Quinlan Covered Bridge Monkton Rd. (TH-36) over Lewis Creek, Charlotte VT October 25, 2010 Presented by VTrans - Mark Sargent Presented to VHB - Mark Colgan Town of Charlotte Vanasse Hangen Brustlin, Inc. Quinlan Covered Bridge Project Overview Quinlan Covered Bridge • National Register of Historic Places – 1974 • One of three covered bridges In Charlotte • One of nine Burr Arch bridges in Vermont Single-span Kingpost Truss with Burr Arch g Single lane - 12’-11” clear width 87’ deck length, 11’-5” vertical clearance Quinlan Covered Bridge g Bridge Location Quinlan Covered Bridge Project Goals Supe st uctu e e ab tat o Superstructure rehabilitation Repair deteriorated timber trusses Keep bridge in use for community vehicles Extend life of 160 year old bridge Quinlan Covered Bridge History Built 1849 Historic Photos • End portal modifications • Shelter panels removed Quinlan Covered Bridge History 12-11” clear width 11’-5” vertical clearance 1985 Rehabilitation • Replaced deck & floorbeams • Added steel girders Other Changes • Relocation of knee braces • Selected member replacement Quinlan Covered Bridge Current Conditions Roofing and Siding Quinlan Covered Bridge Current Conditions Framing Members Quinlan Covered Bridge Current Conditions 2x10 2 10 Timber/Steel Delaminated Wearing Surface Floor Framing Steel Beams Quinlan Covered Bridge Current Conditions Impact Damage - Arches Quinlan Covered Bridge Current Conditions Truss Top Chords Quinlan Covered Bridge Current Conditions Trusses – Top Chords at Roof Framing Quinlan Covered Bridge Current Conditions North Abutment & Wi N th Ab t ll Erosion t Wingwall – E i Quinlan Covered Bridge Current Conditions pp South Approach Quinlan Covered Bridge Current Conditions North Approach Quinlan Covered Bridge Vehicle Loading for Structural Analysis H17 H17 H25 H24 Quinlan Covered Bridge Vehicle Loading Vehicle Equivalent Loading Town Plow Truck (with sand) H25 Fire Engine H24 School Buses School Buses H17 Fuel Oil Truck (full) H17 Town Tandem Dump Trucks (empty) H12 Current Posting ‐ Car Traffic H5 Quinlan Covered Bridge Bridge Rehabilitation - Structural Analysis g g g Alternative 1 - Existing Bridge Configuration • Load sharing between steel girders and timber arch/trusses Alt ti Original Configuration Alternative 2 - O i i l C fi ti • Remove steel girders Alternative 3 - Isolate Trusses from Floor Framing • Steel girders carry deck dead load & vehicle live load • Timber trusses carry truss self-weight & roof loads Quinlan Covered Bridge Bridge Components p • Top/Bottom chords • Diagonals • Arch • Floorbeams • Vertical Posts • Arch bearings Quinlan Covered Bridge Alternative 1 – Existing Configuration Steel girders added in 1985 to support school buses Girders were designed for H15 p live load plus 100% dead load “Backup” system in case of truss failure Quinlan Covered Bridge Alternative 1 – Existing Configuration Analysis Results: • Unrealistic to upgrade for H25 plow truck load • H17 load rating for school bus reasonable • Floorbeam capacity limited and needs upgrading (H10 now) • Steel girder rating H22 bus), Conclusion: Design H17 inventory rating (frequent school bus) and H25 operating rating (infrequent fire truck). No plow truck. Quinlan Covered Bridge Alternative 1 – Existing Configuration Upgrading needed f H17 rating: U di d d for ti • Replace top chord with larger/stronger member • pg g Upgrade arch bearing details • Reinforce end diagonals • Add sister floorbeams • Reinforce bottom chord • Upgrade connections throughout Quinlan Covered Bridge Alternative 2 – Original Configuration Arch provides 30%-40% of strength Deck load capacity rating: H25 Floorbeam load capacity rating: H5 Trusses chords: H5 Conclusion: Design for passenger vehicles only (H5) Quinlan Covered Bridge Alternative 2 – Original Configuration Upgrading needed for H5 rating: • Replace top chord with larger member • Upgrade arch bearing details • g Reinforce end diagonals • Upgrade bracing & connections • Bottom chord has little capacity for overload o Strict load enforcement required Quinlan Covered Bridge Alternative 3 – Truss Isolated from Floor Minimize load on truss = minimize upgrade req’d “Sever” connection b t • “S ” ti between fl b t floorbeams & trusses • Steel girders support all floor loads (inc. live load) • Trusses support only truss self-weight & roof load Quinlan Covered Bridge Alternative 3 – Truss Isolated from Floor Floorbeam Rating: • H17 at inventory (= school bus) • No good for H25 plow truck p g (close enough to H25 fire truck) • H23 at operating ( g ) Girder Rating: • H22 at inventory (ok for school bus) • >H25 at operating (ok for