Table 3.3.1 Selected Bridges For Urgent Rehabilitation

Final ReportThe Study on the Road Network Developmentin the Kingdom of CambodiaOctober 2006The above choice is based on cost and past bridge construction experience in Cambodia.Sincemost bridges are in rural areas, noise produced during pile driving will not be a problem.Although RC and PC Driven piles are still applicable for longer piles ( 20m), the difficulty lies infabricating longer piles that need to be transported or lifted in place prior to driving.splicing longer driven piles requires strict quality control.proposed for bearing layers deeper than 20m.Moreover,RC Cast-in-place piles are thusThis pile type is becoming widely used inCambodia in recent bridge projects.Table 3.3.4ItemsPier on Spread FootingComparison of Foundation TypesPier on RC Driven PilesPier on Steel H-PilesPier on RC Cast-in-PlacePilesSectionRC Driven Piles Applicable to bearinglayer less than 5m deep Used for bearing typenot susceptible to scouraction Used for soft upperlayer Applicable to deepbearing layer Most common typeused in Cambodia Stable to scour actionConstructability Easiest construction Need to embed footingto sandstone layer forstability Need crane for handlingpiles and for piledriving Difficult to drive onhard intermediate layer Difficult to handle longpiles ( 20m) –transportation anddrivingConstructionPeriod Shortest constructionperiodCost Cheapest cabilitySteel H Driven Piles Used for soft upperlayer Applicable to deeperbearing layer than RCdriven piles Stable to scour action Construction period is90% of RCcast-in-place pile period Construction cost is70% of RCcast-in-place pile cost Need crane for handlingpiles and for piledriving; handling iseasier than RC piles Applicable to hardintermediate layer Difficult to handle longpiles ( 20m) –transportation anddriving Construction period is90% of RCcast-in-place pile period Construction cost is120% of RCcast-in-place pile cost Minimal environmentalimpact; care should betaken during excavation Noise and vibrationproduced during driving Not recommended onurban areas Noise and vibrationproduced during driving Not recommended onurban areasRECOMMENDED FORSHALLOW HARDBEARING LAYERRECOMMENDED FORPILE LENGTHS LESSTHAN 20MNOT RECOMMENDEDDUE TO HIGH COST Used for soft upperlayer Applicable to deeperbearing layer thandriven piles Becoming popular typeused in Cambodia Stable to scour action Need facilities fordrilling and rebarfabrication Careful quality controlrequired Applicable for longerpile lengths ( 20m)since piles are drilledand cast-in-place Construction period islonger than other types Construction cost ismore expensive thanother types Requires propermeasure for preventionof water pollution anddisposal of wastematerialsRECOMMENDED FORPILE LENGTHGREATER THAN 20MFor RC Deck Girder or PC I-Girder Bridges with multiple spans, the pier type recommended iscolumn type pier with thinner wall dimensions to minimize river obstruction. Moreover, sinceFS-B-3-24

Final ReportThe Study on the Road Network Developmentin the Kingdom of CambodiaOctober 2006water level during ordinary time in most bridge locations are minimal (or practically none), thetop of pier foundation (footing or pile cap) shall be located at least 1.0m below the river bed.Gabion mattress shall be provided to minimize local scouring on river bed.For RC Slab Bridges with multiple spans, wall pier monolithic with superstructure isrecommended since the slab bridge spans are typically shorter and requires no bearing supports.