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Project Preparation andAdministration
Bridge Module
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R1 Trails Project Preparation
Why are bridges part of this training?
Big cost.
LongProcess
Design iscomplicated
Tough
Decisions
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R1 Trails Project Preparation
But they are Fun!
Trails do nothing more than
connect the Bridges!
Proud crew!
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R1 Trails Project Preparation
Training Focus
Bridge DesignProcess
Decisions to be
made. How to make those
decisions!
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Training Focus
Northern Region Standard Trail Bridge Plans Intended uses
Limitations, Inappropriate Uses
Costs
Maintenance
Wilderness Bridges
Helicopter Usage
Preservative Treatments
If there is time NP Wilderness Bridge ProjectPresentation
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R1 Trails Project Preparation
Authorities All Decisions
Line Office
Approval ofBridge DesignDirector of
Engineering Unless using
RegionalStandard TrailBridge DesignsForest Engineer.
All Trail Bridgesneed to bedesigned!
Bridge in Bob Marshall Wilderness
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Authorities
Design ResourcesAvailable. Forest Engineer
Regional Bridge Group
John Kattell
David Scovell
Our job is to providetechnical assistance toForest personnel and
complete and/orapprove all bridgedesigns.
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ProjectScope**
Location/Survey
Final Design
Construction
Preliminary Design
Bridge Design ProcessFunction (To bridge or not? Replace or remove?)
Who is User? ROS? TMO?Force Account/Contract?
Where is best spot?
Many decisions.
Project Funding and
Scope finalized.
COR
Plans, Specs,
Estimates.
**Contact FE and /or ROduring Project Scope
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R1 Trails Project Preparation
Project Initiation and Scope
Function To Bridge or Not to
Bridge?
Replace or remove?
PreliminaryEngineering needed?
Factors? TMO & ROS
User Safety
Resource Protection
Others?Funding Feasibility
Aesthetics WildernessAlbino Trail Bridge Site - Gal
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R1 Trails Project Preparation
Bridge Design Process
In general, morecomplicated than
road bridges. Why? Defining the User
Location Access
Wilderness
Size?
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Bridge Design Process
Dome Mtn. On Ktn.
24-foot span
Wilderness
6-mile from TH but4000 ft elevationgain.
Force Account
Dangerous work.
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R1 Trails Project Preparation
Bridge Design Process
Iron Springs onD-P
50-foot span
Easy access
Total cost -~$35,000
Contract
Maah-Taah-Hey Trail
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R1 Trails Project Preparation
Project Initiation and Scope
Define the User (TMO & ROS)
Pedestrians
Stock
ATVs
Bicycles
Administrationvehicles
Outfitters / otherpermittees
User affects size, designand cost.
Bridge many times limitsthe user!
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R1 Trails Project Preparation
Project Initiation and Scope
Force Account or Contract?(Effects design
decisions!)
Design (in house or A/E) Complexity of bridge project.
Availability of Forest or RO Engineers
Funding Typically, R1 designs are done in house.
Construction Safety
Force Account capability, skill level, and availability.
Complexity of bridge. Funding
Pros and Cons
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R1 Trails Project Preparation
Force Account or Contract?
Remote siterequired packingall materials.
Simpleconstruction
NP has trainedCrews.
Force Account
Goat Creek on NP
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R1 Trails Project Preparation
Force Account or Contract?
Bridge part of alarger trailconstruction
project.
Short distancefrom trailhead.
Complicated
construction
Contract
Yellow Mule on Gallatin
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R1 Trails Project Preparation
Force Account or Contract?
Site at trailhead.
Working overlarge water
penstock andtracks.
Needed largeequipment
Mystic on Custer
Contract
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R1 Trails Project Preparation
Project Initiation and Scope
SummaryFunction (To bridge or not to bridge)
Define Users.
Force Account versus ContractFunding. Project a go or no go?
May need some preliminary engineering
this early.Who makes these decisions?
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R1 Trails Project Preparation
Location / Survey
Location Narrowest spot?
