bridge launching equipment 1 1

8/11/2019 Bridge Launching Equipment 1 1

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BRIDGE ERECTION MACHINES

Marco RosignoliHNTB Corporation, USA

Key or!s : Beam launchers, self-launching gantries, telescopic gantries, pivoted gantries, overheadand underslung machines, movable scaffolding systems (MSSs), heavy lifters, lifting frames, formtravelers, span carriers with underbridge, design loads, modeling, analysis, load testing, instability,robustness, progressive collapse

Contents

! "ntroduction to Bridge #onstruction Methods$ Main %eatures of Bridge &rection Machines' Beam aunchers

Self- aunching *antries for Span-By-Span +recast Segmental &rection Movable Scaffolding Systems (MSSs) for Span-By-Span #asting Self- aunching Machines for Balanced #antilever #onstruction

. #arriers and *antries for %ull-Span +recasting/ 0esign oads of MSSs and %orm 1ravelers2 0esign oads of 3eavy ifters!4 Modeling and 5nalysis!! "nstability of '0 1russes!$ "nstability of 6ertical Support Members!' oad 1esting! #onclusions5c7nowledgments*lossaryBibliographyBibliographical S7etch

S"##ary

Bridge industry is moving to mechani8ed construction because this saves labor, shortens pro9ectduration and improves uality 1his trend is evident in many countries and affects most constructionmethods Mechani8ed bridge construction is based on the use of special machines

;ew-generation bridge erection machines are comple< and delicate structures 1hey handle heavy

loads on long spans under the same constraints that the obstruction to overpass e


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Bridge erection machines are assembled and dismantled many times, in different conditions and bydifferent crews 1hey are modified and adapted to new wor7 conditions Structural nodes and fieldsplices are sub9ected to hundreds of load reversals 1he nature of loading is often highly dynamic andthe machines may be e


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>n shorter bridges, prefabrication is limited to the girders and the dec7 slab is cast in-place +recast beams are often erected with ground cranes Sensitive environments, inaccessible sites, tall piers,steep slopes and inhabited areas often re uire assembly with beam launchers, and the technologicalcosts increase

?1 and 3S? bridges with '4- 4m spans may be erected by full-span precasting 1he investment isso high that the brea7-even point is reached with hundreds of spans 1he precasting plant delivers $spans per day for fast-trac7 construction of large-scale pro9ects >ptimi8ed material and labor costsadd to the high uality of factory production ?oad carriers and ground cranes may erect four single-trac7 @-girders (two ?1 spans) every night 3eavy carriers with underbridge and gantries fed byS+M1s are the alternatives for ground delivery of 3S? spans +recast spans longer than !44m have

been erected with floating cranes

Medium-span +# bridges may also be cast in-place %or bridges with more than two or three spans itis convenient to advance in line by reusing the same formwor7 several times, and the dec7 is builtspan-by-span #asting occurs in either fi


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5 launching gantry for span-by-span erection of precast segmental bridges also operates on '4- 4mspans but the payload is much higher as the gantry supports the entire span during assembly 1he

payload of an MSS for in-place span-by-span casting is even higher as it also includes the casting cell,although the nature of loading is less dynamic

6ersatile twin-girder overhead machines comprise two trusses that suspend dec7 segments or the

casting cell and carry runways for winch-trolleys or portal cranes 1he field splices are designed for fast assembly and the modular nature of design permits alternative assembly configurations 1hesemachines are easily reusable however, their weight, labor demand and comple


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*% Bea# +a"nc&ers

1he most common method for erecting precast beams is with ground cranes #ranes usually give thesimplest and most rapid erection procedures with the minimum of investment, and the dec7 may be

built in several places at once *ood access is necessary along the entire length of the bridge to position the cranes and deliver the girders 1all piers or steep slopes ma7e erection e