(2)Superstructure TypesThe choice of superstructure for the Urgent Bridge Rehabilitation depends on the scale of thebridge (bridge length, bridge spans, etc.) which is based on the existing topography, riverdischarge and maximum flood level.Table 3.3.5 presents some of the common forms ofsuperstructure applicable to the range of bridges in this study.In this study, concrete bridge is preferred over steel bridge basically because:(1)concrete bridges requires minimal maintenance compared to steel bridges,(2)steel bridges generally cost more than concrete bridges (see Table 3.3.6), and(3)past experience in bridge construction in Cambodia is directed more to concrete bridges.A comparative study of superstructure types for the bridges in “The Project for Rehabilitation ofBridges Along the Main Trunk Roads in Cambodia” (JICA, on-going construction) wasundertaken comparing concrete alternatives with steel alternatives.The results of the alternativetypes study indicate that concrete bridges (precast, prestressed girder type) are more applicableand cost-effective than steel bridges as summarized in Table 3.3.6.For bridge spans 12m or less, cast-in-place reinforced concrete slab bridge is preferred since:(1) it requires less structure depth and advantageous in bridge sites where the existing roadvertical profile has less room for adjustment,(2) this type has the least cost at this span range, and(3) since the bridge scale is small, simple construction methodology using cast-in-placeconcrete is applicable.For bridge spans greater than 12m until 20m, cast-in-place reinforced concrete girder bridge ispreferred since this is most cost-effective at this range.For bridge spans greater than 20m, precast prestressed I-girder is preferred since:(1) this is cost competitive at this span range, and(2) construction period is shorter since the girders are precast and erected in place to supportthe cast-in-place deck slab.FS-B-3-25

Final ReportThe Study on the Road Network Developmentin the Kingdom of CambodiaTable 3.3.5Typical Superstructure Choices for BridgesSPAN LENGTH (M)TYPE0102030SHORT SPANI. CONCRETE BRIDGE51. RC SLAB103. PC I-BEAM(AASHTO)II. STEEL BRIDGE1. PLATE GIRDER(Composite/Noncomposite)4050MEDIUM SPAN607040SHORT SPANMEDIUM SPANADVANTAGESLONG SPANDISADVANTAGES1/20SIMPLEST AND LEAST COST; CAN BE MADECONTINUOUS WITH PIERS AND ABUTMENTSTO RESIST LATERAL LOADS; MINIMALMAINTENANCE REQUIRED; NEAT ANDSIMPLE IN APPEARANCE.LIMITED TO SHORT SPAN RANGE; REQUIRESLONGER CONSTRUCTION TIME DUE TOFALSEWORK ASSEMBLY AND CONCRETING;DIFFICULT ON DEEP RIVERS AND HIGHPIERS1/15 - 1/18ECONOMICAL FOR SPANS 10-20M;SUPERSTRUCTURE NORMALLY ON BEARINGWITH PIERS; MINIMAL MAINTENANCE; NEATAND SIMPLE IN APPEARANCE BUT MANYLINES ON UNDERSIDE.ECONOMICAL UNTIL 20M RANGE;REQUIRES LONGER CONSTRUCTION TIMEDUE TO FALSEWORK ASSEMBLY ANDCONCRETING; DIFFICULT ON DEEP RIVERSAND HIGH PIERS; LESS AESTHETICAPPEARANCE THAN SLAB BRIDGES1/15 - 1/18COMPETITIVE FOR SPANS 20-40M; GIRDERSARE PRECAST, LIFTED IN PLACE AND DECKSLAB CAST-IN-PLACE; CONSTRUCTIONPERIOD SHORTER THAN CAST-IN-PLACETYPE; GIRDERS NORMALLY SIMPLE SPANBUT CAN BE MADE CONTINUOUS WITH LIVELOAD; MINIMAL MAINTENANCE;REQUIRES SPACE FOR FABRICATION OFGIRDERS; TRANSPORTATION OF LONGSEGMENTS CAN BECOME A PROBLEM;REQUIRES CRANE FOR LIFTING PRECASTSEGMENTS; SIMPLE BUT LOOKS CLUTTEREDON UNDERSIDE DUE TO MANY LINES.1/17 - 1/22WIDELY USED FOR SPANS UP TO 30M; STEELGIRDER IS SIMPLY SUPPORTED BUTCOMPOSITE WITH DECK SLAB;CONSTRUCTION IS FASTER THAN CAST-INPLACE CONCRETE; STRUCTURE IS LIGHTERTHAN CONCRETE AND REQUIRES LESSSUBSTRUCTURE SUPPORT;REQUIRES PAINTING MAINTENANCE - COSTAND HAZARD NEED TO BE CONSIDERED;REQUIRES LIFTING AND TRANSPORTATIONOF GIRDERS; CAREFUL QUALITY ANDSAFETY CONTROL REQUIRED; MOREEXPENSIVE THAN CONCRETE; SIMILARLOOKS WITH AASHTO GIRDER BUT MORESLENDER.2010CHARACTERISTICSHEIGHT/SPAN RATIO152. RC DECK GIRDER.October 2006LONG SPAN665NOTE : 1. RC is Reinforced Concrete, normally cast-in-place2. PC is Prestressed Concrete, this can be cast-in-place or pre-castTable 3.3.6Comparison Between Concrete Bridge and Steel BridgeCost Ratio*Superstructure TypeItems24mConstruction AspectPrestressed on2.983.95Other