Bridge_Design_Specifications_Hotel_Creek_3-19-15_(1).pdf

DESIGN SPECIFICATIONS

Pre-Fabricated Web Truss Trail Bridge

Hotel Creek Crossing Denali National Park and Preserve

1. GENERAL

1.1 Scope

These specifications are for a fully engineered clear span bridge of Fiber Reinforced Polymer (FRP) composite construction and shall follow design guidance layout by the AASHTO Guide Specifications for the Design of FRP Pedestrian Bridges.

1.2 Qualified Suppliers

The bridge manufacturer shall have been in business of design and fabrication of bridges for a minimum of five years and provide a list of five successful bridge projects, of similar construction, each of which has been in service at least three years. List the location, bridge size, owner and contact reference for each bridge.

2. DESIGN

Web Truss will be designed to minimize traffic deck height above stringers or deck support members. Because of clearance requirements over a flowing channel, no part of the bridge structure may extend below the sill height more than 8”. Web truss needs to be incorporated into the sides above the deck and double as railings.

Multi component configuration will be used in the design to facilitate transport to remote site.

Because the installation site is limited to a narrow (<8’) wide trail, the bridge needs to be in small transportable components. Maximum weight for a single piece will be 140 lbs.

Simplified assembly designed for field assembly and installation.

Because the site is remote, the assembly of the bridge must be simply enough to be accomplished with hand tools, and installation with scaffolding (on ice capped stream), jacks, and overhead rigging

Cold Weather Suitability designed for temperature ranges from +80F to -50F. Because the site is in interior Alaska, the bridge must be able to withstand extreme temperature ranges. Bridge traffic loading will be primarily in the summer months when temperatures range from 40 to 80 degrees F. During the winter months it is possible to close the bridge to traffic as other routes (over the frozen creek) are available.

2.1 Span

The bridge span will be 80 feet (straight line dimension) and shall be measured from each end of the bridge structure.

2.2 Width

Bridge with shall have a usable deck width 60 inches, structure width not to exceed 96 inches.

2.3 Bridge System Type

Bridge must be designed as a FRP Composite Truss Span.

2.4 Member Components

All members shall be fabricated from pultruded FRP composite profiles and structural shapes as required.

2.5 Camber

Bridge can be precambered to eliminate initial dead load deflections. Cambers of 1% of the total span length can be provided on request.

3. ENGINEERING

Structural design of the bridge structure shall be performed by or under the direct supervision of a licensed Professional Engineer and done in accordance with recognized engineering and principles. All bridge design must meet the governing design specification - AASHTO Guide Specifications for Design of FRP Pedestrian Bridges 2008. P.E. stamped calculations (finite element analysis) and drawings must be submitted for approval to the client prior to fabrication.

Professional Engineer must be registered in the state of Alaska due to the extreme cold and snow issues associated with the project which are unique to Alaska.

3.1 Uniform Live Load

Bridge will be designed for 85 psf.

3.2 Equipment Load

10,000 lbs.

3.3 Wind Load

The bridge will be designed for a minimum wind load of 35 psf on the full vertical projected area of the bridge.

3.4 Seismic Load

Seismic load shall be determined according to the criteria specified in the standard building codes (IBC, ASCE, or UBC). Seismic design Site Class D for soil per IBC 2012.

3.5 Allowable Stress Design Approach

Allowable Stress Design (ASD) approach is used for the design of all structural members.

Allowable stress values shall be limited to 25% of ultimate stress values (Factor of Safety =

4.0 for all members and connections)

3.6 Serviceability Criteria

Live load deflection > L/500 Vertical frequency (fn) > 5 hz./sec.

Horizontal frequency (fn) > 3 hz./sec.

3.7 Snow Load

Snow load shall be 70 psf (sustained)

4. MATERIALS

4.1 FRP Composite

FRP bridge shall be fabricated from high-strength E-glass and isophthalic polyster resin unless otherwise specified. All fiberglass shapes used in the project must be manufactured in the U.S. Material certifications must be provided indicating this.

Weathering and ultraviolvet light protection shall be provided by addition of a veil to the laminate construction. Minimum material strengths and properties are as follows:

Tension 33,000 psi Compression 33,000 psi Shear 4,500 psi Bending 33,000 psi Young’s Modulus 2,800,000 psi The minimum thickness of the FRP Composite shapes shall be as follows unless otherwise specified: Square tube members (closed type shape) shall be 0.25 inches. Wide-flange beams, channel sections, and angles (open type shapes) shall be a minimum thickness of

0.25 inches. Standard plates shall be a minimum thickness of 0.25 inches.

4.2 Decking

Decking will be supplied by the NPS.

4.3 Hardware

Bolted connections shall be A307 hot-dipped galvanized steel unless otherwise specified.

Mounting devices shall be galvanized or stainless steel.

5. SUBMITTALS

5.1 Drawings

Schematic drawings and diagrams shall be submitted to the client for their review after receipt of order. As required, all drawings shall be signed and sealed by a licensed Professional Engineer.

5.2 Calculations

As required, structural calculations shall be submitted to the client. All calculations will be signed and sealed by a licensed Professional Engineer.

6. FABRICATION

6.1 Tolerances

All cutting and drilling fabrication to be done by experienced fiberglass workers using carbide or diamond-tipped tooling to a tolerance of 1/16”. No material deviations beyond industry standards are accepted. All cut edges to be cleaned and sealed.

7. RAILINGS

7.1 Height

Railings for the pedestrian bridge will be 54 inches.

7.2 Safety Rails

Continuous horizontal midrails shall be located on the inside of the trusses. Maximum opening between the midrails shall be available as required, but should not be greater than 9 inches.

7.3 Toeplates

Bridge toeplates are to be 3 inch green channels.

8. FINISHING

8.1 Color

Bridge color shall be olive green.

9. DELIVERY

Delivery is made by truck to a location nearest the site accessible by roads. Contractor will notify the NPS in advance of the expected time of arrival at the site. Bridge will be shipped and delivered as component parts. The greatest weight of any one piece will not exceed 140 lbs.

9.1 Provide assembly drawings and a recommended assembly procedure for building the bridge.

10. WARRANTY

10.1 Contractor shall warrant the structural integrity of all FRP materials, design and workmanship for 15 years. This warranty shall not cover defects in the bridge caused by foundation failures, abuse, misuse, overloading, accident, faulty construction or alteration, or other cause not the result of defective materials or workmanship. This warranty shall be limited to the repair or replacement of structural defects, and shall not include liability for consequential or incidental damages.

Sample Photos

Side Profile Top Profile