Mt s cu hi kh c bn trong khi cc bn tin hnh bo v n tt nghip! Cu hi n tt nghip Cu 5: Nu tc dng ca dm dc (Dm ging)? Gi n nh cho khung ngang chu lc. xc nh cc lc x ngang. Chu ti trng thng ng truyn theo phng dc. Cu 6: Ti sao trong khung b tng ct thp, ct khung li b tr ct thp i xng, cn dm khung li b tr ct thp khng i xng? Ct thp trong ct b tr i xng v ct l cu kin chu nn ct thp chu m men sinh ra do tc dng ca lc x ngang nh gi tri, gi phi. Ct thp trong dm b tr khng i xng v dm l cu kin chu un, ct thp chu m men sinh ra do ti trng tc dng thng ng. Cu 7: Nu s tnh ton ? So snh s tnh khp do v s n hi ? S khp do cho php nt cn s n hi khng cho php nt. S khp do khng c tnh cho sn mi, sn khu v sinh, sn ban cng. S n hi cho php tnh tt c cc loi cu kin. Cu 8: Ti sao khng tnh ct ai trong sn ? Thng thng lc ct trong bn sn nh, b tng kh nng chu ct, nhng trong bng t hp nu c ti trng ln vn phi kim tra theo cng chu ct. Cu 9: Nu cch tnh ton cu thang (Tnh ton bn thang, dm chiu ti, dm chiu ngh ) ? +Bn thang: -Loi c cn thang: tnh nh bn sn truyn lc theo mt phng ( bn loi dm ), hai phng ( bn k 4 cnh ). Cn thang tnh nh dm n gin k ln hai u l dm chiu ti v dm chiu ngh. -Loi khng c cn: bn thang ct dc 1( m ) theo chiu di bn thang sau tnh nh dm n gin k ln dm chiu ngh v dm chiu ti. +Tnh dm chiu ngh v dm chiu ti: tnh nh dm n gin ch lc tp trung khi c cn thang v lc phn b khi khng c cn thang. Cu 10: Cch cht ti khung phng v khung khng gian ? Khung phng cht ti cch tng, cch nhp. Khung khng gian cht ti cch . Cu 11: Trong khung nt no quan trng nht ? V sao ? Trong khung nt trn, trong cng, ngoi cng l nt quan trng nht. V ti mmen ln nht nhng lc dc li b nht. Cu 12: Trong khung phn t no tnh nh, phn t no siu tnh ? Trong khung conson l tnh nh, cn cc phn t cn li l siu tnh. 1

Cu 13: Hy nu cch neo ct thp ca ct trn ti nt ? Ct thp ca ct trn neo t di ln trn. Cu 14: Ct trn khc ct ch nht im no ? Ct trn khc ct ch nht ch l hnh dng, cch b tr thp dc. Ct trn chu lc nn t trong ra ngoi. Cu 15: Khi b tr ct thp trong ct khung ngi ta quan tm n cp ni lc no? Cu 17: Trnh t thit k cng trnh ? -Chn thit k tit din cc b phn kt cu. -Lp s tnh ton khung lin kt. -Xc nh cc loi ti trng tc dng ln kt cu. Sp xp cc loi tnh ti v hot ti. -Tnh ton ni lc cho tng loi ti trng v t hp ni lc. +T hp c bn. +T hp c bit. -Tnh ton cc loi ct thp chu lc, kim tra hm lng v thng k vt liu. Cu 18: Ti sao cn phi bo dng b tng ? cung cp nc m bo qu trnh thu ho xi mng khi b tng tng cng . Trnh b tng b trng mt, r mt. Cu 19: Ti sao b tng thng phm st cao hn b tng th cng ? B tng thng phm dng bm v c thng cha nn c st cao hn c tnh linh ng d hn. Ngoi ra b tng thng phm phI vn chuyn t nh my n nn yu cu lu ng kt hn l b tng trn ti ch. mng Cu 20: Ti sao trong i khng b tr cu to ct thp? Do b tng trong i ln chu lc ct. Cu 21: Cch xc nh chiu cao i mng ? T iu kin m thng khng k thp, hi ? 2d (d: ng knh i cc ). Cu 22: Th no l trng thi cn bng gii hn ? Trng thi s khp do xut hin lm cho kt cu tr thnh h tnh nh. Trng thi gii hn l trng thi ng vi kt cu khng cn kh nng chu lc v khng cn iu kin trn t ra cho n nh iu kin cng , n nh, mi. Cu 23: Tc dng ct thp cu to, ct gi ? Gi n nh cho thp dc chu lc khi b tng v s co ngt t nhin trong b tng. 2

B m cao ? 70 ( cm ), b rng ln th ct gi cn gim s phnh n b tng gia tit din dm, ng thi gi n nh cho ct ai. Cu 24: ngha on neo ct thp ? m bo lc dnh gia b tng v ct thp cho kt cu lm vic. Cu 25: Khi no tnh ton theo s khp do v s n hi ? -S n hi: l s m vt liu cn lm vic trong min n hi. Khi tnh ton theo s n hi th ni lc trong kt cu khng c s phn phi li khi chu lc. -S khp do: l s m vt liu lm vic khi xut hin cc khp do. Khi tnh ton theo s bin dng do th c s phn b li ni lc. +Sn nh cng nghip v sn nh dn dng bnh thng tnh theo s bin dng do tit kim vt liu. +Sn nh chu ti trng ng hoc trong mi trng d b n mn nn tnh theo s n hi (sn WC, panel ). -Nguyn l: +S n hi A ? 0,42 +S bin dng do A ? 0,3. Cu 26: Chn tit din dm da vo yu t no ? - mnh ct nh: -Ti trng tc dng. -iu kin vng cho php. Cu 27: Ti sao phi khng ch hm lng ?max , ?min ? ?min l hm lng ti thiu ct thp chu nhng ng sut ph do co ngt t nhin ca b tng. ?max l tr s khng ch ct thp khng nhiu qu gy ra hin tng co ct thp, ct thp nhiu s cn s co ngt ca b tng, gy nt cho b tng, ng thi tn dng ht kh nng lm vic ca hai loi vt liu ny. Cu 28: V cc mt bng ca kt cu lm g ? xc nh ti trng truyn ln dm khung, xc nh v tr dm khung chu lc ca tng sn. Cu 29: bn panel tnh ton vng nh th no ? f =f1 - f2 + f3 f1: vng do ton b ti trng tc dng ngn hn. f2: vng do ti trng di hn tc dng ngn hn. f3: vng do ti trng di hn tc dng di hn. Cu 30: Ti sao hot ti phi t lch tng, lch nhp ? Hot ti xp lch tng, lch nhp cho c tr s mmen dng dm ln nht l bt li nht. Hot ti t lch tng, lch nhp phn nh gn st vi thc t v iu kin s dng. Khng c trng hp hot ti cht ton khung v nh vy khng phn 3

