BRIDGE REPAIR/REHABILITATION FEASIBILITY STUDY

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accordance with the NFPA Life Safety Code. This can be accomplished with the introduction of additional horizontal timber railing members or stainless steel cables located in between the timber rail elements. Functionality and Safety: The addition of horizontal timber railing members or intermediate cable rails between the horizontal timber rails proposed under the Rehabilitation Scope would increase the safety for pedestrians. Load Capacity: The bridge railings are not considered to contribute to the load carrying capacity of the bridge. As such, there is no reduction in load carrying capacity due to the condition of this element. Maintenance: Replacing the timber railings now would reduce maintenance in the short-term by reducing the need to make periodic repairs to the deteriorating railing members or to reapply inplace preservative treatments. Visual Impacts: Replacing the timber railings in-kind would not introduce a visual impact. The addition of horizontal railing members or intermediate cable rails between the horizontal rail elements is not anticipated to introduce a significant visual impact. 4.2.6 Deck Joints: NBIS Condition Rating: 4 (Poor) Condition Description: The timber deck joints between the bascule leaf and approach spans are currently a concern due to the tight contact between these elements that cause the bascule leaf to periodically become stuck during bridge operation and/or to not seat properly and thus create a discontinuity (typically as much as ½”) in the roadway and sidewalk surfaces. The magnitude of this tight fit varies based on the ambient temperature and moisture content of the deck. It is also possible that the substructure and timber piles are slowly shifting slightly toward the channel as vehicles decelerate and brake while on the bridge, as often found on movable bridges, although this cannot be confirmed. Repair Scope: It is recommended that a wider joint opening be provided between the tip of the bascule leaf and approach span if the timber wearing surface and structural deck are replaced. Rehabilitation Scope: The Rehabilitation Scope would be the same as that above for the Repair Scope (i.e. no upgrades are required to meet current design standards.) The hinged flap in the deck that provides clearance during operation of the bascule span may need to be modified if the location of the pivot is shifted to improve the navigation opening. The length of the flap may need to be increased if the opening angle is increased. A larger flap will likely be heavier and may require a longer lever arm for the operator to lift the flap. Repair/Rehab. Feasibility Study March 10, 2011 Bridge No. C-07-001 (437) 21 Final Report
Functionality and Safety: Eliminating the tight fit of the deck will improve the reliability of the bridge operation and correct the discontinuity in the deck surface, which will improve the smoothness of the ride and safety for motorists. Load Capacity: The bridge joints do not contribute to the load carrying capacity of the bridge. As such, there is no reduction in load carrying capacity due to the condition of this element. Maintenance: Eliminating the tight fit will reduce maintenance by eliminating the need for maintenance personnel to periodically visit the site to address the stuck bridge. It will also increase the service life of the operating equipment, by reducing the load on the equipment. Visual Impacts: Small adjustments in the deck joints to eliminate the tight fit are not anticipated to introduce a visual impact. 4.3 Superstructure 4.3.1 Stringers NBIS Condition Rating: 6 (Satisfactory) Condition Description: The timber stringers are typically sound with no apparent significant decay, although a number of stringers contain splits and checks in varying severity (up to 1/8” in width with varying lengths.) The splits and checks in several isolated stringers are larger and up to 5/16” in width. The larger splits and checks are of a depth that permits fungal spores to access the center of the stringers, where there are no preservatives, which increases the risk for decay. Much of the preservatives have leeched from the surfaces of the stringers increasing the risk of surface decay as well. In general, the timber wearing surface and structural deck minimizes the amount of moisture that accesses the sides and bottom surface of the timber stringers. However, moisture that leaks through the joints between the timber wearing surface and structural deck is likely retained on the top of the stringers, which promotes fungal decay, especially if there are checks and splits in the top surface. With the structural deck bearing directly on top of the stringers, the top surface of the stringers is not accessible for visual inspection, and thus the condition of these surfaces cannot be verified. There is minor impact damage to the underside of the stringers in the bascule span. Repair/Rehab. Feasibility Study March 10, 2011 Bridge No. C-07-001 (437) 22 Final Report
