BRIDGE ERECTION MACHINES Marco Rosignoli HNTB Corporation, USA
Keyor!s: Beam launchers, self-launching gantries, telescopic gantries, pivoted gantries, overhead and underslung machines, movable scaffolding systems (MSS’s), heavy lifters, lifting frames, form travelers, span carriers with underbridge, design loads, modeling, analysis, load testing, instability, robustness, progressive collapse Contents
! "ntrod "ntroduct uction ion to Bridg Bridgee #onstru #onstructio ction n Methods Methods $ Main Main %eatur %eatures es of Brid Bridge ge &rect &rection ion Mach Machine iness ' Beam Beam aunc aunch hers ers Self-aunch Self-aunching ing *antries *antries for for Span-By Span-By-Span -Span +recast +recast Segmen Segmental tal &rection &rection Movable Movable Scaffo Scaffolding lding Systems Systems (MSS’s) (MSS’s) for for Span-By Span-By-Span -Span #asting #asting Self-aunch Self-aunching ing Machine Machiness for Balanced Balanced #antile #antilever ver #onstru #onstruction ction . #arrie #arriers rs and *ant *antrie riess for %ull%ull-Spa Span n +recast +recasting ing / 0esign 0esign oad oadss of MSS’ MSS’ss and and %orm %orm 1rave 1raveler lerss 2 0esi 0esign gn oa oads ds of of 3eavy 3eavy ift ifter erss !4 Modeling Modeling and and 5nalysis 5nalysis !! !! "nstability "nstability of of '0 1russe 1russess !$ "nstability "nstability of 6ertical 6ertical Support Support Members Members !' oad oad 1es 1esting ting ! #onclu #onclusio sions ns 5c7nowledgments *lossary Bibliography Bibliographical S7etch S"##ary
Bridge industry is moving to mechani8ed construction because this saves labor, shortens pro9ect duration and improves uality 1his trend is evident in many countries and affects most construction methods 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 constraints that the obstruction obstruction to overpass overpass e
Bridge Bridge erection erection machines are assembled assembled and dismantled dismantled many times, in different different conditions conditions and by different crews 1hey are modified and adapted to new wor7 conditions Structural nodes and field splices are sub9ected to hundreds of load reversals 1he nature of loading is often highly dynamic and the machines may be e
&very &very bridge bridge constr construct uction ion method method has its own advantag advantages es and wea7 points points "n the absence absence of particular reuirements that ma7e one solution immediately preferable to the others, the evaluation of the possible alternatives is always a difficult tas7 #omparisons based on the uantities of structural materials may mislead 1he technological costs of processing of raw materials (labor, investments for special euipment, shipping and site assembly of euipment, energy) and the indirect costs related to pro9ect duration often govern in industriali8ed countries 3igher uantities of raw materials due to efficient and rapid construction processes rarely ma7e a solution anti-economical ow technological costs are the reason for the success of the incremental launching method for +# bridges #ompared to the use of ground falsewor7, launching diminishes the cost of labor with similar investments #ompared to the use of an MSS, launching diminishes the investments with si milar labor costs "n both cases launching diminishes the technological costs of construction and even if the launch stresses may increase the uantities of raw materials, the balance is positive and the solution is cost effective 1he construction method that comes closest to incremental launching is segmental precasting 1he labor costs are similar but the investments are higher and the brea7-even point shifts to longer bridges Spans of '4-4m are erected span-by-span with overhead or underslung launching gantries onger spans are erected erected as balanced balanced cantilevers cantilevers:: self-launch self-launching ing gantries reach !44-!$4m !44-!$4m spans and lifting frames cover longer spans and curved bridges 3eavy self-launching gantries are used for macro-segmental construction of 24-!$4m spans Span-byspan erection of macro-segm macro-segments ents reuires reuires props from foundations foundations Balanced Balanced cantilever cantilever erection involves casting long dec7 segments under the bridge for strand 9ac7ing into position Both solutions reuire high investments
>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 reuire assembly with beam launchers, and the technological costs increase ?1 and 3S? bridges with '4-4m spans may be erected by full-span precasting 1he investment is so high that the brea7-even point is reached with hundreds of spans 1he precasting plant delivers $ spans per day for fast-trac7 fast-trac7 construction construction of large-scal large-scalee pro9ects pro9ects >ptimi8ed material material and labor costs add to the high uality of factory production ?oad carriers and ground cranes may erect four singletrac7 @-girders (two ?1 spans) every night 3eavy carriers with underbridge and gantries fed by S+M1’s 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 it is convenient to advance in line by reusing the same formwor7 several times, and the dec7 is built span-by-span #asting occurs in either fi
bstruction of the area under the bridge is another limitation 5n MSS comprises a casting cell assembled onto a self-launching frame MSS’s are used for span-byspan casting of long bridges with '4-.4m spans "f the piers are not tall and the area under the bridge is accessible, 24-!$4m spans can be cast with -4m MSS’s supported onto a temporary pier in every span ?epetitive operations diminish the cost of labor, the uantities of raw materials are unaffected, and uality is higher than that achievable with a falsewor7 Bridges crossing inaccessible sites with tall piers and spans up to '44m are cast in-place as balanced cantilevers =hen the bridge is short or the spans everhead travelers are preferred in +# bridges while underslung machines are used in cable-stayed bridges and cable-supported arches =ith long bridges and 24-!$4m spans, two longer casting cells may be suspended from a self-launching girder that also balances the cantilevers during construction '% Main (eat"res o) Bri!ge Erection Erection Mac&ines
1he industry of bridge erection machines is a highly speciali8ed niche &very machine is initially conceived for a scope, every manufacturer has its own technological habits, and every contractor has preferences and reuse e
5 launching gantry for span-by-span erection of precast segmental bridges also operates on '4-4m spans but the payload is much higher as the gantry supports the entire span during assembly 1he payload of an MSS for in-place span-by-span casting is even higher as it also includes the casting cell, although the nature of loading is less dynamic 6ersatile twin-girder overhead machines comprise two trusses that suspend dec7 segments or the casting cell and carry runways for winch-trolleys or portal cranes 1he field splices are designed for fast assembly and the modular nature of design permits alternative assembly configurations 1hese machines are easily reusable however, their weight, labor demand and compleverhe >verhead ad gantri gantries es for balanc balanced ed cantil cantileve everr erecti erection on of precas precastt segme segments nts reach reach !44-!$ !44-!$4m 4m spans spans #ompared to span-by-span erection, the payload is lower as no entire span is suspended from the gantry 1he negative moment from the long front cantilever and the launch stresses on so long spans govern design 6arying-depth trusses are structurally more efficient while constant-depth trusses are easier to reuse on different span lengths Stay cables are rarely used in new-generation machines >verhead MSS’s for balanced cantilever bridges operate in a similar way 1wo long casting cells suspended from a self-launching girder shift symmetrically from the pier toward midspan to cast the two cantilevers 5fter midspan closure and launching to the ne
