Minneapolis Public Schools



SECTION 05 51 00METAL STAIRS- GENERALSUMMARYA. This Section includes Specifications for steel stairs with poured-in-place concrete pan treads and landings; structural steel stair framing and supports; steel pan landings to receive concrete fill; and specifies engineering design of fabricated stairs and components.SYSTEM DESCRIPTIONDesign and fabricate stair system from steel or aluminum to support a uniform live load of 100 pounds per square foot (lb/sq ft) and a concentrated load of 300 pounds (lb.) Deflection of treads, stringers or landing framing shall not exceed 1/360 of span under design live loading.Stair systems shall include stairs, landings, handrails, guardrails, nosings, floor edge channels or angle, and all supports and anchors to adjacent construction. Handrails as indicated on Drawings. Where handrails are attached to walls, include metal backing within walls.Design, fabricate, and test railing assemblies in accordance with the most stringent requirements of ASTM E985 and applicable local code.Design details indicated may be modified by the fabricator subject to the specified requirements.Fabricate metal stairs to comply with NAAMM AMP 510, Class: Architectural.Floor construction, as indicated on the Contract Drawings, includes bearing capacity to support steel stairs and design live loading, except for slab edge supports which are to be provided under the work of this Section. Stair system shall accommodate the surrounding construction indicated. All modifications to structure as required to support or otherwise accommodate the design/build stairs shall be the responsibility of the Contractor. Changes in dimension or location of finish surfaces indicated are subject to prior approval by Resident Engineer.Railing Reactions:Railing attachments shall be capable of resisting a force of 200 lbs at all points in any direction without damage or permanent set.Railing attachments shall be capable of resisting a force of 50 lbs per lineal foot in any direction without damage or permanent set.Interior stair treads, nosings, and landing surfaces shall be concrete-filled steel pans or shop-cast concrete treads as indicated and detailed on Contract Drawings. Risers shall have closed design as detailed. Exterior treads and landings shall be concrete as detailed or indicated on Contract DrawingsRegulatory Requirements:Pre-engineered Metal Stairs shall meet the requirements of the Minnesota Building Code for service stairs.Furnish all calculations, engineer's stamps, drawings, and other items required by the code authorities to obtain approval of the installation.SUBMITTALSProcedures: Section 01 33 00, Submittal.Shop Drawings: Indicate profiles, sizes, connection attachments, reinforcing, anchorage, size and type of fasteners, and accessories.Indicate welded connections using standard AWS A2.4 welding symbols. Indicate net weld lengths.Shop drawings for bidder-designed elements shall include stamp or seal of a Professional Engineer registered in the State of Minnesota on each sheet of the shop drawings.Delegated Design Data:Certifications:Welders and welding procedures: Submit certifications as required.Closeout Submittal:Submit certification by the registered Professional Engineer responsible for this work that all products and all installations for bidder-engineered metal stair items comply with all design requirements.QUALITY ASSURANCEStructural Designer Qualifications: Professional Structural Engineer experienced in design of this work and licensed in the State of Minnesota, or personnel under direct supervision of such an engineer.See Section 05 xx xx Metals for requirements for welders, welding procedures, and inspections.Testing and Inspection: All metal fabrications are subject to special inspection as specified in Section 01 xx xx General Requirements.Regulatory Requirements:Design structural elements to meet all requirements of the Minnesota Building Code.Furnish all calculations, engineer's stamps, drawings, and other items required by the code authorities to obtain approval of installations.- PRODUCTSMANUFACTURERSMetal Stair and Stair Tower Fabricators:The Sharon Companies Ltd. (Medina OH; 330-723-3225).American Stair Corporation (Romeoville, IL; 800-872-7824).O’Keeffe’s, Inc. (San Francisco, CA; 415-822-4222).Substitutions: See Section 01 60 00, Product Requirements.DESIGN-BUILD METAL STAIRS - GENERALMetal Stairs: Provide stairs of the design specified, complete with landing platforms, vertical and horizontal supports, railings, and guards, fabricated accurately for anchorage to each other and to building structure.1. Regulatory Requirements: Provide stairs complying with the most stringent requirements of local, State, and federal regulations; where requirements of the contract documents exceed those of regulations, comply with the Contract Documents.Structural Design: Provide complete stair assemblies complying with the following:Stair Capacity: Uniform live load of 100 lb/sq ft and a concentrated load of 300 lb with deflection of stringer or landing framing not to exceed 1/360 of span for live loads.Seismic importance factor for stairs is 1.25.Dimensions: As indicated on Contract Drawings.Shop-assemble components; disassemble into largest practical sections suitable for transport and access to site.No sharp or rough areas on exposed travel surfaces and surfaces accessible to touch.Separate dissimilar metals using paint or permanent tape.Metal Jointing and Finish Quality Levels:Architectural: All joints as inconspicuous as possible, whether welded or mechanical.Welded Joints: Continuously welded and ground smooth and flush.Mechanical Joints: Butted tight, flush, and hairline; concealed fastenings only.Exposed Edges and Corners: Eased to small uniform radius.Metal Surfaces to be Painted: