Bridge Module (2)

Project Preparation and Project Preparation and AdministrationAdministration

Bridge ModuleBridge Module

R1 Trails Project PreparationR1 Trails Project Preparation

Why are bridges part of this trainingWhy are bridges part of this training??

• Big cost.• Long

Process• Design is

complicated• Tough

Decisions


But they are Fun!But they are Fun!

Trails do nothing more than connect the Bridges!

Proud crew!


Training FocusTraining Focus

• Bridge Design Process Decisions to be

made. How to make those

decisions!


Training FocusTraining Focus• Northern Region Standard Trail Bridge Plans

Intended uses Limitations, Inappropriate Uses Costs Maintenance

• Wilderness Bridges• Helicopter Usage• Preservative TreatmentsIf there is time – NP Wilderness Bridge Project

Presentation


AuthoritiesAuthorities• All Decisions –

Line Office• Approval of

Bridge Design – Director of Engineering Unless using

Regional Standard Trail Bridge Designs – Forest Engineer.

• All Trail Bridges need to be designed!

Bridge in Bob Marshall Wilderness


AuthoritiesAuthorities• Design Resources

Available. Forest Engineer Regional Bridge Group

John Kattell David Scovell

• Our job is to provide technical assistance to Forest personnel and complete and/or approve all bridge designs.


Project Scope**

Location/Survey

Final Design

Construction

Preliminary Design

Bridge Design ProcessBridge Design Process•Function (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 RO during Project Scope


Project Initiation and ScopeProject Initiation and Scope

• Function To Bridge or Not to

Bridge? Replace or remove? Preliminary Engineering

needed?• Factors?

TMO & ROS User Safety Resource Protection Others?

Funding FeasibilityAesthetics WildernessAlbino Trail Bridge Site - Gal


Bridge Design ProcessBridge Design Process

• In general, more complicated than road bridges. Why? Defining the User Location

Access Wilderness

Size?



• Dome Mtn. On Ktn. 24-foot span Wilderness 6-mile from TH but

4000 ft elevation gain.

Force Account Dangerous work.



• Iron Springs on D-P 50-foot span Easy access Total cost -

~$35,000 Contract

Maah-Taah-Hey Trail



Define the User (TMO & ROS) Pedestrians Stock ATVs Bicycles Administration

vehicles Outfitters / other

permittees User affects size, design

and cost. Bridge many times limits

the user!


Project Initiation and ScopeProject 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


Force Account or Contract?Force Account or Contract?

• Remote site required packing all materials.

• Simple construction

• NP has trained Crews.

• Force Account

Goat Creek on NP



• Bridge part of a larger trail construction project.

• Short distance from trailhead.

• Complicated construction

• Contract

Yellow Mule on Gallatin



• Site at trailhead.• Working over

large water penstock and tracks.

• Needed large equipment

Mystic on Custer

Contract



• SummaryFunction (To bridge or not to bridge)Define Users.Force Account versus Contract Funding. Project a go or no go?May need some preliminary engineering

this early.

Who makes these decisions?


Location / SurveyLocation / Survey• Location

Narrowest spot? Not necessarily

Stable stream reach. Where users want it! Good trail

approaches for user (function for hikers vs stock vs snomobiles vs ATV’s)

• Survey - Varies Simple small creek

Profile of trail and stream with few x-sections.

Sketches Complex

Full site survey of area.

Geotechnical (drilling) In general, experienced

bridge engineer may get by with less.


Location / SurveyLocation / Survey

•Holter Cut on Btr.

•No survey done.


Location / Location / SurveySurvey

•Little Salmon on Flathead in Bob Marshall.

•Full site survey completed.

•Needed for hydraulic analysis.


Preliminary DesignPreliminary Design Determine

Span Height Width Bridge Type Foundations FA or Contract Cost

FactorsCrossing and heightFlood waters, Clearance UserSpan, location, aestheticsSite geologySee earlier slideAll of the above.


Preliminary DesignPreliminary Design

Two biggest problems in R1

Bridges too short.

Abutments scour and fail

Resource damage



Bridges are too low!



• Sill-Thru Configuration Little work in

water. Hydraulically

efficient. (less susceptible to scour).

More $ in superstructure, less in abutments.

No wingwalls needed.


Preliminary DesignPreliminary Design• Vertical Wall

Configuration More work in

water. Hydraulically less

efficient. (more susceptible to scour).

Less $ in superstructure, more in abutments.

Need wingwalls



• Span Length Field Estimate (Rule of Thumb) typical spill-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


Preliminary DesignPreliminary Design• Span Length

Field 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?



• What controls bridge height? Trail height Bridge structure

depth Rule of thumb

1/20 x span Clearance for debris

Minimum 2 feet above high water (100 yr flood) to bottom of bridge.