*% Bea# +a"nc&ers
1he most common method for erecting precast beams is with ground cranes #ranes usually give the simplest and most rapid erection procedures with the minimum of investment, and the dec7 may be built in several places at once *ood access is necessary along the entire length of the bridge to position the cranes and deliver the girders 1all 1all piers or steep slopes ma7e erection e
Figure 1: 102m, 90ton launcher for 45m, 120ton beams (Comtec)
Two Two winchtrolle!s s"an between the to" chor#s of the trusses an# lo#ge two winches each$ The main winch sus"en#s the beam an# a translation winch acting on a ca"stan mo%es the trolle! along the gantr!$ gantr!$ & thir# trolle! carries an electric generator that fee#s gantr! o"erations$ 'hen the beams are #eli%ere# at the abut abutmen ment, t, the the winc winche hes s ma! ma! be re"l re"lac ace# e# with with less less e"e e"ens nsi% i%e e long longs str tro oe e c!lin#ers$ & beam launcher o"erates o"erates in one of two wa!s #e"en#ing #e"en#ing on how the beams are #eli%ere#$ *f the beams are #eli%ere# on the groun#, the launcher lifts them u" to the #ec le%el an# "laces them onto the bearings$ bearings$ *f the beams are #eli%ere# #eli%ere# at the abutment, the launcher is mo%e# bac to the abutment an# the winch trolle!s are mo%e# to the rear en# of the gantr!$ The front trolle! "ics u" the front en# of the beam an# mo%es it forwar# with the rear en# sus"en#e# from a stra##le carrier$ 'hen the rear en# of the beam reaches the rear winchtrolle!, the trolle! "ics it u" to release the carrier$ carrier$
The longitu#inal mo%ement of the gantr! is a twoste" "rocess$ &utomatic clam"s bloc the trusses to the crossbeams an# the winchtrolle!s mo%e the beam one s"an ahea#+ then the winchtrolle!s are anchored to the crossbeams, the bloc7s are released and the translation winches push the trusses to the ne
Truss Truss #eections at lan#ing at the "iers are reco%ere# with alignment we#ges$ The alignment force is small but the support saddles must be anchored to avoid displacements or overturning ?ealignment may also be achieved with long-stro7e cylinders that rotate arms pinned to the tip of the truss Similar devices are also applied to the rear end of the gantry to release the support
reaction when launching forward and to recover the deflection when launching bac7ward
Figure 2: -4m, 9.ton singlegir#er shifter for 2.m, /0ton beams (eal) ;ew-generation single-girder launchers are based on two braced "-girders 1he main girder is less e
truss and the gradient of the launch plane 5 vertical vertical pivot connects the two roll assemblies to allow rotations in the hori8ontal plane ateral shifting along the crossbeams is achieved with capstans or light long-stro7e cylinders 5utomatic clamps bloc7 the trusses to the crossbeams during winch-trolley operations aunching occurs along inclined planes and brea7ing of any component of the tow system would leave the gantry unrestraine unrestrained d on low-friction low-friction supports supports ?edundancy of tow systems involves involves oversi8ing oversi8ing and slow operations % Sel)-+a"nc&ing Gantries )or Span-By-Span .recast Seg#ental Erection
Span-by-span erection of precast segmental bridges is used for spans shorter than 4m in highway bridges and '4-m in dual-trac7 ?1 ?1 bridges with bo<-or @-section Single-trac7 Single-trac7 ?1 spans with @section are typically precast full-length for ground delivery and erection with two ground cranes because of the faster erection rate 5ll the segments for a span are placed onto or suspended from the gantry before gluing so that no additional deflections can occur 5fter application of prestress, lowering the gantry releases the span onto the bearings in one operation 1he spans of continuous bridges are released onto 9ac7s and connected with concrete stitches to the pier-head segments 1he solutions of continuity are loc7ed with concrete shims and partial tensioning of a few permanent tendons before casting the closures 1he prestr prestressi essing ng tendon tendonss are tensio tensioned ned from from a front front stressi stressing ng platfo platform rm 5 typical typical 4m simply simply-supported span with epoverhead and underslung gantries are used to support a complete span of segments 5 twin-girder overhead gantry comprises two triangular trusses or braced "-girders supported onto crossbeams (%igure ') 1russes are lighter while "-girders are more stable and solid and allow roboti8ed welding #onnections designed to develop member strength e
%igure ': 2/m, 4ton overhead gantry with ton portal crane for m, 44ton dual-trac7 @-girder ?1 spans (;?S)
5 winch-trolley or a portal crane spanning between the girders lifts and moves the segments into position 5u
%igure : ongitudinal movement of the segment (3;1B) 3eavier overhead gantries are used for span-by-span macro-segmental erection of /4-!44m spans 1he span comprises four segments 5 longitudinal 9oint at bridge centerline divides the bo< girder into two halves, and transverse 9oints at the span uarters divide each half into a pier-head segment and a midspan segment 5 temporary pier supports the front end of the midspan segments in every span, while the rear end is suspended from the front cantilever of the completed bridge 1he temporary pier also balances the pier-head segments (%igure ) 1he construction 9oints have through reinforcement and are closed with in-place stitches and integrative prestressing 1he macro-segments are cast beneath the gantry, on the completed dec7 1he gantry cannot rotate so long and heavy segments so the two casting cells (%igure ) roll along the completed bridge bac7 to the abutment, where they are rotated by !/4C and fed with the prefabricated cage for the con9ugated segment 5fter reaching the gantry, vertical cylinders lift the casting cells from the rails to apply the casting load over the webs of the bo< girder
%igure : m, 4ton pier-head macro-segment placed with a !$m, !$/4ton overhead gantry
%igure : m casting cells for midspan (left) and pier-head (right) macro-segments 1he length of the gantry is about !/ times the typical span 5 pendular =-frame at the rear end of the gantry ta7es support onto the dec7 prior to lifting the segment 5 front pendular leg (%igure ) is used during launching to reposition the front crossbeam 1he two trusses are connected at both ends and cannot be launched individually 1he pier-head segments are inserted under the front crossbeam and temporarily supported onto the pier cap the front winch-trolley pic7s them up again in a more advanced location for final placement #rossbeams support the gantry at the piers with articulated saddles that allow longitudinal and lateral movem movement entss and rotatio rotations ns about about the transv transvers ersee and vertic vertical al a
