I MPLE MPL EMENTAT MENTATII ON OF I NC NCR R EM ENTAL LA LAUNC UNCHI HI NG M PLE LEME NCRE REM ANA NAL LYSI S I N GT STRUDL US USII NG THE PAR ARAME AMETE TERI RI ZATI ZATI ON
D m it rry y Mas M aslov Ma slov I nst nst it ut e Gipros Giprostt roym ost ost Saint ai nt - Petersburg, Russian ussian Feder Feder at ion h t t p: p : / / w w w . g p sm .r .r u
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I ncrem nc rem e nt a l La La unching unc hing is tth he mos use d m e t hod e most m os ostt comm only use f or b r idg e erect erec Russ sia. idge e r ec er ectt ion i n Rus Cantilever and floating methods are used for large structures like cable - stayed or arch bridges but they are rarely build days ys.. buil d now a da Thus, alm ost ost e very p analys lysis is almost almos prr oj e ct of a bri dge involves t he ana a nalysis of increment al launching pr oce oce ss.
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I ncrem nc rem e nt a l La La unching unc hing is tth he mos use d m e t hod e most m os ostt comm only use f or b r idg e erect erec Russ sia. idge e r ec er ectt ion i n Rus Cantilever and floating methods are used for large structures like cable - stayed or arch bridges but they are rarely build days ys.. buil d now a da Thus, alm ost ost e very p analys lysis is almost almos prr oj e ct of a bri dge involves t he ana a nalysis of increment al launching pr oce oce ss.
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The problem of analyzing a continuous beam will never seem very difficult unless the calculations are reiterated m any t im e s, as it happens happens at t he des design of a br idge. The dat a w hi ch h ave t o be pr oces ocess sed ar a r e not a large m ass ass, but because this process is repeated many times it really becomes a large mass of data growing like a snowball, part pa rt icula icularly rly f or m ore t ha han n 3 - span br id ges. ges. idges
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When w e deal w it h an ordinary 3 - span br idg e t o be pushed with temporary piers and a launching nose, we can easily predict t he cri t ical posit ions of t he st ru ct ur e. So w e can be cont ent w it h analysis of t hose posit ion only .
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Somet im es w e w ork on a longer bridge br idge to t o be launched w it h non - linear strengthening elements when temporary piers are prohibited even to be thought of due to a navigable ri ver or elect ri fied fi ed railw ay w hich lie beneat h. IInn that t hat case case it is hard tto o predict posit ions of tthe he st ru ct ur e positions structure in which the significant components of stress - strain state could r each t heir cr it ical values.
So we have to take into accoun t as m any m odels as it is necessary to make sure that no problem will occur in f ield.
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And w hat if t he num ber of posit ions t ends t o a t housand? And what if we find out that the structure has to be reinforced, temporary piers re - located, casting yard re design ed, and som et hi ng else changed? And what if consequent analyses of different positions of the launched bridge threaten with turning into a never ending routine calculations of new parameters and analyt ical models, w hen t he t im e is against us? The pr oblem probl em m ay becom e un solv able un less som e t ools t o aut omat e t he pr ocess of analysis are applied.
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What information is necessary to perform analysis for a launchin g posit ion? The most important geometrical information involves the coordin at es t o all t he j oint s accordi ng t o t he beam camber and t he pier coordin at es in t heir ow n r eference fram e. coordi nat
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When w e t ranslat e t he horizont al j oint coordinates coordinat es int o t he pier coordinat e syst em w e fin d t he j oint s t o be support ed in fi nd t he curr ent posit ion.
Translat ing t he vert ical coordinat es w e find t he t heoret ical non - deformed configuration from which we calculate the ordi nat es of suppor t ed j oint s t o be specif ied as JOI NT DI SPLACEMENTS in addit ion t o t he self w eigh t loadi ng ng..
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There are many ways to calculate the necessary data. For example we drew piers and beam in AutoCAD, then moving t he “ beam ” along t he “ piers” w e found r equir ed coordinat coordi nat es. The sam e oper at ion coul d b e easil y perf or m ed in Ex cel.
I t does not seem a hard problem if w e have enough t im e t o solve it .
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There w as a brid ge being launched over a riv er near t he cit y bridge ri ver of Vologda. 105 m et er s long cent r al span and a t em porary porar y pier decr easing t he span t o 97 m et er s pr om ised no t r oubles. ers But t he surveying m onit oring report ed t hat t he launching monit nose had appr oached t he t em porary ier one met er high er porar y p pier h igher t han it w as supposed t o. One m et er , w hereas w e could allow no m ore t han 25 cm , or w e w ould st art developing a pr oj ect proj for cleanup t he river bed fr om t he bridge wreckage.