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The longitu#inal mo%ement of the gantr! is a two ste" "rocess$ &utomaticclam"s bloc the trusses to the crossbeams an# the winch trolle!s mo%e thebeam one s"an ahea#+ then the winch trolle!s are

anchored to the crossbeams, the bloc7s are released and the translation winches push the trusses to thene


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Figure 2: -4m, 9.ton single gir#er shifter for 2.m, /0ton beams ( eal)

;ew-generation single-girder launchers are based on two braced "-girders 1he main girder is lesse


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%igure ': 2/m, 4 ton overhead gantry with ton portal crane for m, 44ton dual-trac7 @-girder ?1 spans (;?S)


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5 winch-trolley or a portal crane spanning between the girders lifts and moves the segments into position 5u


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%igure .: '$-roll saddle for ' ton service load

%igure /: aunchcylinders

truss 5ssemblies of e uali8er beams follow the fle


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1he lightest twin-girder overhead gantries may be launched with winches and capstans 3ydrauliccylinders lodged within the support saddles and ta7ing contrast into rac7s anchored to the trusses

provide higher thrust forces and safer operations +aired cylinders are often used (%igure /) so thatone cylinder loc7s the truss while the ad9acent cylinder is repositioned

5 single-girder overhead gantry ta7es support onto the front pier of the span to erect and the front

pier-head segment of the completed bridge 1he girder is rigidly framed to the front support legs, alight front e


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girder onto the support bo


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%igure !$: . m, '$ ton underslung gantry with 4toncrane for ' m, 24ton dual-trac7 ?1 span (;?S)

%igure !': 2!m, '''ton pivoted underslung gantry with 4ton crane for ' .m, '2$ton dual-trac7 ?1 spans (;?S)

segments are delivered on the ground, the crane is placed at the front end of the gantry 1he segmentsare placed onto the gantry close to the lifter and rolled into position 5 portal crane may also be used

to lift the segments and move them into position @pon application of prestress, the span is releasedonto the bearings by lowering the gantry

>verturning is controlled with front and rear launching noses and the length of the gantry is more thantwice the typical span length 1his ma7es the standard underslung machines hardly compatible withcurved bridges as the girders conflict with the piers and the completed bridge 1he front ends of themain girders may be connected with a crossbeam that slides along a central self-launchingunderbridge 5 rear #-frame rolling along the completed bridge during launching further shortens therigid portion of the machine 1hese telescopic gantries cope with tight plan radii but re uire a

particular 6-design of the pier caps to create the launch clearance for the front underbridge


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1wo-phase casting restricts the uantity of concrete processed daily and facilitates handling of inner forms Foints at the top slab level also avoid the hori8ontal crac7s that sometimes affect one-phasecasting due to settlement of fresh concrete in the webs 1he main concerns with two-phase casting arerelated to the deflections of the MSS 1he weight of the top slab deflects the casting cell, which maycause crac7ing in the non-prestressed first-phase @-section

#oncrete is poured with conveyor belts or pumps "n the simply supported spans, concrete should be poured starting at the center of the span and progressing symmetrically toward the ends to minimi8ethe deflections of the casting cell in the final phases of filling 1his se uence is labor intensive and theuse of retarding admi


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the outer form and lowers cage and front bul7head into the casting cell in one operation 1he carrier may be e uipped with concrete distribution arms and a covering to protect the casting cell duringconcrete pouring

1he underslung MSSs ta7e support onto pier brac7ets or =-frames on through girders (%igure '/)1he support saddles lodge friction launchers or launch cylinders acting into rac7s 1he pier brac7etsinclude 9ac7s with safety nut or screw 9ac7s that lift the MSS to the span casting elevation and lower it

bac7 onto the launch rollers after application of prestress Some MSSs suspend the pier brac7ets fromthe main girders after dismantling and hydraulic motors move the brac7ets to the new pier for crane-less application

