List of Tables Table 2-2-1 Present Condition and Assessment of Concerned Bridges 2-2-2 Study on the Number of Lanes 2-2-3 The Result of Hydrological Analysis 2-2-4 Selection of Bridge Type 2-2-5 Undertakings of Both Governments 2-2-6 Quality Control for Materials and Concrete 2-2-7 Material Procurement Plan 2-2-8 Procurement Plan of Major Equipment 2-2-9 Implementation Schedule 2-5-1 Estimated Cost for Maintenance 3-1-1 Direct Effects of the Project

Abbreviations AASHTO American Association of State Highway and Transportation Officials DBST Double Bituminous Surface Treatment DESD Department of Economic & Social Development EIA Environmental Impact Assessment EL. Elevation GIP Government Investment Program G.L. Ground Level JICA Japan International Cooperation Agency JIS Japanese Industrial Standard kL kilo liter kVA kilo Volt Ampere PC Prestressed Concrete PIRE The Project for Improvement of the Ring Road in the Efate Island PRBRE The Project for Rehabilitation of Bridges on the Ring Road in the Efate Island PWD Public Works Department RC Reinforced Concrete

SUMMARY

Vanuatu is located on the Pacific rim earthquake belt. A large earthquake with magnitude of 7.2 occurred on 3rd January 2002 at 4:22 am local time which seriously affected the nearby the Efate Island. The epicenter was located 50 km west of the Efate Island at a depth of 21 km. The seismic event caused significant damage to several infrastructure assets in the vicinity of Port Vila. The Public Works Department (PWD) investigated and reported on the damages immediately after the earthquake, and detailed the restorative measures for the governmental assets. Emergency remedial works were undertaken on most structures except a few structures. However, an additional 550 million Vatu is required to perform the essential restoration works in addition to the emergency measures. In regard to the essential restoration works, few projects are executing with the assistance of donors due to insufficient funding.

The road network in the Efate Island is composed of the Ring Road encircling the

island with numerous other subsidiary branch roads. The Ring Road has the vital role of supporting the economic activities and daily life of the inhabitants, as the only arterial road connecting each villages and the capital Port Vila. On the eastern portion of this road, improvement works along 14.2 km section was executed by “the Project for Improvement of the Ring Road in the Efate Island” (PIRE) under the Japan’s Grant Aid in the period 1997 to 2000. As the result of PIRE, road closures caused by the cyclonic waves and storm water on the road were avoided and the serviceability of the road was highly improved.

The concerned bridges in this study, Teouma and Rentapao, are located on the improved section under PIRE. These bridges were damaged by the earthquake occurred on January 2002. The Government of Vanuatu executed urgent repairs for the minor damages but structural deficiencies were not solved. Under these situations, there is a high probability that the bridges may collapse or wash away by the cyclonic flood and so on. When the Ring Road is interrupted, the negative effects to the social and economic activities and daily life of the inhabitants will be huge, because no detour exists around the concerned bridges.

Although the Government of Vanuatu recognizes the necessity and the urgency of the essential restoration works, it is difficult to execute independently due to lack of funding.

Under these situation, the Government of Vanuatu made a request to the Government of Japan for grant aid for the essential restoration of the damaged bridges.

In response to the request, the Government of Japan decided to conduct a basic design study on the said project and entrusted the study to the Japan International Cooperation Agency (JICA). JICA sent to Vanuatu a study team from March 5th to March 28th, 2003. The

team held discussions with the relevant officials of the Government of Vanuatu and conducted field studies at the study area. After returning to Japan, the team prepared a basic design and implementation plan using the most appropriate scheme based on the result of the field studies. The contents of the study were compiled into a draft report. JICA then sent to Vanuatu a draft report explanation team from May 20th to May 30th, 2003, and the team held discussions on the contents of the draft report.

Based on the assessment of the present conditions of the concerned bridges, it is judged that proper restoration can not be achieved by structural repair and reinforcement because of the existence of structural deficiencies on both super-structure and sub-structure. Therefore the reconstruction of both Teouma and Rentapao bridges is required to complete the essential restoration. Finally proposed plan is outlined as follows:

Items Contents Detour / Temporary Bridge

Constructing Detour : 139ｍ＋96ｍ Temporary Bridge : 30.5ｍ＋12ｍ

Demolition of Existing Bridges

Demolition of Existing Teouma & Rentapao Bridges

Reconstruction of Bridges (Teouma & Rentapao)

Driving Foundation, Constructing Abutment, Manufacturing, Assembling & Erecting Truss Girder, Paving Slab Surface (DBST), etc.

Formation of Approach Road

Length of Runoff 230ｍ＋200ｍ, Travelled Way 7.0～6.0ｍ(2 lanes), Base Course (Coral), Surface Course (DBST)

Subsidiary Work Revetment, Road Marking, Guardrail, etc.

If the Project is implemented under the Japan’s Grant Aid, the periods for detailed design and construction are estimated at 2 months and 10 months respectively. Estimated project costs are 189 million Japanese Yen (188 million Yen borne by the Japanese side and 1 million Yen borne by the Vanuatu side).

