A04_Attachment_01B_SA_Ped_Bridge_Specs.docx

BRIDGE SPECIFICATIONS

SANTA ANA PEDESTRIAN BRIDGE

Purpose and Scope These specifications are for a fully engineered clear span bridge of aluminum construction and shall be regarded as minimum standards for design and construction.

Qualified Suppliers

Each bidder is required to identify the intended bridge supplier as part of the bid submittal.

The contractor must provide the following documentation, for any proposed supplier:

Product Literature All documentation to ensure the proposed substitution will be in compliance with these specifications. This shall include:

1. Project specific design calculations

2. Project specific shop drawings

3. Splicing and erection procedures

4. Warranty information

5. Inspection and Maintenance procedures

Part 1 - Materials

1.1) Aluminum: Structural members, decking, and bolts shall be aluminum with mill finish.

1.2) Deck: Decking shall be aluminum plate and meet ADA standards.

Part 2 - Applicable Codes and Standards 2.1) Governing Codes and Standards Bridges shall be designed in accordance with the AASHTO Guide Specification for the Design of Pedestrian Bridges, 2009 edition, where applicable and unless otherwise stated in the document.

2.2) Reference Codes and Standards

· AASHTO LRFD Guide Specifications for the Design of Pedestrian Bridges, 2009

· AASHTO LRFD Bridge Design Specifications, latest edition

· AASHTO LRFD Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals, latest edition

· AASHTO Guide Specifications for LRFD Seismic Bridge Design, latest edition

· Guide to Stability Design Criteria for Metal Structures, latest edition

· Aluminum Design Manual, latest edition

Part 3 - General Design Features 3.1) Span The bridge span shall be 20 feet approximately – Bidders shall take exact measurements reflecting the existing foundations and based on their particular designs. The span shall be a straight-line dimension measured from each end of the bridge structure.

3.2) Width The bridge width shall be 8 feet. The width shall be the clear width to structural members or accoutrements to the structure as measured at deck level.

3.3) Truss Style The bridge shall be designed as a Pratt or similar truss.

3.3.1) The top of the top chord shall not be less than fifty-four inches (48”) above the deck (measured from the high point of the deck surfaces).

3.4.2) Toe plate the bridge shall be supplied with a toe plate mounted to the inside face of both trusses. The toe plate shall be welded to the truss members at a height adequate to provide no more than a two-inch (2”) gap between the bottom of the plate and the top of the deck or the top of the bottom chord, whichever is higher.

3.5) Camber The bridge shall have a vertical camber dimension at midspan equal to one hundred percent (100%) of the full dead load deflection.

3.6) Elevation Difference The bridge abutments shall be constructed to approximately the elevations of the existing foundations. Existing foundations shall be used, modified, or replaced as determined by the bridge design engineer.

Part 4 - Engineering Structural design of the bridge shall be performed by or under the direct supervision of a professional engineer licensed within the United States, and in accordance with recognized engineering practices and principles.

4.1) Design Loads In considering design and fabrication issues, this structure shall be assumed to be statically loaded. No dynamic analysis shall be required, nor shall fabrication issues typically considered for dynamically loaded structures be considered for this bridge.

4.1.1) Dead Loads The bridge structure shall be designed considering its own dead load (superstructure and original decking) only. No additional dead loading shall be considered.

4.1.2) Pedestrian Live Load

i. Main supporting members, including girders, trusses and arches shall be designed for a pedestrian live load of ninety pounds (90lbs) per square foot of bridge walkway area. The pedestrian live load shall be applied to those areas of the walkway to produce maximum stress in the member being designed. Pedestrian live loads shall NOT be reduced.

ii. Secondary members such as bridge decks and supporting floor systems, including secondary stringers, floor beams, and their connections to main supporting members shall be designed for a live load of ninety pounds (90lbs) per square foot, with no reduction allowed.

4.1.3) Vehicle Load for the bridge superstructure, floor system, and decking shall be designed for H-5 Vehicular Loading – 10,000 lb. vehicular limit:

4.1.4) Wind Load

i. Horizontal Forces The bridge shall be designed for a wind load as specified by AASHTO LRFD Guide Specifications for the Design of Pedestrian Bridges, latest edition. The wind load shall be applied horizontally at right angles to the longitudinal axis of the structure.

The wind load shall be considered both in the design of the lateral load bracing system and in the design of the truss vertical members, floor beams, and their connections.

ii. Overturning Forces, the effect of forces tending to overturn structures shall be calculated assuming that the wind direction is at right angles to the longitudinal axis of the structure. In addition, an upward force shall be applied at the windward quarter point of the transverse superstructure width. This force shall be twenty pounds (20lbs) per square foot of deck.

4.1.5) Top Chord Railing Loads The top chord, truss verticals, and floor beams shall be designed for lateral wind loads and in no case shall the load be less than fifty pounds (50lbs) per lineal foot or a two hundred pound (200lb) point load, whichever produces greater stresses, applied in any direction at any point along the top chord, or at the top of the safety system.

4.1.6) Safety Rails The safety rail system shall be designed for all infill loading of two hundred pounds (200 lbs) applied horizontally at right angles, to a one (1) square foot area at any point in the system.

4.2) Design Limitations 4.2.1) Deflection

i. Vertical Deflection The vertical deflection of the main trusses due to service pedestrian Live Load shall not exceed one three-sixtieth (1/360) of the span.