=-frames on through girders are always assembled with ground cranes #ylinders with safety nutsupported onto the through girders lift the =-frame to the span casting elevation and lower it bac7 after application of prestress to release the span Support saddles designed for the total load (weightand payload) are often based on +1%& s7ids 5t the current state of practice, rollers and +1%& slidersare complementary Sliders are used for slow launching of high loads and rollers are used for mediumloads and fast launching

>verturning is controlled with launching noses and the length of these machines is more than twicethe typical span 1he standard underslung MSSs are not suitable for bridges with tight plan radii

pivoted girders with hydraulic hinges have been used in curved bridges in spite of their cost andcomple


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5n au


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%igure !/: %ront support leg

5 front au


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%igure !2: #age carrier for . m spans

Figure 20: 3ar ing area for winch trolle!s

"n machines with a lower level of automation, the web cage is assembled over the new span duringcuring and is suspended from the MSS during launching Monorail winches assist cage assembly andlowering into the casting cell after launching ;ew-generation single-girder overhead MSSs aretargeting 24m spans in tangent highway bridges and .4m spans in 3S? bridges #onstant-depthtrusses are generated with stac7ed assemblies of modular panels and arched overhead trusses further increase the stiffness of the casting cell (%igure $!) 1he modular nature of assembly facilitatesadaptation to shorter spans, although a higher level of automation is often preferred for span-byspancasting of 4- 4m spans

aunching on long spans re uires light machines 1he MSS of %igure $! has ! .2 payloadEweightratio 1russes and space frames are used for form hangers and bottom frame, and hanger bars cross thecasting cell to further lighten the outer form 5s a drawbac7 of the high structural efficiency, the largenumber of field splices increases cost and duration of site assembly and complicates inspections


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%igure $!: ! 4m, ./4ton overhead MSS for .4m, ! 44ton spans (B&?0)

%igure $$: Sensor-controlled . 4M; prestressing for two-phase casting (B&?0)

>ne-phase casting of 24m bo< girders would involve handling .44-244m ' of concrete in a few hours1wo-phase casting reduces the demand on batching plant and concrete delivery lines along thecompleted bridge but re uires control of deflections of the casting cell in so fle


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5% Sel)-+a"nc&ing Mac&ines )or Balance! Cantile0er Constr"ction

Balanced cantilever construction is suited to precast segmental and cast-in-place bridges +recastsegmental construction re uires powerful erection machines but allows industriali8ed casting andfaster erection and is therefore addressed to bridges with a great number of spans Segment assemblywith ground cranes or lifting frames permits free erection se uences while the use of a self-launching

gantry re uires that the dec7 be erected from one abutment toward the opposite one however,directional erection permits delivering the segments along the completed bridge

1he dec7 of in-place bridges is cast in short segments with pairs of form travelers 1ime-scheduledictates the number of form travelers to be used simultaneously =hen the cantilevers from the two

piers face each other at midspan, the closure segment is cast and bottom slab tendons are installed toma7e the dec7 continuous 1he travelers are then lowered to the ground and repositioned onto a new

pier-head segment

Balanced cantilever bridges have bo< girder section ?ibbed slabs have been built in the past and arestill used in the cable-stayed bridges as torsion and most of the negative moment are resisted by two

planes of cables Bo< girders may have constant or varying depth #onstant-depth dec7s are simpler tocast but competitive in a narrow span range ( 4-.4m) while varying-depth dec7s are used on spansranging from .4m to $ 4-'44m 0epth variation adapts the fle


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%igure $': ifting of 24ton pier-head segment (#omtec)

%igure $ : '4m, 24ton lifting frame for ton segments (0eal)

only in cable-stayed bridges 5 mobile lifting frame comprises a motori8ed base frame and acantilever nose that supports a lifting trolley ight segments are lifted with winches and heavier segments with strand 9ac7s 5 lifting frame is much lighter than a wheeled crane as it is devoid of counterweights 1his simplifies placing the machine onto the pier-head segment at the beginning of erection and diminishes dec7 prestressing but re uires anchoring the machine to the dec7 beforelifting of every segment 1he pier-head segment is lifted or cast in-place to establish a platform onwhich one or two lifting frames are secured 5n au


