** Daim ntawv ceeb toom tseem ceeb thiab kev nyab xeeb: ** Qhov no yog cov ntawv sau cia, tsis yog cov qauv tsim, kev suav zoo li qub, cov qauv siv tau, sib koom ua ke nthuav dav lossis kev qhia rau kev tsim kho, vuam, concreting, shoring, prestressing lossis kho dua tshiab. Tag nrho cov qauv qub, cov cim, qhov ntev, cov ntaub ntawv, cov txheej txheem thiab cov ntawv thov raug xa mus yam tsis muaj kev txheeb xyuas raws li cov cai niaj hnub no. Kev tsim thiab kev ua tiav ntawm cov khoom sib txuas steel-pob zeb yog tshwj xeeb rau kev tso cai pej xeem engineers, tus tsim qauv, cov neeg ua haujlwm thiab kev saib xyuas raws li cov khoom tshwj xeeb, thauj khoom, av, khoom siv thiab cov qauv siv tau.
Cov kev sib txuas tsis yog ib qho kev pabcuam tshwj xeeb hauv kev muab rau pej xeem tam sim no ntawm Savo Kusić. Lub hom phiaj tam sim no yog ntoo qhov rais, wood-aluminium Qhov rais thiab qhov rooj kev cai. Rau qhov project qhov rais lossis qhov rooj, koj tuaj yeem xa thov lus.
Introduction
Hauv qee qhov kev tsim kho, siv cov pob zeb ua kom muaj zog ntawm cov kev txhawb nqa steel, xws li pavement slabs ntawm cov choj ntawm I-longitudinal thiab transverse girders lossis ceilings hauv cov tsev ntawm I-girders. Yav dhau los, cov tshuab zoo li no tau ua tiav raws li qhov kev xav tias ob lub ntsiab lus tuaj yeem txav mus rau ib leeg thiab lub sijhawm ntawd nyob rau hauv kev coj ntawm lub ntsiab lus tau txais los ntawm kev txhawb nqa steel nkaus xwb. Lub pob zeb pob zeb tau hloov pauv cov khoom thauj mus rau steel girders, tab sis tsis tau koom nrog kev txais cov txiaj ntsig zoo li qub (daim duab.1).
Image 1 — Coupled carrier, system
Rau txoj kev tsim kho no, cov pob qij txha transverse tau pom nyob rau hauv cov pob zeb pob zeb ntawm lub sijhawm tsis tu ncua, txhawm rau txhawm rau ua kom lub ntsws ntawm cov pob zeb ua kom muaj zog thiab tsis txhob muaj cov kab nrib pleb uas tsis xav tau, piv txwv li kev ntxhov siab ntxiv. Txawm li cas los xij, kev paub dhau los tau pom tias cov rog tiag tiag hauv cov txheej txheem zoo li no txawv ntawm qhov suav. Ntawm qhov kev sib cuag ntawm cov pob zeb ua pob zeb thiab cov hlau txhawb nqa, kev sib txhuam loj (adhesion stress) tshwm sim, kom ob qho tib si ib txwm koom tes.
Qhov tsis zoo ntawm qhov kev sib txuas uas tsis tau xav txog yog qhov tshwm sim ntawm qhov cuam tshuam ntawm cov pob qij txha ntawm pob zeb pob zeb. Shear stresses raws lub abutment nto nce sharply nyob ze ntawm qhov sib koom tes, zoo ib yam li shear stresses ntawm qhov kawg ntawm sab seams. Txij li thaum txoj haujlwm ntawm xoom kab ntawm qhov sib koom ua ke tsis hloov pauv, qhov kev ntxhov siab ib txwm nyob rau hauv kev txhawb nqa hlau tuaj yeem ua tau siab dua li cov kev suav rau kev sib txuas. Pib los ntawm qhov thais no, adhesion mastering tuaj yeem tshwm sim uas kis mus ntxiv. Yog li ntawd, cov pob qij txha nyob rau hauv lub pavement slab tsis ua kom tiav lawv lub luag hauj lwm thiab tsis zoo.