%igure .: '$-roll saddle for 'ton service load
%igure /:
aunch cylinders
truss 5ssemblies of euali8er beams follow the fle
1he lightest twin-girder overhead gantries may be launched with winches and capstans 3ydraulic cylinders 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 that one 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, a light front e
%igure 2: %riction launcher on ad9ustable support bloc7 Some first-generation overhead machines were euipped with stay cables, a deviation tower applied to the support legs at the rear pier, and a long rear balancing truss with counterweights at the end #able-stayed gantries have been abandoned with time in spite of their structural efficiency as the cables complicate and slow sl ow down the operations and increase labor demand 6arying-depth 6arying-depth trusses are also rarely used in span-by-span erection as they are hardly reusable on different span lengths Specia Speciall launch launch devices devices are necessa necessary ry when when the suppor supportt legs legs are integr integral al with with the main main girder girder aunching is achieved by friction, ta7ing advantage of the vertical load that the girder applies to the launcher (%igure 2) Support bo
girder onto the support bo
%igure !4: %riction launchers suspended from the main girder 5fter application of prestress, the rear launcher is moved over the front pier-head segment 1he span is released onto the bearings by retracting the main cylinders cylinders of the front legs and the rear #-frame, #-frame, and the launcher thus lands onto the dec7 5fter anchoring the launcher to the dec7, full retraction of the front cylinders leaves the gantry supported onto the launcher and the rear #-frame, and launching begins =hen the tip of the launching nose reaches the new pier, the winch-trolley places the new pier-head segment, and the front launcher is then moved onto the latter for launch completion 5n au
hydraulic motors %riction launchers offer high intrinsic safety as the worst conseuence of hydraulic faults is launch stoppage &uipment can be designed for the launch loads and overloaded without e
%igure !!: !m, 2ton underbridge and .m, !'$ton main girder for '.m, '4ton dual-trac7 ?1 spans (0eal) Many precast segmental bridges have been erected with underslung gantries 1hese machines are positioned beneath the dec7 with the main girders on either side of the pier pi er 1he gantry supports the bo< girder segments under the wings with ad9ustable sliding saddles for control of cambers underslung gantries are rarely used with @-sections 1he gantry ta7es support onto pier brac7ets, =frames on through girders, or crossbeams hung to the pier cap =hen the piers are short and slender, the pier brac7ets may be supported onto props from foundations to avoid soc7ets in the pier (%igure !$) 1his solution is freuently used us ed in ?1 bridges 1he segments segments are placed onto the gantry with a ground crane or a lifting lifting frame =hen the segments are delivered along the completed bridge, the lifter is placed at the rear end of the gantry =hen the
%igure !$: .m, '$ton underslung gantry with 4ton crane for 'm, 24ton dual-trac7 ?1 span (;?S)
%igure !': 2!m, '''ton pivoted underslung gantry wi th 4ton crane for '.m, '2$ton dual-trac7 ?1 spans (;?S) segments are delivered on the ground, the crane is placed at the front end of the gantry 1he segments are placed onto the gantry close to the lifter and rolled into position 5 portal crane may also be used to lift the segments segments and move them into position @pon application application of prestress, the span is released released onto the bearings by lowering the gantry >verturning is controlled with front and rear launching noses and the length of the gantry is more than twice the typical span length 1his ma7es the standard underslung machines hardly compatible with curved bridges as the girders conflict with the piers and the completed bridge 1he front ends of the main main gird girder erss may may be conn connec ected ted with with a cross crossbe beam am that that slid slides es alon along g a cent centra rall self self-l -lau aunc nchi hing ng underbridge 5 rear #-frame rolling along the completed bridge during launching further shortens the rigid portion of the machine 1hese telescopic gantries cope with tight plan radii but reuire a particular 6-design 6-design of the pier pier caps to create the launch clearance for the front underbridge
+ivoted girders with hydraulic hinges have also been used: the machine of %igure !' may erect 4m dual-trac7 ?1 spans with .m radius +ivoted +i voted girders have also been used in i n overhead machines: the gantry of %igure ' may erect '4m dual-trac7 ?1 spans with 4m radius "f one considers the constraints of precast segmental erection in congested urban areas, it is not surprising that so many innovative bridge erection machines have been designed for ?1 systems systems 1he underslung gantries are simple to design, assemble and operate Segment erection is fast and props from foundations can be used us ed to increase the load capacity when wor7ing low l ow on the ground 3owever, these machines pro9ect beneath the dec7, which may cause interference with straddle bents and #-piers, clearance problems when passing over roads or railroads, and difficulties in the end spans as the abutment walls are wider than the piers 1his problem is solved by applying the rear noses after launching the gantry to the second span over props from foundations 1he front noses are also dismantled before launching the gantry to the last span 1he abutment walls must be tall not to prevent operations in the first and last span /% Mo0a1le Sca))ol!ing Syste#s 2MSS3s4 )or Span-By-Span Span-By-Span Casting
5 +# bridge can be cast span-by-span proceeding from an abutment toward the opposite one =hen the piers are short and the area under the bridge is accessible, the formwor7 can be supported onto a ground falsewor7 "n bridges of length sufficient to amorti8e the investment, the use of an MSS allows transferring the casting cell to the new span in a few hours instead of wee7s 1he savings of labor are substantial, the area under the bridge is unaffected, and uality of construction is better than that achievable on a falsewor7 5n MSS is typically designed to cast an entire span Solid or voided slabs with stiffening haunches at the piers are used for '4-4m highway spans, ribbed slabs with double-1 section are used up to 4m spans, and bo< girders reach 4-.4m spans Bo< girders for railway bridges rarely e
slab$
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-phase casting due to settlement of fresh concrete in the webs 1he main concerns with two-phase casting are related to the deflections of the MSS 1he weight of the top slab deflects the casting cell, which may cause 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 minimi8e the deflections of the casting cell in i n the final phases of filling 1his seuence is labor intensive and the use of retarding admi