The vertical deflection of cantilever spans of the structure due to service pedestrian Live Load shall not exceed one three-sixtieth (1/360) of the cantilever arm length.

The deflection of the floor beams due to service pedestrian Live Load shall not exceed one three-sixtieth (1/360) of its span.

The deflection of the deck and stringers due to service pedestrian Live Load or Vehicle Load shall not exceed one thousandth (1/1000) of their respective spans.

The service pedestrian Live Load shall NOT be reduced for deflection checks.

ii. Horizontal Deflection The horizontal deflection of the structure due to lateral wind loads shall not exceed one three-sixtieth (1/360) of the span.

4.2.2) Vibration The fundamental frequency of the unloaded pedestrian bridge shall be no less than

3.0 Hz to avoid the first harmonic.

4.2.3) Minimum Thickness of Metal The minimum thickness of all structural members shall be three-sixteenths of an inch (3/16”) nominal.

4.2.4) Frequency Frequency analysis shall be completed to determine that the bridge frame is sufficient to avoid resonance due to frequencies likely encountered under normal use for the following load combinations and in accordance with section

Part 5 - Welding 5.1) Welding and weld procedure qualification tests shall conform to the provisions of ANSI/AWS D1.2 “Structural Welding Code, Aluminum.”

5.2) Welders Each welder shall be a properly accredited operator, and shall:

5.2.1) submit certification of satisfactorily passing AWS standard qualification tests for all positions with unlimited thickness of base metal, 5.2.2) have a minimum of six (6) months experience in welding tubular structures and 5.2.3) have demonstrated the ability to make uniform sound welds of the type required. Part 6 - Submittals 6.1) Submittal Drawings Schematic drawings and diagrams shall be submitted to the customer for their review after receipt of order. All drawings shall be signed and sealed by a Professional Engineer. A stamped electronic soft copy shall be provided.

At minimum the following criteria must be included for approval:

· All Relevant Bridge Dimensions

· Bridge Cross sections

· Sufficient Detailing

· Member Cross sections

· General Notes indicating material specifications

· Weld Details

· Detail of Bolted Splices (if applicable)

· Signature and Seal of PE licensed in accordance with this specification

· Camber Details

6.2) Structural Calculations Structural Calculations for the bridge superstructure shall be submitted by the bridge manufacturer. All calculations shall be signed and sealed by a Professional Engineer. The calculations shall include all design information necessary to determine the structural adequacy of the bridge. A stamped electronic copy shall be provided.

Part 7 - Fabrication 7.1) General Requirements 7.1.1) Drain Holes When the collection of water inside a structural tube is a possibility, either during construction or during service, the tube shall be provided with a drain hole at its lowest point to let water out.

7.1.2) Bolt Holes Unless otherwise specified, standard holes shall be used in high strength bolted connections. Oversize holes may be used in any or all plies of slip-critical connections. They shall not be used in bearing-type connections. Cut, drill, mechanically thermal cut, or punch bolt holes perpendicular to metal surfaces. Do not enlarge bolt holes by burning.

7.1.3) Bearing Holes/Slots Cut, drill, mechanically thermal cut, or punch bearing holes/slots perpendicular to steel surfaces.

Part 8 - Finishing 8.1) Aluminum Mill Finishing: All exposed member shall have aluminum mill finish.

Part 9 - Bearing Devices

9.1) Bridge bearings shall consist of a setting or slide plate placed on the abutment or grout pad. The bridge bearing plate which is welded to the bridge structure shall bear on this setting plate. One end of the bridge will be fixed by fully tightening the nuts on the anchor bolts at that end. The opposite end will have finger tight only nuts to allow movement under thermal expansion or contraction.

Part 10 - Foundations

10.1) The Contractor shall procure all necessary information about the site and soil conditions. The bridge manufacturer shall determine the number, diameter, minimum grade and finish of all anchor bolts. The anchor bolts shall be designed to resist all horizontal and uplift forces to be transferred by the superstructure to the supporting foundations. Engineering design of the bridge supporting foundations (abutment, pier, bracket and/or footings), including design of anchor bolt embedment’s, shall be the responsibility of the bridge manufacturer. The bridge manufacturer shall provide all materials for (including anchor bolts) and construction of the bridge supporting foundations. The bridge manufacturer shall install the anchor bolts in accordance with bridge bearing dimensions.

10.2) Minimum 28-day strength for the abutment concrete shall be 4,000 PSI.

10.3) Information as to bridge support reactions and anchor bolt locations will be furnished by the bridge manufacturer after receipt of order and after the bridge design is complete.

Part 11 - Delivery and Erection

11.1) Bridges shall be delivered by truck to a location nearest to the site accessible by roads. Hauling permits and freight charges are the responsibility of the manufacturer.

11.2) The bridge manufacturer will be solely responsible for the off-loading of the bridge structure on site. Necessary equipment for off-loading of the bridge structures shall be the responsibility of the bridge manufacturer.

11.3) The bridge manufacturer will be responsible for erecting the bridge on site. All equipment necessary for erection will be the responsibility of the bridge manufacturer.

11.4) The bridge manufacturer shall provide written inspection and maintenance procedures to be followed by the bridge owner.

Figure 1. Existing Bridge to be Demolished

DESIGN

BUILD

BRIDGE

SPECIFICATION

image1.jpeg