Cov cab kuj
Nyob rau hauv cov ntaub ntawv ntawm kev txhawb nqa sib txuas, nws tau xav tias lub zog shearing ntawm qhov chaw sib cuag ntawm cov hlau txhawb nqa thiab cov pob zeb ua vaj tse tuaj yeem xa mus rau kev nyab xeeb (kev quab yuam hauv cov kab teeb). Txoj cai yog tias cov pob zeb ua vaj tse nyob ncaj qha rau ntawm txoj siv sia sab saud ntawm cov hlau txhawb nqa thiab tsis muaj kev sib txheeb ze. Ntawm qhov no hu ua Nrog rigid coupling, tshwj xeeb txhais tau tias ntawm kev sib txuas yog siv (rods, stirrups, anchors), uas yog embedded rau hauv pob zeb.
Peb yuav xav txog cov ntaub ntawv ntawm cov kab sib txuas nrog cov pob zeb ua pob zeb uas tsis muaj cov pob qij txha. Yog hais tias ib tug tej yam load (xws li khoov lub sij hawm) ua tsuas yog rau ib tug luv luv lub sij hawm, tus coj stresses thiab deformations Δσ, resp. Δε raws li kev tshawb fawb theem pib, zoo ib yam li cov pob zeb muaj zog. Kev ntxhov siab hauv cov hlau thiab pob zeb, ntawm qee qhov elongation, sawv hauv kev sib raug zoo rau lawv cov qauv ntawm elasticity: σst/σb = Est/Eb = n. Yog hais tias lub load yog lub sij hawm ntev, deformations ntawm cov pob zeb tshwm sim vim shrinkage thiab ntws. Yog nrog ε0= s/E0 kos lub deformation vim lub sijhawm luv luv ntawm lub sijhawm _t =0, _ lub deformation nce nyob rau hauv tas li load vim kev sib txhuam kom txog rau thaum lub caij t rau tus nqi εt = ε0(t + φt). Raws li cov xwm txheej zoo ib yam, cov txiaj ntsig deformations raug xam raws li yog tias lawv muaj feem cuam tshuam rau kev ntxhov siab. Yog vim li cas thiaj hais tias Hooke txoj cai siv rau deformations vim ntws. Lub coefficient ntawm ntws φt nyob ntawm lub sij hawm, chav kawm ntawm pob zeb, sab nraud kub, huab cua humidity, lub sij hawm ntawm loading ntawm lub caij, thiab lwm yam.
Tsis txhob khoov raws li Bernoulli\ thiab Navier, qhov sib txawv ntawm kev sib raug zoo tshwm sim, piv txwv li kev faib kev ntxhov siab yuav tsum tau txiav txim siab los ntawm qhov sib txawv sib npaug rau kev ntws. Raws li qhov tshwm sim ntawm kev khiav, qhov kev ntxhov siab hauv cov pob zeb txo qis, thaum cov kev ntxhov siab hauv cov hlau nce. Cov kev ntxhov siab no nyob ntawm seb, ntxiv rau qhov sib txawv ntawm qhov sib txawv, ntawm qhov ntev elastic thiab lub sijhawm thauj khoom. Cov kev tshwm sim zoo ib yam li los ntawm ntws tshwm sim los ntawm shrinkage ntawm pob zeb. Tus nqi ntawm shrinkage ntsuas εs nyob ntawm cov pob zeb, cov txheej txheem ntawm nws cov khoom, nrog rau cov xwm txheej huab cua. Concrete shrinkage tsis nyob ntawm qhov load siv rau lub caij.
Coupling txhais tau tias
Lub coupling txhais tau tias yuav tsum xyuam xim hloov tag nrho cov shearing quab yuam nyob rau hauv lub pob zeb thiab steel nto nyob rau hauv kev sib cuag, vim hais tias cov loads tshwm sim, thiab yog li tiv thaiv slipping. Tsis tas li ntawd, lawv yuav tsum tau txais oblique lub ntsiab tensioning rog, yog tias vim lawv qhov loj me, ntu pob zeb nws tus kheej tsis tuaj yeem txais lawv. Qhov loj ntawm lub zog yog txiav txim siab raws li lub hauv paus kev khoov txoj kev xav. Cov nram qab no coupling agents raug xam tias:
- Coupling anchors: Cov no yog cov hlau puag ncig lossis tiaj tus hlau, welded rau txoj siv sia sab sauv ntawm cov hlau txhawb nqa, uas ua zoo ib yam li khoov khoov ntawm cov kab hlau txuas ntxiv. Lawv yog tsim los ua hooks los yog stirrups, diagonally los yog vertically. Cov thauj tog rau nkoj no tsuas yog ua hauv ib qho kev taw qhia thiab tsis ua haujlwm yog tias lub zog shear hloov kos npe.