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Straddle carriers with cantilever noses on both sides of the machine move from one side of the pier tothe other to lift the segments in turn Straddle carriers with winch-trolleys and spreader beams wider than the top slab can pic7 up the segment at the base of the pier and move it out beneath the cantilever (%igure $ ) >ther types of motori8ed frames move the segment over the dec7 and rotate and lower itinto position Most lifting frames also suspend a stressing platform beyond the segment for fabricationand tensioning of the top slab tendons "n spite of the single-operation-machine nature and thedisruption when moving to the nene or two winch-trolleys lift and transport the segments into position "f the segments are delivered along the completed bridge, the winch-trolley pic7s them up at the rear endof the gantry "f the segments are delivered on the ground, the winch-trolley raises them up to the dec7 level

%igure $ : ! 4m, '$4ton gantry for !4$m spans and !4 ton segments (6S )

1he earliest single-truss overhead gantries were slightly longer than the span to erect 1he length of the truss was sufficient to span between the front cantilever of the completed bridge and the ne


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%igure $ : !4/m, $./ton gantry for m spans and 4ton segments (6S )

%igure $.: +lacement of the first !/$ton down-station segmentwith a !2/m, /. ton gantry for !4!m spans (3;1B)

Short gantries overload the front cantilever of the completed bridge +lacing the pier-head segments isalso more comple< 1he length of new-generation machines is more than twice the span length

(%igure $ ) 1hese machines ta7e support at the piers during span erection and the higher cost of alonger gantry is balanced by less reinforcement and prestressing in the entire bridge +lacement of

pier-head segments and launching are also simplified, and labor demand is lower

1he typical launch se uence for a new-generation gantry for long balanced cantilever spans is asfollows (!) 1he cantilevers are erected with the gantry anchored to crossbeams sitting onto the pier-head segments of the completed bridge and the new pier ($) 5fter midspan closure and tensioning of continuity tendons, the front pendular leg ta7es support onto the front cantilever and the winch-trolleymoves the front crossbeam forward to the ' rd or th segment (') 1he front leg is released and thegantry is launched until the rear end reaches the rear crossbeam ( ) 1he rear au


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moves the front crossbeam onto the new pier-head segment and the rear crossbeam onto the pier-headsegment of the completed bridge (/) 1he front leg is released and the gantry is launched forward andanchored to the crossbeams in the erection configuration for the new span ;o ground cranes arenecessary for launching

=hen the length of the bridge is insufficient to amorti8e the investments of segmental precasting, the balanced cantilever bridges are cast in-place "n-place casting is also the standard solution for curvedspans and spans longer than !$4m

%igure $/: >verhead form traveler

=hen form travelers support the casting cells, the segments are '- m long for reasons of weight andload unbalance - m segments are possible although form fle


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=hen the pier-head segment is .-!4m long, two form travelers can be assembled at the same time "ttypically ta7es $ wee7s to assemble a traveler and another $ wee7s to assemble the casting cell#asting the initial segment ta7es another $ to ' wee7s 1he segments are typically cast on a -daycycle after the learning curve has passed

1he segments are cast in one phase proceeding from the front bul7head bac7wards to minimi8esettlement at the construction 9oint 1he inner shutter is e uipped with windows for concretevibration #oncrete with early high strength is used to shorten the casting cycle

"n the overhead travelers the trusses are supported onto the front dec7 segment and anchored to thesecond segment with tie-downs that prevent overturning (%igure $2) 6ertical cylinders at the frontsupport lift the traveler from the launch rails for casting 5fter tensioning the top slab tendons, theouter form is stripped and the traveler is lowered onto the launch rails 5d9ustable tie-downs roll alongthe rails to prevent overturning during launching

aunching is a two-step process: first the rails are pushed forward and anchored to the new segment,and then the traveler is lowered onto the rails and pulled forward ?ails and traveler are launched withthe same set of hydraulic cylinders aunch cylinders are repositioned alternately #uringlaunching to a%oi# uncontrolle# mo%ements of the tra%eler$