eEvaluation34m0.80Steel Plate ection1.001.00Other works1.001.00Total1.001.08 Construction period issimilar to steel plategirder Construction requiresheavy lifting if girders areprecast Superstructure can be caston site by all stagingmethod andpost-tensioned; requiresonly medium-sized crane Falsework should beplanned carefully duringrainy season Concrete bridgestructures requireminimummaintenance Construction period issimilar to PCDG Construction is easierusing medium-sized crane Deck slab to be cast usingsuspended falsework Requires prefabrication ofsteel girders andtransportation to site Area for storage of steelgirders necessary andmay affect trafficcondition Steel girderrequires regularinspection andmaintenance Use of atmosphericcorrosion resistantsteel minimizessteel maintenancebut is moreexpensive Advantageous interms of total costand requiresminimalmaintenanceRECOMMENDED More expensivethan concrete bridgeand requiresmaintenanceNOTRECOMMENDEDNote: *Based on “The Project for Rehabilitation of Bridges Along the Main Trunk Roads in Cambodia” (JICA, on-goingconstruction)FS-B-3-26

Final ReportThe Study on the Road Network Developmentin the Kingdom of Cambodia3.3.4(1)October 2006Bridge PlanningExisting Bridge Location and River ConditionThe bridges considered for Urgent Bridge Rehabilitation are part of the national roads NR.3,NR.7, NR.11 and NR.33.NR.3 and NR.33 roads were improved under the World Bank projects“Cambodia Road Rehabilitation Project (2001-2005)” and the “Flood Emergency RehabilitationProject (2002-2004)” respectively.On the other hand, NR.7 and NR.11 were improved underthe ADB projects “Primary Road Restoration Project (2000-2004)” and the “Emergency FloodRehabilitation Project (2001-2004)” respectively. The bridges under consideration were part ofthese improved roads but were not improved due to financial constraints.The locations of bridges are fixed by the existing road alignment and the condition of rivers orwaterways.In all eight bridges, the bridge alignment follows the existing road alignment withbridges spanning the existing rivers or waterway opening.The rivers along NR.3, NR.33 andNR.7 are on stable locations and are not expected to migrate in the future.On the other hand,NR.11 is located in the flood plain of the Mekong river and bridges on these locations provideopening for flood discharges from the Mekong river side.The condition of the rivers at the different bridge locations are summarized in Table 3.3.7.BridgeNo.RoadNo.StationTable 3.3.7Existing Bridge River ConditionWaterwayRiver Conditionzz13025 927Riverzz23105 985Riverzzzzz37277 200River084 900FloodPlainOpeningzzz411zzzRemarksThe existing river opening is about 30m wide.Flood level is about 2.02m below the deck levelRiver section is constricted by existing bridge.Upstream and downstream sections wider thanbridge openingzThe existing river opening is about 46m wide.Flood level is about 2.32m below the deck levelRiver is meanderingRiver section is obstructed in A2 sidezThe existing river opening is about 123m wide.Flood level is about 4.78m below the deck levelRiver is meandering upstream and downstreamScouring is observed at A2 side downstreambank. No scouring of banks noted at upstreamsideThe existing river opening is about 41m wide.Flood level is about 1.73m below the deck levelBridge is at Mekong river floodplain andprovides opening during floodBridge opening is protected by gabion mattressFS-B-3-27zzThe original 2-spanconcrete bridge collapseddue to year 2000 floodRiver section should bewidenedThe original 4-span steeland concrete bridgecollapsed due to floodImprove river sectionzOne-span of the original6-span concrete bridgecollapsed due tooverloadingzThe road is improvedunder emergency floodrehabilitation while thebridge remains temporary