nh iu kin s dng thc t. Cu 31: u nhc im bn thang c cn v khng c cn ? Bn thang c cn nhp tnh ton ngn (gia cn) Bn thang khng c cn nhp tnh ton l hai u lin kt, di hn nn cn ch vng. Do bn khng c cn s c vng nhiu hn v bt li hn. Cu 32: Tc dng ca ct ai trong ct ? Ct ai trong cu kin chu nn c tc dng gi n nh cho ct dc chu nn. Ct ai cng c tc dng chu lc ct. Ngi ta ch tnh ti ct ai khi cu kin chu lc ln cn thng thng th b tr theo cu to. Cu 33: Xc nh gi ni v gi ngoi khc nhau nh th no ? -Gi ni: l gi sinh ra b trong lng cng trnh do s chnh lch p lc nhit v p lc kh ng ? bc mi. -Gi ngoi: l gi t bn ngoi tc ng trc tip ln b mt ngoi kt cu ? sinh ra mmen cho khung lm un ct. Cu 34:Khi no th dng sn panen, khi no th dng sn ton khi ? Sn panen c dng cho mt bng c kch thc chun, c iu kin thi cng c gii, thng dng trong cc nh cng nghip. Sn ton khi c dng cho cc loi nh c mt bng khng theo mt qui tc nht nh, nh, hoc cc nh c yu cu c bit, dng trong nh dn dng. Cu 35: Trong nh lm vic theo mt phng v hai phng, kch thc ct lm vic nh th no cho hp l ? Chn kch thc ct ch nht ( vung ) kch thc cnh ln theo phng mmen ln nht hoc an ton ta c th chn ct vung kch thc ly theo mmen ln nht. Cu 36: Ti sao khi tnh ton phi tnh gi theo phng vung gc vi trc nh ? V khi tnh vung gc vi trc nh ti gi s ln nht, nu tnh nghing mt gc a th ti trng gi phi nhn thm cosa ( m cosa thng nh hn 1 ) ? p lc gi s nh. Cu 37: Khi tnh ton nh cao tng trn nn t yu, trnh dao ng bng cch no ? Cc dao ng nu n t bn ngoi th ta tin hnh cch ly nn mng vi khu vc c dao ng ( o mng, rnh ) Khi tnh theo s phng th ta chn phng no nguy him nht tnh khung, mng thng l phng ngn, cu to thp sao cho chu c ti trng nguy him nht theo phng . Cu 38: Hy nu quan nim cu to dm mng ? nhng ni t khng ng nht, trnh ln khng u nn tng cng bng cch lm sn dc (dm mng). V cu to da trn s tnh, phng php tnh, kh nng lm vic, phng lm vic ca kt cu, quan nim tnh ton, tuy nhin phi tun theo cc qui phm. 4

Cu 49: S n c nh hng nh th no n ni lc ca khung ? Gi quyt conson nh th no khi gii khung bng my ? S n lm cho mmen trong khung tng ln mmen m ngay gi v mmen ct. Khi gii khung bng my consol trong khung ta qui v mmen t ti nt khung ca conson hoc c th xem consol l mt phn t gii hn gia hai nt. Cu 40: Hy nu l do thay i kch thc ct ? L do thay i kch thc ct l: tit kim vt liu, tit din hp l vi ti trng, theo yu cu kin trc. Cu 41: C th thay i mc b tng m gi nguyn kch thc ct c khng ? Phi tnh li v hm lng ct thp cng s thay i theo. Cu 42: Khi tnh gi nu mt n gi so le th c xem l phng c khng ? Tnh gi nu mt n gi so le th c th xem l phng c, v khi tnh ti trng gi tc dng vung gc ln b mt cng trnh khi cng trnh cao ? 40( m ) th xt n gi ng. Cu 43: Khi thay i tit din dm, nu tnh theo trc ca dm chnh (ln) th dm no khng an ton ? Dm consol, v dm nh. Cu 44: Cch tnh ch giao nhau gia hai khung ? Tnh theo phng ngang, phng dc sau ly ni lc ln nht t ch giao nhau. Ct t trn dm th ct truyn lc ln dm. Cu 45: Lin kt gia mng v kt cu bn trn dng lin kt g ? Khi lin kt gia mng v kt cu bn trn th ta dng lin kt ngm . Cu 46: Hy cho bit s khc nhau gia khung cng v vch cng ? Khung l mt h dm ct chu ni lc do ti trng cng trnh v ti trng gi gy ra Vch cng l vch chu ni lc do ti trng gy ra. Phng php tnh khung v vch cng: +Phng php chuyn v: phng php tnh bng my. +Phng php lc. Quan nim tnh: +Tnh theo s n hi ( trng thi 1 ) Ti sao chon phng php khanzi ? Chn phng php khanzi v tnh ton n gin, u im ni bt l n c th t ng kh c nhng sai lm trong tnh ton ( thc hin php lp ) ? Bn cht n l phng php chuyn v. Cu 47: Ti sao dm dc v dm ngang khng gia cng thp ? Ti sao phi t ai dy ? Dm dc v dm ngang khng gia cng thp v thng ti trng nh, 5