Figure 29: &nchoring an# launch #e%ices

"n the underslung form travelers for +# bo< girders, a #-frame supported onto the webs of the frontsegment suspends a longitudinal '0 truss on either side of the dec7, beneath the bo< wings "n thecable-stayed bridges the #-frame is replaced with hydraulic hangers rolling along the edge girders toavoid interference with the cables (%igure '4) #ounter-rollers at the rear end of the trusses ta7econtrast against the dec7 soffit to prevent overturning 1he forms are stripped by releasing the vertical cylinders of #-frames and hangers aunch cylinders

push the launch rails over the new segment and then pull #-frames and hangers along the railsaunching an underslung traveler is more comple< but the reinforcement cage for the segment can be

prefabricated as the casting cell is free from obstructions


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%igure '4: $ m, $4$ton underslung traveler for 2


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@nderslung travelers with full-width #-frame are also used for in-place casting of cable-supportedarches (%igure '!) 1he #-frame is anchored to the arch during operations of the casting cell due tothe slope of the arch segments Strand bra7es are incorporated into the launch rails for additionalsafety from uncontrolled movements 1he segment is cast in one phase by filling the casting cellupward 1he top shutter is closed with the progress of filling to facilitate inspection and concretevibration 1he support cables of the arch are installed after launching the casting cell to the ne


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%igure '': Strand-9ac7ing of / 4m, 4ton segment (1hyssenGrupp)

1he MSSs for balanced cantilever casting can be easily adapted to macro-segmental erection 1hecasting cells are replaced with lifting platforms for strand-9ac7ing ong dec7 segments are cast under the bridge and lifted into position (%igure '') 1he pier-head segments are cast in-place with shortcasting cells suspended from the machine =et 9oints with through reinforcement avoid the geometryre uirements of short-line match-casting and allow bridge design for partial prestressing 1hesegments are hung to the main girders during casting of ! 4-! m stitches and application of top-slab

prestressing

6% Carriers an! Gantries )or ("ll-Span .recasting

Many ?1 and 3S? bridges have been built with precast spans %ull-span precasting allows rapidconstruction and high uality from repetitive casting processes in factory conditions Bo< girders are used for 3S? and highway bridges and @-girders are used for 3S? and ?1 bridges1he spans may be longer than !44m when floating cranes are used for placement *roundtransportation is rarely used for spans longer than 4m for 3S? and ?1 bridges and 4m for highway bridges 1he investment needed to set up large precasting facilities and to provide heavyspan transportation and placement machines limits the cost-effectiveness of full-span precasting tolong bridges with many e ual spans, small radii of plan curvature and low gradient 1hese conditionsare met more easily in 3S? bridges


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%igure ' : /m, '$!ton carrier for placementof '! m, . 4ton single-trac7 3S? spans

1he spans are placed onto bearings or seismic isolators to simplify the erection process Simply-supported spans also diminish the thermal stresses in the continuous welded rails of 3S? bridges 1hespans can be connected with in-place stitches to form a continuous structure, although in-placestitches do not offer the same high levels of uality as the rest of the bridge 1he precasting plant is located near the bridge 1he reinforcement cages are prefabricated anddifferent combinations of pre-and post-tensioning are possible 1he spans are removed from thecasting cells with heavy portal cranes or wheeled carriers and stored on temporary foundations for completion of prestressing, application of bearings and finishing 1he precasting plant delivers two to

four spans every day in relation to the erection rate of the delivery and assembly lines %or 3S? viaducts over land, the spans are transported along the completed bridge with wheeledcarriers 5 span carrier (%igure ' ) comprises two wheeled trolleys connected by a bo< girder supporting two winch-trolleys Movement and steering are governed by hydraulic motors powered bydiesel engines +ic7ing up the span from the casting cell involves a comple< se uence of operations 1he carrier ismoved alongside the span, the trolleys are rotated by 24C by pivoting about hydraulic props, and thecarrier is moved transversely over the span 5fter applying the spreader beams and lifting the span,the carrier is moved bac7 to the transportation route and realigned with an inverse se uence of operations 1he same operations are repeated to place the span onto the supports of the storage areaand to pic7 it up for final delivery

