Ts.nguyn nh tinB mn c hc t nn mng HXD chng m u I- Vai tr, nhim v ca nn mng Ktcubntrn:(nh,cu, duong,d, dp...) Vtliu:gach,d,b tng, btct, thp, dt dp ..Mng:mornghonktcu bn trn Vt liu: gach, d, b tng, btct, thp, dt dp ... Nn dt, dTaicngtrnh mngungsutphtsinhnnbindang(ln,truot) anhhuongtrolaicng trnhMng: B phn kt cuduoi chn ct khung hay tuong, tip nhn tai trong tu trn xungv truyn tai xung nn.Nn: B phn cui cng cua cng trnh, tip nhn tai trong cng trnh truyn qua mng. Hnhdangvkchthuoccuannphuthucvoloai dtlmnn,phuthucvoloaimng v cng trnh bn trn Tam hiu l: nn l b phn huu han cua khi dt m trong d ung sut, bin dang do taitrong cng trnh gy ra l dng k.Nn, Mng l nhung b phn cng trnh rt dc bit, rt duoc ch trong boi v: +Dt l vt th roi, rt phuc tap, s liu v n kh dat d tin cy cao, dng thoi l thuyt v nn mng cn sai khc nhiu so voi thuc t. Nn mng l mt khoa hoctng hop v dt d, kt cu v ki thut thi cng. +Mng o trong mi truong phuc tap v thuong o trong nhung diu kin bt loi cho vt liu (m uot, n mn ...). +Thi cng v dc bit khi sua chua rt kh khn di khi di hoi ga thnh cao +Phn lon cng trnh hu hong hoc lng ph do nhung sai st phn nn mng Mng c nhiu loai, phu thuc vo nhiu yu t:+Nn dt+Nuoc trong dt+Kt cu cng trnhShare-connect.blogspot.com 1Ts.nguyn nh tin B mn c hc t nn mng HXD h1132312e) a) b) c) d)+Yu cu d tin cy (muc d quan trong cua cng trnh)+Mi truong xy dung+Thi cng. II- Cc loi nn, mng. Mng: + Chiu su:Mng nng v mng su + Vt liu: Gach, d, b tng, d hc, b tng ct thp, thp... + Thi cng:Ton khi, lp ghp, bn lp ghp, + Hnh dang: Don, bng, b, hp, vo+ Hnh thuc kt cu: Dm, dai, ban, khi+ D cung kt cu: Cung, mmNn: + Tu nhin+ Giac:thayth(dm),truvtliuroi,gingct,nntruoc, dmthm,hanuocngmIII- Cc h hng cng trnh do nn mng gy ra III.1. Cng trnh s dng khng bnh thung do: - Ln nhiu: lm sai ct thit k, d v duong ng, nh huong dn cng trnh ln cn - Lch nhiu: ung sut phu thm trong kt cu i nut ne, thm, dt v c th dn dn ph hoai cc b phn kt cu.Thuong do cc nguyn nhn:+ Mng khng ph hop: v du: Pizza, 32 Lng ha, E6 Quynh li ... + Cng trnh c tai trong phn b khng du+ Nn dt yu, diu kin dia cht phuc tap, bt loi (hnh a ) + Nn dt khng dng nht v xen kep phuc tap (hnh b,c,d,e ) - Trong qu trnh thi cng, dt bi bin di manh kh xc dinh dng, gy ra cc rui ro cho cng trnh, trong d thuong do sai st trong dnh gi v nn dt xy dung.Share-connect.blogspot.com 2Ts.nguyn nh tin B mn c hc t nn mng HXD PghIII.2.Cng trnh mt n d[nh vi nn dt, c th dn ti b[ ph hoai . Cc truong hop nn bi ph hoai:- Truot tri: thuong gp voi mng nng, khi ti dung lon, gia tai voi tc d nhanh trn nnc kt chm, bo ho: - Truot su: thuong xy ra di voi mi dt, phn lop nghing lon, mng su - Truot ngang: tuong ung voi truong hop tai ngang lon nhu dp, tuong chn, cu, cang,cng trnh bin- Lt: thuong xy ra di voi cc cng trnh cao, lch tm lon, tuong chn dt.- Tm lai cc sai st c th do: + Khao st. + Th nghim khng dng, khng ph hop voi diu kin lm vic thuc t.