718.01 Description.
Complete and accepted relocated overhead roadway sign structures, measured as noted above, will be paid for at the contract lump sum price bid for each sign structure, which shall be full compensation for all work and materials, except sign panels, necessary for the removal and relocation of the sign structure (panel, lights, walkway, and supports) complete in place on its supports at the designated locations, for the cleaning of the panels, for furnishing all hardware or other material necessary for the reinstallation of the sign structure, for the satisfactory removal of the existing footings, if necessary, including the excavation and backfill of the areas (old area and new area of the installation), disposal of excess materials, for new foundations for supports, for inspection and testing of welds, and for all other materials, equipment, tools, labor, and incidentals necessary to complete this item of work.
b.Payment will be made under Item No .: 717-A Overhead Roadway Sign Structure No. _____ Renova tion - per lump sum 717-B Overhead Roadway Sign Structure No. _____ Relocation - per lump sum STRUCTURES FOR TRAFFIC CONTROL DEVICES AND HIGHWAY LIGHTING
718.01 Description.
This Section shall cover the design, fabrication, and construction of overhead roadway sign, luminaire, traffic signal, and traffic surveillance support structures. All designs and details shall be approved before actual fabrication of a structure is started. Within 30 days after the award of the contract, the Contractor shall notify the Project Manager by letter of the names, addresses and telephone numbers of all structural fabricators along with the fabricator's proposed fabrication schedule. The notification shall be furnished for all structural fabricators that are subcontractors to a structural fabricator.
718.02 Materials.
a.General . Materials shall comply in general with the requirements given in the applicable Sections of Division 800, M ATERIALS. Particular structural material and fabrication requirements are given in Section 891, STRUCTURAL MATERIALS FOR TRAFFIC CONTROL DEVICES AND HIGHWAY LIGHTING. Materials shall also comply with requirements that may be given on the Plans. Concrete for foundations shall comply with the requirements of Section 501 for Class A concrete concrete. Reinforcing steel shall meet the requirements of Section 502, Steel Reinforcement, and shall be Grade 60 {400} billet steel.
b.Overhead Roadway Sig n Structures . Overhead sign structures shall be constructed of steel only.
c.Traffic Signal Poles . Unless otherwise shown on the plans, traffic signal poles shall be steel poles.
d.Luminaire and Traffic Surveillance Poles . Unless otherwise shown on the plans, luminaire and surveillance poles may be constructed of steel, concrete, glass fiber reinforced polymer (GFRP), or aluminum.
718.03 Design.
a.General .
1.Design Data. The details of pole foundations for Traffic Signals (Section 730) and Roadway Lighting (Section 750) are shown on the plans. When details of a structure or foundation are not shown on the Plans, or if the Contractor proposes alternate structure or foundation details, the Contractor shall submit complete designs and details.
718.03 Design.
Geotec hnical borings may be shown on the plans. These borings may not be representative of the actual conditions encountered throughout the project. The Contractor shall be responsible for any assumptions made from these borings. The Contractor shall obtain any additional geotechnical data that is necessary for determining the actual subsurface conditions.
2.Design Requirements. All structures shall be designed in accordance with the requirements given in the AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals, 2009 Edition , and the requirements given in this Section. Fatigue importance factors shall be as follows: STRUCTURE FATIGUE IMPORTANCE FACTOR CATEGORY Strain Poles No Fatigue Mast Arm Poles / Lighting Poles less than 45 ft. in height Category II with 25 year service life High Mast Poles / Sign Structures / Overhead Sign Bridges / Lighting Poles 45 ft. or greater in height Category I Wind pressures shall be calculated in accordance with “Appendix C: Alternate Method for Wind Pressures”. Minimum design wind speed shall be 100 miles per hour {165 km/hr} for Mobile and Baldwin Counties and 80 miles per hour {130 km/hr} elsewhere in the State. The Combined Stress Ratio (CSR), shall be less th an or equal to 0.9, for all load cases.
3.Foundations. Foundations shall be located to avoid damaging existing underground installations and avoid conflicting with known future installations such as pipes, conduits, guardrail posts, lighting standards, etc. The design shall be sufficient to provide a minimum factor of safety of 2.0 against overturning and torsion induced displacement.