- Brackets: Lawv txuas rau saum npoo ntawm cov hlau txhawb nqa, lawv tuaj yeem tau txais lub zog shear rau ob qho tib si. Ib qho kev sib txawv yuav tsum tau ua los ntawm cov nqaij mos thiab lub hlwb txhav nyob rau hauv cov kev taw qhia ntawm lub shearing quab yuam. Mos hlwb hlwb raug kev txom nyem loj deformations thiab unevenly faib lub shearing rog dhau lawv nto. Lub hlwb txhav muab kev faib tawm zoo dua ntawm lub zog ntawm cov deformations me.
Duab 2 — Choj hla Ruhr River ze Herdecke
- Kauv qhov cuab lub zog: Nws so ntawm kev txhawb nqa steel thiab yog welded ntawm cov ntsiab lus ntawm kev sib cuag. Spirals tsis haum rau kev sib txuas tseem ceeb. Tib yam muaj tseeb rau corrugated round steel. Raws li ib qho piv txwv ntawm txhais tau tias rau coupling ntawm choj, nyob rau hauv daim duab. 2 tau pom cov girders ntawm tus choj hla Ruhr ze Herdecka (girders 60x40 nrog ntsug stirrups ϕ12, uas yog welded mus rau lawv tus kheej), tsis txhob txuas ntxiv mus rau gi. hauv fig. 3 txhais tau hais tias rau kev sib txuas ntawm transverse girders ntawm ib tug choj, nyob ntawm seb qhov loj ntawm lub transverse quab yuam, tom qab welded stirrups rau lub girders, nrog rau ncaj qha welded stirrups rau sab sauv siv nrog tshwj xeeb girders, tau thov. Nyob rau hauv cov ntaub ntawv ntawm ntev stirrups, lub stirrups kuj yuav welded rau opposite sab, fig. 4a. Hauv daim duab. 4b yog cov tshuaj qhia nrog slanted stirrups.
- Daim duab 3 — Kev them nyiaj yug Transverse ntawm ib tug choj*
Image 4 — Lub paj hlwb nrog stirrups
Nyob hauv kev tsim kho vaj tse, nruj stirrups nrog stirrups los yog tsuas yog stirrups kuj tau siv, tab sis cov kev daws teeb meem nrog mos stirrups kuj tau ntsib, xws li piv txwv li. riveted cov ces kaum. Rau cov laj thawj kev lag luam, kev sib txuas cov anchors feem ntau yog siv, uas yog pob tw-welded rau kev txhawb nqa steel (daim duab 5a), lossis so ntawm kev txhawb nqa nrog ib qho kawg khoov (daim duab 5b). Hauv daim duab. 5c qhia txog cov kev daws teeb meem nrog cov hooks tshem tawm. Hauv daim duab. 6 qhia txog ib qho kev daws teeb meem rau lub qab nthab hauv kev tsim vaj tsev, uas yog a) kev txhawb nqa ua ke ntawm I-beams, b) ua los ntawm T-beams, uas yog tsim los ntawm kev txiav I-beams. Thaum kawg ntawm cov kev txhawb nqa, tshwj xeeb tshaj yog muaj zog kawg braces yuav tsum yeej ib txwm muab (daim duab. 7). Inclined anchors yog siv los qhia cov kev ntxhov siab los ntawm qhov shrinkage thiab kub rau hauv cov slab.
- Daim duab5- Coupling anchors *
- Daim duab6- Kev them nyiaj yug ntawm mezzanine qauv *
Dimensioning ntawm txhais tau tias rau coupling yog ua raws li lub hauv paus ntsiab lus. Tus kheej txhais tau tias yuav tsum tau txais lub zog shear sib haum rau lawv qhov sib nrug. Thaum dimensioning lub welded kev twb kev txuas ntawm lub hlwb, lub overturning lub sij hawm yuav tsum tau coj mus rau hauv tus account.