khng chu lc chnh. t ai dy trnh ph hoi theo tit din nghing ( hay cn gi l chng ct ) ai gia cng t gi n lc tp trung u tin t trong khong l L/4. Cu 48: Hy nu phng php tnh cu thang ? Khi tnh cu thang tnh theo dm n gin ( hai u l khp ). Quan nim tnh theo s n hi ( hay ni cch khc phng php tnh cu thang theo kt cu h tnh nh ) Cu 49: Nu tc dng ca khe nhit v khe ln ? Tc dng ca khe nhit l lm cho kt cu khng b bin dng khi nhit thay i. Khe nhit tnh t mt mng ln n ht mi (phn ngm coi nh khng b bin dng do nhit). Tc dng ca khe ln l lm cho kt cu khng b bin dng khi ln. Khe ln tnh t y mng n ht mi) Cu 50: i vi nh cao tng khi c ti trng gi th c k n chuyn v khng ? i vi nh cao tng khi c ti trng gi th phi k n chuyn v. lp ngi trn cao ta phi dng my vn thng, cn cu, gi ngi khng bay ta phi trnh gi ni bc mi. Cu 51: Khi no dng lin kt cng, khi no dng lin kt khp ? Dng lin kt cng khi kt cu l mt h siu tnh. Dng lin kt khp khi kt cu l mt h tnh nh. Cu 52: Dng mng cc gii quyt vn g l ch yu ? Hn ch c bin dng ln c tr s ln, bin dng khng ng u ca nn, m bo n nh khi c ti trng ngang tc dng, rt ngn thi gian thi cng, tit kim c vt liu trong thi cng. Cu 53: p cc khi no khng cn p tnh ? Khi cng trnh ngoi vi thnh ph khng nh hng n xung quanh. Cu 54: Xc nh mng trn nn t, khc nhau nh th no ? Khi no phi thit k mng bng theo hai phng ? Xc nh mng trn nn t da vo ti trng tiu chun tnh ton theo trng thi gii hn II bin dng ( ln). Xc nh mng trn nn l da vo ti trng tnh ton, kim tra theo trng thi gii hn cng (khng cn tnh ln). Khi ti trng ln, nn t yu th ta thit k mng bng theo hai phng. Cu 55: Nh nhiu tng trn nn t yu trnh dao ng bng cch no ? Khi tnh ton ta chon trng hp bt li nht, h s an ton cao ? khng kinh t. Cch ly cng trnh vi nhng giao ng do tc ng ngoi. Khi tnh theo s phng th ta chn phng no c dao ng ln nht tnh. 6

Cu 56: Khi tnh mng hp da vo vn g ? Khi tnh mng hp da vo biu ni lc ca kt cu m tnh. Cu 57: Khi chon tit din cc da trn c s no ? Ti sao ? Trnh t thit k cc? Chn tit din cc da trn chiu su chn cc (chiu di cc), cng sut thit b vn chuyn v mng cc. Ngoi ra chiu di tit din, cng vt liu v ct thp dc c quan h cht ch vi nhau. *Gii thch ti sao: Trnh t thit k cc sau khi xc nh ti trng truyn xung mng. +Chn vt liu lm cc v kt cu mng +Chn chiu su t i cc da vo iu kin a cht. +Xc nh sc chu ti ca cc +Xc nh s b kch thc i cc +Xc nh s lng cc (lc ny ti trng phi k thm t ph trn i v i cc) +Cu to v tnh ton i cc +Kim tra lc tc dng ln cc phi nh hn sc chu ti ca cc +Kim tra lc tc dng ln nn t +Kim tra ln ca mng cc +Xc nh chi thit k ca cc +Kim tra cc khi vn chuyn v cu lp Cu 58: Phng php ng cc v cc khoan nhi khc nhau nh th no ? +ng cc: dng my p hoc ng xung nn t +Khoan nhi: khoan ly t ln to l, sau t ct thp v b tng. Cu 59: Dng cch no kim tra su cc ? Trc khi ng cc trn cc ta vch nhng mc thc su, khi ng nhn vo kim tra. Cu 60: Cc ng t trong ra ngoi hay t ngoi vo trong ? Khi ng cc th ta ng cc theo hnh xon c t trong ra ngoi. Cu 61: Khi no cn tnh chi ? Khi cn kim tra kh nng chu tc dng ca ti trng cng trnh (nu chi thc t nh hn chi thit k th cc c kh nng chu c tc dng ca ti trng). Nu chi thc t ln hn chi thit k th cn b sung hoc thit k li cc trong mng. Cu 62: Lm th no bit cc chu un ? Khi ti trng ngang rt ln. Khi thi cng cc p, ni cc theo phng php hn bn thp ni vi bn thp ch sn v nh v bng cc tim ch sn. p lc p chn bng 1,3 ? 2 ln sc chu ti tnh ton ca cc l hp l. Dng ai xon nhm tng cng kh nng chu chn ng khi ng cc, 7