b.Submittal of Designs and Details . Details shall be submitted on six sets of prints of drawings including f oundation details for sign structures when required. Each sheet shall be stamped and signed with the original signature of a Professional Engineer licensed in the State of Alabama, and not employed by the State of Alabama. The details shall include fabrica tion requirements such as the welding requirements for sign frames and tensioning and detensioning procedures for prestressed concrete poles. Design computations shall be submitted in duplicate. Each set of design computations shall be prepared, stamped a nd signed by a Professional Engineer registered in the State of Alabama, and not employed by the State of Alabama. The design computations shall address all members, connections (welds, bolts, etc.), anchor bolts, and foundations. The designer shall note o n the design computations where the design of each member meets the design requirements and deflection tolerances. Design computations, shall include all formulas used and a copy of all calculations and/or computer printouts for each structure that cover a ll members, connections (welds, etc.), footings and details necessary for a complete structure design. Where computer generated designs are used, the printouts shall consist of the applied loadings, structure geometry, effective wind area and location of attachments (sign panels, signals and light fixtures), component sizes, moments, shears, reactions, component forces, component stresses, allowable component stresses, combined stress ratios, and deflections for each group loading specified in the AASHTO S ign Specifications. The method of solution used by the computer program, including all formulas used, shall be submitted. For overhead roadway sign structures only, the Contractor shall furnish one set of reproducible drawings (mylar or equal) on standard size plan sheets (22” x 34”){559 mm x 864 mm} for record and distribution purposes, after final approval.
c.Drilled Shaft Foundations . Drilled shaft foundations shall be placed only in undisturbed material or in fill made by controlled compaction. Dr illed shaft foundations for cantilever structures shall be designed to resist the torsional effects of the wind loads.
718.03 Design.
d.Concrete Spread Footings . Footings shall be placed only in undisturbed material or in fill areas constructed by controlled compaction . Footings for cantilever structures shall be designed to resist the torsional effects of the wind loads.
e.Direct Embedment of Support . Prestressed concrete poles shall be installed by direct embedment in the ground. GFRP poles may be installed by direc t embedment in the ground. The design and details of the direct embedment shall be submitted as Working Drawings for Structures. The required embedment is the responsibility of the contractor, however the minimum depth of embedment shall not be less than L/6, where L is the above ground length of the upright member or pole.
f.Pile Foundations . Pile foundations may be required in areas where the upper soil layers will not support a drilled shaft or spread footing. The foundations may be designed with steel piles or prestressed concrete piles. However, steel piles shall not be used in brackish or salt water locations in Mobile or Baldwin counties, or other locations with corrosive environments. Piles shall meet the requirements of Section 505, Piling.
g.Anchor Bolts . Foundation anchor bolts for overhead highway sign structures and high mast lighting assemblies shall be Charpy V -Notch tested in accordance with the requirement provided in Section 891. Anchor bolts shall be a minimum one inch in diamet er. Overhead sign structures with single pole uprights shall be anchored with at least eight anchor bolts in each base plate. Overhead sign structures with double pole (truss type) uprights shall be anchored with at least four anchor bolts in each base pl ate. Traffic signal poles and luminaire poles shall be anchored with at least four anchor bolts. High mast lighting assembly poles shall be anchored with at least eight anchor bolts.
h.Base Plates . All base plates shall be designed by calculating the bending moment about a line that is taken at the edge of the upright and is the shortest diagonal across the plate. The required thickness of the plate shall be based on the section modulus at the diagon al line using 60 % of the width of that line. The allowable stresses for a base plate shall be: • 90 % of the yield strength of the base plate for plates that are designed for the yield moment of the upright or; • 90 % of the allowable stresses for the Group loading for plates that are designed for the actual upright service load moment.
i.Overhead Roadway Sign Structures . All overhead sign structures shall be supported by a reinforced concrete footing. The overhead portion of the structure shall be attached to the footing by means of base plates and anchor bolts. The vertical dead load deflection of cantilever sign structures shall not exceed L/120, where "L" is the cantilever length in inches {millimeters}. The vertical support for a cantilever stru cture shall be a round uniform diameter tube which has adequate moment of inertia, without additional reinforcement, to limit the dead load deflection of the arm, including the deflection caused by bending in the vertical support, to L/120 and to a maximum angular deflection of the centerline of the upright, at the top, in relation to the centerline at its base, of 1°40'. Horizontal trusses (span type) shall be limited to a vertical dead plus ice load deflection of L/240, where "L" is the total truss lengt h center to center of supports in inches {millimeters}. A uniform camber, in accordance with the requirements of Section 9 of the AASHTO Sign Specifications , shall be provided for all horizontal portions of a structure. The use of full penetration circu mferential welds on upright poles is not allowed. Horizontal trusses of triangular cross- section are not allowed. Flange plates that are used for splicing overhead truss chords and uprights shall be designed using the requirements given for BASE PLATES. Design and basic member shape once selected shall be used throughout the project. The detail drawings shall list all ASTM or AASHTO material specifications to be used for all the structural elements. Brackets shall be provided for the mounting of the requ ired flat panel signs. These brackets shall permit mounting the sign faces at an angle of five (5) degrees from vertical except for louvered panels
718.04 Construction.
which shall be mounted vertically. This five degree angle shall be obtained by rotating the front top edge o f the sign away from the vertical position. All brackets shall be of lengths sufficient for the heights of the signs being supported. Where required by the contract plans, tubular structures shall have electrical outlets provided on a front chord member a nd shall have hand holes within twelve inches of the base of vertical supports. If necessary, in order to comply with design requirements, compensation for loss in section shall be accomplished by reinforcement. Maintenance walkways, when required by the p lans, shall be provided in front of the lower front chord. No part of the walkway shall be located so as to obstruct normal viewing of the lower portion of the sign.