- Daim duab7- a) Xaus lub paj hlwb nrog anchoring; b) anchoring *
Elastic coupling
Cov kev nthuav qhia yav dhau los tau raug xa mus rau rigid coupling, qhov chaw txheeb ze ntawm kev txhawb nqa steel thiab phaj yog sib npaug rau xoom, thiab kev sib txuas txhais tau tias ua tsis tu ncua. Lub deformation ntawm coupling txhais tau tias, lub zos deformation ntawm cov pob zeb thiab cov hlau txhawb tau neglected.
- Daim duab8- Bracket nrog elastic coupling *
Raws li qhov kev xav ntawm kev sib txuas tsis sib xws, cov rog xa los ntawm ib tus neeg txoj kev sib txuas yog proportional rau lub transverse force thiab qhov sib nrug ntawm lub hlwb. Yog tias muaj kev cuam tshuam tseem ceeb ntawm kev txhawb nqa steel thiab cov pob zeb ua vaj tse tshwm sim hauv qee qhov chaw, qhov no ua rau muaj kev sib koom ua ke ntawm cov rog. Qhob tuaj yeem ua ib feem tsis ua raws li lub phaj siab ntawm cov nqaj sib txuas, uas yog qhov siab tshaj plaws ntawm cov shear rog tau txo qis. Hauv daim duab.8Ib qho piv txwv ntawm kev tsim kho nrog kev sib txuas elastic yog muab, zoo ib yam li tus choj hla Rhine, Koln-Rodenkirchen. Hauv daim duab.9Cov nyhuv ntawm elastic coupling ntawm ib qho kev txhawb nqa tas mus li yog qhia, rau lub zog muaj zog thiab muaj peev xwm sib npaug sib npaug. Qhov kev txav chaw ψ, uas yog ib qho kev ntsuas ntawm qhov nruj ntawm qhov sib txuas rau kev txais shear, yog txhais hauv daim duab.8. Lub zog ntawm elastic coupling yog li ntawd loj heev, yog hais tias tus yam ntxwv ntawm lub coupling yog xaiv lub hom phiaj kom tau txais shear.
- Daim duab9- Piv txwv rau tus choj nrog elastic coupling *
Kev suav ntawm kev sib txuas ua ke
Hauv txoj ntsiab cai, nws yog kev lag luam uas lub thickness ntawm cov pob zeb ua vaj tse yuav tsum yog me me li sai tau, thaum qhov tsawg kawg nkaus thicknesses txiav txim siab los ntawm cov kev cai yuav tsum tau ua raws li.
Statically txiav txim cov qauv
Nyob rau hauv cov ntaub ntawv ntawm statically txiav txim siab kev tsim kho (xws li cov kab teeb yooj yim), cov static influences nyob rau hauv cov seem rau ib tug tej yam load yog tas li, los yog ywj siab ntawm lub sij hawm. Tsuas yog lub sijhawm khoov thiab lub zog ib txwm nyob hauv qee qhov ntawm ntu yog qhov hloov pauv vim qhov cuam tshuam ntawm ntws thiab shrinkage.
Cov nyhuv ntawm shrinkage tuaj yeem sawv cev raws li qhov sib txawv ntawm qhov sib txawv ntawm cov hlau girder thiab cov pob zeb ua vaj tse. Raws li qhov tshwm sim ntawm pob zeb shrinkage, kev ntxhov siab sab hauv tshwm sim nyob rau hauv qhov sib txuas, uas yog tensile stresses los ntawm shrinkage nyob rau hauv lub pob zeb, uas nws shrinkage yog tiv thaiv los ntawm lub zog ntawm cov hlau txhawb (nrog rau lub reinforcement nws tus kheej), thaum sib xws compressive stresses tshwm sim nyob rau hauv lub steel seem (Fig.10). Shrinkage nce nrog lub sij hawm mus rau qhov kawg tus nqi raws li ib tug exponential muaj nuj nqi. Txij li thaum shrinkage stresses kuj nce nrog shrinkage deformations, qhov no tshwm sim nyob rau hauv thiaj li hu ua shrinkage flow.