i ny chu lc tt nhng thi cng kh. Cu 63: Cc di vch cng v di mng c khc nhau khng ? Khng khc nhau v cch lm vic ca cc nh nhau. Mng c xem l tuyt i cng: l khi mng hon ton khng chu un ( mng cng l mng chu un rt t hay ni cch khc l rt nh ). Cu 64: Ti sao b tr ct thp u trong cc ? Ti sao u cc phi t ct ai dy ? B tr thp u trong cc l v khi cu lp c mmen m v dng ? chu c c hai. u cc t ct ai dy nhm tng kh nng chu ti khi ng (ti trng cc b) ? trnh v u cc. Cu 65: Mng bng khi tnh ton nguyn h v chia ra thnh cc phn khc nhau th cch no l hp l v kinh t? Mng bng khi tnh nguyn h th hp l hn v kinh t hn. iu kin b u tha ca mng bng l: +Ngay ti cc khe ln +Ngay ti ct u tin ( do M = 0) +Thi cng c ct mng bng trn mt khi khng b nt. Cu 66: Mng bng v mng n c g khc nhau ? (u, khuyt im, gi thnh, n nh ). Cn c vo h s a cht ( h khoan, tnh cht c l ca t ). Cn c vo cao qui hoch ca khu v cao thit k ca cng trnh. Cu 67: Hy nu s khc nhau gia mng bng v mng kp ? Mng bng l mng c sn, ti trng phn b trn chiu di sn ( phn lc nn ) Mng kp l mng khng c sn, bn chu lc, ti trng tc dng tp trung ging nh mng n. Cu 68: Khi tnh bin dng nn phi chp nhn gi thit g ? ln tnh ton Stt ? [S] ?S ? [?S] Cu 69: V tr v dm ging phi b tr nh th no i vi khung bn trn v mng bn di cho hp l ? Dm ging b tr ngay ti mi ni gia ct thp dc ca ct v thp ch ca ct chn sn trong mng, ch ni thp ny c chn ni thun tin cho thi cng c th ngay mt mng hoc c th mt nn nh. Cu 70: Hy nu s khc nhau gia ln v ln lch ? Ln l bin dng ca nn t khi chu ti trng. Ln lch l s chnh lch bin dng ca nn mng khi chu ti trng. Ln lch nguy him hn n s gy ph hoi kt cu cng trnh. Cu 71: Lc ct khc vi lc xuyn thng nh th no ? Lc ct l ni lc ca kt cu sinh ra do ng sut tip trong qu trnh chu ti. Xuyn thng l lc dc ( ni lc ) sinh ra do ng sut ko chnh. 8

Cu 72: Cn c vo c s no chn lp t p ? Lp t gia ti ? Nu l cc u tin th nh ln ri khoan mi cho qua khi lp sau ng su theo thit k. Nu l cc th th ta p b u cc coi nh n l t v ng tip cho cc hng k. Nu hng no cng vy ( thng 2 ? 3 hng ) phi xem xt tnh ton li. Cu 73: Th no l nn WRINKLER ? u v khuyt im ? Nn WRINKLER l phng php h s nn gi thit l ti mi im mt y mng ca dm trn nn n hi, cng ca ti trng ( R ) t l bc nht vi ln ( ln ny bng vng ca dm s = y ) nh vy R, C, Y, ( X ) vi C l h s nn. +Nn WRINKLER cn gi l nn n hi bin dng cc b. +M hnh l dy v s l so lm vic c lp vi nhau. -u im: n gin, tin dng trong tnh ton, thit k gn ng vi thc t c dng nhng nn t yu, rt yu. -Nhc im: Khng phn nh c tnh phn phi hay lin h c ca t nn v t c tnh ma st trong nn khi chu trng ti cc b th t c th li ko hay gy ra ln vng ln cn ( ngoi phm vi t ti ) cng lm vic chung. +Khi nn t ng nht th trng ti phn b u lin tc trn dm, theo m hnh ny dm s ln u v bin dng nhng thc ra khi trng ti tc dng phn b u th dm vn b un ( vng ) gia nn nh hng xung quanh nhiu hn nh vy s ln nhiu hn u dm. +Khi mng tuyt i cng, ti trng t i xng th mng s ln u theo m hnh ny nh vy ng sut y mong s phn b u nhng theo o c thc t thi ng sut phn b khng u. +H s nn C c tnh cht qui c khng r rng, C khng phi l mt hng s. forever 01-10-2008, 09:13 PM Cu 74: Ti sao khi mng cc i cao ? Di thp ? Cch kim tra xuyn thng ? Tnh mng cc i cao khi cng trnh nm ni t thp, nhiu nc kh thi cng i, cn phi thi cng nhanh, gp rt mng. Tnh mng cc i thp khi cng trnh nm nhng ni t cao, mc nc ngm su, tuy nhin vt liu v ti trng nhiu nhng b li th mng cc i thp n nh hn. +Kim tra xuyn thng: Nu cc nm trong phm vi hnh thp p lm th khng cn kim tra Nu kim tra th Pct < 0,752.k1.h.b. Cu 75: Khi ng cc gp phi mt lp t hay mt lp no khc m 9