Final ReportThe Study on the Road Network Developmentin the Kingdom of CambodiaTable 3.3.7BridgeNo.RoadNo.StationOctober 2006Existing Bridge River Condition ( Continued)WaterwayRiver Conditionzz511088 094FloodPlainOpeningzzThe existing river opening is about 83m wide.Flood level is about 0.75m below the deck levelBridge is at Mekong river floodplain andprovides opening during floodBridge opening is protected by gabion mattressand gabion guide banks are provided at bothabutmentsRemarkszzzz611089 060FloodPlainOpeningzzzThe existing river opening is about 53m wide.Flood level is about 1.30m below the deck levelBridge is at Mekong river floodplain andprovides opening during floodBridge opening is protected by gabion mattresszzz711103 475FloodPlainOpeningzzz8(2)33036 540RiverzzThe existing river opening is about 48m wide.Flood level is about 0.59m below the deck level– flood freeboard insufficientBridge is at Mekong river floodplain andprovides opening during floodThe existing river opening is about 27m wide.Flood level is about 1.37m below the deck levelBridge is located in low-lying swampy area.Dam exist in the upstream sidezzThe road is improvedunder emergency floodrehabilitation while thebridge remains temporaryNeed to raise bridge levelto provide sufficient floodfreeboardThe road is improvedunder emergency floodrehabilitation while thebridge remains temporaryNeed to raise bridge levelto provide sufficient floodfreeboardThe road is improvedunder emergency floodrehabilitation while thebridge remains temporaryNeed to raise bridge levelto provide sufficient floodfreeboardBridge is located inrelatively flat areaBridge Length and Span LengthsThe bridge length is decided based on the existing topography at bridge site, existing bridgelengths and condition, river design flood discharge, maximum flood water level and the conditionof the river and banks.The span length is decided based on existing span lengths, river hydraulic and expected debrisflow, depth of superstructure to minimize approach road profile adjustment and depth of existingwater to minimize construction of piers on river.As a guide policy, the minimum span length is recommended to be:i.S 20 0.005Q for 500 m3/s Q 2,000 m3/sii.S 30 0.005Q for Q 2,000 m3/swhere : S span length in metersQ river discharge in m3/sTable 3.3.8 presents the proposed bridge length and span compared to the existing bridges.Asindicated in the table, most of the bridge span lengths are increased except for 1-span baileybridges (Bridge No.1 and No.8) where the span lengths are reduced due to small river discharge.Moreover, the bridge length of Bridge No.1 is increased to 60m since the existing bridge isobserved to constrict the river section causing backwater and flood on the upstream section.The span length of Bridge No. 7 is increased to 35m utilizing precast, prestressed girders toFS-B-3-28

Final ReportThe Study on the Road Network Developmentin the Kingdom of CambodiaOctober 2006improve the river section opening due to large river discharge.Table 3.3.8Existing and Proposed Bridge Length and SpansExisting BridgeBridge RoadNo.No.Station*Length(m)Span(m)Min.Discharge Span(m3/s)Length(m)**Proposed BridgeLength(m)Spans(m)Remarks13025 900.00037.037.0284-60.620Existing bridge constricts the riversection, bridge length extended23105 958.44248.012.0238-54.618Span length chosen to minimizeroad profile adjustment37277 129.970130.021.71,77528.9140.835Span length increased to 35m dueto large river discharge411084 878.35942.014.0150-42.621Span length increased to improvewaterway and use similarstructure type along NR.11511088 047.59184.014.057322.992.623Span length increased to 23m dueto waterway discharge611089 025.37254.010.845420.069.623Span length made similar tobridge no. 5 since discharge isalmost 500 m3/s711103 448.05848.012.0177-54.618Existing span length is sufficient833036 524.16730.030.062-30.610Span length reduced due to smallriver discharge and minimize roadprofile adjustmentNote:(3)*Station is revised to proposed new Stationing for new bridge length.