%igure !: 2.m, 24ton underslung MSS for m, !!24ton dual-trac7 3S? spans (1hyssenGrupp) (1h yssenGrupp) "n a second procedure, concrete is poured starting at the front bul7head and proceeding bac7ward 1his seuence reuires less labor and facilitates finishing, and larger fle
the outer form and lowers cage and front bul7head into the casting cell in one operation 1he carrier may be euipped with concrete distribution arms and a covering to protect the casting cell during concrete pouring 1he underslung MSS’s 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 brac7ets include 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 MSS’s suspend the pier brac7ets from the main girders after dismantling and hydraulic motors move the brac7ets to the new pier for craneless application =-frames on through girders are always assembled with ground cranes #ylinders with safety nut supported 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 (weight and payload) are often based on +1%& s7ids 5t the current state of practice, rollers and +1%& sliders are complementary Sliders are used for slow launching of high loads and rollers are used for medium loads and fast launching >verturning >verturning is controlled controlled with launching launching noses and the length length of these machines machines is more than twice the typical span 1he standard underslung MSS’s 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 and comple
%igure
!: !!4m, !24ton overhead MSS with 4ton crane for .m, !'/4ton single-trac7 3S? spans
5n au
Figure 1/: 110m, .90ton singlegir#er o%erhea# for 4-$5m, ./0ton s"ans
Brac7ets overhanging from the main girder suspend form hangers with telescopic connections for setting of camber +inned splices at bridge centerline divide the bottom crossbeams of the outer form into into two halves halves 3ydra 3ydraulic ulic e
%igure !.: >pened outer form during la unching (5+ Bridge #onstruction Systems) 1he front support of the MSS comprises a bo< leg on either side of the main girder and an upper bo< diaphragm that creates a #-frame &very leg includes a base cylinder with safety nut and a telescopic assembly for e
%igure !/: %ront support leg 5 front au
%igure !2: #age carrier for .m spans
Figure 20: 3aring area for winchtrolle!s "n machines with a lower level of automation, the web cage is assembled over the new span during curing and is suspended from the MSS during launching Monorail winches assist cage assembly and lowering into the casting cell after launching ;ew-generation single-girder overhead MSS’s are targeting 24m spans in tangent highway bridges and .4m spans in 3S? bridges #onstant-depth trusses 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 facilitates adaptation to shorter spans, although a higher level of automation is often preferred for span-byspan casting of 4-4m spans aunching on long spans reuires light machines 1he MSS of %igure $! has !.2 payloadEweight ratio 1russes and space frames are used for form hangers and bottom frame, and hanger bars cross the casting cell to further lighten the outer form 5s a drawbac7 of the high structural efficiency, the large number of field splices increases cost and duration of site asse mbly and complicates inspections
%igure $!: !4m, ./4ton overhead MSS for .4m, !44ton spans (B&?0)
%igure $$: Sensor-controlled .4M; prestressing for two-phase cast ing (B&?0) >ne-phase casting of 24m bo< girders would involve handling .44-244m ' of concrete in a few hours 1wo-p 1wo-phas hasee castin casting g reduc reduces es the demand demand on batchi batching ng plant plant and concre concrete te delive delivery ry lines lines along along the completed bridge but reuires control of deflections of the casting cell in so flen the other hand, span-by-span cast castin ing g of .4-2 .4-24m 4m span spanss with with wee7 wee7ly ly casti casting ng cycle cycle is much much faste fasterr than than balan balance ced d cant cantile ileve ver r construction, design of reinforcement and prestressing is more efficient, and the operators of bridge erection machines must be accurately trained anyway
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 +recast segmental segmental constructio construction n reuires reuires powerful powerful erection erection machines machines but allows industriali8ed industriali8ed casting and faster erection and is therefore addressed to bridges with a great number of spans Segment assembly with ground cranes or lifting frames permits free erection seuences while the use of a self-launching gantry reuires 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-schedule dictates 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 to ma7e 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 are still used in the cable-stayed bridges as torsion and most of the negative moment are resisted by two planes of cables Bo< girders may may have constant or varying depth #onstant-depth #onstant-depth dec7s are simpler to cast but competitive in a narrow span range (4-.4m) while varying-depth dec7s are used on spans ranging from .4m to $4-'44m 0epth variation adapts the fle
%igure $': ifting of 24ton pier-head segment (#omtec)
%igure $: '4m, 24ton lifting frame for ton segments (0eal) only in cablecable-stay stayed ed bridg bridges es 5 mobile mobile lifting lifting frame compri comprises ses a motori motori8ed 8ed base base frame frame and a cantilever 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 reuires anchoring the machine to the dec7 before lifting of every segment 1he pier-head segment is lifted or cast in-place to establish a platform on which one or two lifting frames are secured 5n au
Straddle carriers with cantilever noses on both sides of the machine move from one side of the pier to the 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 it into position Most lifting frames also suspend a stress ing platform beyond the segment for fabrication and tensio tensionin ning g of the top slab tendons tendons "n spite spite of the single single-op -opera eratio tion-m n-mach achine ine nature nature and the disruption 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 end of 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 !4ton segments (6S) 1he earliest single-truss single-truss overhead overhead gantries gantries were slightly slightly longer than the span to erect erect 1he length of the truss was sufficient to span between the front cantilever of the completed bridge and the ne
%igure $: !4/m, $./ton gantry for m spans and 4ton segments (6S)
%igure $.: +lacement of the first !/$ton down-station segment with 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 is also 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 a longer gantry is balanced by less reinforcement and prestressing in the entire bridge +lacement of pier-head segments and launching launching are also simplified, and labor demand is lower lower 1he typical launch seuence for a new-generation gantry for long balanced cantilever spans is as follows (!) 1he cantilevers are erected with the gantry anchored to crossbeams sitting onto the pierhead 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-trolley moves the front crossbeam forward to the ' rd or th segment (') 1he front leg is released and the gantry is launched until the rear end reaches the rear crossbeam () 1he rear au
