Steel kem, tseem hu ua welded box seem los yog kaw ua - seem, yog fabricated los ntawm welding plaub daim hlau mus rau hauv lub hollow square los yog rectangular prism. Lawv kaw geometry muab symmetrical txhav txog ob axes, siab torsional tsis kam thiab zoo heev ua hauj lwm nyob rau hauv hnyav axial loads, uas ua rau lawv ib tug qauv xaiv rau siab -nce cores, ntev -span txuas hniav thiab industrial thav duab. Cov lus nug uas txhua pab pawg ua haujlwm ntsib thaum ntxov yog: kab yuav loj npaum li cas? Cov lus teb yog los ntawm kev tsim qauv, tsis yog los ntawm phau ntawv teev npe, thiab phau ntawv qhia no piav qhia txog cov xwm txheej thiab cov tshev uas txiav txim siab nws.
Dab tsi yog Steel Box Kem?
Lub thawv steel kem yog ib tug kaw, hollow structural tswv cuab, ib txwm ua los ntawm vuam plaub steel phaj ua ke los ua ib tug square los yog rectangular cross-section. Piv nrog rau cov seem qhib xws li I- lossis H- kab teeb, lub thawv ntu muab:
Symmetrical biaxial txhav:tsis muaj zog los yog tsis muaj zog axis, yog li cov kem resists bending sib npaug nyob rau hauv tag nrho cov lus qhia.
High torsional tsis kam:lub kaw lus kaw tiv thaiv torque deb zoo dua li qhib seem.
High compressive efficiency:cov khoom raug faib tawm ntawm lub centroid, muab lub vojvoog loj ntawm gyration rau thaj tsam seem.
Zoo heev hauv zos buckling tswj:plaub phab ntsa tuaj yeem faib ua kom tau raws li cov kev txwv compactness ntawm txoj cai tswj hwm.
Cov kab ke hauv lub thawv tau dav siv los ua cov kab hauv tsev siab -nce thav duab, ua cov piers thiab pylons, thiab ua cov tswv cuab tseem ceeb hauv cov tsev lag luam thiab pej xeem.
Factors Uas Tsav Box Kem Sizing
Tsim Loads
Tus ntoo khaub lig-section yuav tsum tiv thaiv cov axial load, khoov lub sij hawm los ntawm lub ntiajteb txawj nqus thiab lateral loads, thiab shear, ua ke raws li txoj cai tswj. Ob qho tib si lub zog thiab kev ua haujlwm txwv lub xeev yuav tsum txaus siab.
Unbraced Qhov siab thiab siv tau ntev
Ntev ntev unbraced nce lub slenderness ntawm kem thiab txo nws compression peev xwm. Qhov ntev ntev yog qhov khoom ntawm qhov ntev thiab K- qhov tseem ceeb uas qhia txog qhov kawg kev txwv: tsau, pinned lossis ib feem txwv kev sib txuas rau saum thiab hauv qab ntawm tus tswv cuab.
Xaus kev txwv thiab ciam teb tej yam kev mob
Cov hauv paus ruaj khov thiab lub sijhawm- txuas cov saum toj kawg nkaus txo qhov ua tau zoo ntawm qhov ntev, thaum pinned bases thiab kev sib txuas yooj yim nce nws. Cov xwm txheej kev txhawb nqa yuav tsum tau ua qauv kom raug vim tias lawv ncaj qha tswj xyuas buckling check.
Qib Steel
Siab dua - qib zog xws li S355 (EN 10025-2), ASTM A572 Qib 50 lossis Q355B (GB/T 1591) tso cai rau cov seem me me rau tib lub load, ntawm tus nqi ntawm tus nqi siab dua thiab nruj dua vuam thiab fabrication yuav tsum tau. Qib yuav tsum tau xaiv nrog lub zog tsim thiab lub peev xwm fabrication hauv siab.
Dav -rau-Thickness Ratio (Local Buckling)
Lub phaj phab ntsa ntawm ib lub thawv ntawv yuav tsum tau muab faib ua kom tsis txhob muaj cov buckling hauv zos ua ntej seem mus txog nws lub zog tag nrho. Codes txhais cov kev txwv compactness nyob rau hauv cov nqe lus ntawm qhov dav - mus rau -thickness ratio; Piv txwv li, AISC 360 teeb tsa qhov kev txwv dav - rau -thickness ratio rau slender cov ntsiab lus nyob rau hauv uniform compression, thiab GB 50017 thiab EN 1993-1-1 muab sib npaug zos buckling cov cai. Tus qauv tsim yuav tsum xyuas kom meej tias cov phaj tuab uas tau xaiv ua tau raws li qhov kev txwv.