5fter reaching the abutment, automatic drive systems controlled by ultrasound sensors govern themovement of the carrier over the webs of the bo< girders or within the @-section 1he automatic-drivespeed of the machine of %igure ' is ' 4 7mEh at full load and 4 7mEh unloaded 1he carrier spreadsthe load onto two spans and the a


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%igure ' : #arrier moving forward along a ./m, $!/ton underbridge

%igure ' : . m, $4ton gantry with '/m, /4ton underbridge for placement

of ''m, 244ton dual-trac7 3S? spans (Bei9ing =ow9oint Machinery)

wheels of the carrier are released 1he motors of front saddle and rear trolley are synchroni8ed tomove the carrier along the underbridge 5fter reaching the span lowering location, the rollers of theunderbridge are released and the motor of the support saddle is inverted to launch the underbridge tothe ne


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plate, the load cells are removed and the span is lowered onto the bearings %inally, the underbridge ismoved bac7ward to release the front trolley onto the new span 1ransverse wheel spacing re uired for operations of the underbridge allows the presence of other machines on the bridge during spandelivery for earlier start of finishing wor7

3eavy gantries with underbridge are also used for placement of 3S? spans in combination withS+M1s that deliver the spans along the completed bridge (%igure ' ) 1he front winch-trolley of thegantry pic7s up the front end of the span and moves it forward while the rear end slides along asupport girder on the S+M1 1hen the second winch-trolley pic7s up the rear end of the span torelease the transporter

aunching the gantry to the ne


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1he loads applied to MSSs and form travelers are grouped into two load conditions oad #ondition "is the normal operational condition, which includes permanent loads, payload, load of personnel andstored items on wor7 platforms, loads applied by lifting devices, and wind and thermal loads oad#ondition " is also used to analy8e the launch stresses oad #ondition "" is the out-of-servicecondition, which includes permanent loads, partial load on wor7 platforms (snow if more demanding)and out-of-service wind =ind in load #ondition " is chec7ed for any possible configuration of themachine while out-of-service wind is chec7ed in anchored conditions

oad #ondition " is also used to analy8e the application of prestress 5s prestress is applied, the spanlifts up from the casting cell 5s the weight is relieved, however, the casting cell recovers thedeflection 5n MSS is more fle


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$9% Mo!eling an! Analysis

1he optimum level of detail for the numerical model of a bridge erection machine depends onnumerous factors 1he more refined the model, the more accurate the results of analysis and thecambers to assign to the casting cell 3owever, simple models allow rapid investigation of differentload and support conditions, facilitate the research of the design-governing conditions, and providethe stress magnitude to be e


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bottom chords during launching, and the trusses may be supported with out-of-node eccentricity evenduring span casting (') 1he gravity a


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$$% Insta1ility o) *D Tr"sses

1he stability of a freestanding truss is influenced by the degree of fiut-of-plane buc7ling of a launching gantry is analy8ed by simulating the placement of segments5nalysis is simpler in an MSS as the casting cell is fi


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&


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%igure 4: %lange buc7ling in a 2 m, ' 4ton MSS

ocal buc7ling of flanges can trigger critical situations in the bo< girders as during launching thesupport sections are devoid of diaphragms "n a twin-girder overhead MSS the left bo< girder (on theright in %igure 4) was slightly misaligned left-bound =hen the front launch cantilever was /mlong, the operator decided to realign it 5 crossbeam was placed at the front support to sustain two flat