Page 1 and 2: BRIDGE REPAIR/REHABILITATION FEASIB
Page 3 and 4: 1.0 EXECUTIVE SUMMARY The existing
Page 5 and 6: such there is a risk that the proje
Page 7 and 8: 3.0 BRIDGE DESCRIPTION Bridge Numbe
Page 9 and 10: Photo 2 - Present Mitchell River Br
Page 11 and 12: 4.0 ELEMENT CONDITION & REHABILITAT
Page 13 and 14: Based on the 1997 load rating analy
Page 15 and 16: promotes growth in the number and s
Page 17 and 18: 4.2.2 Deck NBIS Condition Rating: 5
Page 19 and 20: Rehabilitation Scope: In order to m
Page 21: 4.2.5 Railings NBIS Condition Ratin
Page 25 and 26: Although in-place preservative trea
Page 27 and 28: The bascule span timber stringers c
Page 29 and 30: Repair Scope: Although the timber m
Page 31 and 32: Use of an all steel counterweight w
Page 33 and 34: additional force effects, the speci
Page 35 and 36: typically loose. The steel guardrai
Page 37 and 38: Functionality and Safety: The cap b
Page 39 and 40: The surface decay and deterioration
Page 41 and 42: the interior of the piles where the
Page 43 and 44: Load Capacity: The current loss in
Page 45 and 46: Visual Impacts: Replacement of the
Page 47 and 48: Condition Description: There are cu
Page 49 and 50: 5.0 OTHER CONSIDERATIONS 5.1 Naviga
Page 51 and 52: SUMMARY OF TIMBER ELEMENT SERVICE L
Page 53 and 54: 5.3 Funding The project is currentl
Page 55 and 56: navigation opening. The estimated c
Page 57 and 58: • Continued replacement, repair a
Page 59 and 60: APPENDICES A. Existing Bridge Plans
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APPENDIX B Structures Field Inspect
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PAGE 3 OF 22 CITY/TOWN B.I.N. BR. D
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CITY/TOWN B.I.N. BR. DEPT. NO. 8.-S
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PAGE 2 OF 7 CITY/TOWN B.I.N. BR. DE
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APPENDIX C Load Rating Summary (199
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MAINTENANCE AND REHABILITATION OF T
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Figure 14-1. - Many covered bridges
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(discussed later in this chapter),
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Figure 14-5. - Liquid wood preserva
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wood, and other openings to the atm
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Table 14-1. - Number and size of ho
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member noting treatment information
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Figure 14-11. - Splicing and scabbi
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STRESS LAMINATING Stress laminating
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ond between separated sections, inc
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onding the old and new pile section
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GENERAL PROCEDURES FOR EPOXY REPAIR
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openings will allow epoxy to escape
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Another quality control problem is
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6. Avent, R.R. 1985. Factors affect
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Integrated Remedial Protection of W
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Figure l-Effect of fumigant applica
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Table 1- Residual MITC content in D
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of reinvasion (Forsyth and Morrell,
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might represent the best option, wh
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In: Ritter, M.A.; Duwadi, S.R.; Lee
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Present and Potential Commercial Ti
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2 U.S. DEPT. OF AGRICULTURE HANDBOO
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10 U.S. DEPT. OF AGRICULTURE HANDBO
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APPENDIX F FRP Pile Jackets
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about its hazard to human health. T
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Fig. 5. Cross section of wood pile
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(Lopez-Anido et al. 2004c). For exa
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Table 1. Cost Items for FRP Composi
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Hardcore Composites. (2000). Hardsh
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CALCULATION COVER SHEET Project Nam
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URS Corp. 260 Franklin Street Bosto
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APPENDIX I Correspondence
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BRIDGE REPAIR/REHABILITATION FEASIBILITY STUDY

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