moves the front crossbeam onto the new pier-head segment and the rear crossbeam onto the pier-head segment of the completed bridge (/) 1he front leg is released and the gantry is launched forward and anchored to the crossbeams in the erection configuration for the new span ;o ground cranes are necessary 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 curved spans 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 and load load unbala unbalance nce -m -m segment segmentss are possib possible le althoug although h form form fle
=hen the pier-head segment is .-!4m long, two form travelers can be assembled at the same time "t typically 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 -day cycle after the learning curve has passed 1he segments are cast in one phase proceeding from the front bul7head bac7wards to minimi8e settlem settlement ent at the constr construct uction ion 9oint 9oint 1he 1he inner inner shutter shutter is euipp euipped ed with windows windows for for concre concrete te vibration #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 the second segment segment with tie-downs that prevent prevent overturnin overturning g (%igure (%igure $2) 6ertica 6erticall cylinders cylinders at the front support lift the traveler from the launch rails for casting 5fter tensioning the top slab tendons, the outer form is stripped and the traveler is lowered onto the launch rails 5d9ustable tie-downs roll along the 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 with the same same set of hydra hydraulic ulic cylind cylinders ers aunch aunch cylind cylinders ers are reposi repositio tioned ned altern alternate ately ly #uring
launching 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 front segment suspends a longitudinal '0 truss on either side of the dec7, beneath the bo< wings "n the cable-stayed bridges the #-frame is replaced with hydraulic hangers rolling along the edge girders to avoid interference with the cables (%igure '4) #ounter-rollers at the rear end of the trusses ta7e contrast against the dec7 soffit s offit 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 rails aunching an underslung traveler is more comple< but the reinforcement cage for the segment can be prefabricated as the casting cell is free from obstructions obstructions
%igure '4: $m, $4$ton underslung traveler for 2<$m, '$4ton dec7 segments (6S)
%igure '!: !/.m, !$$ton underslung traveler for .2m, $.ton arch segments (;?S) 1he underslung form travelers for cable-stayed bridges are heavy due to the wide dec7 and the long segmen segments ts based based on cable cable spacin spacing g 0eflect 0eflection ionss are contro controlled lled with with stiff stiff longit longitudi udinal nal trusses trusses and transverse '0 trusses or space frames that support the bottom form table of the casting cell and control torsion in the main trusses 5u
@nderslung travelers with full-width #-frame are also used for in-place casting of cable-supported arches (%igure '!) 1he #-frame is anchored to the arch during operations of the casting cell due to the slope of the arch segments Strand bra7es are incorporated into the launch rails for additional safety from uncontrolled movements 1he segment is cast in one phase by filling the casting cell upward 1he top shutter is closed with the progress of filling to facilitate inspection and concrete vibration 1he support cables of the arch are installed after launching the casting cell to the ne
%igure '$: !/m, !44ton MSS for balanced cantilever casting of !$4m spans with !!'m, /4ton two-phase segments (1hyssenGrupp) 1he use of a suspension-girder MSS is suitable for spans up to !44-!$4m and tangent or slightly curved bridges of adeuate length 1he length of the main girders is about !' times the ma
%igure '': Strand-9ac7ing of /4m, 4ton segment (1hyssenGrupp) 1he MSS’s for balanced cantilever casting can be easily adapted to macro-segmental erection 1he casting cells are replaced with lifting platforms for strand-9ac7ing ong dec7 segments are cast under the bridge and lifted into position (%igure '') 1he pier-head segments are cast in-place with short casting cells suspended from the machine =et 9oints with through reinforcement avoid the geometry reuir reuireme ements nts of shortshort-lin linee matchmatch-cas castin ting g and allow allow bridge bridge design design for partia partiall prestre prestressi ssing ng 1he 1he segments are hung to the main girders during casting of !4-!m stitches and application of top-slab prestressing 6% Carriers an! Gantries )or ("ll-Span .recasting
Many ?1 and 3S? bridges have been built with precast spans %ull-span precasting allows rapid construction and high uality from repetitive casting processes in factory conditions Bo< girders are used for 3S? and highway bridges and @-girders are used for 3S? and ?1 bridges 1he 1he span spanss may may be longe longerr than than !44m !44m when when float floatin ing g cran cranes es are are used used for for plac placem emen ent t *rou *round nd transportation is rarely used for spans longer than 4m for 3S? and ?1 bridges and 4m for highway bridges 1he investment needed to set up large precasting facilities and to provide heavy span transportation and placement machines limits the cost-effectiveness of full-span precasting to long bridges with many eual spans, small radii of plan curvature and low gradient 1hese conditions are met more easily in 3S? bridges
%igure ': /m, '$!ton carrier for placement of '!m, .4ton single-trac7 3S? spans 1he spans are placed onto bearings or seismic isolators to simplify the erection process Simplysupported spans also diminish the thermal stresses in the continuous welded rails of 3S? bridges 1he spans can be connected with in-place stitches to form a continuous structure, although in-place stitches do not offer the same high levels of uality as the rest of the bridge 1he precas precastin ting g plant plant is locate located d near near the bridg bridge e 1he reinfo reinforcem rcement ent cages cages are prefab prefabric ricate ated d and different combinations of pre-and post-tensioning are possible 1he spans are removed from the casting 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 wheeled carrie carriers rs 5 span carrie carrierr (%igur (%iguree ') compri comprises ses two wheeled wheeled trolley trolleyss connec connected ted by a bo< girder girder supporting two winch-trolleys Movement and steering are governed by hydraulic motors powered by diesel engines +ic7ing up the span from the casting cell involves a comple< seuence of operations 1he carrier is moved alongside the span, the trolleys are rotated by 24C by pivoting about hydraulic props, and the carrier 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 seuence of operations 1he same operations are repeated to place the span onto the supports of the storage area and to pic7 it up for final delivery 5fter reaching the abutment, automatic drive systems controlled by ultrasound sensors govern the movement of the carrier over the webs of the bo< girders or within the @-section 1he automatic-drive speed of the machine of %igure ' is '4 7mEh at full load and 4 7mEh unloaded 1he carrier spreads the load onto two spans and the a
