638Structural Supports for Overhead signs

638.1General Description

This item includes the materials, design requirements, fabrication, and erection of structural supports for overhead signs, including excavation, foundations, anchor bolt assemblies, backfill, redressing, and re-grassing but exclusive of signs. 638.1.01 Definitions Structural supports for overhead signs are defined generally as follows: Type Description I A SIGN BRIDGE type structure that spans the roadway with more than two horizontal chords supported by two columns, one at each end. Each column shall have at least two braced vertical members. II A CANTILEVER type structure with two or more horizontal chords supported by a single column at one end. III A BUTTERFLY type structure with two or more horizontal chords extending an equal distance in opposite directions from a single column. IV A COMBINATION (Bridge-Cantilever) type structure with more than two horizontal chords supported by two columns, only one at one end and one at an intermediate point. Each column shall have at least two braced vertical members. V A CANTILEVER type structure with a maximum of two horizontal chords supported by a single column at one end. VI A SIGN BRIDGE type structure that spans the roadway with a maximum of two horizontal chords supported by two columns, one at each end. VII A BRIDGE MOUNTED (attached to a highway bridge) structural frame. VIII A BUTTERFLY type structure with a maximum of two horizontal chords extending an equal distance in opposite directions from a single column. Type II and V structures' maximum horizontal dimension shall be 32 ft. (9.75 m). The horizontal dimension is measured from the column's centerline to the furthest point of the structure or sign. Type III and VIII structures' maximum horizontal dimension shall be 25 ft. (7.6 m). The horizontal dimension is measured from the furthest point of the structure or sign on one side to the furthest point of the structure or sign on the other side. Place the sign(s) on the structure to create a slightly unbalanced condition about the column’s centerline during wind loads. Types V, VI, and VIII structural supports shall be used with flat sheet aluminum signs. If the vertical dimension of the largest sign is 42 in. (1050 mm) or less, one horizontal chord may be used. A walkway is required only when called for on the signing plans. 1116 1116 1116 1116 1116

638.1.02 Related References

AASHTO LRFD Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals, with interims (SLTS) AASHTO LRFD Bridge Design Specifications Current edition of the Manual on Uniform Traffic control Devices for Streets and Highways (MUTCD) ASTM A 53 ASTM A 123/A 123M ASTM A 139 ASTM A 153/A 153M ASTM A 252 ASTM F 436/F 436M ASTM A 563 ASTM A 709 ASTM F 1554 ASTM F 3125 ANSI/ASME B1.1 API 5L 1117 1117 1117 1117 1117

Current issue of AASHTO Standard Specification for Transportation Materials and Methods of Sampling and Testing 638.1.03 Submittals Submit to the Engineer shop drawings and design calculations for the structural supports, anchor bolt assemblies, and foundations for review and approval. Submission should be made electronically in a portable document format (pdf) and include an index. Format all drawings to fit 11 in. x 17 in. (279 mm x 432 mm) paper. Present calculations to fit 8.5 in. x 11 in. (216 mm x 297 mm) paper. The submission shall be prepared and stamped by the Design Engineer who shall be registered as a Professional Engineer in the State of Georgia. The Engineer will distribute submitted documents to the Bridge Engineer (SLTS@dot.ga.gov) for review and provide the State Traffic Operations Engineer with a copy of the transmittal letter. For installations governed only by a permit, and not a GDOT contract, drawing and calculation submission should be made directly to the Bridge Engineer for review and approval, with a copy to the District Permit Engineer. Detail the shop drawings to permit replacement of all members and include all dimensions, construction tolerances, elevations at top and bottom of foundations, and sizes of members. The shop drawings shall include the material designations of the structure and of the hardware for attaching the sign, the lane delineation of the roadway under the structure, and the walkway. See Figure 1, Figure 2, and Figure 3. 1118 1118 1118 1118 1118

