EDMUND FINLEYTRISHA LOWE

NICK MENCHELANNA SLEETER

BOLIVIA BRIDGE:FINAL DESIGN

PROJECT BACKGROUND

DESIGN ALTERNATIVES

CONSIDERED ALTERNATIVESCulvert Hardened

RoadwayTrench

Cost (2) 2 2 1

Materials (3) 1 1 1

Tools (3) 1 1 1

Material Availability (1)

2 1 1

Feasibility (2) 2 3 1

Flow Capacity (1) 1 3 2

Time (3) 2 2 1

Maintenance (1) 1 2 3

Lifespan (1) 1 3 2

Failure Modes (1)

1 3 2

Expertise (2) 3 2 1

Adaptability (3) 2 1 1

Totals 38 41 29

CONCEPTUAL DESIGN

30%/60% DESIGN

FINAL DESIGN

DESIGN DILEMMAS

Site Inaccurate/inadequate surveying data Lack of flow data (rainfall, size of flood plain) Lack of soil data

Constructability Limited materials Unknown skill sets of laborers Quantity of laborers Time No heavy machinery!

ASSUMPTIONS

Site Cross-section we were asked to build for is near Obrajes 1,

Cross-Section 3 data, so we will use this as an approximation Extrapolated max flow from assuming waterline is at its

highest touching the bank; also considered slope of land from using surveying data of the Obrajes 1 crossing

Assumed the soil had low bearing capacityConstructability

Were able to get a materials list from NGO, Engineers in Action

Assuming unskilled labor Time/manual labor available – can’t do much to change Simple design

TOOLS

To find internal bending moments and shear forces Dr. Gavin’s “three_moment.m” Matlab file for continuous

beams Uses the three moment equation Inputs: spans (between supports), live loads (point loads),

dead loads (distributed loads) Outputs: Max internal bending moments, shear forces,

displacementsTo test design dimensions

Dr. Nadeau’s “Beam Design” excel worksheet, from CE 133 (Concrete Design)

Uses design variables and material properties to determine if, for a given cross-section, a “beam” can carry the internal moment

Also outputs reinforcement specifications

CALCULATIONS

Loading conditions: Live Loads:

Worst case scenario: a 17’ U-Haul sized vehicle, fully loaded, assumed 75% of weight is carried by back tires

Dead Loads: Curb designed for safety Self-weight of the components Weight of parts being supported

Positions: Mid-span and at supports are the worst

CURB DESIGN

SLAB DESIGN

Dead Load

Live Load

SLAB DIMENSIONS

ΦVn ≥ 1.6VL + 1.2VD

VL = 1.74 x 104 N, VD = 1.52 x 10-1 N … d ≥ 6.95 in + at least 1.5 in clear coverh = 22 cm (~8.66 in)Slab is 3.5m across, and 6.2m between piers

BEAM DESIGN

OUTER BEAMS

Dead Load w=wcurb+wslab

Live Load Fvehicle

INNER BEAMS

Dead Load w=wslab

Live Load Fvehicle

BEAM DIMENSIONS

ML = 35.53, MD = 18.5 (outer), 29.23 (inner), kip-ft

From Beam Design worksheet…Outer beam: could be 12 in x 18 inInner beam: needs to be 12 in x 20 inWent with 12 in x 20 inReinforcement: 1 layer, (5) #6 Longitudinal

bars + #3 shear stirrups every ~14.5 in

RETAINING WALL DESIGN

Piers on sides by fill and culverts needed to be designed as retaining walls

Stem thickness set to 12” for constructability purposes

Height: 10.505 ftBase thickness: 0.955 ftBase length: 10 ftHeel length: 6 ftToe length: 3 ft

PIER AND FOOTING DESIGN

Designed pier by considering a one foot section as a column

Strip footingWall thickness set at 18”

for constructability purposes

Base length: 1.8 mBase thickness: 0.3 m1 #3 bar/ft

ARMORING

Design a retaining wall to sit in between culverts

Above top of culverts, have a second, unreinforced concrete slab, at an angle

Culvert

Road Bed

FILL

Water flow

Angled slab

Retaining wall

APPROACHES

Not to be greater than 15 degree slopeWill depend on actual site conditions and

therefore will be determined on-site Needs to follow existing roadway

Sloping can begin on area over culverts as long as minimum required soil covering (depending on culvert size) is maintained

OTHER DESIGN CONSIDERATIONS

FLOW CALCULATIONS

Existing railroad bridge is the limiting factorRailroad bridge – two streams;

Our bridge – one stream;Comparable cross-sections = OK!

Assumed water height up to bank, and used this assumption to calculate an existing flow

If our culverts run full we are still OK as cross sectional area is larger than original cross sectional area

Will implement a grading plan, “just in case”

TOPOGRAPHY

SATELLITE IMAGE

RAILROAD BRIDGE

CONSTRUCTION PLAN

MATERIALS/COSTS

Based on volume of concrete of 40 m3 and volume of fill of 300 m3 and assumed 3:2:1 concrete mix ratio (ratio will be determined after speaking with locals who have experience with concrete)

Summarized material list: Portland cement, gravel, sand, culverts, wood for construction, protective gear, nails/fasteners, shovels, wheelbarrows, other tools

Total estimated cost: ~$9500 (US), NOT INCLUDING rebar costs

See design book for cost breakdown

OPERATION & MAINTENANCE

Sign posted that only one vehicle may pass at a time… Could post weight limit as well

Regular inspections should occur every 2 years (during the dry season)

Culverts need to be checked ever 6 months for debris/blockage, and cleared if necessary

Inspections should also be made after especially heavy storms

Maintenance up to community members/Prefectura in Oruro

FINAL DESIGN

QUESTIONS?