Nyob rau hauv ntau yam txheej txheem, engineers yuav tsum tau soj ntsuam lub zog ntawm cov pob qij txha ua los ntawm welds thiab mechanical fasteners.Niaj hnub no, mechanical fasteners feem ntau yog bolts, tab sis cov qauv qub yuav muaj rivets.
Qhov no tuaj yeem tshwm sim thaum hloov kho, kho dua tshiab, lossis txhim kho qhov project.Ib qho kev tsim tshiab yuav xav tau bolting thiab vuam ua haujlwm ua ke hauv ib qho kev sib koom ua ke uas cov khoom yuav tsum tau koom ua ntej bolted ua ke thiab tom qab ntawd welded los muab tag nrho lub zog rau kev sib koom tes.
Txawm li cas los xij, kev txiav txim siab tag nrho cov peev txheej ntawm kev sib koom ua ke tsis yooj yim li ntxiv cov lej ntawm tus kheej cov khoom (welds, bolts, thiab rivets).Qhov kev xav zoo li no tuaj yeem ua rau muaj kev puas tsuaj loj.
Bolted kev sib txuas tau piav qhia hauv American Institute of Steel Structures (AISC) Structural Joint Specification, uas siv ASTM A325 lossis A490 bolts li nruj mount, preload, lossis zawv zawg qhov tseem ceeb.
Tightly tightened kev sib txuas nrog ib qho kev cuam tshuam cov ciaj ntswj los yog locksmith siv ib tug pa ob-sided ciaj ntswj los xyuas kom meej tias cov khaubncaws sab nraud povtseg nyob rau hauv nruj kev sib cuag.Nyob rau hauv ib qho kev sib txuas prestressed, cov bolts tau teeb tsa kom lawv tau txais qhov tseem ceeb tensile loads, thiab cov hlau yuav raug compressive loads.
1. Tig lub txiv ntseej.Txoj kev tig cov txiv ntseej yuav tsum nruj lub bolt thiab tom qab ntawd tig cov txiv ntoo ib qho ntxiv, uas nyob ntawm txoj kab uas hla thiab qhov ntev ntawm lub bolt.
2. Calibrate tus yuam sij.Cov txheej txheem calibrated ciaj ntswj ntsuas lub torque uas yog txuam nrog bolt nro.
3. Torsion hom nro kho ntsia liaj qhov rooj.Twist-off nro bolts muaj me me studs ntawm qhov kawg ntawm lub ntsia liaj qhov rooj opposite lub taub hau.Thaum lub torque yuav tsum tau mus txog, lub stud yog unscrewed.
4. Ncaj rub Performance index.Direct nro indicators yog tshwj xeeb washers nrog tabs.Tus nqi ntawm compression ntawm lub lug qhia txog qib ntawm nro thov rau lub bolt.
Nyob rau hauv cov lus layman, bolts ua zoo li pins nyob rau hauv nruj thiab pre-tensioned pob qij txha, zoo li ib tug tooj dag tus pin tuav ib pawg ntawm perforated ntawv ua ke.Qhov tseem ceeb zawv zawg pob qij txha ua haujlwm los ntawm kev sib txhuam: preload tsim downforce, thiab kev sib txhuam ntawm cov chaw sib txuas ua haujlwm ua ke los tiv thaiv kev sib tsoo ntawm qhov sib koom ua ke.Nws zoo li ib daim ntawv khi uas tuav ib pawg ntawm cov ntaub ntawv ua ke, tsis yog vim lub qhov yog xuas nrig ntaus hauv daim ntawv, tab sis vim tias lub binder nias cov ntaub ntawv ua ke thiab kev sib txhuam tuav cov pawg ua ke.
ASTM A325 bolts muaj lub zog tensile yam tsawg kawg nkaus ntawm 150 txog 120 kg ib square inch (KSI), nyob ntawm txoj kab uas hla, thaum A490 bolts yuav tsum muaj lub zog tensile ntawm 150 txog 170-KSI.Rivet pob qij txha coj zoo li cov pob qij txha nruj, tab sis nyob rau hauv cov ntaub ntawv no, cov pins yog rivets uas feem ntau yog ib nrab muaj zog li A325 ntsia liaj qhov rooj.