Structural supports shall be designed to the following wind speeds using a 1700 Mean Recurrence Interval (MRI) for the listed counties: • 150 mph: Bryan, Camden, Chatham, Effingham, Glynn, Liberty, McIntosh • 140 mph: Brantley, Bulloch, Charlton, Evans, Long, Screven, Tattnall, Wayne • 130 mph: Appling, Bacon, Brooks, Burke, Candler, Clay, Clinch, Decatur, Early, Echols, Emanuel, Grady, Jeff Davis, Jenkins, Lowndes, Miller, Pierce, Seminole, Thomas, Toombs, Ware • 120 mph: For all counties not listed above Structural supports shall be designed using the following criteria: • Fatigue Category 1 • Truck induced gusts included Design structural supports to use interchangeable components whenever feasible. Design Type I, IV, and VI supports for 100 percent of the design sign area shown on the plans and 100 percent of the wind pressure as calculated by the SLTS. Design bases for a minimum of four anchor bolts per column. Design Type II, III, V, and VIII supports for 100 percent of the design area shown on the plans and 150 percent of the wind pressure as calculated by the SLTS. Design bases for a minimum of 8 anchor bolts per column. Design Type VII supports for 100 percent of the design sign area shown on the plans and 100 percent of the wind pressure as calculated by the SLTS. Type VII bridge mounted structural frames may be attached to concrete barrier, parapet, or deck or steel beams. Structural Supports shall not be attached to prestressed, post-tensioned, or reinforced concrete beams unless inserts were placed in beams during fabrication or construction. Make attachments to the concrete by bolting through the concrete or using chemical anchors not in direct tension. Mechanical anchors will not be allowed. Attachments shall be flush on the traffic side of the concrete barrier, parapet, or deck. No attachments shall be welded to beams. When bolting to ASTM A 709 Grade 50W (A 709 M Grade 345 W) steel; bolts, nuts and washers shall be made from a steel that meets mechanical properties of ASTM A 325 (A 325M) and has weathering characteristics comparable and compatible to ASTM A 709 Grade 50W (A 709 M Grade 345W) steel. If the Structural Support is attached to a bridge beam, additional bracing will be required between the exterior beam and the first interior beam.

When walkways are required by the signing plans, place walkways in front of the signs and extend them at least 1 ft. (300 mm) outside of the edge of all overhead signs and at least 2 ft. (600 mm) outside of the right edge of paving, or as directed by the Engineer. Provide walkways in front of the lower front chord, and do not locate a portion higher than the lowest part of any sign. Make the walkway continuous from end to end with a railing along the front side that can be folded down flush with the walkway when not in use.

Anchor bolt assemblies shall be of the proper length, area, and perimeter to transfer loads from the base plates to the foundations. The permanent template may be used in developing anchor bolts. Anchor bolts shall be at least 1-1/2 in. (38 mm) in diameter. Anchor bolt assemblies shall consist of a permanent template at the base, anchor bolts, leveling nuts, washers, temporary template, securing nuts, and #4 (#13) reinforcing bars. The distance between the base plate and the top of the stem shall not exceed 4 in. (100 mm). Do not use grout between the base plate and the top of the stem. The anchor bolt shall project 1/4 to 1 in. (6 to 25 mm) above the securing nut. See Figure 1, Figure 2, and Figure 3. 1119 1119 1119 1119 1119

Unless otherwise required on the plans, design foundations as spread footings with a maximum factored bearing pressure of 3 KSF (140 kPa). No overstressing will be permitted. Drilled shaft foundation shall be used when called for on the plans and will require a soil investigation report that shall be included with your submittal. Drilled shafts shall not be used with Type II and V structures. Unless otherwise shown on the plans: • The top of the footing shall be at least 2 ft. (600 mm) below the finished ground surface. • The bottom of the foundation shall be placed on or below the original ground or on fill compacted to at least 95 percent of the maximum laboratory dry density according to Section 208. • The clearance between the anchor bolt assembly and the stem reinforcement shall be 2-1/2 in. (65 mm) minimum. • One foundation per structure shall have a minimum of 2 in. (50 mm) rigid, galvanized steel conduits stubbed up 6 in. (150 mm) above the stem and capped a minimum of 3 ft. (1 m) outside the footing and a minimum of 18 in. (450 mm) below the finished ground surface for connecting to the underground power source or for future use.

638.2Materials

Except for the Type VII structure, all structural members shall be tubular shapes. All materials shall meet the requirements of the applicable Specification. Do not use a material until the Office of Materials and Testing approves it. Furnish one legible, reproducible copy of certified mill test reports including chemical analysis and physical test results covering steel and aluminum.

Materials for aluminum structures shall comply the SLTS.

All components of steel structures shall be galvanized in accordance with ASTM A 123/A 123 M or ASTM A 153/A 153 M, whichever is applicable. All components galvanized in accordance with ASTM A 123/A 123 M shall be quenched immediately upon removal from the zinc bath. If the contract plans require painting of the structural supports, the structural supports shall be painted with an approved paint system after galvanization. • Structural steel, including base plates—Shall meet the requirements of the SLTS. • Steel pipe—Shall meet the requirements of ASTM A 53 Types E or S. Grade B; ASTM A 139 Grade B; ASTM A 252 Grade 2; API 5L-X42; or API 5L-X52. The hydrostatic requirements are waived. Other alloys of steel may be accepted if minimum yield strength of the material is less than or equal to 60,000 psi. • Walkway and sign connection bolts including U-bolts—Shall meet the requirements of Subsection 852.2. All other connections shall be made with high strength ASTM A 325 (A 325 M) bolts with washers and nuts meeting all the requirements of Subsection 852.2.

