Tech Specs for Aluminum Gangway Ramps
1. DESIGN CRITERIA
All construction is to be in accordance with the minimum provisions of the 2009 International Building Code (IBC). Where these specifications do not state otherwise the provisions of the IBC shall apply.
Design of the aluminum gangway shall be in accordance with the Aluminum Association ‘Specifications for Aluminum Structure’. Analysis of gangway truss shall utilize Holt’s method for determining top chord buckling as outlined in ‘Guide to Stability Design Criteria for Metal Structures’, 4th Edition, by Theodore B. Galambos.
1.2 DEAD AND LIVE LOADS
Gangway deck and structural components shall be designed to support the dead load of the gangway plus Utilities and a Uniform Live Load of 100 pounds per square foot for Public/Commercial Use and 40 pounds per square foot for Private/Residential Use. Maximum deflection under these loads shall not exceed L/360.
The deck and structural components shall be designed to support a concentrated load of 400 pounds applied to any 12 inch by 12 inch area.
Lateral design Wind Load shall be IBC 85 mph, exposure ‘D’.
A Utility Load allowance of 30 pounds per lineal foot shall be included in all calculations. Or to suit project criteria.
The gangway shall have continuous “Mantle” handrails along both sides of the walking surface and shall extend a minimum of one foot beyond the primary walking surface at each end. The top [of the handrails shall not be less than 34 inches nor more than 38 inches above the walking surface. The ends shall be returned into the truss body or terminate with no sharp or catching edges.
The handrail portion of the handrails shall not be less than 1 quarter inches nor more than 2 inches in cross-sectional dimension, or the shape shall provide an equivalent gripping surface. Mantle custom extruded handrailing is required. The handgrip portion of the handrails shall have a smooth surface with no sharp corners. A minimum of 1-1/2 inches clearance shall be provided between the gangway truss and the backside of the handgrip portion.
The mounting and components of the handrails shall be capable of withstanding a load of 50 pounds per lineal foot, Lateral.
The top chord of the truss serves as the guardrail provided that it’s not less than 42 inches above the walking surface of the gangway.
Continuous full-length intermediate rails shall be provided to prevent passage of a 4-inch sphere, anywhere below the handrails, on both sides of the walking surface. Intermediate rails and supports shall be capable of withstanding a load of 25 pounds per square foot applied horizontally to the rails.
1.5 UTILITY ATTACHMENTS (IF REQUIRED)
Aluminum ‘Uni-Strut’ bar shall be welded to the floor beams on 4 foot center to center minimum. Any conduits or piping to be attached to this ‘Uni-Strut”shall be isolated from contacting aluminum framing.
1.6 TRANSITION PLATES
Full width, hinged transition plates shall be provided at both ends of the ramp. The length of both shall be long enough to provide a slope which does not exceed the maximum slope of the gangway. The leading edge of each transition plate shall be UHMW that has been profiled to create no more than a quarter inch rise. Transition plates shall have arc-sprayed “Thermion” Ceramic Core TH604 anti-skid aluminum garnet traction coating.
1.7 ROLLERS AND ROLLER GUIDE TRACKS
The gangway shall be supplied with two solid UHMW rollers or UHMW skid shoes. Rollers shall have a solid stainless axle. Rollers, axles and skid shoes shall be designed to accommodate all loads to ramps and any job specific requirements.
Roller/skid shoe tracks shall be provided ready to install to the float surface. These guide tracks shall be long enough to allow for full longitudinal movement through all water elevation changes. The guide tracks shall restrict any lateral movement of the gangway at the landing.
The hinged connection at the shore end of the gangway shall be a ‘Mantle’ swing-shackle utilizing an approiatly sized galvanized steel safety-pin anchor shackle. The shackle shall be isolated from any dissimilar metal contact with UHMW bushings and washers. This mounting arrangement shall provide a minimum of 3 axis of ramp movement. There shall not be a gap between the ramp deck and the shore mount. This shore mount shall be designed to be site specific and its design is to be included in the engineers support calculations.
Shop drawings of all components and details shall be submitted for written approval prior to any fabrication.
Sealed support calculations provided by a registered engineer experienced in the design of aluminum structures showing analysis and design review shall be submitted with the shop drawings.
Catalog cuts and loading charts shall be provided for decking information.
All structural aluminum, including tubes, plates, angles, and pipe shall be alloy 6061-T6 per ASTM B308. All bolts shall be stainless steel appropriate for use with aluminum in marine environments. Isolators shall be used when connecting dissimilar metals.
Gangway decking shall be per project specifications, or, shall be aggressively slip and skid resistant and made from aluminum or other marine grade material appropriate for this use. Samples and/or catalog cut sheets shall be provided for approval prior to fabrication. Method of securing the decking product to the ramp frame shall be described and approved prior to fabrication.
2.3 STRUCTURAL STEEL
All structural steel shall be ASTM A36, hot dipped galvanized per ASTM A123 or A153 after fabrication. All steel bolts (if used) shall be grade ASTM A-307, minimum, and also hot dip galvanized finish.
3. FABRICATION AND WORKMANSHIP
Design, fabrication, delivery, handling and installation of the aluminum gangway shall conform to the latest revisions of the aluminum construction manual and all applicable standards and data as described by the Aluminum Association. Edges shall be cut true, smooth and free from burrs. Corner edges shall be ground smooth. Weld splatters, burrs and weld flash shall be removed from all exposed surfaces. Mill stamps shall be removed if required by project specification.
Materials delivered and stored at the manufacturing facility shall be properly marked and inventoried on vertical racks located in a lockable heated warehouse.
Completed gangways shall be stored on dunnage or by other appropriate means to prevent direct contact with the ground and unnecessary damage.
Completed ramps shall bear an identification decal showing the date of manufacture, live load capacity and the identifying serial number. Every gangway ramp shall be directly traceable to the manufacturer.
Job files for every gangway ramp shall be kept, holding all information including shop drawings, submittals, material purchase orders, as-built shop drawings, material certifications for all components, shipping information and any correspondence. Also included shall be the QC report.
Gangway Manufacturer must be regularly engaged in the design and fabrication of aluminum bridge and gangway structures and shall show proof of having successfully completed a minimum of twenty similar projects within the last two years. Additionally, the manufacturer shall show proof of having liability insurance for the manufacture of these structures. All gangway design, engineering and manufacturing process shall be performed by American tradesman. No out of country design, engineering or manufacturing shall be allowed.
All connections to be welded shall be of new material, clean and free of any contaminants. All joints shall fit properly and be prepared for the appropriate weld as described in the shop drawings.
All welding shall be performed by currently certified welders, per AWS D1.2- 97′ for structural aluminum and per AWS D1.1-2000 for structural Steel. Welders proof of certification shall be provided upon request. Weld procedure qualifications shall be kept on file.
The gangway shall be installed on the floating dock and the toe end adjusted as to allow the dock system free movement to travel the full range of water levels without binding or stressing the gangway or dock system.
The gangway roller guide tracks shall be adjusted to suit the full range of lateral movement of the rollers and shall be adequately secured to the dock surface as per the gangway manufacturer recommendations.
The gangway shore mount shall be installed as per the project specifications or as per the ramp manufacturer recommendations.