fire truck) Conclusion: Design for H17 inventory (school bus) ti (fire truck), l truck & H25 operating (fi t k) no plow t k Quinlan Covered Bridge Summary of Alternatives Alternative 1 Alternative 2 Alternative 3 Existing Configuration Original Configuration Isolate Trusses Inventory H17 H5 H17 Live Load School bus Passenger car School bus Operating H25 No vehicles larger than H25 Li L d Live Load Fire truck Fi t k passenger cars Fire truck Fi t k Req’d ‐ Upgrade bracing & ‐ Upgrade bracing & ‐ Upgrade bracing & Structural connections connections connections Upgrades ‐ Larger top chord ‐ Larger top chord ‐ Upgrade arch bearings ‐ Upgrade arch bearings ‐ Reinforce end diagonals ‐ Reinforce end diagonals ‐ Sister floor beams ‐ Add tension diagonals near midspan ‐ Improve bottom chord Improve bottom chord Quinlan Covered Bridge Rehabilitation Most of the required timber rehabilitation work is to address deterioration which is required for all three alternatives. Some additional work is needed for structural upgrades; scope varies depending on the selected alternative. alternative Quinlan Covered Bridge Selection of Rehabilitation Alternative Vermont Historic Covered Bridge Guidelines • Priority of Use – achieve maximum users • Priority of Treatments – maintain character of materials g p g g • Maintain working components of original bridge timbers Quinlan Covered Bridge Alternative 1 – Existing Configuration Consistency with Historic Covered Bridge Plan: • Bridge remains in service for up to H20 loading (40,000 lbs) • Alternate route exists for heavier vehicles g • Existing timber members remain in functional use use. This Priority of Use maintains existing vehicle use Quinlan Covered Bridge Alternative 2 – Original Configuration Consistency with Historic Covered Bridge Plan: • Bridge remains in service for light traffic (passenger cars) • Relatively short alternate route exists or can be constructed • g g Restore bridge to original condition • Existing timber members remain in functional use This Priority of Use does not maintain existing use. Quinlan Covered Bridge Alternative 3 – Isolate Trusses Consistency with Historic Covered Bridge Plan: • Bridge remains in service for up to H20 loading (40,000 lbs) • Alternate route exists for heavier vehicles g y g g • Truss members are no longer carrying live load thus bridge effectively becomes a “steel beam bridge” This Priority of Use maintains existing vehicle use but does not maintain use of original timber bridge components. components Quinlan Covered Bridge Rehabilitation September 2010 Covered Bridge Committee Unanimously Recommended Alternative 1 - Existing Condition Priority of Use is the closest fit • Satisfies intent of Historic Covered Bridge Plan • Maximizes preservation of historic fabric • Original components remain functional parts of the structure • co-functional system” Steel girder in spirit of “co-functional reversible system Quinlan Covered Bridge Rehabilitation – Alt 1 (Existing Configuration) • Replace Top chord with larger member • Sister floorbeams at posts with 6x12’s • Notch intermediate floorbeams • Paint steel girders Quinlan Covered Bridge ( g g ) Rehabilitation – Alt 1 (Existing Configuration) • Top chord replacement • Reinforce end diagonals • Sister floorbeams at • pg g Upgrade arch bearings posts • Replace connections Quinlan Covered Bridge ( g g ) Rehabilitation – Alt 1 (Existing Configuration) • Sister floorbeams at • Notch intermediate posts floorbeams Quinlan Covered Bridge Rehabilitation Deck - Add curbs to keep vehicles centered Steel Girders - Clean & paint, replace bearings End Portal • Reconstruct portal similar to original • Express knee braces at exterior to warn drivers • Maintain existing clear height Quinlan Covered Bridge Rehabilitation Abutments & Wingwalls • Patch deteriorated concrete surfaces • Patch sink hole, remove debris Approaches • Add wingwalls/reinforce slopes to prevent erosion at roadway • Re-grade stone file & remove existing trees • Add end posts to guardrails so not connected to bridge Quinlan Covered Bridge Rehabilitation Fire Protection & Detection Options • Treat all exposed surfaces with fire retardant to slow spread of fire • Install heat detecting cable with alarm to alert fire department Dry i kl t (deluge t • D sprinkler system (d l ) ith t d i for ti type) with standpipe f connection to pumper truck Quinlan Covered Bridge Schedule Begin Final Design Engineering 2010 Environmental Permitting underway Complete engineering and permitting end 2011 Construction 2012 or 2013 Quinlan Covered Bridge Questions/Comments?
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