Anchor bolts, nuts and washers shall meet the requirements of Subsection 852.2, or ASTM F 1554 (F 1554 M), A 563 (A 563 M) and F 436 (F 436 M), except that threads shall be rolled and shall be 8 UN/8 UNR thread profile according to ANSI B1.1). Bolts shall have Class 2A threads, and nuts shall have Class 2B threads. The permanent template shall meet the requirements of ASTM A 709 Grade 36 or 50 (A 709 M Grade 250 or 345)

or shall be an approved equal. Construct temporary templates from a material rigid enough to prevent any

movement and misalignment of the anchor bolts. 11201120112011201120

Class A concrete shall comply with Section 500.

Reinforcement steel shall comply with Section 853, Grade 60 (420).

Silicone caulking sealant shall comply with Subsection 833.2.06.A.1.a.1), Type A.

Neoprene, or its approved equal, shall be approved by the Office of Materials and Testing.

Ground rods shall comply with Subsection 894.2.04.

Ground wire shall comply with Section 922.

Threadlocker adhesive shall be an anaerobic threadlocking and sealing compound approved by the Office of

Materials and Testing.

Rigid steel conduit shall be a 2 in (50 mm) rigid steel conduit meeting the requirements of Subsection 923.2.01.A.2

638.2.01 Delivery, Storage, and Handling

During shipment and handling, protect the metal components to prevent bending the components and damaging the

galvanized coating.

Handle galvanized steel components with rope slings or other methods approved by the Office of Materials

and Testing.

Do not use metal slings, chains, or hooks on galvanized surfaces.

Repair minor damage to galvanizing, as determined by the Engineer, according to Section 645. Extensive galvanizing

damage is cause for rejection.

638.3Construction Requirements

638.3.01 Personnel

General Provisions 101 through 150.

638.3.02 Equipment

General Provisions 101 through 150.

638.3.03 Preparation

Footings may be designed as spread footings with a maximum factored bearing pressure of 3 KSF (144 kPa).

Include a soil investigation and report for other footings in the submittal.

ground. Place the footings to miss present and known future underground installations. 11211121112111211121

and cap at a distance of 3 ft. (1 m) outside the foundation. Place the conduit at least 18 in. (450 mm) below

the ground level to connect to the underground power feed or for future use.

638.3.04 Fabrication

Fabrication of structural supports and anchor bolt assemblies shall be according to the approved shop drawings and

the plans. Only use fabricators of structural supports and anchor bolt assemblies that are listed on the Department’s

Qualified Products List as a qualified fabricator of structural supports and anchor bolt assemblies.

Use aluminum or steel supports for signs. Steel supports shall be galvanized after fabrication. Connections may

be welded, bolted, riveted, or fastened by other means if the connecting method ensures adequate strength and

does not distract from the aesthetics of the structure. Do not weld splice structural members.

Fabricate columns, chords, and struts from one piece of material by using one longitudinal seam weld. Bolted

splicing of truss chords may be allowed if shown on approved shop drawings. Use struts to brace all truss chords.

Provide an electrical outlet on the front horizontal chord with a cover for connecting to the power source or for

future use. Weld into the column near the base the column with the conduit in the foundation, a handhole

assembly, curved on the front to follow the contour of the column. Ensure that the handhole reinforcing frame has

a tapped hole to accommodate the grounding lug and secure a cover to the frame with at least two screws. The

column shall have a J-hook wire support welded inside near the top.

Provide brackets for mounting signs. These brackets shall be adjustable to permit mounting the sign faces at any

angle between a truly vertical position and three degrees from vertical. Obtain this three-degree angle by rotating

the top edge of the sign downward toward approaching traffic. All brackets shall be equal in length to the vertical

dimension of the signs being supported.

All welding shall be done in the shop by current GDOT certified welders. The welders will weld the steel structures

according to the latest AWS Structural Welding Code as modified by the GDOT Specifications and will weld

aluminum structures according to Subsection 638.1.02.

Fabricate components in a jig or fixture to prevent distortion during and after welding and to ensure exact

alignment at the time of erection.

Carefully check welds by visual and non-destructive inspection, by destructive testing of weld samples fabricated

during welding, or by other methods approved by the Engineer. Sufficiently test weld samples to verify the

reliability of production welding.

After fabrication, thoroughly clean and galvanize all components of steel structures, including clamps and

brackets, using the hot-dip process according to ASTM A 123/A123 M or ASTM A 153/A153 M, whichever

is applicable.

Clean and galvanize interior and exterior surfaces of hollow sections. All components galvanized according to

ASTM A 123/A 123 M shall be immediately quenched when removed from the zinc bath.