cc khng th vt qua th phi x l nh th no ? Mng n thit k thi cng n gin, gi thnh r nhng ch s dng c cho nhng cng trnh c ti trng nh, nn t tng i tt. Mng bng tnh ton thi cng phc tp hn, gi thnh cao ? n nh hn s dng cho nhng cng trnh c ti trng tng i ln, nn t yu. Cu 76: Ti sao khi thit k mng bng thng chn bn mng nm di, dm mng nm trn ? Khi tnh mng bng ta tnh nh dm ch T cho nn i vi trng hp tnh trn m hnh WRINKLER th ngay chn ct y mng chu ko, ngay gia nhp y mng chu nn do ta thit k bn mng nm di ( cnh ch T nm trong vng chu nn) s tit kim vt liu hn v tng cng chu nn ca kt cu hn, hp l hn. mng nm trn l do mt trn chu ko m b tng khng tnh cho chu ko nn v mt cng c gi tr tit nh tit din ch nht ( bxh ) nn b tr nh vy l hp l v mt tnh ton v biu s tit kim c vt liu. +Ch : Khi thit k mng bng m bn mng nm trn, dm mng nm di l da vo biu ni lc ca kt cu, khi ton b kt cu chu ko ? tit din lm vic l ( bcxli ) khng phi l ( b x h ). +Ch khi gii FEAP -i vi consol : ngi ta a v dng mt lc tp trung v mt m momen ti ngay nt consol ( mc ch gim bt s nt phn t, n gin tnh ton, nhng nu nguyn cng c ). -i vi cc lin kt bin: ti ti nt cc lin kt bin, ch t c theo cc phng t do, cn cc phng b kho th khng t c. V d: Lin kt bin l ngm ti nt khng t ti P v M c. Lin kt bin l gi c nh th ti nt khng t ti P c nhng M th c. Lin kt bin l gi di ng th ti nt khng t ti P theo phng Y c, nhng theo phng X v M th c. Cu 77: Thp mng v thp sn l thp chu un hay chu ct ? Thp mng v thp sn l thp chu un . Khong cch 1, trong thc t c khi n < 1 kt cu li nguy him hn, nh lc ta tnh s n nh ca i nc m bo khng b nghing, th khi tnh trng lng i nc trng thi nh hn bnh thng . Nh cao my tng tr ln th c xem l nh cao my loi I ? Nh cao t 9 tng tr ln th oc xem l nh cao tng loi I. Cu 81 :S kt cu cng l g ? L nhng nh v cng trnh m kt cu ca n c kh nng c bit chu ni lc gy ra bi bin dng ca nn . Cu 81:Mng cng l g ?Mng tuyt i cng l g ? Mng cng l mng ch chu lc nn (mng hc, mng gch ) mng cng khng xt n kh nng chu ko do un ca vt liu lm mng, gc m ? ca mng cng nh hn hoc bng ?max, tc l t s H/L khng nh hn tr s nu trong qui phm cotg? ? 2 (vi ?=300) -Mng tuyt i cng l mng lm bng b tng hc, gch. Cc loi mng ny cu to sao cho khng xut hin ng xut ko trong chnmng lm cho mng b nt, mun vy th phi ly cotg?=H/L. Cu 82 : Chiu di on ct thp chn vo mng di bao nhiu ? on ct thp chn vo mng vi cc thanh chn su vo sut chiu cao v chiu di bng 30d (k c on b ngang). on thp khung ni vo thp ch ?30 d Cu 83: Ti sao gi l nn n hi ?Tnh dm trn nn n hi ? -Nn n hi : s dng khi cngtrnh t trn t mm, di tc dng ca ti trng cng trnh, nn t c bin dng ln lm cho cng trnh bn trn cng b bin dng theo, do gy ra cc ng lc trong kt cu ca cng trnh, cc nn t c bin dng ln ngi ta gi l nn n hi. -Dm trn nn n hi: dm c t trn nn n hi gi l dm trn nn n hi (mng bng c gi l mng dm ). 11

+Ti sao gi l tnh dm trn nn n hi ? -Tnh ton trng thi ng sut, bin dng ca cng trnh xy dng trong iu kin cng lm vic vi nn mm ( ngha l cng bin dng vi nn ) c gi l tnh ton dm ( kt cu ) trn nn n hi. +Khi no th tnh dm trn nn n hi ? -Khi kt cu c cng hu hn ngi ta quen gi l kt cu mm ( EJ = 0 ), khi nn bin dng kt cu trn nn pht sinh ni lc ( do bin dng ): mng bng -Kt cu mm tuyt i ( EJ = 0 ) khi nn bin dng th kt cu bin dng theo, v vy m trong kt cu khng sinh ni lc. -Kt cu cng tuyt i ( EJ = ?) d nn bin dng th no th kt cu khng bin dng g, nhng tht ra c bin dng nh c th b qua c ( nh: tr cu, mng mi, kiu ng khi ). -Khi kim tra iu kin p lc nhm m bo cho vng bin dng do trong nn hi bin dng. Pth < Rtc Pmax ? 1,2.Rtc Do c th coi nn l bin dng tuyn tnhv ch khi nn la bin dng tuyn th mi xc nh c ng sut trong nn theo cac cng thc ca l thuyt n hi va mi tnh c bin dng ca t nn theo cc phng php hin nay. +Cc m hnh nn t: M hinh WRINKLER. M hnh bn khng gian n hi. M hnh nn mng. M hnh nn tm. M hnh n hi vi hai h s nn. M hnh lp n hi hu hn. +Ti sao tnh dm n hi trn nn WRINKLER ? i vi nhng nn t mm m hnh WRIKLER ph hp, gn ng vi thc t, va n gin, va tin dng trong tnh ton thit k. Trong iu kin nc ta nhng vng ng bng sng Hng, sng cu Long t mm cha nhiu nc, mc nc ngm cao: Tnh phn phi t yu do ta chn m hnh nn t l m hnh WRINKLER . Cu 84: Khi no th s tnh ton mng bng l dm lin tc ? l khi kt cu bn trn tuyt i cng ( EJ = ?), nhng iu ny thc t khng sy ra v kt cu phn trn khng tuyt i cng. Cu 85: Khi chn chiu su chn mng th chon theo iu kin no ? Khi chn chiu su chn mng thng chn bng 1/15 n 1/12 ln chiu cao ngi nh. Cu 86: Trong tnh ton nn mng th cc ch tiu no phi ly ch tiu tnh ton ? Cc ch tu nh: ?, ?, ?, ?, ?, e, phi ly ch tiu tnh ton. 12