- Daim duab10- a) Shrinkage ntawm lub phaj dawb tsis muaj coupling; b) kev ntxhov siab vim kev poob qis hauv kev txhawb nqa ua ke *
Nyob ntawm cov txheej txheem zoo li qub uas xav tias tus kheej qhov hnyav ntawm cov pob zeb pob zeb, nws txawv: kev sib txuas tsuas yog rau kev txav mus los (tsuas yog cov hlau txhawb nqa nws tus kheej qhov hnyav, thiab lub kaw lus sib txuas tau txais cov khoom thauj uas ua tiav ntawm cov qauv tiav), coupling rau tus kheej qhov hnyav thiab txav load (tag nrho nws tus kheej qhov hnyav thiab kev txav txav ntawm qhov sib txuas ua ke).
Thawj rooj plaub tshwm sim thaum steel girders pab raws li formwork girders, tsis tau txais kev txhawb nqa, thiab thaum lub sij hawm concreting, lawv muaj peev xwm khoov rau hauv lub tshav pob (daim duab.11a). Hauv qhov no, kev txhawb nqa steel nws tus kheej yuav siv qhov hnyav ntawm cov pob zeb thiab formwork. Bonding tshwm sim tsuas yog thaum lub pob zeb nyuaj txaus (Fig.11b), thiab kev txhawb nqa yuav tsum tsis txhob thauj khoom tam sim ntawd tom qab concreting, txhawm rau kom tsis txhob muaj kev puas tsuaj lossis ntau dhau ntawm cov pob zeb.
Hauv qhov thib ob, thaum tus kheej qhov hnyav ntawm cov pob zeb ua pob zeb kuj tau txais los ntawm kev sib txuas ua ke (daim duab 11c), nws xav tias kev txhawb nqa steel tau txais kev txhawb nqa thaum lub sij hawm concreting nyob rau hauv qhov chaw txaus, kom nws tsis tau txais lub sij hawm tseem ceeb bending. Kev faib hluav taws xob tom qab tshem tawm cov scaffolding yog qhia hauv daim duab. 11d.
- Daim duab 11 - Coupling rau tsiv thiab tuag load, nrog voltage distributions ua ntej thiab tom qab tshem lub scaffolding *
Preload
Nyob rau hauv cov ntaub ntawv ntawm cov kab teeb yooj yim, me me tensile stresses tshwm sim nyob rau hauv lub pob zeb tsuas yog vim shrinkage thiab kub sib txawv. Kev nyuaj siab tensile ntau tshwm sim nyob rau hauv overhang beams, nruam girders thiab lwm yam qauv, thiab cov no yuav ua rau tawg nyob rau hauv lub pob zeb. Yog tias cov kab nrib pleb tshwm nyob rau thaj tsam ntawm lub sijhawm tsis zoo, cov nyhuv coupling ploj. Yog li ntawd, nws yog ib qho tseem ceeb rau induce me compressive stresses nyob rau hauv lub pob zeb slab ua ntej nyob rau hauv thiaj li yuav xyuam xim zam lub tsim ntawm tawg vim pob zeb shrinkage. Tensile stresses nyob rau hauv lub pob zeb slab ntawm coupling beams yuav txo tau:
1. Los ntawm kev coj tsis zoo pre-loading ntawm steel girder (pre-tensioning ntawm ntug sab sauv). Nyob rau tib lub sijhawm, cov kab ke ntawm concreting yuav tsum tau ua tib zoo kawm.
2. Los ntawm kev txhawb nqa thiab txo qis nruab nrab ntawm kev txhawb nqa txuas ntxiv. yog li ntawd, nrog rau cov txheej txheem tsim nyog, kev ntxhov siab tuaj yeem tshwm sim hauv cov pob zeb ua ke ntawm kev txhawb nqa txuas.