9ac7s on +1%& plates 1he 9ac7s had to be inserted under the webs to pull the bo< girder right-boundalong the low-friction surface 1he procedure was misunderstood and after lifting the bo< girder withthe flat 9ac7s, the +1%& plates were inserted between the bo< girder and the main support 9ac7s

"n the initial phases of realignment the bottom flange of the bo< girder resisted the transverse bendinggenerated by the increasing eccentricity in the support reactions &ventually the outer flange and thecentral flange panel buc7led upwards 1his generated two low-friction inclined planes that gave raiseto uncontrolled right-bound sliding of the bo< girder #ollapse was avoided because the edge of the

bottom flange impacted against the end bloc7 of the crossbeam aunch rails welded under the websimprove load dispersal, transfer lateral forces and also remind distract operators where the supportreactions must be applied

$'% Insta1ility o) :ertical S"pport Me#1ers

1he load of an erection machine is transferred to the bridge foundations through comple< load pathsthat include structural, mechanical and electro-hydraulic components 1he support legs of thesemachines are affected by specific forms of instability

1he pendular legs are among the most delicate components because their length must be varied tota7e support onto the pier cap and onto the dec7 (%igure ) 1his is achieved with articulated legs androtation cylinders, and the presence of multiple hinges along the vertical load path ma7es the legs

prone to out-of-plane buc7ling when fully e


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%igure !: 1hree-hinge load path in a pendular =-frame

with the dec7 webs, so the crossbeam was windowed at the ends 5s a result, the torsional constant inthe windowed end sections dropped to about one-thousandth of the bo< girder constant =hen the support cylinders are at the ends of the crossbeam, the vertical load path is a three-hingescheme where the central hinge has minimal rotational stiffness due to the low torsional constant of

the windowed section 1he buc7ling factor for self-weight was as low as 4 4 Bo


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%igure $: Bracing deficiencies in a !2m support tower

%igure ': *antry collapse

%orensic investigation detected design and assembly deficiencies in the tower oad eccentricity andthermal loads were disregarded in the design ateral fle


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%igure : %irst buc7ling mode of the collapsed tower

5s a matter of fact, buc7ling should always be chec7ed with prudent load factors in these temporarystructures5ll ad9ustment screws should be regarded as potentially prone to local buc7ling @pon completion of launching, gantries and MSSs for span-by-span construction are lifted to the span erection level

3ydraulic cylinders with safety nut or screw 9ac7s are used to support the girders after lifting =henthe screw 9ac7s are e


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result in inade uate geometry of the first span oad testing may be performed by applying awaterproof membrane and filling the casting cell with water 5dditional load can be applied bysuspending concrete bloc7s

$ % Concl"sions

"nnovation in bridge erection methods is a need for industriali8ed countries to preserve their e


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(riction la"nc&er : Support device able to generate longitudinal movements in the main girder by friction

Hangers : Bars suspending precast segments or the casting cell from an overhead self-launching frame

Hea0y li)ter : Self-propelled machine e uipped with heavy lifting devices #ranes, straddle carriers, derric7s,

cable cranes, beam launchers, lifting frames, gantries and span carriers are designed with standards for heavy

lifters

HSR : 3igh-Speed ?ailway

Hy!ra"lic &inge : 3ydraulically interconnected cylinders that allow differential movements at the supported

points with e uali8ed forces

+a"nc&ing nose : &


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boo7let provides guidance for design of base plates and anchor rodsN

Boggs, 0 +eter7a, F (!22$) Wind Speeds for Design of Temporary Structures +roceedings of the !4 th 5S#&Structures #ongress, San 5ntonio, @S5 5merican Society of #ivil &ngineers (5S#&) 1his paper defineswind load to be used in the design of falsewor7 and other types of temporary structuresN

BS" (!2/$) Code of "ractice for alse!ork British Standards "nstitute (BS") 1his boo7let provides generaldesign and technical guidance for falsewor7 in the @ G N

bridge launching equipment 1 1

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