Direct beneficiaries of the Project are the people residing in the Efate Island, amounting to 42,128 in 1999. The expected direct effects of the Project are as follows:

Present Issues Measures on the Project Direct Effect

It is concerned about the interruption of

the road by the collapse or washing

away of existing bridges because the

bridges are structurally unstable and

freeboards are insufficient

Remaining life : not presumed

(within 1year ~ less than 10years)

The reconstruction of the

bridges which structurally and

hydro- logically sound

(Teouma Bridge & Rentapao

Bridge)

To secure the road transport on

the Ring Road over the future

and to sustain the effects

brought by PIRE

Remaining life : over 50 years

Existing bridges have only one lane so

the vehicles are passing alternately. It

becomes a danger zone for travel on

the Ring Road such as seen by the

number of traffic accidents due to the

lack of necessary sight distance.

Necessary sight distance : 474m

to confirm the opposite vehicle at 60

km/hr which can not be secured due

to the road alignment

Possible running speed :

15 km/hr

To secure the 2 lanes

(elimination of one lane section)

and provide sidewalk

To improve the safety and

running quality by the

elimination of danger factors

Necessary sight distance : 75m

for stopping distance from 60

km/hr which is secured

Possible running speed :

60 km/hr

Additionally the improvement of the living convenience are expected by securing an all

weather road throughout the year.

As the result of this study, it is judged that the implementation of the Project under the Japan’s Grant Aid is appropriate by the reason that the project will bring great benefits to the ordinary citizens in particular within the rural areas, the implementation of the Project has the urgency as prioritized in the Government Investment Program, the Vanuatu side has sufficient ability in the organization, personnel & technology to maintain the facilities, no negative impact for the environment is expected, and so on.

To realize and sustain the effects of the Project, the Vanuatu side shall undertake the periodic inspection and adequate maintenance of not only the bridges but also the road.

TABLE OF CONTENTS

Preface Letter of Transmittal Location Map Perspective List of Tables Abbreviations Summary

Page Chapter 1 Background of the Project .......................................................................................... 1 Chapter 2 Contents of the Project................................................................................................ 3 2-1 Basic Concept of the Project....................................................................................... 3 2-2 Basic Design of the Requested Japanese Assistance .................................................. 3 2-2-1 Design Policy ................................................................................................... 3 2-2-2 Basic Plan ......................................................................................................... 6 2-2-2-1 Design Standard........................................................................................ 6 2-2-2-2 Number of Travel Lanes ........................................................................... 6 2-2-2-3 Design High Water Level and Freeboard.................................................. 7 2-2-2-4 Bridge Type .............................................................................................. 9 2-2-2-5 Foundation Type ....................................................................................... 12 2-2-2-6 Design Elements ....................................................................................... 12 2-2-2-7 Subsidiary Facilities.................................................................................. 13 2-2-2-8 Detour Plan ............................................................................................... 14 2-2-3 Basic Design Drawing ...................................................................................... 14 2-2-4 Implementation Plan......................................................................................... 59 2-2-4-1 Implementation Policy.............................................................................. 59 2-2-4-2 Implementation Conditions....................................................................... 59 2-2-4-3 Scope of Works......................................................................................... 60 2-2-4-4 Consultant Supervision ............................................................................. 61 2-2-4-5 Quality Control Plan ................................................................................. 62 2-2-4-6 Procurement Plan...................................................................................... 62 2-2-4-7 Implementation Schedule ......................................................................... 64 2-3 Obligations of Recipient Country ............................................................................... 66

2-4 Project Operation Plan ................................................................................................ 66 2-5 Estimated Project Cost................................................................................................ 67 2-5-1 Estimated Cost of Japan’s Grant Aid Project ................................................... 67 2-5-2 Estimated Cost for Maintenance....................................................................... 68 Chapter 3 Project Evaluation and Recommendations ................................................................. 69 3-1 Project Effect .............................................................................................................. 69 3-2 Recommendation ........................................................................................................ 69 Appendices Appendix 1 Member List of the Study Team Appendix 2 Study Schedule Appendix 3 List of Parties Concerned in Vanuatu Appendix 4 Minutes of Discussion Appendix 5 Cost Estimation Borne by the Vanuatu Side Appendix 6 Traffic Survey