%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 =ow9oint Machinery) wheels of the carrier are released 1he motors of front saddle and rear trolley are synchroni8ed to move the carrier along the underbridge 5fter reaching the span lowering location, the rollers of the underbridge are released and the motor of the support saddle is inverted to launch the underbridge to the ne
plate, the load cells are removed and the span is lowered onto the bearings %inally, the underbridge underbridge is moved bac7ward to release the front trolley onto the new span 1ransverse wheel spacing reuired for operations of the underbridge allows the presence of other machines on the bridge during span delivery for earlier start of finishing wor7 3eavy gantries with underbridge are also used for placement of 3S? spans in combination with S+M1’s that deliver the spans along the completed bridge (%igure ') 1he front winch-trolley of the gantry pic7s up the front end of the span and moves it forward while the rear end slides along a support girder on the S+M1 1hen the second winch-trolley pic7s up the rear end of the span to release the transporter aunching aunching the gantry to the ne
1he design loads of MSS’s MS S’s and form travelers are distinguished in permanent loads and varying loads +ermanent loads include self-weight and superimposed dead load 6arying loads include weight and pressure of fresh concrete, the reinforcement cage, the load redistribution at the application of prestress, the actions transferred by lifting devices applied to the MSS, the load of personnel and stored materials on the wor7 platforms, the actions of snow and wind, and the thermal variations 1he casting cell is designed for the weight of forms and reinforcement, the filling seuence and the load redistribution at the application of prestress Shutters are designed for the pressure of fluid concrete and the stress distribution generated by supports, ties and anti-floating anchorages between inner and outer forms ateral pressure of concrete may be computed with hydrostatic distribution in the upper portion and constant value in the lower portion %orm design for full hydrostatic pressure is specified for fast filling or when retarding admi
1he loads applied to MSS’s and form travelers are grouped into two load conditions oad #ondition " is the normal operational condition, which includes permanent loads, payload, load of personnel and stored items on wor7 platforms, loads applied by lifting devices, and wind and thermal loads oad #ondit #ondition ion " is also used to analy8 analy8ee the launch launch stresse stresses s oad oad #ondit #ondition ion "" is the out-of-s out-of-serv ervice ice condition, 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 the machine 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 span lifts up from the casting cell 5s the weight is relieved, however, the casting cell recovers the deflection 5n MSS is more fleverloading of young concrete is avoided by releasing the span in stages as prestress is applied or by tensioning only a part of the tendons prior to releasing the span 1he span is released by lowering the MSS to minimi8e stress redistribution within the casting cell Both service (SS) and strength (@S) limit states are chec7ed SS’s correspond to the loss of functionality of the machine (displacements of components, rotations of field splices that alter the geometry of the casting cell, etc) unit load factors are used for the two load conditions and the resistance factors are prescribed by the design standards @S’s are related to critical conditions such as rigid euilibrium (overturning, uncontrolled sliding, etc), rupture of connections, yielding, and local and global (out-of-plane) buc7ling, and the two load conditions are chec7ed with different load factors 8% Design +oa!s o) Hea0y +i)ters
1he load combinations for the design of beam launchers, lifting frames, launching gantries and span carriers are more comple< because of the dynamic nature of loading 1he discussion that follows is based on %&M-!44! but load classifications and combinations can be easily adapted to different design standards 1he heavy lifters are grouped into classes in relation to the tas7s they perform during their service life 1he classif classifica ication tion determ determine iness the load load amplif amplificat ication ion factor factor used used for the design design of the struct structura urall components, which varies from !44 for 5!-class units to !$4 for 5/-class units 1he class is determined based on the number of load cycles and the load level 5 load spectrum relates the entity of loading with the number of cycles Since most load cycles cycles of these machines machines occur at or near the load capacity, the spectral factor is typically high 3owever, the number of cycles is low and these machines are often designed as 5$-class units with load factor !4$ 5 similar classification applies for the mechanical components 1he load amplification factor varies from !44 for M!-class units to !'4 for M/-class units 1he bridge erection machines are typically designed as M$-or M'-class units with !4 and !4/ load amplification factor, respectively 1he amplification factors for structural and mechanical components are applied to the loads and the load combinations are then processed with load and resistance factors per design standard 1he design loads are divided into four groups: forces that act regularly during normal operations, forces that arise occasionally in the machine in service, e
generators +ayload includes lifted accessories 6ertical rtical inertia inertiall forces forces derive derive from from the sudden sudden applic applicatio ation n or remova removall of the load load ( e.g. .g. precast segments segments on barges with rough sea), positive or negative negative acceleratio accelerations ns during load movements, movements, and the intervention of the emergency bra7es upon electric blac7-out ongitudinal inertial forces derive from accelerations or decelerations of winch-trolleys or portal cranes along the runways 1he occasional forces are wheel impacts, wind, snow, ice and thermal differences =heel impacts are often disregarded when the field splices in the rails are welded and ground away at dismantling of the machine Snow and ice are often disregarded in ordinary weathers 1he eut-of-plane buc7ling of primary members is a more ris7y event than local buc7ling of web panels or secondary members ;o postcritical domain or alternative load paths e
$9% Mo!eling an! Analysis
1he optimum level of detail for the numerical model of a bridge erection machine depends on numerous factors 1he more refined the model, the more accurate the results of analysis and the cambers to assign to the casting cell 3owever, simple models allow rapid investigation of different load and support support conditions, conditions, facilitate the research research of the design-governin design-governing g conditions, conditions, and provide provide the stress magnitude to be e
%igure '.: '0 frame model of the MSS of %igure ! 1win-truss overhead machines are supported onto the overhangs of long crossbeams and '0 frame models of the entire machine are necessary to evaluate the effects of crossbeam deflections "n the MSS of %igure ! the casting cell is suspended on either side from two paired trusses 5 third truss controls controls out-of-plane out-of-plane buc7ling and carries carries the runway for the portal crane 1he secondary secondary truss and one of the main trusses are e