Ib qho ntawm ob yam tuaj yeem tshwm sim thaum ib qho kev sib koom ua ke sib koom ua ke raug rau cov quab yuam shear (thaum ib lub ntsiab lus zoo li xaub dua lwm qhov vim yog siv zog).Bolts lossis rivets tuaj yeem nyob ntawm ob sab ntawm lub qhov, ua rau cov bolts lossis rivets txiav tawm tib lub sijhawm.Qhov thib ob muaj peev xwm yog tias kev sib txhuam los ntawm lub zog clamping ntawm cov pretensioned fasteners tuaj yeem tiv taus shear loads.Tsis muaj kev poob siab rau qhov kev sib txuas no, tab sis nws muaj peev xwm ua tau.
Ib qho kev sib txuas nruj yog siv tau rau ntau daim ntawv thov, vim tias kev swb me ntsis tsis tuaj yeem cuam tshuam rau cov yam ntxwv ntawm kev sib txuas.Piv txwv li, xav txog ib lub silo tsim los khaws cov khoom granular.Tej zaum yuav muaj kev swb me ntsis thaum thauj khoom thawj zaug.Thaum plam tshwm sim, nws yuav tsis tshwm sim dua, vim hais tias tag nrho cov tom ntej loads yog tib yam.
Load reversal yog siv nyob rau hauv ib co kev siv, xws li thaum rotating ntsiab yog raug rau alternating tensile thiab compressive loads.Lwm qhov piv txwv yog ib qho dabtsi yog khoov uas raug rau tag nrho rov qab loads.Thaum muaj kev hloov pauv tseem ceeb hauv kev thauj khoom, kev sib txuas ua ntej yuav tsum tau ua kom tshem tawm cyclic plam.Qhov plam no nws thiaj li ua rau plam ntau dua hauv cov qhov elongated.
Qee cov pob qij txha muaj ntau lub voj voog uas tuaj yeem ua rau qaug zog.Cov no suav nrog cov xovxwm, kev txhawb nqa crane thiab kev sib txuas hauv cov txuas hniav.zawv zawg qhov tseem ceeb sib txuas yuav tsum tau thaum qhov kev sib txuas yog raug rau qaug zog loads nyob rau hauv rov qab kev taw qhia.Rau cov hom kev mob no, nws yog ib qho tseem ceeb heev uas qhov sib koom ua ke tsis plam, yog li cov pob qij txha tseem ceeb yuav tsum tau ua.
Kev sib txuas bolted uas twb muaj lawm tuaj yeem tsim thiab tsim rau ib qho ntawm cov qauv no.Rivet kev sib txuas yog suav tias yog nruj.
Welded pob qij txha yog nruj.Cov pob qij txha yog qhov nyuaj.Tsis zoo li cov pob qij txha nruj, uas tuaj yeem plam hauv qab, welds tsis tas yuav ncab thiab faib cov ntaub ntawv thov rau qhov loj.Feem ntau, welded thiab bearing hom mechanical fasteners tsis deform nyob rau hauv tib txoj kev.
Thaum welds siv nrog cov neeg kho tshuab fasteners, lub load yog pauv los ntawm qhov nyuaj, yog li lub vuam tuaj yeem nqa tau yuav luag tag nrho cov load, nrog me ntsis sib koom nrog lub ntsia liaj qhov rooj.Yog li ntawd, yuav tsum tau saib xyuas thaum vuam, bolting thiab riveting.Specifications.AWS D1 daws qhov teeb meem ntawm kev sib xyaw cov tshuab txuas thiab vuam.Specification 1: 2000 rau cov qauv vuam - steel.Nqe lus 2.6.3 hais tias rau rivets los yog bolts siv nyob rau hauv bearing-hom pob qij txha (piv txwv li qhov twg lub bolt los yog rivet ua raws li ib tug pin), mechanical fasteners yuav tsum tsis txhob xav tias yuav muab cov load nrog lub vuam.Yog tias siv vuam siv, lawv yuav tsum tau muab los nqa tag nrho cov khoom sib koom ua ke.Txawm li cas los xij, kev sib txuas welded rau ib lub caij thiab riveted lossis bolted rau lwm lub caij raug tso cai.
Thaum siv cov bearing-type mechanical fasteners thiab ntxiv cov welds, lub peev xwm ntawm cov ntsia liaj qhov rooj feem ntau tsis saib xyuas.Raws li txoj cai no, lub vuam yuav tsum tau tsim los hloov tag nrho cov khoom thauj.