**Based on river dischargeDeck ElevationSince the bridges are improvement of existing bridges, it is desired to keep the existing deckelevation as much as possible.However, the minimum freeboard or vertical clearance from thedesign flood level (DFL) to the bottom of the major structural element (girders or slab) shall besecured as discussed in the design criteria.Since the superstructure type is governed by the span length requirements in bridges, the bridgeprofile is adjusted considering the depth of the superstructure and the required freeboard from thedesign flood level.Table 3.3.9 presents the existing bridge elevations and the proposed bridgeprofile elevations based on the structure type and the minimum freeboard.It is seen that almost all bridge elevations have to be adjusted except for Bridge No.3 at NR.7which has sufficient clearance from the design flood based on the site topography.Minimaladjustment in bridge profile is necessary for Bridge No.8 since the bridge type (Continuous RCSlab) does not require much structure depth.However, bridges along NR.11 have considerable deck profile elevation adjustments due tochange in span length and structure type (prestressed concrete girder) and the required minimumfreeboard clearance from the design flood water.A common form of structure is selected forthese bridges since they lie in the same alignment and for ease of construction execution.FS-B-3-29

Final ReportThe Study on the Road Network Developmentin the Kingdom of CambodiaTable 3.3.9Bridge RoadNo.No.StationOctober 2006Bridge Deck Profile AdjustmentExisting Design Flood ProposedMin.BridgeLevelBridge FreeboardElev. (m) (Elev. in m) Elev. (m)(mm)Remarks13025 900.00014.76712.74015.400800Road profile to be raised-up to maintainminimum freeboard and accommodate newsuperstructure type.23105 958.44229.81527.50030.000800Road profile to be raised-up to maintainminimum freeboard and accommodate newsuperstructure type.37277 129.97063.18658.41063.2501000Road profile to be maintained sinceexisting clearance from design flood issufficient.411084 878.3599.2287.50010.140800Road profile to be raised-up to maintainminimum freeboard and accommodate newsuperstructure type.511088 047.5919.5158.77011.6001000Road profile to be raised-up to maintainminimum freeboard and accommodate newsuperstructure type.611089 025.3729.4528.15010.800800Road profile to be raised-up to maintainminimum freeboard and accommodate newsuperstructure type.711103 448.0588.7918.20010.840800Road profile to be raised-up to maintainminimum freeboard and accommodate newsuperstructure type.833036 524.1673.1741.8103.600600Raising-up of road profile minimal due totype of superstructure.3.3.5Bridge Design(1)SuperstructureAs discussed earlier, the choices of superstructure type follows the requirements for bridgeplanning which includes span lengths and bridge lengths.Table 3.3.10 presents the proposedsuperstructure type and bridge lengths for the eight bridges while Figure 3.3.2 illustrates thebasic bridge cross-sections for RC Slab, RCDG and PCDG bridges.As discussed in the designcriteria, all eight bridges shall have 10m wide travel lanes (2@1.5m shoulders and 2@3.5mtraffic lanes). A 1.0m wide sidewalk is provided since these bridges are located in major arterialroutes.As seen in Table 3.3.10, PCDG is proposed for span lengths greater than 20m which is moreappropriate in terms of cost and construction.However, f

Bailey Bridge 37.0 4.5 1-span bailey bridge with steel deck Old concrete abutment 15 Poor 3,525 Original concrete bridge washed-out by flood. Bailey bridge resting in old bridge abutment 2 3 Kampot 105 985 Bailey Bridge 48.0 4.2 4-span bailey bridge with steel deck Old concrete abutment and piers 1