- 1 -

Chapter 1 Background of the Project

The road network in the Efate Island is composed of the Ring Road encircling the island with numerous other subsidiary branch roads. The Ring Road, where the concerned bridges are located, is an important arterial road providing benefits to 1/3 of the national population. Consequently the road is regarded as one of the fundamental infrastructure assets in the island, which supports the economic activities and the daily life of the inhabitants, as the only arterial road connecting each villages and the capital Port Vila. On the eastern portion of this road, improvement works along 14.2 km section were started in 1997 by “the Project for Improvement of the Ring Road in the Efate Island” (PIRE) under the Japan’s Grant Aid, and the project was completed in February, 2001. As a result of PIRE, road closures caused by the cyclonic waves and storm water on the road were avoided and the serviceability of the road was highly improved. The concerned bridges in this study are located on the improved section under PIRE. As the result of the basic design study on PIRE, the reconstruction of the bridges was not considered a priority for the project. Instead of that, paving the bridge surface and installing bridge railing and guardrail at approaches were planned to remedy deficiencies. It was recommended that Vanuatu side shall take adequate measures for structural changes of the bridges in the future. However, Teouma and Rentapao bridges were damaged by the earthquake occurred on January, 2002, and their deficiencies were beyond the limits of maintenance assumed by Vanuatu side. The Government of Vanuatu executed urgent repairs for the minor damages but structural deficiencies were not solved. Under these situations, there is a high probability that the bridges may collapse or wash away by the cyclonic flood and so on, because the destabilized condition of the bridges still remains and the hydro logical flow capacity of the bridges is insufficient for the designated flood volume. In the case the Ring Road is cut by damage of the bridge, which is located on the south of the island, the people residing the east of the island will be forced to travel the additional 100km to the reverse direction, because no detour exists around the concerned bridges. In addition, the people residing in the southern area between the Teouma and Rentapao Bridges, amounting to approximately 900, will be isolated if both bridges become impassable. Consequently, when the Ring Road is interrupted, the negative effects to the economic activities and daily life of the inhabitants will be huge and also the benefits brought by PIRE will not be sustained. Although the replacement of the existing bridges with two lanes is proposed by the Public Works Department (PWD) for the essential restoration apart from the emergency measures, nothing is scheduled due to the insufficient financing. But the danger of collapse or washing

- 2 -

away of the bridges still exists. As a contingency measure, PWD procured used Bailey Bridge from New Zealand to be able to secure the road transport for emergency bridging in the event that one of the bridges collapse or is washed away. Thus the importance of the concerned bridges were recognized well, but the commencement of the essential restoration is dependant on the assistance of the donors. Any work has been deferred more than 1 years, so the execution of the essential restoration of the concerned bridges is an urgent subject for Vanuatu. Under these situation, the Government of Vanuatu made a request to the Government of Japan for grant aid for the essential restoration of the bridges damaged by the earthquake. The items of the request finally confirmed in this study are as follows: - Reconstruction of the Teouma bridge with 2 lanes and a walkway for the pedestrians - Reconstruction of the Rentapao bridge with 2 lanes and a walkway for the pedestrians - Riverbank protection around the above-mentioned bridges

- 3 -

Chapter 2 Contents of the Project

2-1 Basic Concept of the Project

1) Overall Goal and Objective of the Project Because of the earthquake happened on January 2002, several infrastructures assets suffered damage around the capital Port Vila in the Efate Island. The Government of Vanuatu executed the emergency measures, but the essential restoration for other structures is not scheduled.

Against this condition, the Government of Vanuatu regards the completion of the proposed essential restoration as an urgent subject. In particular, the top priority is allocated to the restoration of road network supporting the economic activities of the nation and daily life of the inhabitants in the island. Among those, this project aims to maintain the function of the Ring Road through the essential restoration of the damaged bridges.

2) Basic Concept of the Project

This project covers the essential restoration and maintenance of the damaged Teouma Bridge and Rentapao Bridge on the Ring Road to achieve the overall goal outlined above. By implementing the project, it is expected to avoid the collapse/washing away of the bridges. This will; - Secure the road traffic over the future - Improve the traffic safety - Improve living convenience The Japan’s Grant Aid will be extended for the reconstruction of Teouma and Rentapao bridges and the formation of the road approach.

2-2 Basic Design of the Requested Japanese Assistance 2-2-1 Design Policy

1) Assessment of the Present Condition The content of the request from the Government of Vanuatu is the reconstruction of Teouma Bridge and Rentapao Bridge damaged by the earthquake. It studied the adequacy of restoration by repair / reinforcement or reconstruction based on the result of the detailed inspection on the condition and extent of the damages.

- 4 -

The present condition of bridges and its assessment are shown in Table 2-2-1.

Table 2-2-1 Present Condition and Assessment of Concerned Bridges Parts Present Condition Assessment

Super Structure

Broken element between pier and girder Inclined and subsided largely by the damage of sub structure

It is not realistic to repair because of the necessity of reconstruction of sub structure after jacking up the super structure.

Sub Structure

Inclined and buckled pile bent type pier and broken pile Dislocated and inclined gabion type abutment

It is difficult to stop additional buckling and inclining due to the structural nature, so reconstruction is only essential counter measure.

Teou

ma

Brid

ge

Other Parts

Filled one span of the bridge on the left bank side with masonry as an urgent counter measure

Concern exists regarding the bridge washing away because of un-jointing super structure and lack of freeboard during high flood water levels

Super Structure

Broken end part of main girder Cracked and split concrete generally and corroded steel bars

There is a deficiency at the point of max. shearing stress and corrosion of main reinforcement, so reconstruction is the only essential counter measure.

Sub Structure

Dislocated gabion type abutment

It is difficult to stop movement of the abutment due to the structural nature, so reconstruction is only essential counter measure.

Ren

tapa

o B

ridge

Other Parts

Serious scour adjacent to the bottom of abutments

Concern exists regarding the bridge washing away because of un-jointing super structure and lack of freeboard during high flood water levels

As the result of the study, it is judged that proper restoration can not be achieved by structural repair and reinforcement because of the existence of structural deficiencies on both super-structure and sub-structure at both bridges. Moreover, the existing bridges don’t have the necessary freeboard against flood water levels, so it requires the raising of the bridge elevation. Therefore, the scope of the Japanese Assistance Project shall be the reconstruction of Teouma Bridge and Rentapao Bridge and formation of road approaches.