Sanded or ground smooth, suitable for highest quality gloss finish.Service: Exposed joints tight with face surfaces aligned; underside of stair not covered by soffit is not considered exposed to view.Welded Joints: Welded on back side wherever possible.Welds Exposed to View: Ground smooth; not required to be flush.Bolts Exposed to View: Countersunk flat or oval head bolts; no exposed nuts or screw threads.Metal Surfaces to be Painted: Sanded smooth, suitable for satin or matte finish.Fasteners: Same material or compatible with materials being fastened; type consistent with design and specified quality level.Anchors and Related Components: Same material and finish as item to be anchored, except where specifically indicated otherwise; provide all anchors and fasteners required.METAL STAIRS WITH CONCRETE PAN TREADSJointing and Finish Quality Level: Architectural, as defined above.Risers: Closed.Metal Pan Treads: Metal pan with field-installed concrete fill.Concrete Depth: 2 inches, minimum.Tread Pan Material: Steel sheet.Tread Pan Thickness: As required by design; 14 gage, 0.075 inch minimum.Pan Anchorage to Stringers: Continuously welded, from top or bottom.Concrete Reinforcement: Welded wire mesh.Concrete Finish: Steel-troweled.Risers: Same material and thickness as tread pans.Riser/Nosing Profile: Sloped riser with rounded nosing of minimum radius.Nosing Depth: Not more than 1-1/2 inch overhang.Nosing Return: Flush with top of concrete fill, not more than 1/2 inch wide.Stringers: Hot-Rolled steel channels or plates.Stringer Depth: As indicated on Contract Drawings but not less than 12 inches.End Closure: Sheet steel of same thickness as risers welded across ends.Landings: Same metal pan construction as treads, supported and reinforced as required to achieve design load capacity.Under-Side of Stair: Where exposed to view, to be finished same as specified for other exposed to view surfaces.MATERIALSSteel Sections: ASTM A36/A36M.Steel Plates: ASTM A283.Ungalvanized Steel Sheet: ASTM A1008/A1008M, Designation SS, Grade 33, Type 1.Galvanized Steel Sheet: ASTM A653/A653M, Structural Steel (SS) Grade 33/230 with G40/Z120 coating.Gratings: Bar gratings complying with NAAMM MBG 531 or NAAMM MBG 532, whichever applies based on bar sizes.Concrete Fill: Minimum 28-day compressive strength of 3,000 psi as specified in Section 03 xx xx Concrete.Concrete Reinforcement: Mesh type as specified in Section 03 20 00, Concrete Reinforcing.Steel Bolts, Nuts, and Washers: ASTM A325 (ASTM A325M), Type 1, galvanized to ASTM A153/A153M where connecting galvanized components.Welding Materials: AWS D1.1; type required for materials being welded.SHOP FINISHINGShop finishing of ferrous metal items is specified in Section 05 xx xx Metals. No shop finishing, other than cleaning is required for aluminum PONENTSMetal Pan Stair Treads: Concrete in metal pan; 2 inches deep; smooth surface; non-slip edge.FABRICATION - GENERALFit and shop assemble components in largest practical sections, for delivery to site.Fabricate components with joints tightly fitted and secured.Continuously seal joined pieces by intermittent welds and plastic filler (bondo).Grind exposed joints flush and smooth with adjacent finish surface. Make exposed joints butt tight, flush, and hairline. Ease exposed edges to small uniform radius.Exposed Mechanical Fastenings: Flush countersunk screws or bolts; unobtrusively located; consistent with design of component, except where specifically noted otherwise.Supply components required for anchorage of fabrications. Fabricate anchors and related components of same material and finish as fabrication, except where specifically noted otherwise.Fabricate components accurately for anchorage to each other and to building structure.FABRICATION - PAN STAIRS AND LANDINGSFabricate interior stairs and landings with closed risers and treads of metal pan construction using ungalvanized steel sheet, ready to receive concrete.Fabricate exterior stairs and landings with closed risers and treads of metal pan construction using galvanized steel sheet, ready to receive concrete.Form treads and risers with minimum 18 gage sheet steel stock.Secure reinforced tread pans to stringers with clip angles; welded in place.Form stringers with hot-rolled steel channels, 12 inches deep. Weld fascia plates to channels using 14 gage steel sheet across channel toes.Form landings with minimum 18 gage sheet stock. Reinforce underside with angles to attain design load requirements.- EXECUTIONEXAMINATIONVerify that field conditions are acceptable and are ready to receive work.PREPARATIONWhen field welding is required, clean and strip primed steel items to bare metal.Supply items required to be cast into concrete and embedded in masonry with setting templates.INSTALLATIONInstall components plumb and level, accurately fitted, free from distortion or defects.Provide anchors, plates, angles, hangers, and struts required for connecting stairs to structure.Allow for erection loads, and for sufficient temporary bracing to maintain true alignment until completion of erection and installation of permanent attachments.Provide welded field joints where specifically indicated on Contract Drawings. Perform field welding in accordance with AWS D1.1.Other field joints may be either welded or bolted provided the result complies with the limitations specified for jointing quality levels.Obtain approval prior to site cutting or creating adjustments not scheduled.After erection, prime welds, abrasions, and surfaces not shop primed or galvanized, except surfaces to be in contact with concrete.ERECTION TOLERANCESMaximum Variation from Plumb: 1/4 inch per story, non-cumulative.Maximum Offset from True Alignment: 1/4 inch.END OF SECTION 05 51 00 ................
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