Galvanize Type VII bridge mounted structural frames except where the support is attached to weathering steel.

When attached to weathering steel, fabricate the support of ASTM A 709 Grade 50W (A 709 M Grade 345W) steel

or paint with an approved paint system to match the color of the weathering steel after galvanization. 11221122112211221122

638.3.05 Construction

During shipment and handling, protect all metal components to prevent damage to galvanized coatings.

Handle galvanized steel components with rope slings or alternate methods approved by the Office of Materials

and Testing before use. Do not use metal slings, chains, or hooks on galvanized surfaces.

Repair minor damage to galvanizing, as determined by the Engineer, according to Sections 645. Metal

components will be rejected if they have extensive damage to galvanizing.

For construction methods, see Sections 207, 500, and 511.

Chamfer the edges of the stems 3/4 in. (19 mm). Stems shall have a Type III finish to at least 6 in. (150 mm) below

the finished ground surface unless otherwise noted on the plans. The Engineer shall inspect the anchor bolt

assembly installation before the placement of concrete. Complete the anchor bolt assembly installations so as to

prevent movement during the concrete placement. Tolerance for the placement of anchor bolt assemblies shall be

3/8 in. (10 mm) horizontally and 1:20 (3 degrees) vertically. Do not remove the temporary template until the footing

and stem concrete have been in place at least 24 hours.

The Office of Materials and Testing (OMAT) shall inspect the Type II and V sign structure footings before the

column is erected. OMAT will perform a second inspection after the column is erected and will also perform

ultrasonic testing of the anchor bolts at this time. Type II and V sign structures will not be accepted until the

footing inspections have been performed and approved.

Erecting the structure shall include placing and leveling a leveling nut on each anchor bolt. Use a washer with each

leveling nut. Set the column on the washers without the horizontal structure, and place and tighten a washer and

securing nut on each anchor bolt. Tightening is turning the nut an eighth of a turn after the nut is snug tight, and

then applying the threadlocker adhesive.

After tightening, inspect the connections to ensure full bearing of the top and the bottom washers on the base

plate and to ensure that the distance between the top of the stem and the bottom of the base plate does not

exceed 4 in. (100 mm). No structure will be accepted if this dimension is greater than 4 in. (100 mm).

Attach the horizontal structure to the column with ASTM A 325 (A 325 M) bolts. Install ASTM A 325 (A 325 M) bolts

according to Subsection 501.3.04.F, High-Tensile Strength Bolt Connections. Do not reuse bolts and nuts after

tightening them.

Coat with silicone sealant all surfaces that are in contact with concrete. Separate with neoprene or an approved

equal material all surfaces that are in contact with dissimilar metals.

Install ground rods for each structural support adjacent to the foundation with the conduit as indicated below:

the finished ground.

to the grounding nut of the column.

parallel ground rods a minimum of 6 ft. (1.8 m) center-to-center in a horizontal pattern and at least 12 in. (300

mm) below the finished ground. Join these rods and connect them to the grounding nut of the column with #6

bare copper, 7-strand wire and suitable ground rod clamps. 11231123112311231123

Ensure that the finished ground surface matches the typical section adjacent to the structural support. Do

not adjust the ground surface around the stem to obtain 12 in. (300 mm) minimum projection above finished

ground surface.

638.3.06 Quality Acceptance

General Provisions 101 through 150.

638.3.07 Contractor Warranty and Maintenance

General Provisions 101 through 150.

638.4Measurement

The quantity measured for payment shall be each structure type at the specified location completed and accepted.

This shall include design, fabrication, and construction of structural supports including anchor bolt assemblies,

foundations, excavation, backfill, redressing, and re-grassing; but exclusive of signs.

638.4.01 Limits

General Provisions 101 through 150.

638.5Payment

This item, measured according to Subsection 638.4, “Measurement,” for each structural support for overhead highway

signs, is paid for at the Lump Sum Contract Unit Price bid for the complete structure.

Payment will be made under:

Item No. 638 Structural support for overhead highway sign, type I–sta.___ Per lump sum

Item No. 638 Structural support for overhead highway sign, type II–sta.___ Per lump sum

Item No. 638 Structural support for overhead highway sign, type III–sta.___ Per lump sum

Item No. 638 Structural support for overhead highway sign, type IV–sta.___ Per lump sum

Item No. 638 Structural support for overhead highway sign, type V–sta.___ Per lump sum

Item No. 638 Structural support for overhead highway sign, type VI–sta.___ Per lump sum

Item No. 638 Structural support for overhead highway sign, type VII–sta.___ Per lump sum

Item No. 638 Structural support for overhead highway sign, type VIII–sta.___ Per lump sum

638.5.01 Adjustments

General Provisions 101 through 150.. 1124 1124 1124 1124 1124