Little Salmon on Flathead



• Span Length – Vertical Wall abutment

Span Length = Bankfull +. Must be able to pass flood without damage to bridge or stream.

Footings must be ‘below stream bed as minimum unless on bedrock.

Span Length (L)

BH



Factors for Bridge Width - Users - Railing

Bridge w/o railing



Variable widths• Single log – 14”• Stock w/railing – 8’• Snowmobile –

16’+• Manual guidance

but can be anything.

Bridge with railing


Preliminary DesignPreliminary Design• Bridge Types

Single Log Timber stringer Glu-lam stringer Truss Suspension Packable

• FactorsSpan Access

Aesthetics Materials



• Foundations Spread footings Gabions Geocell Walls

• Generally we use spill-thru configuration with timber sill on gabion or geocell.

• Factors Site geology Site materials Access Scour Potential



• 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)


Preliminary DesignPreliminary Design• Costs - continued

Materials 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


Preliminary DesignPreliminary 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)



• Typical work items to accomplish for labor.

Project Management Mobilization Excavation Build Abutments Install Superstructure Build Approach walls Build Approach fills

• Less Common Work Items Helicopter use. Packing Materials Supply Camp Install Falsework.



• Nail Lam built 15 years ago.

• Replace with glu-lam stringer bridge.

• On sills.• Wilderness• Use Helicopter to fly

in stringers.• Estimate based on

Contract Construction

Flood Creek – Custer



Preliminary DesignPreliminary DesignWhose Responsibility / Authority for

preliminary 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.



• At this pointRe-evaluate Project Scope!Re-evaluate Funding!

• Why?Many times each site has several

alternatives being evaluated.Must select Final Design Alternative.


Final Design, PS&EFinal 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 detailsSuperstructure detailsMiscellaneous details



• SpecificationsFP-03, Standard Specifications for

Construction of Roads and Bridges on federal Highway Projects.

Special Project Specifications as needed.



• EstimatesEstimated Construction Costs

Update of preliminary estimateEstimated Schedule for Construction


Final Design, PS&EFinal Design, PS&E• Plans, Specs and Estimates

All 3 required.Any difference for Force Account vs

Contract? Shouldn’t be!

Authorities Regional Engineer must approve PS&E

package, UNLESS Using Standard Plans, then FE has authority

to approve PS&E package.


ConstructionConstruction• All Trail Bridge Construction is to be

administered and inspected by Certified COR, Level IIIWith appropriate technical endorsements.Any difference for Force Account vs

Contract? NO!

RO will assist as needed or requested.


Trail Bridge Standard PlansTrail Bridge Standard Plans

• Pre-designed and detailed drawings for: Typical Trail

Bridge Superstructures

Typical simple substructures (sills).

Iron Springs on Maay-Daay-Hey Trail


Trail Bridge Standard PlansTrail 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 difficult

abutments. Still requires, survey,

hydraulic analysis, soils, etc.


Trail Bridge Standard PlansTrail Bridge Standard PlansTypical 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


Trail Bridge Standard PlansTrail Bridge Standard PlansTypical abutment details Drawing #

Various types of sills used R1930-34

Will need to be customized for each site.


Trail Bridge Standard PlansTrail Bridge Standard Plans• Sawn Timber Stringer

Spans 10 to 40 feet Any width Stringers 3x10 to 8x24 ROS - ??? Economical if you have

used stringers. But stringer quality large

than 4x10 gets iffy. Costs increase

significantly with larger stringers.


Trail Bridge Standard PlansTrail Bridge Standard PlansSawn StringerSawn Stringer


Trail Bridge Standard PlansTrail Bridge Standard Plans• Log Stringer

Spans 10 to 45 feet. Any width. Diameter from 8” to

22” ROS – ??? Costs are higher

Than other types for similar spans.

More difficult to build and maintain.


Trail Bridge Standard PlansTrail Bridge Standard PlansLog StringerLog Stringer


Trail Bridge Standard PlansTrail Bridge Standard Plans• Glu-laminated Stringer

Spans 25 to 60 feet. Any width. Stringers 3.125 x 15 to

8.75 x 39. Requires diaphragms. ROS - ???? Most ecomomical for

spans 40 feet or longer. Easy construction but

requires larger equipment. Low maintenance.


Trail Bridge Standard PlansTrail Bridge Standard PlansGL StringerGL Stringer


Trail Bridge Standard PlansTrail Bridge Standard Plans• GL Longitudinal Slab

Spans 10 to 35 feet. Best for widths < 8’. Come in panels, max

4’ width. ROS - ??? Very ecomomical Easy to build. Low maintenance Handrail more difficult

to attach.


Trail Bridge Standard PlansTrail Bridge Standard PlansGL Longitudinal SlabGL Longitudinal Slab


Trail Bridge Standard PlansTrail Bridge Standard Plans

• Single Log Stringer User is hiker only. Spans 10 to 45 feet. Diameters 16” to 24” ROS – ???. Handrail is hard to

attach and align. Handrail may be

maintenance problem.