2) Natural Condition

Efate Island belongs to a tropical oceanic climate and the temperature fluctuates between 15℃and 32℃. Because of the limited temperature range, the structural parts and construction conditions are not affected by significant thermal movement or extreme temperature. Only concrete placement work shall be considered as hot-weather concreting.

The rainy season extends from December to April and may also include many cyclones which may hit the island. The maximum daily rainfall for the last 10 years

- 5 -

is 377.4 mm, so the work in the river basin becomes difficult during the rainy season due to the flash flooding after the heavy rain. This situation affects not only the construction of the sub-structure and the size of the temporary bridge detour but also the erection method of the super-structure. Therefore, for the selection of super-structure type, it is necessary to study the required construction period.

Vanuatu belongs to the Pacific rim earthquake belt and has experienced a large number of earthquakes like the one experienced in 2002. Therefore it is applying the seismic resistant design in this project.

The concerned bridges are located inland from the sea and the sea breeze does not adversely affect the site. But both rivers levels at the concerned bridges can be influenced by the tidal height, so the rust and salt damage will be accelerated by the salt in the air. In the selection of the bridge type, it is necessary to study a structure that can tolerate an environment where rust and salt damage is a concern.

3) Social Condition

The right of way for the Ring Road is a reserve 20m in width and the land outside of right of way is owned by private persons. Considering the effects to the social environment, it is necessary to avoid the need for land acquisition. Therefore the horizontal alignment shall not be changed and the new bridges will be constructed at the existing locations. But it is necessary to raise the road approaches as a consequence of the new bridge elevation. With a higher embankment, the embankment toe may impinge upon the boundary of the right of way, so there is a benefit to lower the bridge surface level to the minimum during the selection of bridge type. This concept of using a lower level on the approach road will decrease the direct cost related to the reduced work volume.

Both concerned bridges on the two lane road are one lane, and vehicles are passing alternately at present. This creates a danger zone for the vehicles which has resulted in fatal accidents, so it is a requirement of the design that it considers the safety for the road user and the social environment. In particular, it studies and adopts the cross section composition of the bridge with due attention to the social environment.

4) Construction Condition

Vanuatu is an archipelago of small islands and the demand for civil works is small. There is general purpose equipment for the construction, but there is a lack of large equipment and specialized equipment locally e.g. large crane, pile driving equipment, tensioning jacks for prestressing and launch hydraulic pumps for bridge

- 6 -

construction. In the selection of bridge type, it studies the construction method without the need for such large equipment and special equipment to reduce the project cost. The commonly used coarse aggregate for concrete is crushed coral produced in the Efate Island, but high strength concrete is not attained due to the insufficient strength of the coarse aggregate. Generally it is known that concrete using coral material for the aggregate may easily neutralize with the carbonic acid gas in the atmosphere due to the lower density and higher porosity of the coarse aggregate. In the case high strength concrete is used in the project, it will be costly because the coarse aggregate will be imported such as abrasion resistant aggregate used for DBST of the road surface. For the selection of bridge type, it adopts economic considerations and ease of maintenance under the local construction conditions.

5) Construction Period

Shortening of the construction period, which relates to cutting down indirect costs, is an important factor for the reduction of project costs on the project with a small direct cost as in this case. Therefore this project shall be planned to execute with a single financial year’s budget, and it studies construction period not only with the possibility of completion within the given period but also with being more shortened during the selection of bridge type.

2-2-2 Basic Plan 2-2-2-1 Design Standard

There is no specific Vanuatu design standard for the bridge and most designs are based on the design standard of neighbours Australia and New Zealand. Road design on PIRE was based on AUSTROADS of Australia. As mentioned in previous paragraph, this project applies seismic resistance design for the bridge design, so the design for the bridges is in accordance with the Japanese Road Bridge Design Standards, which is well advanced in seismic analysis methods. With regard to the road design, it follows the precedent set under PIRE, which followed the AUSTROADS standards.

2-2-2-2 Number of Travel Lanes

Although the road section improved by PIRE has 2 lanes, the width of concerned both bridges is only 1 lane with a narrowing of the road approaches. It studied the necessary number of lanes for the reconstructed bridges. Table 2-2-2 shows the result of the study.

- 7 -

Table 2-2-2 Study on the Number of Lanes Item Result Outlines of the Study

Road Grade 2 lane The Ring Road is the arterial road in the road network and its role is not limited within a community. 2 lanes are required according to the road classification.

Alignment 2 lane In the case of one lane, the necessary sight distance to recognize the opposite vehicle is not attained due to the road alignment. 2 lanes are required by the alignment.

Design Standard

2 lane Design standard regulates that the number of lanes shall be the same as the approaching road even on the bridge. 2 lanes shall be secured in accordance with the design standard.

Traffic Capacity

1 lane Even if one lane is applied, traffic capacity is enough for approximately 300 vehicle/hour, which will not lead to traffic congestion in future.

Safety 2 lane There were fatal accidents at the concerned bridges, and the dangerous nature shall be reduced with the adoption of 2 lanes which is the same as the approach road.