Cu 87: Ti sao khi thit k nn mng li s dng ti tiu chun ? Khi thit k nn mng ( la chn kch thc ca mng ) l vic kim tra bin dng, xc nh theo tnh ton khng c vt qu tr s gii hn do cc qui phm qui nh m bo iu kin bnh thng ca mng. Hin tng vt ti ( khi tnh ti trng tnh ton ), trong s dng thng gy ra trong thi gian ngn nn khng cn k n khi tnh ton theo trng thi gii hn v bin dng m ch dng ti trng tiu chun. Cc nn t cng 1/2 t, 1/2 khi chu ti s t ti trng thi th I, trc khi sut hin trng thi II. Cc nn t mm ngc li gy ra bin dng rt ln d ti trng cn rt nh, i vi iu kin vng chu th sng Hng, vng ng bng sng Cu Long t mm ch yu tnh theo trng thi gii hn II l gii hn v bin dng ( phn x l a cht chn ? = 0.85 ). Cu 88: Tnh h s nn c my cch ? Tnh h s nn c hai cch: +Cch 1: tin cy, chnh xc l dng th nghim nn. +Cch 2: da vo bng tra. Cu 89: Hy nu trnh t tnh ton mng bng v mng n ? Chn kch thc s b tnh Rtc. Chn kch thc chu ti. Kim tra ?tb, ?max, ?min, < Rtc ( 1.2Rtc ). Tnh v b tr thp. Cu 90: C my s tnh khung ? C hai s xc inh ni lc khi tnh khung: +S n hi. +S bin dng do. Cu 91: C my loi lin kt nt khung ? khuyt im ca n ? Lin kt cng (ngm): cng ca khung cao, bin dng t, mmen un phn b ra u n hn gi nt v cc thanh, do cc thanh lm vic hp l hn, lm c nhp ln hn (nu ct lin kt cng vi mng thng l n gin, ph bin nht mmen ti chn ct ln ? tit din mng ln). Khung ton khi l c cu to vi nt cng. Lin kt khp: cng ca khung ln, ti trng gy ra mmen ln cho b phn trc tip chu tc dng ca n, mmen tp trung vo gia v chn ct, cc tit din chu ni lc ln, thanh lm vic t hp l ( nu ct lin kt khp vi mng ) th ti y M = 0 mc ch l gim kch thc mng khi gp nn su, tuy nhin lin kt khp chn ct s lm tng mmen un u ct v nhp x, lm cho cc cu kin b trn nng hn khp chn ct cn c tc dng gim bc siu tnh ca khung, do cng gim c ni lc pht sinh do khng nn u ca gi ta, do co ngt v t bin ca b tng. Ngoi ra cn hiu rng cc lin kt cng vi mng ch l tng i v di tc dng ca ti trng t nn s bin dng v lm cho mng b xoay i d ch l rt t, khi mng b xoay th mmen chn ct gim 13

xung cn mmen u ct v u x s tng sy ra s phn b ni lc. Cu 92: Trong n ln ca cc mng ly bng my ? i vi mng n: 0.05 ? 0.06 ( cm ) i vi mng bng: 0.08?0.1 ( cm ) i vi mng cc: 0.028?0.033 ( cm ) Cu 93: Th no gi l cc chng ? Khi kh nng chu lc ca cc ti hn m kh nng chu lc ca t cha ti hn th gi l cc chng, d t mi cc khng phi l t cng. Cu 94: ?max, ?min trong dm v ct l g ? +?min : l hm lng ct thp qu t b ph hoi t ngt ( ph hoi gin ) khi b tng b nt th ton b lc ko do ct thp chu, trnh iu cn phi m bo ? > ?min. +?max: l lng ct thp qu nhiu, trng hp ny cn phi trnh v khng vn dng kh nng lm vic ca ct thp, v rt nguy him v dm b ph hoi khi bin dng cn nh, kh phng. kt cu lm vic hp l m bo khng xy ra ph hoi do th ?min < ? < ?max tn dng ht kh nng lm vic ca b tng v ct thp. Cu 95: ?max ca dm khc vi ?max ca ct nh th no ? ?max dm < ?max ct. ?max dm = 1.5( % ) ?max ct =3( % ), c th l =6?8 ( % ) Cu 96: Ct thp trong ct ti sao thng i xng ? Mmen trong ct c cng tr s nhng khc nhau. Thun tin thi cng trnh t nhm thp. Hnh dng ct i xng Pn v Rn chnh lch nhau khng ln khi tnh ct khng i xng. Cu 97: Hy nu nguyn tc lm vic ca ct xin ? Cu 98: Hy nu nguyn l lm vic ca ct ai ? Cu 99: Hy nu cch t ct thp tit din ch T? Cu 100: Khi no th lin kt gia sn vi dm l ngm ? L khp ? L ngm khi: hs < 1/3 hd L khp khi: hs > 1/3 hd Cu 101: Khi no th lin kt gia dm vi ct l ngm ? L khp ? Khi cng n v ca ct ln hn 6 ln cng n v ca dm th xem dm ngm vo ct. Khi cng n v ca dm ln hn 4 ln cng n v ca ct th xem dm k ln ct. Cu 102: Khi no lin kt gia ct v mng l ngm ? L khp ? +Lin kt l ngm khi ln ca mng nh. +Lin kt l khp khi mng c ln ln. Cu103: Nt cng l g ? Nt cng l mt khi nim yu cu cc thanh ng qui ti nt. 14

Cu 104: Ngm n hi l g ? Ngm n hi l lin kt c cng va phi, khi ni lc ln khng cn l ngm. Cu 105: Khi a lc tp trung v lc phn b th ta s dng iu kin g ? C mt lc tp trung a v lc phn b bng cch nhn lc tp trung vi khong cch chu lc ca kt cu . Lc phn b tam gic bng 5/8 tam gic u. Cu 106: Trong cng trnh xy dng mmen do ti trng gi v mmen do ti trng thng ng th mmen no gy ra ln hn ? Tu thuc vo mt bng v chiu cao c th, thng thng nh nh hn 10 tng th mmen do ti trng gi nh. Cc cng trnh cao tng th phi tnh ton c th. Cu 107: Khi cng trnh c tng lng th tng lng c chu ti trng khng ? Khi cng trnh c tng lng th tng lng vn chu ti trng gi bnh thng. Cu 108: Lm th no c c cp ni lc nguy him nht trong t hp ni l ? Phi xt t hp ti trng: -T hp c bn 1: tnh ti + hot ti thng xuyn + mt hot ti -T hp c bn 2: tnh ti + hot ti thng xuyn + tt c cc hot ti -T hp c bit: tnh ti + hot ti thng xuyn + hot ti c bit. Cu 109: Khi tnh ct th c my cp ni lc kim tra ? Khi tnh ct th c 3 cp ni lc kim tra : +Mmax, Nt +Mmin, Nt +Nmax, Mt Ngoi ra cn xt: +Qmax +Mmax, Qt i vi dm. Cu 110: Khi bit M, N kch thc axb hp l khi no ? Nu M nh th nn cu to mng vung ( a = b). Nu M ln nn cu to mng c tit din ch nht. Mng c thit k hp l khi: ng sut di y mng tng i u, vi mng lch tm th: +Pmin > 0. +Pmax < 1.2Rtc +Pth < Rtc Cu 111: Khi no th tnh mng cng ? Mng cng c tnh khi t nn tt, n nh, ti trng tc dng ng tm. Mng cng c cu to bng gch, , b tng.

