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beepedblacksmithUrban and Civil

Nov 29, 2013 (3 years and 11 months ago)

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Project

Constraints

Maximum

Expected

Traffic

Load
:


2

twenty
-
ton,

2
-
axle

trucks

per

week

Channel

Size
:

app
.

6

ft

wide

x

5
.
5

ft

deep

Available

Reinforcement

Sizes
:

European

sizes
:

6
,

8
,

10
,

14
,

16
,

&

20

mm

Available

Construction

Equipment
:

Front


end

loader,

simple

hand
-
held

tools

Additional

Concerns
:

There

is

a

field

of

large

granitic

boulders

that

makes

app
.

300

meters

of

the

road

leading

up

to

the

site

impassable

to

most

vehicles
.


Conclusion


The

concrete

pipe

culvert

solution

was

found

to

be

infeasible
.

The

final

design

is

a

double

box

culvert
.


Final

design

dimensions

and

reinforcement

of

the

culvert

and

gabion

wing

wall

are

shown

in

Fig
.

2



4
.

Results



The

Structure

was

designed

for

a

maximum

positive

moment

of

10

k
-
ft

and

a

maximum

negative

moment

of

7

k
-
ft
.


Only

one

size

of

reinforcement

was

used

for

flexure

in

all

members

to

reduce

the

need

for

cutting
.


The

Soil

was

found

to

be

type

A
2
-
5
,

good

bearing

soil
.


The

28
-
day

strength

of

the

concrete

mix

used

in

the

region

is

1500
psi
.



SCB

was

found

to

be

most

economical

pavement

solution

at

$
121
,
660

per

mile
.



Future

Directions

A

concrete

mix

shall

be

designed

and

tested

as

a

replacement

for

current

mixing

practices

in

the

area

in

order

to

raise

the

strength

of

the

concrete
.

The

structures

could

not

be

designed

according

to

code

at

a

strength

of

any

less

than

3000

psi
.

Continuing

communication

and

cooperation

with

all

involved

parties

will

be

necessary

to

eventually

implement

these

proposed

solutions
.

Abstract

In

Wum
,

Cameroon,

a

seasonally

flooding

stream

has

become

an

impediment

to

industry

and

social

progress

in

the

surrounding

area
.

A

permanent

crossing

structure,

especially

one

that

can

sustain

vehicular

traffic,

would

facilitate

the

exchange

of

goods

between

the

villages

and

open

the

way

for

a

planned

cooperative

village
-
wide

cash
-
crop

project

that

has

since

been

put

on

hold
.

The

area

in

which

the

structure

will

be

built

poses

challenging

constraints,

as

only

locally

available

materials

and

skills

may

be

used
.

Two

alternative

designs

were

created

under

guidance

from

the

AASHTO

LRFD

Bridge

Design

Manual

to

cross

the

400

cfs

stream,

a

reinforced

concrete

pipe

culvert

and

a

reinforced

concrete

double

box

culvert
.

The

double

box

culvert

was

found

to

be

more

economical

and

simpler

to

execute
.


References

AASHTO LRFD Bridge Design Specifications, 4
th

edition with 2008 Interim
Revisions

Concrete Pipe Association Concrete Pipe Design Manual

Wight, James K. &
MacGregor
,, James G.;
Reinforced Concrete Mechanics
and Design
, 5
th

e. 2009

Hibbeler
, R. C.;
Structural Analysis
, 7
th

e. 2009


Methods

Geotechnical


Soil

Samples

from

the

site

were

tested

to

explore

soil

conditions
.

The

soil

was

classified

using

the

AASHTO

Classification

System
.


All

structural

solutions

were

investigated

for

settlement

and

bearing

capacity

of

the

underlying

soil



The

wing

walls

(as

cantilever

walls)

were

investigated

for

external

stability

under

static

and

seismic

loads

using

AASHTO

LRFD

Bridge

Design

Specifications,

2008
.


The

slopes

leading

down

to

the

bridge

site

were

analyzed

for

global

stability

using

WinStabl
,

to

assess

whether

the

additional

traffic

l o a d s

e x p e c t e d

as

a

result

of

the

bridge’s

construction

will

cause

stability

issues
.

Concrete

/

Pavement


A

concrete

mix

similar

to

that

used

in

the

region

was

created

and

tested

for

14
-

and

28
-
day

strength
.


The

following

solutions

for

paving

of

the

route

from

the

main

village

to

the

crossing

site

were

investigated

using

FHWA

Standards
:


Rigid

(Concrete)

Pavement


Flexible

(Macadam)

Pavement


Cement

Modified

Soil

(CMS)


Soil

Cement

Base

(SCB)


Methods

for

removal

of

large

obstacles

and

diversion

of

river

flow

for

construction

were

explored
.


Structural


Two

alternative

solutions

using

reinforced

concrete

were

investigated,

a

pipe

culvert

and

a

double

box

culvert
.


Concrete

Pipe

Culvert
:

Pipe

designed

using

Concrete

Pipe

Association’s

Concrete

Pipe

Manual
,

Indirect

Design

Method
.


Double

Box

Culvert
:

Structure

designed

according

to

AASHTO

LRFD

Bridge

Design

Specifications,

2008
.

Software

analysis

was

performed

using

RISA,

hand

analysis

was

performed

using

the

Moment

Distribution

Method
.

Where

applicable,

reinforcement

was

designed

for

combination

flexure

and

axial

load
.

Figure 1: Current Temporary Foot Bridge

Figure
3: Reinforcement Details

Figure
4: Wing Wall Dimensions

Figure
5: RISA diagram of moment
envelope created by applied loads

Figure
2: Design Dimensions

Figure
6: Concrete
Cylinders After
Compression Testing
for 28
-
day Strength