Bridge Module

8/3/2019 Bridge Module

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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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But they are Fun!

Trails do nothing more than

connect the Bridges!

Proud crew!


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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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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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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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Bridge Design Process

In general, morecomplicated than

road bridges. Why? Defining the User

Location Access

Wilderness

Size?


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Dome Mtn. On Ktn.

24-foot span

Wilderness

6-mile from TH but4000 ft elevationgain.

Force Account

Dangerous work.


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Iron Springs onD-P

50-foot span

Easy access

Total cost -~$35,000

Contract

Maah-Taah-Hey Trail


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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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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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Force Account or Contract?

Remote siterequired packingall materials.

Simpleconstruction

NP has trainedCrews.

Force Account

Goat Creek on NP


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Bridge part of alarger trailconstruction

project.

Short distancefrom trailhead.

Complicated

construction

Contract

Yellow Mule on Gallatin


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Site at trailhead.

Working overlarge water

penstock andtracks.

Needed largeequipment

Mystic on Custer

Contract


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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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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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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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Preliminary Design

Two biggest problems in R1

Bridges too short.Abutments scour and fail

Resource damage


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Preliminary Design

Bridges are too low!


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Preliminary Design

Sill-Thru

Configuration

Little work inwater.

Hydraulicallyefficient. (lesssusceptible toscour).

More $ in

superstructure,less in abutments.

No wingwallsneeded.


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Preliminary Design

Vertical WallConfiguration

More work inwater.

Hydraulically less

efficient. (moresusceptible toscour).

Less $ insuperstructure,

more inabutments.

Need wingwalls


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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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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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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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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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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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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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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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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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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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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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Final Design, PS&E

Estimates

Estimated Construction Costs

Update of preliminary estimate

Estimated Schedule for Construction


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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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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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Trail Bridge Standard Plans

Pre-designedand detaileddrawings for:

Typical TrailBridgeSuperstructures

Typical simplesubstructures

(sills).

Iron Springs on Maay-Daay-Hey Trail


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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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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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Typical abutment details Drawing #Various types of sills used R1930-34

Will need to be customized for each site.


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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.



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Trail Bridge Standard PlansSawn Stringer


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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.



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Trail Bridge Standard PlansLog Stringer


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Trail Bridge Standard Plans Glu-laminated Stringer


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.



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Trail Bridge Standard PlansGL Stringer


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Trail Bridge Standard Plans GL Longitudinal Slab


Best for widths < 8.

Come in panels, max4 width.

ROS - ??? Very ecomomical

Easy to build.

Low maintenance

Handrail more difficult

to attach.



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Trail Bridge Standard PlansGL Longitudinal Slab

T il B id S d d Pl


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Single Log Stringer

User is hiker only.


Diameters 16 to 24

ROS ???.

Handrail is hard toattach and align.

Handrail may bemaintenanceproblem.



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Trail Bridge Standard PlansSingle Log

T il B id S d d Pl


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Trail Bridge Standard PlansNail-Lam Longitudinal Slab


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.



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Trail Bridge Standard PlansNail Laminated Slab


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Trail Bridge Standard PlansPrefabricated Truss

T il B id St d d Pl


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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.



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Trail Bridge Standard PlansPackable Bridge

T il B id St d d Pl


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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.



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g ypTimber Truss

Others Trail Bridge T pes


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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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Unique

What isappropriate?

What can youbuild?

Is a bridgeneeded?

Bob Marshall Wilderness



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Design Process

Add conceptualdesign before Project

Scope Need alternatives

Bridge Type

Construction methods

Materials

Costs

Conceptual Design

Project Scope

Location/Survey



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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)



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What is lifeexpectancy ofpermanent bridge?

Life of untreatedmaterial?

15 to 20 years

Life of treatedmaterial?

50 + years



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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



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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

Documents

Bridge Module