15

Cu 112: Khi chn tit din ngang ca mng bng cn c vo u ? Chn chiu rng mng bng: -Cn c vo a cht cng trnh ( cng ca t nn ) -Ti trng tc dng. -iu kin bin dng ca t nn ( ln ca mng ). Chn chiu cao mng bng: -Ti trng tc dng. -p lc ca t nn. -Kch thc ct. Cu 113: Hy nu cc bc tnh mng bng ? Xc nh ti trng tc dng xung mng. nh gi iu kin a cht thu vn. Chn chiu su chn mng. Xc nh kch thc s b ca mng. Xc nh cng ca t nn. Kim tra ln cho mng. Xc nh chiu cao mng v kch thc dm mng. Tnh ni lc. Tnh ton ct thp. Tnh ct ai, v ct xin. Kim tra cht lng ct thp. Cu 114: Mng bng l dm trn nn no ? Mng bng l dm trn nn n hi. M hnh tnh ton l m hnh WRINKLER ( m hnh v bin dng cc b ). Mng bng thit k theo phng ngang tt hn theo phng dc v cng theo phng ngang ln hn cng theo phng dc. Phn nn mng Cu 01: Nu cng dng ca lp b tng lt mng ? B tng lt trc khi b tng mng c cng dng lm sch y b tng mng, ngn cn s mt nc xi mng ca b tng mng vo t nn. Cu 02: Nu nguyn nhn gy ln khng u ? Do tnh nn ln ca nn t phn b khng ng u trong mt bng v do a hnh phc tp. Do t b ph v kt cu. Do nc chuyn ng di t. Do ti trng t lch tm v tng phn cng trnh c ti trng khc nhau. Cu 03: Nu tc hi ca s ln khng u ? c bit khi c tr s ln rt nguy him cho kt cu siu tnh, gy cn tr cho vic s dng cng trnh v lm mt m quan ca cng trnh. 16

Cc kt cu nh tng, khung, sn mi,...s xut hin cc ni lc b sung c th lm nt hng kt cu. Cu 04: Cng trnh c cn lm ging mng khng ? Cng trnh phi lm ging mng v ging mng ni cc mng trong cng trnh li vi nhau to thnh h khng gian cng. Chu ni lc sinh ra khi c s ln lch ca mng. Ngoi ra cn to lin kt khng gian chng trt, cc mng phn b u ng sut xung mng tng n nh ct. Cu 05: Th no l nn ? Nn l chiu dy cc lp t trc tip chu ti trng ca cng trnh do mng truyn xung. Cu 06: c im cu to mng hp khi (cch tnh ton ) ? Khi tnh ton cc mng n di ct cc trc gn nhau to thnh mng hp khi. Mng hp khi l mng c chung bn mng v c t 2 ct tr ln. Tnh ton nh bn dm c ti trng tc dng l p lc t tc dng ln mng. Cu 07: Khi chn loi nn mng cn c vo nhng yu t no ? c im ca cng trnh. Tr s ca ti trng. Nn v mng cng trnh ln cn. iu kin a cht cng trnh, iu kin a cht thu vn. Cc yu t khc nh chn ng,..

Cu 08: Th no l mng cng, mng mm ? Mng cng l mng khng b un khi chu tc dng ca ti trng. Khi xc nh ng xut tip xc di y mng ta khng k n un ca mng. Gm cc loi mng gch , b tng, mng n b tng di ct, mng bng b tng ct thp di tng. Mng mm ( mng c cng hu hn ) l mng b un ng k khi chu tc dng ca ti trng. S un ny phn b li ng sut tip xc, phi k n nh hng ca un gm: mng bng, mng bng giao thoa b tng ct thp di cc dy ct. Cu 09: Bng thng k ct thp lm g ? lp d ton v lp tin thi cng, d ton trc gi thnh cng trnh, cng nhn ct, un thp theo thit k. Cu 10: Nu cc ch tiu xc nh t nn ? Trng lng ring ca t t nhin. Trng lng ring ca ht t. m. Gii hn chy. Gii hn do. H s thm. Gc ma st trong. 17

Lc dnh n v. H s nn. M un bin dng tng qut. nh gi t theo st. nh gi ct theo rng. Cu 11: Khi tnh ton mng ( cng nh cc cu kin khc ) khi no s dng ti trng tnh ton, khi no s dng ti trng tiu chun ? Khi tnh ton cu kin theo trng thi gii hn 1 ( Kh nng chu lc, sc chu ti, n nh ) th ta tnh vi ti trng tnh ton. Khi tnh cu kin theo trng thi gii hn 2 ( bin dng, ln, vng, khe nt ) ta tnh vi ti trng tiu chun. Cu 26: Ti sao tnh vng li dng ti trng tiu chun ? Ti trng tiu chun l ti trng da theo qui phm thit k, theo kch thc hnh hc v ti trng ca chng loi vt liu l ti trng tng i chnh xc v gy t bin mi lu di nn gy vng (???) Cn ti trng tnh ton c k thm h s tin cy, k n yu t bt li lm tng gi tr ti trng do ti lch vi thit k, sai lch khi thi cng, s tng ti trng t ngt. M nhng trng hp khng gy bin dng, t bin m hot ng c khng k n. Cu 12: Khi thi cng mng cn ch nhng g ? Cn ch tim chun, ct chun. Cu 13: iu kin thi cng xong mt cc ? Chon b tng n su thit k. Th ti m bo sc chu ti khng c khuyt tt. Cu 1: Tc dng ca thp cu to, ct gi ? Gi n nh ct dc chu lc khi b tng, khi chu lc, chu ng sut ct. B rng ca dm rng th n cn gim s phnh, gi n nh cho ct ai. Cu 2 : Tc dng ca thp phn b sn ? Gi n nh cho ct dc, chu lc theo phng kia. Cu 3: ngha ca lp bo v ct thp ? Chng xm thc n mn ct thp, to lc dnh gia b tng v ct thp. Yu cu: Dm h > 250 an = 2 cm. Bn hb < 10 cm an = 1 cm; hb < 1cm an = 1,5 cm. Mng an = 5 ? 7 cm Cu 4: ngha ca on neo ct thp ? m bo lc dnh gi b tng v ct thp. Ct thp khng b ko tut dn n b tng v ct thp cng kt hp lm vic. Cu 5: Khi no tnh ton theo s khp do, s n hi ? Tnh ton theo s khp do: BT mc < 300; A < 0,3; tnh cho nhng 18