Coordination 2 lane Out of 5 bridges and 4 box culverts located on the improved section of Ring Road, only the concerned 2 bridges are narrower than the road width.

Cost 1 lane A one lane bridge has an advantage on the project cost due to the reduction of surface area of bridge and sub-structure.

On the items of design standard and safety listed above, which is considered particularly important, it is judged to be a two lane bridge. Considered with the social environment, it is never allowed to disregard the safety aspect. Therefore the proposed bridges in this project shall be designed in a two lane format which is the same as the approach road.

2-2-2-3 Design High Water Level and Freeboard

Design high water level is based on the time of concentration and discharge volume calculated by the hydrological analysis. The data of rainfall intensity, which was analyzed from rainfall data over the last 51 years, is available in Vanuatu and utilized in this project. For the design calculations the Kiripich Formula is applied on the time of concentration and The Rational Formula is applied on the discharge volume. The respective formulae are shown below.

Kiripich Formula TC = LS

1.15 / 51H0.385 TC : Time of Concentration (min) LS : Length of longest watercourse in the watershed (m) H : Elevation differences with most far point (m)

- 8 -

Rational Formula QP = 0.278 CIA

QP : Discharge volume (m3/s) C : Runoff coefficient I : Rainfall Intensity (mm/hr) A : Watershed area (km2)

Teouma River has 82km2 of watershed area and 22km of watercourse length and is a normal river with a shape ratio of 0.17. The distance from river mouth to the bridge is approximately 2.8km and the tidal effect is comparatively small. Although ordinal velocity is observed between 0.3 and 0.6m/s, it is estimated to be 2～3m/s during a flood. So it is observed the traces of erosion on the riverbank. Rentapao River has 44km2 of watershed area and 15km of watercourse length and is a normal river with a shape ratio of 0.22. The tidal effect is large due to the 1.3 km in distance from river mouth to bridge and the low elevation of the riverbed at the bridge site. The results of the hydrological analysis are shown in Table 2-2-3.

Table 2-2-3 The Result of Hydrological Analysis

Discharge Vol.(m3/s) Flood level (EL.m)

Watershed

area

River

Elevation ∆Elv. Grade

50yr 20yr 10yr 50yr 20yr 10yr Past Max.

Teouma 82.1km2 0.1m 487m 2.26％ 475.6 385.1 303.0 7.73 6.81 5.88 6.8

Rentapao 44.0km2 -2.2m 332m 2.29％ 236.1 188.3 145.7 3.94 3.29 2.72 3.3

Past maximum flood level shown in the above table is based on interviews with the inhabitants living near the bridges, and it approximately corresponds to the 20 years return period flood level. At both bridges, the river overflows and flood water covers the bridge surface and approach road during the past maximum flood. In the case where the bridge and road approaches are at a higher elevation, the flood level may increase at the upstream because of the damming effect of the high embankments of the road approaches. Therefore it is important to position the bridge surface level lower to the utmost. Considered all factors including the land acquisition mentioned in the previous paragraph, it is decided that the design high water levels shall be adopted as shown below. Teouma Br. : Design High Water Level EL. 5.8m + Freeboard 1.0m, Bottom of Girder - EL. 6.8m Rentapao Br. : Design High Water Level EL. 2.3m + Freeboard 1.0m, Bottom of Girder - EL. 3.3m

- 9 -

In summary the bridges will not be submerged at the past maximum flood level corresponding to the 20 years return period flood, but they will be submerged at the 50 years return period flood. Consequently it is necessary to allow for all considerations in designing the bridge for the submergence.

2-2-2-4 Bridge Type

For the selection of bridge type, it studies components based on the seismic resistance, constructability, construction period, structure height (bridge surface level), project cost and maintenance procedures. The results of the study are shown in Table 2-2-4 and it was decided to adopt the simple pony truss type on both Teouma and Rentapao bridge, which was judged as having the general advantages.

Tabl

e 2-

2-4　

Sel

ectio

n of

Brid

ge T

ype

1/2　

(Teo

uma

Brid

ge)

Type

Sim

ple

PC T

Sha

pe G

irder

Sim

ple

Plat

e G

irder

Sim

ple

Pony

Tru

ss2-

span

Sim

ple

Com

posi

te H

shap

e G

irder

Side

view

Sect

ion

Stru

ctur

alH

eigh

t

Brid

ge su

rfac

e be

com

es h

ighe

r with

stru

ctur

al h

eigh

t 1.8

5m, s

o ne

edin

g ne

wly

land

acq

uisi

tion

and

dam

min

g th

e flo

od b

yem

bank

men

t of a

ppro

ach

road

Brid

ge su

rfac

e be

com

es h

ighe

r with

stru

ctur

al h

eigh

t 1.8

4m, s

o ne

edin

g ne

wly

land

acq

uisi

tion

and

dam

min

g th

e flo

od b

yem

bank

men

t of a

ppro

ach

road

Brid

ge su

rfac

e ca

n se

tup

low

er le

vel

with

stru

ctur

al h

eigh

t 0.8

m d

ue to

the

thro

ugh

brid

ge.