Trail Bridge Standard PlansTrail Bridge Standard PlansSingle LogSingle Log


Trail Bridge Standard PlansTrail 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 but

labor is higher. Good for sites short

distance from trailhead but not accessible for equipment

Moderate maintenance. Handrail difficult to attach.


Trail Bridge Standard PlansTrail Bridge Standard PlansNail Laminated SlabNail Laminated Slab


Trail Bridge Standard PlansTrail Bridge Standard Plans• Prefabricated Steel

Truss Spans > 60’ (Standard

Plans limited to 100’) Any width. ROS – ??? Requires heavy

equipment. Too heavy for economical

use of helicopters. Requires manufacturer

design and shop drawings.

Low maintenance.


Trail Bridge Standard PlansTrail Bridge Standard PlansPrefabricated TrussPrefabricated Truss


Trail Bridge Standard PlansTrail 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 PlansTrail Bridge Standard PlansPackable BridgePackable Bridge


Trail Bridge Standard PlansTrail Bridge Standard Plans• Abutment Details

Sill designs - Spill-thru Keep away from stream

edge. Not applicable if scour

issues. Do not stack sills to gain

height. Place on geocell, gabion,

or concrete pad. Need to be site adapted.


Timber Cribbing & Rock GabionsTimber Cribbing & Rock Gabions

Sill on Gabion

Sill on Timber crib on geocell


Others Trail Bridge TypesOthers Trail Bridge TypesTimber Truss

Spans 50 to 100+ feet.

Any width ROS – ??? Labor intensive. Difficult to build Moderate

maintenance. Can be built with

semi- primitive tools or heavy equipment.


Others Trail Bridge TypesOthers Trail Bridge TypesTimber TrussTimber Truss


Others Trail Bridge TypesOthers Trail Bridge Types• Suspension

Bridges Spans > 100 feet Up to 8 feet. ROS – ??? Very difficult to

build. Very high

maintenance. Very high cost


General GuidanceGeneral 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 GuidanceGeneral GuidanceRailing – 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 curbs substituted for rails when an appropriate analysis as described below has been completed:

An analysis has identified and evaluated the potential users and determined that the potential hazards along the trail are the same or greater than that of a bridge without a rail. The analysis shall include the possibility of using a rail on only one side of the bridge. In general, rural and urban ROS settings are likely to have small children and less experienced users. Thus, a railing is warranted in most instances. In backcountry or wilderness settings, where users are normally more experienced, rails may not be needed.


General GuidanceGeneral Guidance Pettibone to left, Goat to

below on NP. Selway wilderness.



Dome Mtn. Kootenai. Cabinet Wilderness

No Handrail!


Type ROS Spans Equipment Maint. CostSawn 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 High

Tbr. Truss > 60’ Light/Heavy Moderate High

Suspension > 100’ Medium High High



Wilderness Trail BridgesWilderness Trail Bridges

• Unique What is

appropriate? What can you

build? Is a bridge

needed?

Bob Marshall Wilderness



• Design Process• Add conceptual

design before Project Scope

• Need alternatives Bridge Type Construction methods Materials Costs

Conceptual Design

Project Scope

Location/Survey



• Minimum Tool analysis.• Use of helicopters• Force Account or Contract.• Logistics!!

Wilderness bridges are the most complicated and expensive. Need special attention.


Helicopter UsageHelicopter 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 UsageHelicopter 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 UsageHelicopter 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 bridge

superstructure)


Preservative TreatmentsPreservative Treatments

• What is life expectancy of permanent bridge?

• Life of untreated material? 15 to 20 years

• Life of treated material? 50 + years



• Treated vs Untreated. Manual Direction fpr

permanent structures design life of 50 yrs

However, exceptions are made.

Who decides? Forest

Treated material is strongly recommended.

Papoose Creek on Clwt NF



• Protect the integrity of Treatment. Cutting ends, drilling

holes, all ruins treatment.

• Field treatments have limited success.

• To apply field treatments, person needs training and certification. Hassle!Blue Sky Bridge on Ktn NF


Preservative TreatmentPreservative Treatment• Any laws against

Treatment? Only 1 by EPA Can not use CCA in

members in direct contact with peoples skin.

No others.• However, do we

want oily treatment on handrails?


Preservative TreatmentPreservative Treatment• Options

Substructure, stringers, deck, curbs

Penta, Copper Naphthenate

Handrail Treated – many

choices Untreated –

redwood or Red Cedar

• Changing constantlyIron Springs - DPGL

Bridge Module (2)

Documents

controls bridge

bob marshall

preliminary

approve psamp

preliminary

psamp

span length

force account