary signs above or below Type A or B signs, as such work will be considered part of the fabrication of those signs.
Payment will be made under:
Type ______ Signs, Fabrication Square Foot
Milemarkers, Fabrication Square Foot
Overlays For Type _____ Signs, Fabrication Square Foot