Qhov no yog qhov tseem ceeb tib yam li AISC LRFD-1999, clause J1.9.Txawm li cas los xij, tus qauv Canadian CAN / CSA-S16.1-M94 kuj tso cai rau kev siv ib leeg thaum lub zog ntawm cov neeg kho tshuab fastener lossis ntsia liaj qhov rooj siab tshaj qhov vuam.
Hauv qhov teeb meem no, peb cov txheej txheem zoo ib yam: qhov muaj peev xwm ntawm cov neeg kho tshuab fastenings ntawm cov kabmob thiab qhov muaj peev xwm ntawm welds tsis ntxiv.
Tshooj 2.6.3 ntawm AWS D1.1 kuj tham txog cov xwm txheej uas cov bolts thiab welds tuaj yeem ua ke hauv ob feem sib koom ua ke, raws li pom hauv daim duab 1. Welds ntawm sab laug, bolted ntawm sab xis.Tag nrho lub zog ntawm welds thiab bolts tuaj yeem raug coj mus rau hauv tus account ntawm no.Txhua feem ntawm tag nrho cov kev sib txuas ua haujlwm ntawm nws tus kheej.Yog li, txoj cai no yog ib qho kev zam rau lub hauv paus ntsiab lus uas muaj nyob rau hauv thawj feem ntawm 2.6.3.
Txoj cai nyuam qhuav sib tham siv rau cov tsev tshiab.Rau cov qauv uas twb muaj lawm, kab lus 8.3.7 D1.1 tau hais tias thaum kev suav cov qauv qhia tau hais tias lub rivet lossis bolt yuav dhau los ntawm tag nrho cov khoom thauj tshiab, tsuas yog cov khoom qub uas twb muaj lawm yuav tsum tau muab rau nws.
Cov kev cai tib yam yuav tsum tau hais tias yog lub rivet los yog ntsia liaj qhov rooj tsuas yog overloaded nrog zoo li qub loads los yog raug rau cyclic (nkoos) loads, txaus lub hauv paus hlau thiab welds yuav tsum tau ntxiv los txhawb tag nrho cov load.
Kev faib tawm ntawm kev thauj khoom nruab nrab ntawm cov neeg kho tshuab fasteners thiab welds tau txais yog tias cov qauv yog preloaded, hauv lwm lo lus, yog tias slippage tau tshwm sim ntawm cov khoom sib txuas.Tab sis tsuas yog cov khoom zoo li qub tuaj yeem muab tso rau ntawm cov neeg kho tshuab fasteners.Nyob loads uas tuaj yeem ua rau ntau dua slippage yuav tsum tau tiv thaiv los ntawm kev siv cov welds muaj peev xwm tiv taus tag nrho cov load.
Welds yuav tsum tau siv los tiv thaiv tag nrho cov ntaub ntawv thov los yog dynamic loading.Thaum cov neeg kho tshuab fasteners twb dhau lawm, kev sib koom thauj khoom tsis raug tso cai.Nyob rau hauv cyclic loading, load sib koom yog tsis tso cai, vim hais tias lub load yuav ua tau mus tas li slippage thiab overload ntawm weld.
ua piv txwv.Xav txog ib tug ncej puab uas yog thawj bolted nruj (saib daim duab 2).Cov qauv ntxiv lub zog ntxiv, thiab kev sib txuas thiab cov khoom sib txuas yuav tsum tau muab ntxiv los muab ob npaug rau lub zog.Ntawm daim duab.3 qhia txog lub tswv yim yooj yim rau kev ntxiv dag zog rau cov ntsiab lus.Yuav ua li cas kom muaj kev sib txuas?
Txij li cov hlau tshiab yuav tsum tau koom nrog cov hlau qub los ntawm cov welds, tus kws tshaj lij txiav txim siab ntxiv qee qhov fillet welds ntawm qhov sib koom ua ke.Txij li thaum cov bolts tseem nyob rau hauv qhov chaw, lub tswv yim qub tsuas yog ntxiv cov welds uas xav tau los hloov lub zog ntxiv rau cov hlau tshiab, cia siab tias 50% ntawm cov khoom thauj mus los ntawm cov bolts thiab 50% ntawm cov khoom thauj mus los ntawm cov welds tshiab.Nws puas tau?
Cia peb pib xav tias tsis muaj cov khoom zoo li qub tam sim no siv rau kev sib txuas.Hauv qhov no, kab lus 2.6.3 ntawm AWS D1.1 siv.