Not necessarily
Stable stream reach.
Where users want it!Good trail
approaches for user(function for hikers vsstock vs snomobiles vs
ATVs)
Survey - Varies Simple small creek
Profile of trail andstream with few x-sections.
Sketches
Complex
Full site survey ofarea.
Geotechnical (drilling)
In general, experiencedbridge engineer may getby with less.
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Location / Survey
Holter Cut
on Btr.
No survey
done.
L i /
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Location /Survey
Little Salmon on
Flathead in BobMarshall.
Full site survey
completed.
Needed for
hydraulic analysis.
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R1 Trails Project Preparation
Preliminary Design
Determine Span
Height
Width
Bridge Type Foundations
FA or Contract
Cost
FactorsCrossing and height
Flood waters, Clearance
User
Span, location, aestheticsSite geology
See earlier slide
All of the above.
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R1 Trails Project Preparation
Preliminary Design
Two biggest problems in R1
Bridges too short.Abutments scour and fail
Resource damage
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R1 Trails Project Preparation
Preliminary Design
Bridges are too low!
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R1 Trails Project Preparation
Preliminary Design
Sill-Thru
Configuration
Little work inwater.
Hydraulicallyefficient. (lesssusceptible toscour).
More $ in
superstructure,less in abutments.
No wingwallsneeded.
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R1 Trails Project Preparation
Preliminary Design
Vertical WallConfiguration
More work inwater.
Hydraulically less
efficient. (moresusceptible toscour).
Less $ insuperstructure,
more inabutments.
Need wingwalls
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R1 Trails Project Preparation
Preliminary Design
Span Length
Field Estimate (Rule of Thumb) typicalspill-thru bridge.
Estimated Span Length (L) = BW + 3 x BH BW Channel bottom width
BH Bridge height from channel bottom to trail tread.
Span Length (L)
BH
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Preliminary Design
Span LengthField estimate must be verified on paper.
Do not undersize.
Better to spend more on span than abutments.
Evaluate existing bridge (did it function OK)
Iterative process with what?
Bridge height
What controls bridge height?
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Preliminary Design
What controls bridgeheight? Trail height
Bridge structure
depth Rule of thumb
1/20 x span
Clearance for debris
Minimum 2 feet
above high water(100 yr flood) tobottom of bridge.
Little Salmon on Flathead
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R1 Trails Project Preparation
Preliminary Design
Span Length Vertical Wall abutment
Span Length = Bankfull +. Must be able to passflood without damage to bridge or stream.
Footings must be below stream bed as minimumunless on bedrock.
Span Length (L)
BH
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R1 Trails Project Preparation
Preliminary Design
Factors for Bridge Width
- Users
- Railing
Bridge w/o railing
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Preliminary Design
Variable widths Single log14
Stock w/railing8
Snowmobile16+
Manual guidancebut can beanything.
Bridge with railing
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Preliminary Design Bridge Types
Single Log
Timber stringer
Glu-lam stringer
Truss
Suspension
Packable
FactorsSpan Access
Aesthetics Materials
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R1 Trails Project Preparation
Preliminary Design
Foundations
Spread footings
Gabions
Geocell
Walls
Generally we use spill-thru configurationwith timber sill on gabion or geocell.
Factors
Site geology
Site materials
Access
Scour Potential
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R1 Trails Project Preparation
Preliminary Design
CostsVery difficult to estimate.
No rules of thumb.
Procedure Take off and price materials (variable)
Crew up labor. $2500/day for crew of 4 with misc.tools/equipment
Or use Davis Bacon rates
Estimate Equipment needed (cranes,backhoe, helicopter)
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R1 Trails Project Preparation
Preliminary Design
Costs - continuedMaterials
Sawn Timber $1350/mfbf
GL timber $2500/mfbf
Bolts/hardware $3.00/lbs.
