BRIDGE REPAIR/REHABILITATION FEASIBILITY STUDY

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protection. The substructure over the waterway consist of pile bents with timber piles and 16x14 sawn lumber caps and 6x12 sawn lumber lateral and longitudinal timber bracing members. The bascule span provides 19’-4” of horizontal clearance between fenders and approximately 7’- 4” of vertical clearance above mean high water with the bascule leaf in the lowered position. The pivot for the bascule leaf is located on the west side of the navigation channel. The bascule leaf is approximately 23’-8” from pivot to tip and rotates to a maximum angle of approximately 75 degrees from the horizontal position in the fully raised position. With the bascule leaf in the fully raised position, the bascule leaf overhangs the west fender and provides unlimited vertical clearance for a width of approximately 15’-2” between leaf tip and east fender. The timber stringers for the bascule leaf are located in between the timber stringers of the approach spans. The bascule leaf superstructure pivots about a 1” diameter stainless steel rod that passes through 1¼” diameter stainless steel pipe sleeves with threaded flanges inserted through and secured to each of the bascule leaf and approach span timber stringers. A manually operated 1’-8” wide hinged portion of the deck (deck flap) above the pivot provides clearance between the timber stringers and deck when the bridge operates. The reconstructed bridge was originally provided with steel pins driven through guides and receivers attached to the top of the timber curb on each side of the joint between the bascule span and approach spans to secure the leaf in the lowered position. Padlocks were specified on the pins to prevent unauthorized operation. The pins have been removed, but padlocks are still used. In order to reduce the loads on the operating machinery, the bascule leaf is balanced with a counterweight hung from the underside of an extension of bascule leaf timber stringers that extends under the approach span deck a length of 9’-2” from the pivot. The counterweight consists of a galvanized steel box filled with concrete and steel ballast. The bascule span is operated by a pair of electric winches, one located in each sidewalk on the approach spans west of the bascule span. Each winch draws in and pays out 5/8” wire operating rope attached to a pulley system for additional mechanical advantage. The pulley system is attached to a 7/8” wire rope attached to the ends of a lifting beam under the bascule leaf deck near the tip ends of the leaf that deflects over a 15” diameter deflector sheave located at the top of a sheave pole. Each sheave pole consists of a 12x12 sawn lumber mast with 5/8” guy wire attached near the top of the mast and to the bridge superstructure. The wire rope, pulleys and deflector sheaves are all stainless steel. The operating equipment was specified to open or close the bascule leaf in approximately 120 seconds at a maximum pull in each 7/8” wire rope of 5,000 pounds. An electrical control cabinet is located on the northwest quadrant of the bridge. Traffic is controlled during bridge operations using electrically operated horizontally pivoting warning gates and post mounted traffic signals located along the roadway approaching the bridge. Repair/Rehab. Feasibility Study March 10, 2011 Bridge No. C-07-001 (437) 9 Final Report
4.0 ELEMENT CONDITION & <strong>REHABILITATION</strong>/<strong>REPAIR</strong> SCOPE The following discussion summarizes the current condition of the bridge along with required repair and rehabilitation work. The condition evaluation is based on review of the available Massachusetts Department of Transportation - Structures Inspection Field Reports and limited field reviews to verify conditions described in these reports. The inspection of the timber structure used in preparation of Structures Inspection Field Reports included routine visual and tactile (sounding and probing) inspection and does not include more in-depth inspection techniques such as moisture meters, drilling and coring, sonic testing, x-rays or tomography scanning. The following discussion also considers function and safety, load capacity, service life, future maintenance, and potential environment and visual impacts. 4.1 Overall Condition 4.1.1 Sufficiency Rating: The current Sufficiency Rating for the bridge is 45.9. Sufficiency ratings are based on a scale of 0 to 100, where 100 is excellent and 0 is very poor. In accordance with the Code of Federal Regulations, Title 23 Part 650D (23 CFR 650D), the sufficiency rating is a method of evaluating highway bridge data by calculating factors to obtain a numeric value, which is indicative of bridge sufficiency to remain in service. The sufficiency rating includes the following applicable primary factors: 1. Structural Adequacy and Safety including: a. Superstructure Condition b. Substructure Condition c. Load Carrying Capacity 2. Serviceability and Functional Obsolescence including: a. Deck Condition b. Overall Structural Condition c. Roadway Geometry d. Traffic Volume 3. Essentiality for Public Use Including: a. Traffic Volume b. Detour Length c. Probability of Bridge Closure Sufficiency Ratings are used in part to determine whether a bridge is eligible for Federal Highway Bridge Program replacement funds. A bridge with a Sufficiency Rating less than 50 and that is classified as “Structurally Deficient” is eligible for bridge replacement or bridge rehabilitation funds. Repair/Rehab. Feasibility Study March 10, 2011 Bridge No. C-07-001 (437) 10 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: Photo 2 - Present Mitchell River Br
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 and 22: 4.2.5 Railings NBIS Condition Ratin
Page 23 and 24: Functionality and Safety: Eliminati
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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