Tsim Kev Tshawb Fawb rau Cov Kab Kem
Sizing ib kem kem yog ib qho txheej txheem rov qab los ntawm kev xav ib ntu, xyuas nws, thiab kho. Cov kev kuaj xyuas tseem ceeb, ua nrog txoj cai tswj hwm (piv txwv li AISC 360, EN 1993-1-1 lossis GB 50017), yog:
Axial zog:tus tsim compressive lub zog yog lub nominal lub zog txo los ntawm qhov tsim nyog qhov tseem ceeb, qhov nominal lub zog tso nyiaj rau flexural buckling txog qhov tseem ceeb axis thiab yog raws li qhov zoo slenderness KL / r.
Combined axial thiab dabtsi yog khoov:cov tswv cuab nyob rau hauv axial load ntxiv rau lub sijhawm raug txheeb xyuas nrog cov kev sib npaug sib npaug ntawm cov cai, uas sib xyaw cov kev siv ntawm axial quab yuam thiab lub sijhawm.
Slenderness txwv:compression cov tswv cuab feem ntau txwv rau qhov siab tshaj qhov sib piv (piv txwv li KL / r tsis ntau dua 200 rau cov tswv cuab tseem ceeb hauv qab AISC 360; qhov sib npaug ntawm GB 50017 yog siv rau cov tswv cuab tseem ceeb compression).
Local buckling:lub phaj dav -rau-thickness ratios raug soj ntsuam los ntawm cov kev txwv compactness ntawm txoj cai kom seem tuaj yeem txhim kho nws cov yas lossis elastic peev xwm raws li xav tau hauv kev tsim.
Serviceability:lateral drift, axial shortening thiab vibration raug tshuaj xyuas tiv thaiv qhov project txwv.
Vim hais tias cov geometry cuam tshuam nrog cov kev kuaj xyuas lub zog, qhov kawg qhov loj yog qhov zoo tshaj plaws los ntawm tus kws tsim qauv tsim qauv siv software paub txog, nrog lub khw kos duab npaj los ntawm kev pom zoo suav.
Tswv yim Sizing Qhia los ntawm Daim Ntawv Thov
| Daim ntawv thov | Kwvtij Tshooj Class | Cov piv txwv qhia qib | Key Xaiv Tsav Tsheb |
|---|---|---|---|
| Cov chaw nyob thiab lub teeb coj mus muag thav ntawv | Compact seem, me me phab ntsa thickness | Q235B (GB/T 1591) los yog S235JR (EN 10025-2) | Qhov chaw efficiency, kev lag luam, kev sib txuas yooj yim |
| Industrial nroj tsuag thiab warehouses | Cov ntu nruab nrab nrog qhov nruj txaus | Q355B (GB/T 1591) los yog S355JR (EN 10025-2) | Crane loads, cuam tshuam thiab vibration, drift tswj |
| High -nce thiab coj mus muag yees | Cov ntu loj, phab ntsa tuab | Q355B, Q420 (GB / T 1591) lossis ASTM A572 Qib 50/60 | Siab axial muaj peev xwm, nruj compactness tswj, seismic nthuav dav |
| Txuas hniav thiab infrastructure | Cov ntu sib sib zog nqus, cov phaj hnyav, cov ntsiab lus qaug zog | S355K2 (EN 10025-2) lossis ASTM A572 Qib 50 | Dynamic loads, qaug zog, corrosion nyiaj |
| Cov qauv kev txhawb nqa ib ntus | Nruab nrab ntu, bolted kev sib txuas | Q355B (GB/T 1591) los yog S355 | Reusability, transportability, ceev erection thiab dismantling |
Cov lus qhia tsuas yog: kev tswj hwm cov ntaub ntawv, qhov ntev thiab cov cai yuav tsum tau ua ua ntej, thiab qhov ntev npaum li cas yuav tsum yog los ntawm kev suav cov qauv.