j.Traffic Signal Poles . The structural analysis of a pole shall be made at the base of the pole, and at every tenth point interval up the pole. The maximum deflection of the centerline at the top of the pole in relation to the centerline at its base, due to the moment load of the signal and support bracket, shall not exceed two and one half percent of the pole height. Calculations shall be submitted to verify this deflection. At intersections involving four traffic signal poles, each pole shall be designed equally for the most severe loading condition at the intersection. The pole base desig n shall conform to the following table of standard parameters if the maximum bending moment in the pole is less than or equal to 300 kip- ft. TRAFFIC SIGNAL POLE BASE STANDARD PARAMETERS Pole Type Moment Range (kip-ft.) Bolt Circle (Diameter) (inches) Bolt Diameter (inches) Bolt Quantity Base Plate Thickness (inches) P-120 Up to 120 20 2 4 2 P-170 121 – 170 20 2 6 2 P-225 171 – 225 22 2 6 2 P-300 226 – 300 26 2 8 2 If the bending moment is greater than 300 kip- ft, the bolt circle or bolt quantity, or both, shall be different from that given in the table for the standard parameters. If the proposed difference is in the diameter of the bolt circle, the diameter shall b e a minimum of 27 inches.
k.Luminaire Poles . High mast lighting assembly poles shall be supported by a reinforced concrete footing. A luminaire pole shall be analyzed at the base of the pole, at every tenth point interval up the pole, at section changes and at the points above and below each slip joint splice. Design calculations shall be submitted to verify that the maximum allowable deflections will not be exceeded.
l.Traffic Surveillance Poles . Poles used for mounting traffic surveillance devices, o r other similar devices, shall be designed in accordance with the requirements given for luminaire poles and any additional criteria (i.e., more stringent deflection, vibration damping, etc.) provided on the contract plans.
718.04 Construction.
a.General . The overhead roadway sign structures, luminaire supports and traffic signal supports shall be constructed in accordance with the plans, specifications, foundation design calculations and approved shop drawings. All parts of a structure unit shall be assembled on the project and the Engineer shall be provided with adequate field erection details before permission will be given to erect the structure. Once the installation of structure is started, the work shall be diligently prosecuted until its com pletion.
b.Concrete Foundations . Excavation for foundations shall conform to the neat lines shown on the plans. The Contractor shall inform the Project Manager when the excavation is complete, and no concrete shall be poured until the Project Manager has approved the excavation for each individual footing. The foundations may be cast directly against earth or cast with forms. When forms are used they shall be true to line and grade and securely braced in place. Both forms and ground, which will be i n
718.04 Construction.
contact with the concrete, shall be thoroughly moistened before placing concrete. Forms shall not be removed until the concrete has thoroughly set. Tops of foundations shall be finished to the elevations shown on the plans. Ordinary surface finish sha ll be applied to the exposed surfaces of concrete. Exposed edges shall be chamfered. All concrete foundations and bases shall reach a compressive strength of 2400 psi {17 MPa} before any structures are installed thereon. All embedded items shall be instal led securely and inspected by the Project Manager before concrete is poured.
c.Direct Burial . Excavation shall be to the depth and diameter determined from the design calculations. The pole shall be placed in position and temporarily braced, prior to backfilling. The backfill material shall be limestone screenings or washed sand. The backfill shall be saturated with water to consolidate the backfill material during placement .