cng trnh bnh thng, thng khng c xm thc ct thp. Tnh ton theo s n hi, khng nt i vi nhng cng trnh quan trng. Cu 6: S cc th nn tnh l bao nhiu ? S cc th nn tnh l 1% v = 1 cc. Cu 7: on p b tng u cc l 10d on hn v lentenite l 1m. Cu 8 : Cch xc inh chiu di ct khung mt tng 1? K t nh mng tr ln mc sn. Cu 9: K thut b tng i cc ? Bng bm. Cu 10: b tng bng phng php bm khc phng php th cng ch no ? st th cng 3 ? 4cm; bng bm 10 ? 15 cm. Cu 11: Ti sao b tng bng phng php bm yu cu st cao hn ? b tng c tnh linh ng hn khi i qua ng ca my bm. Cu 12: Ti sao phi kim tra st b tng trc khi b tng mng ct, mng khung ? st phn nh do v tnh linh ng ca va b tng, nn b tng c st hp l mi chui qua khong cch ct thp to nn lp bo v v t b r mt (Nhng phi khng ch v lin quan n thi gian ninh kt v cng ca b tng). Cu 13: Chn tit din dm da vo nhng yu t no ? - mnh ca ct nh : -Kinh nghim. -Ti trng tc dng. Cu 14: Chn tit din dm da vo nhng yu t no ? Xut pht t iu kin vng cho php. Cu 15: Cch kim tra kt qu chy my ? Tch mt phn t khung v kim tra vi ti trng tc dng. Kim tra 3 phng trnh cn bng: Cu 16 : Gii thch cch lp tin thi cng, phng php lp, mc ch v da vo u lp c ? Cu 17: Cch iu chnh h s k1, k2 ; da vo u lp c hm s no. iu chnh tin bng cch lp tin thi gian hnh thnh cc qu trnh xy dng. -Nu biu nhn lc, vt liu khng iu ho th ch yu m bo s lng cng nhn khng iu ho, nu thiu th phi iu ho ( ch thay i 10 ? 15%) S cng d / Tng s cng. -Nu iu chnh th nn iu chnh h s k1 v Amax gim i ng thi s cng cng gim i, thay i c li, nhng gim Amax th ko di thi gian thi cng. 19

-Nu tng Ath th c th rt ngn thi gian, cng v k1 > 1 ko theo k2 = 0. Cch b tr cc trong i l 3,6.d. -Khong cch cc < 3d. Cc cc lm vic gn v gim s ma st gia cc cc v khong cch mng qui c nh. -Khong cch gia cc cc > 6d cc cc lm vic nh cc n c lp. Cu 18: Khung nh cao tng khc khung nh thp tng cch b tr ct thp. -Yu cu nt khung do ( ct ai nh th no ). -Nt khung do chng nhng chn ng do ng t v dao ng cng trnh. Cu 19: Nguyn tc b tr ct thp trong cc khoan nhi, cng dng ca thp dc v thp ai ? -Thp dc chu un v nn. -Thp ai gi n nh ct dc, cng ct dc to li m khi b tng cho b tng trong ct ai chu nn tt hn. -Ti sao ko thp sut cc. V khi tnh ton sc chu ti ca cc ly tr s Pv. Cu 20: Vai tr dy neo ging vn khun ct. (Ch ct bin pha bn kia khng chng mi cn) Cu 22: V cc mt bng kt cu lm g ? xc nh ti trng truyn ln dm khung, xc nh v tr dm khung chu lc ca mng. Cu 23: Ct v ni thp trong ct, ct u, khi no c ct ? Ni thp chn ct th thun li cho thi cng n < 4 thanh ni 1 v tr n = 5?8 thanh ni 2 v tr n>8 thanh ni 3 v tr a. Khi ct thp chu nn ng tm v lch tm b (e0 < 0,2h0) th c ct ni mt v tr d mt thanh hay bao nhiu thanh. b. Khi ct chu nn lch tm ln (e0 > 0,2h0)th tun theo qui nh trn Cu 24: Qui nh din tch s thanh thp c ct , 1/3, 1/2 chiu di dm. 1/3ld : Ct = 2 thanh v = 1/3 ln 1/4ld : Ct s thanh cn li. Vi mmen dng v tr ct = 1/5ld Cu 27: Cng dng ca ct ai trong ct, ti sao on ni thp, ct ai phi dy, cu to ct ai. Cng dng: chu lc ct, gi n nh ct ai, chu lc khi thi cng v chu lc khi phn ni ct thp, ct ai t dy. Cu 28: Nu tnh ton khung theo tnh cht i xng th s nh th no? 20

Cc thanh thp dc phn ni c tnh cht gim nn khong cch ct ai dy cn hn ch s n hng ca b tng ct lm tng cng b tng ln.

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