Concrete $600 - $1000/cy
Reinforcing Steel $1.25/lb
Gabions $125/cy
Geocell $15/cy
Geocell fill $25-$75/cy
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Preliminary Design
Costs - continued Equipment
Excavator $130/hr
Backhoe $80/hr
Dump Truck $75/hr
Crane (Light) $350/hr
Crane (medium) $650/hr
Helicopters See later slides
Packing $225/mule trip
(180 lbs per mule)
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R1 Trails Project Preparation
Preliminary Design
Typical work items toaccomplish for labor. Project Management
Mobilization Excavation
Build Abutments
Install Superstructure
Build Approach walls Build Approach fills
Less Common WorkItems Helicopter use.
Packing Materials Supply Camp
Install Falsework.
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R1 Trails Project Preparation
Preliminary Design
Nail Lam built 15years ago.
Replace with glu-lam stringer bridge.
On sills. Wilderness
Use Helicopter to flyin stringers.
Estimate based onContractConstruction
Flood Creek Custer
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R1 Trails Project Preparation
Preliminary Design
Whose Responsibility / Authority forpreliminary decisions?
Forest!
However, Engineering must assist!
Why?
Call FE and or RO during Project Scope for
assistance with alternatives and options.Meet with Rec staff and Ranger to discuss
preliminary design options and alternatives.
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Preliminary Design
At this point
Re-evaluate Project Scope!
Re-evaluate Funding!
Why?
Many times each site has severalalternatives being evaluated.
Must select Final Design Alternative.
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R1 Trails Project Preparation
Final Design, PS&E
Typically done by Engineering
Plans (as a minimum)
Title Sheet (signatures)
Bridge Layout (Plan and Elevation)
On site plan from survey.
Abutment/foundation details
Superstructure details
Miscellaneous details
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Final Design, PS&E
Specifications
FP-03, Standard Specifications forConstruction of Roads and Bridges onfederal Highway Projects.
Special Project Specifications asneeded.
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R1 Trails Project Preparation
Final Design, PS&E
Estimates
Estimated Construction Costs
Update of preliminary estimate
Estimated Schedule for Construction
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R1 Trails Project Preparation
Final Design, PS&E
Plans, Specs and EstimatesAll 3 required.
Any difference for Force Account vsContract?
Shouldnt be!
Authorities
Regional Engineer must approve PS&E
package, UNLESS Using Standard Plans, then FE has authority
to approve PS&E package.
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R1 Trails Project Preparation
Construction
All Trail Bridge Construction is to beadministered and inspected by
Certified COR, Level III
With appropriate technical endorsements.
Any difference for Force Account vsContract?
NO!
RO will assist as needed or requested.
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R1 Trails Project Preparation
Trail Bridge Standard Plans
Pre-designedand detaileddrawings for:
Typical TrailBridgeSuperstructures
Typical simplesubstructures
(sills).
Iron Springs on Maay-Daay-Hey Trail
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Trail Bridge Standard Plans
Intended Uses Simple, single spans
Spans less than 60 feet
Adapted for each site.
FE can approve.
Limitations At discretion of FE only.
Not for complex bridges.
Not for difficultabutments.
Still requires, survey,hydraulic analysis, soils,etc.
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Trail Bridge Standard Plans
Typical Superstructures: Drawing #
Solid Sawn Timber Stringer R1920
Log Stringer R1921
Glu-lam timber stringer R1922
Glu-lam longitudinal slab R1923 Single log R1924
Nail-lam longitudinal slab R1925
Prefabricated steel truss R1926
Packable spliced stringer R1927
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Trail Bridge Standard Plans
Typical abutment details Drawing #Various types of sills used R1930-34
Will need to be customized for each site.
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R1 Trails Project Preparation
Trail Bridge Standard Plans Sawn Timber Stringer
Spans 10 to 40 feet
Any width
Stringers 3x10 to 8x24
ROS - ???
Economical if you haveused stringers.
But stringer quality largethan 4x10 gets iffy.
Costs increase
significantly with largerstringers.