Brid

ge su

rfac

e ca

n se

tup

low

er le

vel w

ithst

ruct

ural

hei

ght 0

.67m

,but

a p

ier h

ampe

rsw

ater

flow

so d

esig

n flo

od le

vel s

hall

bera

ised

.Se

ism

icR

esis

tanc

eB

ehin

d fo

r sei

smic

resi

stan

ce b

y th

e he

avy

supe

r-st

ruct

ure

whi

ch a

ll m

ade

by c

oncr

ete

Adv

ance

for s

eism

ic re

sist

ance

with

ligh

tsu

per-

stru

ctur

eA

dvan

ce fo

r sei

smic

resi

stan

ce w

ith li

ght

supe

r-st

ruct

ure

Beh

ind

for s

eism

ic re

sist

ance

than

1-

span

due

to b

eing

pie

r with

2 p

oint

s

Wor

kabi

lity

& N

eces

sary

Tim

e

[All

stag

ing

met

hod]

Con

cret

e fo

r sla

ban

d gi

rder

can

pla

ce a

t the

sam

e tim

e,bu

t nee

ding

to se

tup

stag

ing

in th

e riv

er.

Con

stru

ctio

n pe

riod

is 1

5 m

onth

s

[Ere

ctio

n w

ith c

rane

met

hod]

It n

eeds

larg

e cr

ane

for e

rect

ion

of g

irder

whi

ch is

13 t/

gird

er, a

nd h

andi

ng w

ill b

e di

ffic

ult

due

to it

s 30m

in le

ngth

Con

stru

ctio

n pe

riod

is 1

3.5

mon

ths

[Lau

nchi

ng e

rect

ion

met

hod]

Eac

h pa

rts is

smal

l and

no

larg

e eq

uipm

ent i

s nec

essa

ryto

ere

ct. (

use

Ren

tapa

o br

idge

as l

aunc

hing

nose

)C

onst

ruct

ion

perio

d is

13

mon

ths

[Sta

ging

or s

uspe

nded

stag

ing

met

hod]

It

incr

ease

s wor

k vo

lum

e of

pie

r and

nee

dsco

ffer

dam

and

wor

king

stag

e fo

r its

cons

truct

ion

wor

k.C

onst

ruct

ion

perio

d is

15

mon

ths

Mai

nten

ance

Bec

ause

of c

oncr

ete

stru

ctur

e, it

isdi

ffic

ult t

o m

aint

ain

salt

dam

ages

and

neut

raliz

atio

n of

con

cret

e

In p

rinci

ple,

stee

l par

ts a

re m

aint

enan

cefr

ee b

y pr

otec

ted

with

hot

dip

ped

galv

aniz

ed. R

C sl

ab w

ill b

e ne

edin

gre

plac

emen

t in

futu

re b

y sa

lt da

mag

e an

dne

utra

lizat

ion

of c

oncr

ete.

In p

rinci

ple,

stee

l par

ts a

re m

aint

enan

cefr

ee b

y pr

otec

ted

with

hot

dip

ped

galv

aniz

ed. C

oncr

ete

surf

ace

of sl

ab w

illpr

even

t sal

t dam

age

and

neut

raliz

atio

n by

cove

red

with

dec

k pl

ate

and

bitu

men

.

Bot

tom

of H

gird

er is

pro

tect

ed w

ith h

otdi

pped

gal

vani

zed

for m

aint

enan

ce fr

ee,

but i

t is d

iffic

ult t

o m

aint

ain

salt

dam

ages

and

neut

raliz

atio

n of

con

cret

e po

rtion

Cos

t

Nee

ding

impo

rt of

agg

rega

te a

nd n

ewly

proc

urem

ent o

f mix

ing

plan

t for

con

cret

ean

d in

crea

sing

wor

k vo

lum

e of

app

roac

hro

ad

Nee

ding

larg

e cr

ane

for e

rect

ion

and

incr

easi

ng w

ork

volu

me

of a

ppro

ach

road

, but

shor

ten

cons

truct

ion

perio

d

Not

nee

ding

larg

e eq

uipm

ent,

decr

easi

ngw

ork

volu

me

of a

ppro

ach

road

and

shor

ten

cons

truct

ion

perio

d

Not

nee

ding

larg

e eq

uipm

ent a

ndde

crea

sing

wor

k vo

lum

e of

app

roac

hro

ad, b

ut in

crea

sing

wor

k vo

lum

e of

foun

datio

n an

d su

b-st

ruct

ure

Ass

essm

ent

C :

Prob

lem

s on

the

mai

nten

ance

B :

Beh

ind

on h

ydro

logy

, mai

nten

ance

, etc

A :

Adv

ance

on

alm

ost a

ll ite

ms

C :

Prob

lem

s on

the

mai

nten

ance

- 10 -

Tabl

e 2-

2-4　

Sel

ectio

n of

Brid

ge T

ype

2/2　

(Ren

tapa

o B

ridge

)Ty

peSi

mpl

e R

C T

Sha

pe G

irder

Sim

ple

Plat

e G

irder

Sim

ple

Pony

Tru

ssSi

mpl

e C

ompo

site

H sh

ape

Gird

er

Side

view

Sect

ion

Stru

ctur

alH

eigh

t

Brid

ge su

rfac

e be

com

es h

ighe

r with

stru

ctur

al h

eigh

t 1.2

5m, s

o ne

edin

gne

wly

land

acq

uisi

tion

and

dam

min

g th

eflo

od b

y em

bank

men

t of a

ppro

ach

road

Brid

ge su

rfac

e be

com

es h

ighe

r with

stru

ctur

al h

eigh

t 1.2

4m, s

o ne

edin

gne

wly

land

acq

uisi

tion

and

dam

min

g th

eflo

od b

y em

bank

men

t of a

ppro

ach

road

Brid

ge su

rfac

e ca

n se

tup

low

er le

vel

with

stru

ctur

al h

eigh

t 0.8

m.