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For three days we tried to figure out whether our “ patient ” w as alive rat her t han dead, or dead rrat at her t han alive. For three days we considered how to proceed with the launching. For t hree days t he cant ilever w as w obbling w it h t he w ind, and t he st resses r esses w er e very close t o t he ult im at e cri t ical value.
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Finally we managed to discover that the builders had bolted the nose to the span incorrectly and it was possible t o go on aft er rraising aising t he t op of t em porary pier.
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We built a bridge w it h 147 m et er long cent ral span over t he main navigable channel connecting the basin of the Volga ri ver w it h t he Whit e and Balt ic seas.
Because of that no temporary pier was allowed within the central span. As it was prohibited inside, we placed temporary piers outside the central span and put the r eceivin g beam on t hem.
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The structure behavior after the connection was strictly dependent on the angle with which the nose would be bolt ed t o t he receiving beam . I t so happened t hat t he cant ilever displacem ent s did not m at ch t heir t heoret ical values. At each m ove w e st opped launching t o perf orm analysis for t he curr ent sit uat ion. Each st ep t ook about an hour t o analyze w it h draw ing scheme and t r ansferr ansf er r ing dat a fr om one applicat ion t o another.
At t hat t im e tthe he builders w ere t ossing st ones int o t he w at er and w at ching t he spreading circles.
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The difference between the theory and the practice grew larger f rom one m ove t o another anot her unt il w e found out t hat a cradle w as dangling r ight at t he launching n ose ttiip. p. When it w as r em oved all t he coordin at es became ex act ly as predicted.
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We fi gurred ed out t hat w e had to figu t o im prove t he process in order to decrease time needed to complete the calculations, especially for a bridge being monitored during the launching.
We decided t o appl ya apply t echn iqu e called “ parameterization ” t hat w e successf ulllly y successfu used f or solvin g ot her problems.
status support support #for var s = 0 to NumPier to NumPier - 1 #if (sn[s ] == -1) or (sty[s ] == 0) (sn[s] (sty[s] then continue ' N%&d 1000+sm[s]%' ' N%&d 1000+sm[s]% #next #back 1 joint releases #var Flag = true #for var s = 0 to NumPier to NumPier - 1 #if (sn[s ] == -1) or \ (sn[s] (sty[s] sty[s] == 0) then continue continue #if Flag then N%&d ' 1000+sm[s]%' ' mom z N%&d 1000+sm[s]% #Flag = false #continue #continue #endif N ' N%&d 1000+sm[s]%' for x mom z #next status support support 'N1228' 'N1246' 'N1194' joint releases 'N1228' mom z 'N1246' for x mom z 'N1194' for x mom z
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What is param et eri zat ion? I t is nothing not hing but a facilit y of using m at hem at ical expr ession s as w ell as num er ic const ant s in analyt ical m odel. I t is nothing not hing but a facilit y of using pr ogram m ing programm st at ement s such as loops and condit ionals as w ell as com m ands of GT STRUDL problem pr oblem orient ed language. langu age.
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We developed an appli cat ion applicat t o ext end t he comm and language, t o t urn t he m aking of an analyt ical m odel a bit int o the program m ing. programm The pr ogr am has a scr ipt language w it h built - in feat ur es as befit befi t a progr am m ing language. So w e ar e able t o pr epar e a m odel and, w hen necessary, t o m odify odif y iitt easily changing only a few param et er s inst ead of paramet alt ering t he ent ire m odel. I n ot her oth er w ords w e developed a t ool t o make “ cust om w izards ” .
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The parameterization proved especially useful at the increm ent al launching analysis. We w rot e a scri pt w hich could be call ed “ launching w izard ” . I n order t o make th e analyt ical m odel for t he f or a beam posit ion only three parameters have to be changed: the number of blocks being launched, the number of a pier the beam is pushed beyond, and t he dist ance bet w een t he nose ti p and t hat pier. t ip
All t he rem aining in for m at atiion on is specifi ed for t he ent ir e bri dge , and it has t o be m odified only w hen th e proj ect ’ s paramet ers t he are rrevi evised. sed.
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The pr oj ect of t he Sout hern Br idge over t he Daugava River in Rig a, Lat vi a. Riga,
803 m et er long 7 span beam of an ext radosed bri dge w ill be br idge launched w it h a nose and a r einf orcing em ade of 4 einfor cing f r am ame made cable - st ays in t he leadin g span.
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At the very beginning we believed we knew the positions where we had to pay attention to the strength of beam, nose, and cabl e - stays.
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Lat er w e found out t hat non - lin ear cable behavior had t o be t aken int o account .
That broke all our expectations and caused the analysis of t he ent ire launching fr om t he fir st st ep t o t he last . first
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Later we found that some blocks had to be re - designed because of t heir in suf f icient st r engt h at som e posit ions. i nsuf The calcul at ion s w ere repeat ed … ions Lat er t he block m ount ing sequence w as r econsidered. The calcul at ion s w ere repeat ed … ions Later … I t happened m any t im es t hat t he calculat ions w ere repeat ed. And each turn consisted of 803 analytical models. An hour for a model. How much time would it take? Over five months? Wit hout paramet erizat ion it could.