bottom chords during launching, and the trusses may be supported with out-of-node eccentricity even during span casting (') 1he gravity aut-of-node eccentricities and steps in the gravity a
%igure '/: 0ismantling of a ==-frame frame on through girders 1he reliability of internal releases of degrees-of-freedom should be critically reviewed 1he twingirder overhead machines ta7e support onto fle
$$% Insta1ility o) *D Tr"sses
1he stability of a freestanding truss is influenced by the degree of fiut-of-plane buc7ling can rarely be assessed with bibliographic values of the critical elastic moment moment in so comple< structures #ommercial software for structural analysis can depict buc7ling in every member of a truss but analy8ing many buc7ling modes with comple< numerical models involves long computational times >ut-of-plane buc7ling is therefore analy8ed numerically and the local modes are chec7ed with the load magnification factors prescribed by the design standards in relation to the effective length of members
%igure '2: %irst buc7ling mode at segment lifting Buc7ling analysis investigates the stability of the elastic euilibrium of a structure under a given set of loads Since buc7ling modes and factors depend on the load, buc7ling is analy8ed for different load conditions "nertial load amplification also affects the buc7ling factor during movements of the load >ut-of-plane buc7ling of a launching gantry is analy8ed by simulating the placement of segments 5nalysis is simpler in an MSS as the casting cell is fi
&verloaded members may buc7le suddenly and inspections are necessary during assembly and at regular intervals 0amaged diagonals must be reinforced or replaced even when they seem to be in non-critical locations as the load and support conditions vary so much in these machine that they could become become the critical element 0iaphragms 0iaphragms should also be inspected inspected freuently freuently and the reasons reasons for out-of-flat should be investigated as this ma7es the members susceptible to local buc7ling 1he robustness of a machine depends on the stability of members against local buc7ling and on the overall response of the machine to local failure ocal buc7ling of a primary member is often critical in the support towers while stable alternative load paths often e
%igure 4: %lange buc7ling in a 2m, '4ton MSS ocal buc7ling of flanges can trigger critical situations in the bo< girders as during launching the support sections are devoid of diaphragms "n a twin-girder overhead MSS the left bo< girder (on the right in %igure 4) was slightly misaligned left-bound =hen the front launch cantilever was /m long, 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-bound along the low-friction surface 1he procedure was misunderstood and after lifting the bo< girder with the flat 9ac7s, the +1%& plates were i nserted 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 bending generated by the increasing eccentricity in the support reactions &ventually the outer flange and the central flange panel buc7led upwards 1his generated two low-friction inclined planes that gave raise to 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 webs improve load dispersal, transfer lateral forces and also remind distract operators where the support reactions must be applied $'% Insta1ility o) :ertical :ertical S"pport Me#1ers
1he load of an erection machine is transferred to the bridge foundations through comple< load paths that include structural, structural, mechanical mechanical and electro-hy electro-hydraulic draulic components components 1he support legs of these machines are affected by specific forms of instability 1he pendular legs are among the most delicate components because their length must be varied to ta7e support onto the pier cap and onto the dec7 (%igure ) 1his is achieved with articulated legs and rotation cylinders, and the presence of multiple hinges along the vertical load path ma7es the legs prone to out-of-plane buc7ling buc7ling when fully e
%igure !: 1hree-hinge load path in a pendular =-frame =-frame with the dec7 webs, so the crossbeam was windowed at the ends 5s a result, the torsional constant in the 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-hinge scheme scheme where the central hinge has minimal minimal rotational rotational stiffness stiffness due to the low torsional torsional constant constant of the windowed section 1he buc7ling factor for self-weight was as low as 44 Bo<-stiffeners were applied to increase the torsional constant and stabili8e the frame =hen a machine is supported onto temporary towers, the load applied to the towers is always eccentric 5s cantilevers partially fi
%igure $: Bracing deficiencies in a !2m support tower
%igure ': *antry collapse %orensic investigation detected design and assembly deficiencies in the tower oad eccentricity and thermal loads were disregarded in the design ateral fle 244! uality management systems "n spite of a !$2 buc7ling factor with theoretical geometry, geometry, the tower did buc7le
%igure : %irst buc7ling mode of the collapsed tower 5s a matter of fact, buc7ling should always be chec7ed with prudent load factors in these temporary structures 5ll ad9ustment screws should be regarded as potentially prone to local buc7ling @pon completion of launching, gantries and MSS’s 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 =hen the screw 9ac7s are e
Bridge erection machines are load tested after the first assembly ;ew load tests and comparisons with previous tests should follow every ma9or reassembly reassembly Beam launchers, launching gantries, lifting frames and span carriers may be sub9ected to static and dynamic dynamic tests 1he static test load is !4 to 4A higher higher than the design load load oad testing consists of slowly lifting a progressively increasing load until reaching the full test load 1he load is lifted at different locations to reach full design stresses in the critical components of the machine and the deflections are compared with the theoretical values 1he dynamic test load is typically !4 to $4A higher than the design load 1he movements are tested individually at increasing speed Blac7-out tests can also be performed to chec7 the intervention of the emergency bra7es 1he MSS’s are sub9ected to static tests 1he load is increased in steps and the deflections are surveyed at every step 1he full load is 7ept for a certain time, the MSS is unloaded and the residual deflections are measured 1esting 1esting the MSS during casting of the first span is not advisable because loading cannot be interrupted 1he deflections deflections may also differ from the e
result in inadeuate geometry of the first span oad testing may be performed by applying a waterproof membrane and filling the casting cell with water 5dditional load can be applied by suspending concrete bloc7s $% Concl Concl"si "sions ons
"nnovation in bridge erection methods is a need for industriali8ed countries to preserve their e