Brid

ge su

rfac

e ca

n se

tup

low

er le

vel

with

stru

ctur

al h

eigh

t 0.6

7m.

Seis

mic

Res

ista

nce

Beh

ind

for s

eism

ic re

sist

ance

by

the

heav

ysu

per-

stru

ctur

e w

hich

all

mad

e by

con

cret

eA

dvan

ce fo

r sei

smic

resi

stan

ce w

ith li

ght

supe

r-st

ruct

ure

Adv

ance

for s

eism

ic re

sist

ance

with

ligh

tsu

per-

stru

ctur

eB

ehin

d fo

r sei

smic

resi

stan

ce b

y th

ehe

avy

supe

r-st

ruct

ure

Wor

kabi

lity

& N

eces

sary

Tim

e

[All

stag

ing

met

hod]

Con

cret

e fo

r sla

ban

d gi

rder

can

pla

ce a

t the

sam

e tim

e,bu

t nee

ding

to se

tup

stag

ing

in th

e riv

er.

Con

stru

ctio

n pe

riod

is 1

4 m

onth

s

[Ere

ctio

n w

ith c

rane

met

hod]

No

stag

ing

is n

eces

sary

and

it c

an sh

orte

nth

e tim

e fo

r the

ere

ctio

n w

ork.

Con

stru

ctio

n pe

riod

is 1

2.5

mon

ths

[Lau

nchi

ng e

rect

ion

met

hod

with

cra

ne]

No

stag

ing

is n

eces

sary

and

it c

ansh

orte

n th

e er

ectio

n w

ork.

Con

stru

ctio

n pe

riod

is 1

2 m

onth

s

[Sta

ging

or s

uspe

nded

stag

ing

met

hod]

Even

ado

pted

susp

ende

d st

agin

g, it

'sne

edin

g su

ppor

t fix

ing

in ri

ve fo

r sca

ffol

d.C

onst

ruct

ion

perio

d is

13

mon

ths

Mai

nten

ance

Bec

ause

of c

oncr

ete

stru

ctur

e, it

isdi

ffic

ult t

o m

aint

ain

salt

dam

ages

and

neut

raliz

atio

n of

con

cret

e

In p

rinci

ple,

stee

l par

ts a

re m

aint

enan

cefr

ee b

y pr

otec

ted

with

hot

dip

ped

galv

aniz

ed. R

C sl

ab w

ill b

e ne

edin

gre

plac

emen

t in

futu

re b

y sa

lt da

mag

e an

dne

utra

lizat

ion

of c

oncr

ete.

In p

rinci

ple,

stee

l par

ts a

re m

aint

enan

cefr

ee b

y pr

otec

ted

with

hot

dip

ped

galv

aniz

ed. C

oncr

ete

surf

ace

of sl

ab w

illpr

even

t sal

t dam

age

and

neut

raliz

atio

n by

cove

red

with

dec

k pl

ate

and

bitu

men

.

Bot

tom

of H

gird

er is

pro

tect

ed w

ith h

otdi

pped

gal

vani

zed

for m

aint

enan

ce fr

ee,

but i

t is d

iffic

ult t

o m

aint

ain

salt

dam

ages

and

neut

raliz

atio

n of

con

cret

e po

rtion

Cos

tN

eedi

ng n

ewly

pro

cure

men

t of m

ixin

gpl

ant f

or c

oncr

ete

and

incr

easi

ng w

ork

volu

me

of a

ppro

ach

road

Incr

easi

ng w

ork

volu

me

of a

ppro

ach

road

but

shor

ten

the

cons

truct

ion

perio

dR

educ

ing

wor

k vo

lum

e of

app

roac

h ro

adan

d sh

orte

n th

e co

nstru

ctio

n pe

riod

Nee

ding

new

ly p

rocu

rem

ent o

f mix

ing

plan

t for

con

cret

e an

d de

crea

sing

wor

kvo

lum

e of

app

roac

h ro

adA

sses

smen

tC

: Pr

oble

ms o

n th

e m

aint

enan

ceB

: B

ehin

d on

hyd

rolo

gy a

nd m

aint

enan

ceA

: A

dvan

ce o

n al

mos

t all

item

sC

: Pr

oble

ms o

n th

e m

aint

enan

ce

- 11 -

- 12 -

2-2-2-5 Foundation Type Geotechnical drilling investigation was carried out during the site survey for the confirmation of the soil characteristics for the bridge foundation. At the Teouma bridge, the layer from ground level to G.L. -6m is clayish sand, and the layer down to G.L. -20m is sand. The groundwater level is higher and soil layer displays low capacity with N-value between 3 and 11. At Rentapao bridge, the layer from ground level to G.L. -7m is a calcareous layer with N-value between 3 and 10, and layer down to G.L. -15m is a weathered coral layer with comparatively high N-value over 12. On both bridges pile foundations are employed because of the large depth to the bearing layer. Regarding pile type, a precast pile has an advantage on the constructability and construction period. The H shape Universal Column type steel pile, which will be driven by a vibro hammer, is the most advantageous considering the cost reduction and minimization of the pile driving equipment.