3. Los ntawm prestressing. Cov ntaub ntawv yooj yim tshaj plaws yog thaum lub pob zeb dawb yog prestressed, thiab tsuas yog tom qab txuas nrog kev txhawb nqa steel. Qhov kom zoo dua ntawm cov txheej txheem no yog ib qho me me prestressing quab yuam, txij li thaum lub compressed siv ntawm steel txhawb tsis yog prestressed. Lub girder no tau txais kev khoov lub sijhawm tsuas yog vim qhov ntws thiab shrinkage ntawm cov pob zeb pob zeb, yog li nws tseem ncaj vim yog lub zog prestressing. Hauv daim duab.12thiab qhov kev faib tawm kev ntxhov siab rau qhov xwm txheej ntawm qhov kev ntxhov siab yog qhia (t =0), thiab hauv fig.12b lub xeev kawg ntawm qhov kawg ntawm ntws (t=tE) thiab hauv daim duab.12c dabtsi yog khoov stresses vim lub sij hawm luv luv loading (t=a). Hauv daim duab.12d qhia qhov voltage faib rau t =0 nyob rau hauv cov ntaub ntawv ntawm prestressing lub bonded pob zeb slab.
- Daim duab12- Prestressing ntawm ib tug dawb-sawv pob zeb slab nrog tom ntej coupling *
Statically indeterminate kev tsim kho
Nruam girders thiab cov qauv zoo sib xws tau txais lub sijhawm khoov tsis zoo, uas feem ntau ua rau muaj zog tensile siab nyob rau hauv cov pob zeb uas muaj zog ntxiv. Cov kab nrib pleb yog qhov tsis xav tau tshwj xeeb tshaj yog nyob rau hauv cov txuas hniav, xav txog lub neej kev pab cuam ntawm cov kab sib txuas thiab cov txiaj ntsig ntawm qhov chaw ntawm cov kab nrib pleb. Statically indeterminate systems yog xam rau lub sij hawm luv luv loads (moving loads) raws li ib txwm txoj kev ntawm statics rau ib tug unchanged system. Qhov sib npaug zoo li qub thiab deformations yog tib yam li hauv cov txheej txheem elastic. Nyob rau hauv cov nyhuv ntawm qhov chaw thau khoom tas li, tshwj xeeb tshaj yog high prestressing, loj txaus ib txwm tshwm sim. Thaum txiav txim siab lub zog prestressing, qhov kev sib txhuam ntawm cov bent prestressing ntsiab yuav tsum raug coj mus rau hauv tus account. Thaum lub sij hawm tsim kho, lub overhang ntawm txuas txuas txuas yuav tsum tau ua tib zoo xaiv. Cov kev txhawb nqa npaj ua ke yog nruj heev, yog li nws yuav luag tsis yooj yim sua kom rov kho qhov siab ntawm txoj hauj lwm. Qhov kawg theem yog ua tiav tsuas yog tom qab ob peb xyoos, xav txog qhov ntws. Qhov kev ntsuas ntawd tsis paub meej rau qee qhov, vim tias qhov cuam tshuam ntawm shrinkage thiab ntws yog qhov sib txawv, nyob ntawm qhov xwm txheej huab cua uas tsis tuaj yeem kwv yees.
Xaus
Daim ntawv thov kev sib txuas tsis txwv rau cov kab hlau hlau, tab sis kuj tseem tuaj yeem suav nrog kev txhawb nqa rau kev nruj Langer beams, ncua kev txuas txuas, thiab lwm yam nrog rau cov kab lattice girders nrog rau txoj hauv kev nce lossis nqis. Lattice txuas hniav - siab tensile stresses tshwm sim nyob rau hauv txoj kev slabs nyob ze ntawm txoj kev hauv qab no, vim cov slabs yuav tsum tau ua raws li ib tug ntau dua los yog tsawg npaum li cas elongation ntawm tensioned siv ntawm lub ntsiab girder. Tsim nyog longitudinal prestressing yog yuav tsum tau kom tsis txhob tawg. Hauv daim duab.13muaj ib tug ciam teb rooj plaub nyob rau hauv uas lub steel daim phiaj tsis muaj ib tug qis dua txoj siv nyob rau hauv tag nrho, thiab nws lub luag hauj lwm yog kiag li coj los ntawm ib tug reinforced pob zeb slab prestressed nyob rau hauv ob qho tib si kev taw qhia. Hauv daim duab.13b cov kwj dej ntawm ntu yog pom60x180mm hauv kev txhawb nqa nws tus kheej.
- Daim duab13—Gahle choj: a) seem; b) ntawm txoj siv qis, sab laug ntawm qhov chaw nres tsheb loj, sab xis ntawm Vešaljka *