Trail Bridge Standard Plans
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R1 Trails Project Preparation
Trail Bridge Standard PlansSawn Stringer
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Trail Bridge Standard Plans
Log Stringer
Spans 10 to 45 feet.
Any width.
Diameter from 8 to
22 ROS ???
Costs are higherThan other types for
similar spans.More difficult to build
and maintain.
Trail Bridge Standard Plans
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Trail Bridge Standard PlansLog Stringer
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R1 Trails Project Preparation
Trail Bridge Standard Plans Glu-laminated Stringer
Spans 25 to 60 feet.
Any width.
Stringers 3.125 x 15 to8.75 x 39.
Requires diaphragms. ROS - ????
Most ecomomical forspans 40 feet or longer.
Easy construction but
requires larger equipment. Low maintenance.
Trail Bridge Standard Plans
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R1 Trails Project Preparation
Trail Bridge Standard PlansGL Stringer
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R1 Trails Project Preparation
Trail Bridge Standard Plans GL Longitudinal Slab
Spans 10 to 35 feet.
Best for widths < 8.
Come in panels, max4 width.
ROS - ??? Very ecomomical
Easy to build.
Low maintenance
Handrail more difficult
to attach.
Trail Bridge Standard Plans
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R1 Trails Project Preparation
Trail Bridge Standard PlansGL Longitudinal Slab
T il B id S d d Pl
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Trail Bridge Standard Plans
Single Log Stringer
User is hiker only.
Spans 10 to 45 feet.
Diameters 16 to 24
ROS ???.
Handrail is hard toattach and align.
Handrail may bemaintenanceproblem.
Trail Bridge Standard Plans
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Trail Bridge Standard PlansSingle Log
T il B id S d d Pl
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R1 Trails Project Preparation
Trail Bridge Standard PlansNail-Lam Longitudinal Slab
Spans 12 to 30 feet.
Best for widths < 8.
Materials 2x6 to 2x14.
ROS - ???
Labor intensive.
Materials less expensive butlabor is higher.
Good for sites shortdistance from trailhead butnot accessible for
equipment Moderate maintenance.
Handrail difficult to attach.
Trail Bridge Standard Plans
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Trail Bridge Standard PlansNail Laminated Slab
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Trail Bridge Standard Plans
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R1 Trails Project Preparation
Trail Bridge Standard PlansPrefabricated Truss
T il B id St d d Pl
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R1 Trails Project Preparation
Trail Bridge Standard Plans Packable Bridge
Span 36 feet or less.
Any width.
ROS - ???
Alternative to
helicopter use. Expensive materials.
Labor intensive.
More difficult to
build. Increased
maintenance.
Trail Bridge Standard Plans
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Trail Bridge Standard PlansPackable Bridge
T il B id St d d Pl
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Trail Bridge Standard Plans
Abutment Details Sill designs - Spill-thru
Keep away from streamedge.
Not applicable if scour
issues. Do not stack sills to gain
height.
Place on geocell, gabion,or concrete pad.
Need to be site adapted.
Ti b C ibbi & R k G bi
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Timber Cribbing & Rock Gabions
Sill on Gabion
Sill on Timber crib on geocell
Oth T il B id T
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Others Trail Bridge Types
Timber Truss Spans 50 to 100+
feet.
Any width
ROS ???
Labor intensive.
Difficult to build
Moderatemaintenance.
Can be built withsemi- primitive toolsor heavy equipment.
Others Trail Bridge Types
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g ypTimber Truss
Others Trail Bridge T pes
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Others Trail Bridge Types
SuspensionBridges
Spans > 100 feet
Up to 8 feet.
ROS ??? Very difficult to
build.
Very high
maintenance. Very high cost
General Guidance
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General Guidance
Trail Types Clear width Rail HeightHiking 4 42
Mountain Biking 4 54
Pack and Saddle 5 w/o rail6 w/rail 54
Cross Country Skiing 6 42
Snowmobile 6 Site specific
Motorcycle 42 42
ATV 50 27
General Guidance
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General Guidance
Railing Are they needed?