5+ Bridge Bridge #onstructio #onstruction n Systems, Systems, Bei9ing Bei9ing =ow9oint ow9oint Machinery Machinery,, B&?0, B&?0, #omtec, #omtec, 0eal, 3;1B, "mpresa +i88arotti L #, ;?S, ?i88ani de&ccher, 1hyssenGrupp and 6S are gratefully than7ed for author authori8i i8ing ng the publica publication tion of photog photograp raphs hs of their their machi machines nes or relate related d to indepe independe ndent nt design design chec7ing or technological consultancy assignments performed by the author Glossary Align#ent Align#ent e!ge: 1russ 1russ e
(riction la"nc&er: Support device able to generate longitudinal movements in the main girder by friction Hangers: Bars Bars suspen suspending ding precast precast segmen segments ts or the castin casting g cell cell
from an overhe overhead ad self-la self-launchi unching ng frame frame
Hea0y li)ter: Self-propelled machine euipped 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 euali8ed forces forces +a"nc&ing nose: &
is applied to the front end of the main girder in the launch direction 1he rear nose is applied to the rear end Both noses are euipped with alignment wedges or lifting arms for progressive recovery of the elastic deflection (front end) and progressive release of the support reaction (rear end) +i)ting ar#: 3ydraulic system to recover the elastic deflection of the tip of the front nose and to release the
support reaction at the rear nose 5 long-stro7e cylinder rotates a pivoted arm to lift the tip of the launching nose to the launch elevation and to lower it to release the support reaction +i)ting )ra#e: Beam-and-winch assembly for lifting and handling of precast segments +RT: ight ?apid 1ransit 1ransit MSS: Movable Scaffolding System for in-place casting of +# bridges 5 dec7-supported dec7-supported MSS for balanced
cantilever bridges is called form traveler One-p&ase casting: #asting techniue for solid or voided slabs, ribbed slabs and bo< girders where the entire
cross-section is cast at once O0er&ea! #ac&ine: Bridge erection machine where precast segments or a casting cell are suspended from a
self-launching frame .ayloa!: weight of the segment or the span before, during and after the application of prestress .C: +restressed #oncrete .en!"lar leg: 5rticulated 5rticulated auA?>C: Kuality 5ssurance and Kuality #ontrol Re0erse la"nc&ing: Bac7ward transfer of a bridge erection machine along the completed bridge to erect a
second parallel bridge Roller: 5ssembly of cast-iron rolls onto one or more euali8er beams Sel)-la"nc&ing gantry: Self-launching machine for erection of precast segmental bridges or spans S+S: Serviceability imit State Span carrier: Multi-wheel machine for delivery and placement of precast spans along the completed bridge "t
includes two motori8ed trolleys connected by a bo< girder euipped with lifting winches 1he load on the wheels is euali8ed hydraulically or electronically electronically S.MT: Self-+ropelled Modular 1ransporter Sprea!er 1ea#: 5d9ustable suspension system for precast segments Stra!!le carrier: =heeled portal crane for handling of precast girders and segments Stressing plat)or#: =or7 =or7 area for fabrication and stressing of permanent prestressing tendons
S"pport cross1ea#: Support girder for overhead machines euipped with ad9ustable support legs and support
saddles for the main girders that shift laterally along the crossbeam 5 crossbeam crossbeam comprises braced "-girders or a bo< girder with stiffening stiffening diaphragms diaphragms at the support legs S"pport sa!!le: +ivoted assembly of rollers that supports the main girder and allows rotations about the vertical and transverse a
end of the main girder slides along the underbridge during launching Tra0ersing : ateral shifting of the gantry along support brac7etsEcrossbeams brac7etsEcrossbeams during launching along curves To-p&ase To-p&ase casting: #asting techniue for bo< girders where bottom slab and webs are cast in a first time and
the top slab is cast in a second time T"nnel )or#: #ollapsible inner form for one-phase casting of bo< girders U+S: @ltimate imit State Un!er1ri!ge: Self-launching front support girder for telescopic gantries and for placement of precast spans
with wheeled carriers Un!ersl"ng #ac&ine: Bridge erection machine where precast segments or a casting cell are supported onto a self-launching frame @-)ra#e: 1russed assembly of crossbeam and diagonals supported onto through girders crossing the pier longitudinally to support underslung machines 6ertical ad9ustment is achieved with cylinders located between the through girders and the support frame @inc&-trolley: 1rolley that rolls along the main girders and lodges a main lifting winch and a secondary
translation winch acting on a capstan "n some machines the translation capstan is replaced with hydraulic motors
Bi1liograp&y 55S31> 55S31> ($44') Guide Specifications for Design and Construction of Segmental Concrete Bridges 5merican 5ssociation of State 3ighway and 1ransportation >fficials (55S31>) 1his standard provides guidance on design and construction of segmental +# bridges in the @S "t includes loads and load combinations for analysis of staged constructionN Construction Handbook for Bridge Tempora Temporary ry Works Works 5meric 55S3 55S31> 1> ($44/) ($44/) Construction 5merican an 5ssocia 5ssociation tion of State State 3ighway and 1ransportation >fficials (55S31>) 1his manual provides general information for falsewor7 construction in the @SN
55S31> 55S31> ($44/) Guide Design Specifications for Bridge Temporary Works 5merican 5ssociation of State 3ighway and 1ransportation >fficials (55S31>) (55S31>) 1his manual provides design guidance for ground falsewor7 and other temporary wor7s for bridge construction in the @SN 55S3 55S31> 1> ($4! ($4!4) 4) LRD Bridge Design Specifications 5merica merican n 5ssoc 5ssociat iation ion of State State 3ighwa 3ighway y and 1ransportation >fficials (55S31>) 1his standard rules bridge design practice in the @S "t includes some guidance on bridge erection euipmentN 55S31> 55S31> ($4!4) ($4!4) LRD Bridge Construction Specifications 5merican 5ssociation of State 3ighway and 1ransportation >fficials (55S31>) 1his standard rules bridge construction in the @S "t includes some guidance on bridge erection euipmentN 5#" ($44) ($44) Guide to orm!ork for Concrete 5merican #oncrete "nstitute (5#") 1his manual provides general information and design guidance for formwor7N Construction "ractices Handbook for Concrete Concrete Segmental and Cable#Suppo Cable#Supported rted Bridges. Bridges. 5SB" 5SB" ($44/ ($44/) ) Construction 5merican Segmental Bridge "nstitute (5SB") 1his handboo7 is an international reference for construction of segmental +# bridges "t provides broad information on the technical and technological aspects of most erection methods for +# bridgesN
5"S# 5"S# ($44) ($44) Base "late and $nc%or Rod Design 5merican "nstitute of Steel #onstruction (5"S#) 1his
boo7let provides guidance for design of base plates and and anchor rodsN Boggs, 0 +eter7a, F (!22$) Wind Speeds for Design of Temporary Structures +roceedings of the !4th 5S#& Structures #ongress, San 5ntonio, @S5 5merican Society of #ivil &ngineers (5S#&) 1his paper defines wind load to be used in the design of falsewor7 and other types of temporary structuresN structuresN "ractice for alse!ork alse!ork British Standards "nstitute (BS") 1his boo7let provides general BS" (!2/$) Code of "ractice design and technical guidance for falsewor7 in the @GN