Nyob rau hauv cov kabmob no sib koom ua ke, lub vuam thiab ntsia liaj qhov rooj tsis tuaj yeem txiav txim siab los faib cov khoom thauj, yog li qhov tshwj xeeb weld loj yuav tsum loj txaus los txhawb tag nrho cov khoom zoo li qub thiab dynamic load.Lub peev xwm ntawm cov bolts hauv qhov piv txwv no tsis tuaj yeem suav nrog, vim tias tsis muaj qhov zoo li qub, kev sib txuas yuav nyob rau hauv lub xeev slack.Lub weld (tsim los nqa ib nrab ntawm cov load) pib ruptures thaum lub load tag nrho.Tom qab ntawd lub ntsia liaj qhov rooj, kuj tsim los hloov ib nrab ntawm cov load, sim hloov cov load thiab so.
Ntxiv mus, xav tias ib qho static load yog siv.Tsis tas li ntawd, nws tau xav tias qhov kev sib txuas uas twb muaj lawm txaus los nqa cov khoom thauj mus tas li.Hauv qhov no, kab lus 8.3.7 D1.1 siv.Cov welds tshiab tsuas yog yuav tsum tau ua kom muaj zog zoo li qub thiab dav dav nyob loads.Cov khoom thauj uas twb muaj lawm tuaj yeem muab rau cov neeg kho tshuab fasteners uas twb muaj lawm.
Nyob rau hauv tas li load, qhov kev twb kev txuas tsis sag.Xwb, cov bolts twb ris lawv lub nra.Muaj qee qhov slippage hauv kev sib txuas.Yog li, welds tuaj yeem siv tau thiab lawv tuaj yeem xa cov dynamic loads.
Lo lus teb rau lo lus nug "Qhov no puas tau?"nyob ntawm load tej yam kev mob.Nyob rau hauv thawj rooj plaub, nyob rau hauv tsis muaj ib tug static load, cov lus teb yuav tsis zoo.Raws li cov xwm txheej tshwj xeeb ntawm qhov xwm txheej thib ob, cov lus teb yog yog.
Tsuas yog vim hais tias qhov kev thauj khoom zoo li qub tau siv, nws tsis yog ib txwm muaj peev xwm kos qhov xaus.Cov theem ntawm cov loads zoo li qub, qhov txaus ntawm cov khoom sib txuas uas twb muaj lawm, thiab qhov kawg ntawm qhov kawg loads - txawm tias zoo li qub lossis cyclic - tej zaum yuav hloov cov lus teb.
Duane K. Miller, MD, PE, 22801 Saint Clair Ave., Cleveland, OH 44117-1199, Welding Technology Center Manager, Lincoln Electric Company, www.lincolnelectric.com.Lincoln Electric tsim cov khoom siv vuam thiab vuam siv thoob ntiaj teb.Welding Technology Center engineers thiab cov kws tshaj lij pab cov neeg siv khoom daws teeb meem vuam.
American Welding Society, 550 NW LeJeune Road, Miami, FL 33126-5671, phone 305-443-9353, fax 305-443-7559, website www.aws.org.
ASTM Intl., 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, xov tooj 610-832-9585, fax 610-832-9555, website www.astm.org.
American Steel Structures Association, One E. Wacker Drive, Suite 3100, Chicago, IL 60601-2001, xov tooj 312-670-2400, fax 312-670-5403, website www.aisc.org.
FABRICATOR yog North America tus thawj coj steel tsim thiab tsim cov ntawv xov xwm.Cov ntawv xov xwm tshaj tawm xov xwm, cov lus qhia thiab cov dab neeg ua tiav uas ua rau cov tuam txhab ua lawv txoj haujlwm zoo dua.FABRICATOR tau nyob hauv kev lag luam txij li xyoo 1970.
Tam sim no nrog tag nrho nkag mus rau FABRICATOR cov ntawv luam tawm digital, nkag tau yooj yim rau cov peev txheej lag luam muaj txiaj ntsig.
Cov ntawv digital ntawm The Tube & Pipe Journal yog tam sim no nkag mus tau yooj yim, muab kev nkag tau yooj yim rau cov khoom lag luam muaj txiaj ntsig.
Tau txais tag nrho cov digital nkag mus rau STAMPING Journal, muaj cov thev naus laus zis tshiab, kev coj ua zoo tshaj plaws thiab xov xwm kev lag luam rau kev lag luam hlau stamping.
Tam sim no nrog rau tag nrho cov kev nkag mus rau Cov Fabricator en Español, koj muaj kev nkag tau yooj yim rau kev lag luam muaj txiaj ntsig.