Proposed manual direction says:In general, rails shall be required for all trail and pedestrian bridges.However, railings may be eliminated and potentially curbssubstituted for rails when an appropriate analysis as describedbelow has been completed:
An analysis has identified and evaluated the potential users anddetermined that the potential hazards along the trail are the same orgreater than that of a bridge without a rail. The analysis shallinclude the possibility of using a rail on only one side of the bridge.
In general, rural and urban ROS settings are likely to have smallchildren and less experienced users. Thus, a railing is warranted inmost instances. In backcountry or wilderness settings, where users
are normally more experienced, rails may not be needed.
General Guidance
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General GuidancePettibone to left, Goat to
below on NP. Selwaywilderness.
General Guidance
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General Guidance
Dome Mtn.
Kootenai.
Cabinet
Wilderness
No
Handrail!
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Type ROS Spans Equipment Maint. Cost
Sawn Stgr. 10 to 40 Light Low Low/Med
Log Stgr. 10 to 45 Light/Med Low Low/Med
GL Stgr. 25 to 60 Medium Low Low/Med
GL Slab 10 to 35 Light Low Low
Single Log 10 to 45 Primitive/Light Low Low
NL Slab 12 to 30 Primitive/Light Moderate Medium
Steel Truss > 60 Heavy Low High
Packable < 36 Primitive/Light Moderate HighTbr. Truss > 60 Light/Heavy Moderate High
Suspension > 100 Medium High High
General Guidance
Wilderness Trail Bridges
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Wilderness Trail Bridges
Unique
What isappropriate?
What can youbuild?
Is a bridgeneeded?
Bob Marshall Wilderness
Wilderness Trail Bridges
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Wilderness Trail Bridges
Design Process
Add conceptualdesign before Project
Scope Need alternatives
Bridge Type
Construction methods
Materials
Costs
Conceptual Design
Project Scope
Location/Survey
Wilderness Trail Bridges
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Wilderness Trail Bridges
Minimum Tool analysis.
Use of helicopters
Force Account or Contract. Logistics!!
Wilderness bridges are the most complicatedand expensive. Need special attention.
Helicopter Usage
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Helicopter Usage
Helicopter contracts
Type I (Heavy) Sky cranes, etc
Can pick up to 25,000 lbs.
On call contract $9000/hour
Must come out of West Coast. Mob costs prohibitive.
Type II (Medium)
5000 to 12,000 lbs.
On call contract $4500/hour
Several in Montana, but not readily available.
Helicopter Usage
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Helicopter Usage
Helicopter contractsType III( Light)
Can pick up to 5000lbs.
On call contract $1800/hour For up to 3000 lbs, readily available.
Need to plan ahead and try to coordinate
with other work in the area to lower costs.
Helicopter Usage
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Helicopter Usage
Helicopter Use - best value?
Small helicopter
More trips More on-site labor (fly one stringer at a time)
Big Helicopter
Less trips.
Less on site labor (fly in entire bridgesuperstructure)
Preservative Treatments
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Preservative Treatments
What is lifeexpectancy ofpermanent bridge?
Life of untreatedmaterial?
15 to 20 years
Life of treatedmaterial?
50 + years
Preservative Treatments
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Preservative Treatments
Treated vs Untreated. Manual Direction fpr
permanent structures
design life of 50 yrs
However, exceptions aremade.
Who decides?
Forest
Treated material isstrongly recommended.
Papoose Creek on Clwt NF
Preservative Treatments
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Preservative Treatments
Protect the integrity ofTreatment. Cutting ends, drilling
holes, all ruins treatment.
Field treatments havelimited success.
To apply fieldtreatments, person
needs training andcertification. Hassle!Blue Sky Bridge on Ktn NF
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Preservative Treatment
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Preservative Treatment Options
Substructure,stringers, deck,curbs Penta, Copper
Naphthenate
Handrail Treated many
choices
Untreatedredwood or RedCedar
Changing constantlyIron Springs - DPGL