2-2-2-6 Design Elements As mentioned in the previous section, the Japanese Road Bridge Standard is utilized as the design standard for the bridges. Design elements, decided through the discussion with Vanuatu side and Japan side, are as follows: 1) Design Load

- Live Load : A Live Load (P1=0.35 t/m2, P2 =1.0 t/m2, loading length 6.0m) - Sidewalk Live Load : 0.35 t/m2 - Impact Load : i=20/(50+L), L means Span Length (m) - Seismic Load : seismic coefficient=0.26 (estimated from previous earthquake and

soil conditions)

2) Materials - Steel : Rolled Steel H Shape (JIS SS400, SM490) Rolled Steel Plate (JIS SS400, SM400, SM490) High Tension Bolt (JIS F8T) - Corrosion Protection : Hot Dipped Galvanizing (JIS HDZ55) Standard bond volume Truss Parts : more than 550 g/m2 Deck Plate & High Tension Bolt : more than 350 g/m2 - Concrete : Compressive Strength δC = 21 N/mm2 - Steel Bar : Tension Strength (Normal) δS = 160 N/mm2 Tension Strength (Seismic) δS = 270 N/mm2

- 13 -

3) Soil Condition

Classification of Soil : Sand (Teouma Bridge) Clayish Sand (Rentapao Bridge) N-Value : N=10 (Teouma Bridge) N=20 (Rentapao Bridge) Unit Weight of Soil : γ = 18 kN/m3 Internal Friction Angle : φ = 25°

4) Maintenance

As the basic policy of the design, it seeks to minimize the lifecycle cost of both super-structure and sub-structure. - If normal paint is used, it is necessary to periodically repaint the steel structure

due to the deleterious effect of salt damage. For rust and corrosion protection, steel parts shall be coated by hot dipped galvanizing.

- Minimum concrete cover for the sub-structure shall be secured 70mm to counteract the potential for salt damage and neutralization of concrete.

2-2-2-7 Subsidiary Facilities

1) Revetment It is estimated the flood water velocity achieves 2 to 3m/s on both Teouma and Rentapao bridges. To protect the river bank from erosion and to prevent scouring at the bottom of abutments, wire cylinder revetments shall be constructed.

2) Guardrail

Although the bridge width is widened the road approaches will narrow due to the reduction in the shoulder width. Both rivers normally have a significant water depth which will create a dangerous situation if a vehicle leaves the road formation and as a result falls into the river and becomes submerged. To secure the safety of vehicle and passengers, guardrail shall be installed at both road approaches to the bridge. The steel elements of the pony truss have a relatively small cross section, which may be easily bent by vehicle impact, so the guardrail will be provided on the kerb.

3) Road Marking

Centerline and edge line shall be painted on the new road surface and bridge surface to be the same with other road portion. Additionally delineators shall be installed on the kerb of bridges to improve the visibility at night because of the lack of lighting at the bridge sites.

- 14 -

2-2-2-8 Detour Plan It is necessary to provide at least one lane for the detour for the present traffic because the proposed bridge will be constructed at the existing bridge location. Moreover a separate working stage will not be constructed so construction equipment will also utilize the detour for the site movement. The detour at the Teouma Bridge will be constructed on the downstream side and the temporary bridge (L=30m) is placed by utilizing the Bailey bridge owned by PWD. After the removal of temporary bridge, the Bailey bridge shall be properly maintained and returned. The timber deck slab owned by the PWD will not be used because it may be severely damaged during the utilization, so it is planned to procure new timber deck slab under this project. The detour at the Rentapao Bridge will be constructed on the downstream and the temporary bridge (L=12m) is constructed using timber deck slab and I beams procured under this project. The temporary bridges shall be constructed approximately 50cm above normal water levels to effectively reduce the embankment height. Abutments will be constructed with gabions to mitigate the water pollution by the mud. The detour shall be removed at the end of the project and restored the river bank to the original condition.

2-2-3 Basic Design Drawing

Finally proposed plan is outlined as follows:

Detour / Temporary Bridge

Constructing Detour : 139ｍ＋96ｍ Temporary Bridge : 30.5ｍ＋12ｍ

Demolition of Existing Bridges

Demolition of Existing Teouma & Rentapao Bridges

Reconstruction of Bridges (Teouma & Rentapao)

Driving Foundation, Constructing Abutment, Manufacturing, Assembling & Erecting Truss Girder, Paving Slab Surface (DBST), etc.

Formation of Approach Road

Length of Runoff 230ｍ＋200ｍ, Travelled Way 7.0～6.0ｍ(2 lanes), Base Course (Coral), Surface Course (DBST)

Subsidiary Work Revetment, Road Marking, Guardrail, etc. Basic Design Drawings are shown after this page.

- 15 -

- 16 -

- 17 -

- 18 -

- 19 -