Fabrication thiab Quality Control
Welded kem kab xav tau kev qhuab ntuas kev tsim kho vim tias qhov chaw kaw ua rau sab hauv welds nkag tsis tau tom qab sib dhos:
Vuam:plaub lub ces kaum seams feem ntau yog welded los ntawm submerged arc vuam (SAW) nrog kev tswj cov sequences; Cov txheej txheem vuam yuav tsum tsim nyog rau AWS D1.1, EN 1090 lossis cov cai siv tau.
Internal stiffening:transverse diaphragms ntawm qhov taw qhia cov ntsiab lus thiab, qhov twg yuav tsum tau, longitudinal stiffeners tswj cov buckling hauv zos thiab nthuav dav zog.
Tsis yog -kev kuaj kev puas tsuaj:Cov welds tseem ceeb raug tshuaj xyuas los ntawm kev kuaj ultrasonic (UT), nrog cov khoom sib nqus (MT) lossis kuaj hluav taws xob (RT) qhov twg cov lus qhia yuav tsum tau ua.
Khoom siv traceability:zeb xeem daim ntawv pov thawj raws li EN 10204 (hom 3.1) sau cov phaj chemistry thiab txhua yam khoom.
Kev tiv thaiv corrosion:Cov nplaim tawg tau raug ntxuav kom huv rau Sa 2.5 thiab coated rau ISO 12944 rau pawg raug, lossis kub-dip galvanized qhov twg teev.
Kev sib dhos:Cov kab uas nyuaj lossis siab ntev tau sim- sib dhos hauv lub khw los txheeb xyuas qhov sib npaug thiab cov duab kos ua ntej xa khoom.
Cov lus nug nquag
Q: Cov duab ntawm lub thawv ntawv dab tsi muaj?
Square thiab rectangular hollow seem yog feem ntau; tapered thiab stepped kem kem yog tsim thaum architectural los yog load xav tau hu rau ib tug sib txawv seem raws li qhov siab.
Q: Kuv yuav xaiv cov qib steel dab tsi rau lub thawv kem?
Rau kev thauj khoom nruab nrab, Q235B (GB/T 1591) lossis S235JR (EN 10025-2) yog kev lag luam. Rau siab-nce, choj thiab hnyav kev lag luam kev siv, Q355B / Q420 (GB / T 1591), S355 (EN 10025-2) los yog ASTM A572 Qib 50/60 yog ib txwm. Qib raug xaiv ua ke nrog rau kev tsim lub zog thiab kev tsim khoom.
Q: Lub phab ntsa thickness txiav txim li cas?
Phab ntsa thickness yog teem los ntawm axial thiab dabtsi yog khoov lub zog checks, lub zos buckling (dav- mus rau -} tuab) txwv ntawm txoj cai, thiab tej kev tiv thaiv corrosion yuav tsum tau rau ib puag ncig. Phab ntsa Thicker yog siv nyob qhov twg lub slenderness los yog lub zos buckling check tswj.
Q: Dab tsi yog qhov dav dav zoo - rau - thickness piv rau kab kem?
Tsis muaj ib tus nqi ruaj khov. Qhov kev txwv qhov dav -rau-thickness ratio yog txhais los ntawm txoj cai tswj hwm (piv txwv li kev txwv kev txwv hauv AISC 360, GB 50017 lossis EN 1993-1-1) thiab nyob ntawm qhov tawm los ntawm cov hlau thiab qib kev ntxhov siab ntawm phab ntsa. Tus tsim yuav tsum txheeb xyuas cov seem tawm tsam qhov kev txwv.
Q: Cov kab kem puas tuaj yeem txuas rau ntawm qhov chaw?
Yog lawm. Field splices yog tsim nrog bolted splice daim hlau los yog nrog tag nrho -kev nkag groove welds, ntxaws thiab xyuas raws li txoj cai. Khw -fabricated kawg kev npaj thiab sim sib dhos pab lav kev sib tw ntawm qhov sib tw.
Q: Cov ntaub ntawv dab tsi nrog cov khoom tsim cov kab ke?
Cov ntaub ntawv ib txwm muaj xws li daim ntawv pov thawj zeb xeem (EN 10204 hom 3.1), vuam txheej txheem kev tsim nyog thiab cov ntaub ntawv vuam, NDT cov ntaub ntawv, cov ntaub ntawv soj ntsuam qhov ntev thiab cov duab kos duab pom zoo.