d.Anchor Bolts . A temporary template shall be installed approximately 6 inch es {155 mm} from the top and a permanent steel template shall be installed 6 inches {155 mm} from the bottom of anchor bolts so that the anchor bolts remain plumb after the placement of concrete. The template shall be fabricated with openings to facilitate the placement of concrete above and below the template. Care shall be taken to ensure that the anchor bolt threads are not damaged prior to installation of the support structure. Out-of-position anchor bolts and anchor bolts greater than 1:40 out -of-plumb are cause for rejection of the base. Bending of the anchor bolts to straighten or move into position will not be permitted. The number and configuration of the nuts and washers required for anchor bolts shall be in accordance with the details shown on the plans. Anchor bolts for slip bases shall have the nuts installed in accordance with the requirements given in Section 710. Anchor bolts for non slip bases shall have their top nuts tightened by the turn of the nut method as follows: • All leveling nuts (bo ttom nuts) and washers shall be brought to full bearing on the bottom of the base plate. The bottom of a leveling nut must be kept as close to the concrete base as practical, and shall not be greater than 1 inch {25 mm} away from the top of the concrete base. A leveling nut shall be adjusted on the anchor bolt so that, after the installation of all plates and nuts, there is at least a 1/4 inch {6 mm} projection of the anchor bolt above the top or lock nut (when in its final position). • Tighten all top nut s to a "snug" condition defined as the tightness that exists when the plies of the joint are in firm contact. This may be attained by a few impacts of an impact wrench or the full effort of a man using an ordinary spud wrench. • At this point, the nuts and washers above the base plate and below the base plate must be in full bearing on the base plate. If any gap exists between the nuts, washers and the base plate, a beveled washer shall be added to eliminate the gap. The beveled washer shall be stainless steel type 304, shall be the same diameter as the other washers, and shall be beveled as required to eliminate the gap between the nuts, washers and the base plate. • Using an extension on the nut wrench as required, rotate all top nuts an additional one third turn. There shall be no rotation of the leveling nut during top nut tightening. • Tightness of the nuts shall be checked in the presence of Department personnel a minimum of forty eight hours after the nuts have been rotated the additional one third turn. An y nuts found loose shall be tightened in accordance with the above procedure. • Lock nuts shall be brought to a "snug" condition as previously described.
e.Overhead Roadway Sign Structures Attention is directed to the fact that the structure design as we ll as shop drawings for the fabrication of the structure must be approved before actual fabrication of a structure is started. All parts of a structural unit shall be assembled on the project and the Engineer provided with adequate field erection details before permission will be given to erect the structure. The Contractor shall temporarily brace the structure as needed.
f.Traffic Signal Poles Strain and mast arm poles shall be installed with the proper vertical offset (or rake), as recommended by th e manufacturers so as to assure a substantially vertical set when the load is applied.
720.05 Basis of Payment.
Threaded adjusting nuts shall be used to establish the "rake" in accordance with the requirements for the installation of leveling nuts on anchor bolts. The use of shims or other leveling devices will not be permitted. Hardware and fittings shall be installed as shown on the contract plans and approved shop drawings. Messenger cable supporting traffic signal heads shall not be sagged to a vertical distance greater than fi ve percent of the length of the span between strain poles. Messenger cable supporting signal control cable only shall be sagged to a vertical distance not greater than two percent of the length of the span between strain poles. Tether cables shall not be s agged to a vertical distance greater than five percent of the length of the span between strain poles.
g.Luminaire and Traffic Surveillance Poles Extreme care shall be taken during installation of the luminaire assembly and surveillance devices to ensure that no damage occurs to these devices. Double nuts and washers shall be used to plumb the pole about its center axis if a twin bracket is used. When a single arm type is used, the back side of the pole shall be plumbed after the luminaire and sur veillance devices and hardware have been installed, thus providing a slight rake from the traveled way. SECTION 720 VEHICULAR IMPACT ATTENUATOR ASSEMBLY
720.01 Description.
This Section shall cover the work of furnishing and installing vehicular impact attenuator assemblies of the design shown in the detailed plans at the locations designated by the plans, the proposals or directed.
720.02 Materials.
Materials furnished for use in the manufacture of the assembli es shall comply with the requirements noted in the detailed plans. Materials used in the actual installation of the attenuation in the work shall comply with appropriate provisions of these specifications.
720.03 Construction Requirements.
Any installation which is to be performed under traffic shall be provided with adequate warning and protective devices until such time as the assembly becomes usable. Once work is begun, it shall be prosecuted diligently and continuously until the assembly is completely i nstalled.
720.04 Method of Measurement.
Vehicular impact attenuators of the design designated by the plans or proposal will be measured in assembly installations, complete in place at the designated locations.
720.05 Basis of Payment.
a.Unit Price Covera ge. The accepted impact attenuator assemblies, measured as noted above, will be paid for at the contract price bid for each assembly. Said unit price bid shall be full compensation for the furnishing of all materials and the installation of the designated assembly on its foundation, in its designated location, and includes furnishing of all equipment, tools, labor and other incidentals necessary to complete the work and provide an operational assembly complete in place.
b.Payment will be made under Item N o.: 720-A Vehicular Impact Attenuator Assembly ( * ) - per each * Description and Model of Attenuator Assembly
Source: Alabama Standard Specifications for Highway Construction, 2022 Edition. Pages 617–621 of 934.