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Usin g ou r “ launching w izard ” w e analyzed t hr ee t o four posit ions a min ut e.
When somethin g w as something changed t he new result s appeared in n o m ore t han no t w o days.
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There w as som et hin g w hich suspended t he analysis: w e had to deal with pier detachments manually because it is im possible t o use absolut ely r igid u nil at er al suppor t s.
When w e found a negat ive support react ion w e excluded t he pier from the model and repeated analysis watching for negat ive j oint displacem ent w hich w as t he sign t hat t he pier w as r eally at t ached. And so on and on and on, ged. on , unt il t he pr ocess conver conv erged.
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This winter, during the launching of a bridge over a river in West ern Siber ia, 11 4 m et er long lon g cant il ever collapsed and l ay on t he pier i t had been hangin g above.
The steel samples taken near the breach proved that the m at erial conform ed t o all t he requirement s. The I nst it ut e Giprostroymost was commissioned to make expert exam inat ion and inquir e whether w het her the t he accident accident had had occurred occur red examination inquire due t o som e calcul at ion i ncorr ect ness.
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We applied our “ launching wizard ” and m anaged t o confir m all analytical statements and perform complete analysis for further launching after mending the breach. It took two w eek s as schedu led.
Actually there were no analytical errors and the bridge crashed because of stress concentration after violation of w elding eldin g t echnologi es.
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The second problem of incremental launching arises when the analysis is completed. How should we work up megabytes of the results? We need the envelope for forces, moments, and reactions. Also we need joint coordinates in deformed configu rat ion at every st ep.
We developed a post - processing application to deal with the r esul t s t aken f r om t he t ext f ililes es cr eat ed by COUTPUT com m and. The progr am r eads dat a fr om a group of t ex extt fi filles es and t ransm it s t o Excel t he inform at ion in t he proper f orm .
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I n order t o feed t he post - processor with necessary information t he “ launching wizard ” writes to the resulting files the output of MEMBER FORCES, LI ST DI SPLACEMENTS, and LI ST REACTI ON com m ands. Also it w r it es addit ional in f orm at ion: correspondence between pier numbers and supported joint identifiers, joint coordinates in non - deformed configuration, and sect ion m odulu s ( t o buil d st r ess envelopes) .
The progr am w ork s very program fast and delivers fr om possible err ors w hich m ight occur dur ing t he m anual dat a t ransferr ing.
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The t echniqu e w e invent ed allow s us t o dramat ically im prove t he perf orm ance of increm ent al launching analysis.
I t can be applied t o any br idge, even for f or spat ial models including plat e fin it e elem ent s. finit element There ar e no lim it s but engineer ing m ind and ex perience.
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A language t o descr descriibe be an analyt ical m odel is a great feat f eat ur e. A language like l ik e GT GT STRUDL ’ s is a great er f eat ur e. And a language with parameterization is one of the greatest facilities which expand t he class of pr oblems oblem s t o be solved w it h a progr am. Unfortunately there are not so many programs having parameterization (or what it ’ s called) as a built - in feature. And t heir pri ce grow s m ore th an a hun dred t housand dollars and mor e. The parameterization is a useful and convenient tool for us. And w e t hink it could be useful for ot her GT STRUDL s. STRUDL user users. Of course, the creation of parameterized analytical models demands a m ore com pet ent engineer. But t he ski ll com es quickly because the parameterization language is much easier than BASI C. Anyon e w ho k now s w hat ‘ variable’ means, anyone who is able t o input a form ula, is able t o use t he param et eri zatiion. on. eterizat
Our recom m endat ions for fu t ur e GT STRUDL develop m ent :
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1. GENERATE and REPEAT commands to create a group of rigid bodies as w ell as fin it e elem ent s. 2. ACTI VE and I NACTI VE comm ands f or r igi d b odi es. 3. Draw ing r igid bodies as lines fr om t he mast er j oint t o t he slaves. ( !) 4. Keeping SLAVE RELEASES information while saving the text in GT MENU. ( !) 5. A command like LOAD LIST MEMBER M1 ‘ M1’ MAX FORCE X that means “ find the loading in which axial force of member ‘ M1 ’ is m aximal and m ake t hat loading act ive for t he result s out put . 6. A command like LIST ENVELOPE MIN MOMENT Z that means “ print member forces for loadings in which bending m oment s along Z- axis are min im al” . 7. Displaying t he dir ect ions of element pr incipal st resses in GT MENU. 8. UNDO and REDO in GT MENU. ( !) 9. More t han 8 charact er long ident if iers. ( !)