+ Phuong n mng khng ph hop voi nn dt.+ So d v phuong php tnh ton khng ph hop, khng dy du.III.3. Cc phuong hung x l- Cc bin php v kt cu bn trn: giam ti, tng d cung h mng kt cu trn, cu taoh ging- Cc bin php v mng: ging mng, khe ln, tuong chn dt, mng coc, thay di kch thuoc mng ph hop voi diu kin dia cht.- Cc bin php v nn gia c.IV- Cc nguyn tc v trnh t thit k Nn mng theo phng php ri rc Thit k kt cu cng trnh ni chung v nn mng ni ring du phai tun theo nguyn tc:- Thoa mn cc diu kin k thut: bn, an ton v su dung bnh thuong,- Thi cng kha thi, c kha nng co gioi ho cao, thoi han ngn,...- Kinh t: chi ph thp khi so snh nhiu phuong n, chon ra phuong n ti uu. Share-connect.blogspot.com 3Ts.nguyn nh tin B mn c hc t nn mng HXD M01PNo1P01M0iNoiP0iphmCc diu kin k thut di voi phn nn, mng theo phuong php roi rac cu th nhu sau. IV.1- Tnh mng: - Voi vt liu ph bin l BTCT, vic tnh ton theo nguyn tc tnh cu kin chiu un, nn, ko d duoc gioi thiu trong gio trnh KCBTCT I v II. (Kt cu b tng ct thp). V d: di vi cu kin chju un v yu cu tnh ton: + TTGH 1: Tnh ton cuong d trn tit din dung v tit din nghing voi tai trong l tai trong tnhton ung voi moi t hop tai. Tnh ton cuong d trn tit din nghing tai vi tr c Qmax . Nu khng k anhhuong cua ct thp, tuc luc ct Qmax chi do b tng chiu:Q QbVoi Q- luc ct tai tit din mt cua vt nut nghing. Qb - kha nng khng ct cua b tng tai tit din nghing. Qb = K. Rk.ho.btb K -h s thuc nghim phu thuc vo d dc cua mt nghing. Rk-cuong dchiukocuabtng;hochiucaolmviccuamng(ho=habv);btbcanhtrung bnh cua mt dm thung Tnh ton cuong d trn tit din thng gc tai vi tr c M lon, xc dinh luongct thp cn thit tuong ung. Tnh theo nguyn l ct don:Fa = o a h RM

M m men tai tit din tnh ton (thuong Mmax)Ra- cuong d chiu ko cua ct thp, h0 - chiu cao lm vic cua mng + TTGH 2: Tnh ton d vng v nut voi tai trong tiu chun ung voi t hop co ban. Divoi phn mng hu nhu khng tnh ton tru mt s truong hop nhu ban mng b cua bchua, mng trong mi truong xm thuc manh (c th xem l thuyt tnh ton o trang 83- KCBTCT I ) Tai trong tc dung ln kt cu mng l tai trong cng trnh bn trn ( Noi, Moi, Qoi) v phan luc dt tc dung tai cc b mt tip xc cua h mng - nn dt ( p, t )IV.2- Nn dt (l thuyt co so l mn co hc dt)- TTGH 1: (hoc goi l tnh ton kim tra kha nng chiu tai cua nn dt voi tai trong l taitrong tnhton ung voi moi t hop tai).Share-connect.blogspot.com 4Ts.nguyn nh tin B mn c hc t nn mng HXD luc gy truot, lt+ Nu mt dt bng phng, dng nht th suc chiu tai tnh ton cua nn c th xc dinhbng cng thuc giai tchsmsghFc . C h '. . B 2 / b . . AFpR p+ += = Trong d Fs- h s an ton( 1) A,B,C - h s an ton b, hm - b rng v d su mng, - trong luong ring cua dt duoi v trn dy mngp - p luc dt tai mt tip xc mng - dt.Truong hop nn phn lop, nhiu truong hop cho php tnh suc chiu tai cua lop dtR2 bng cng thuc trn voi b thay bng btd, hm = h1 v tt nhin c cc chi tiu vtl, co hoc cua lop 2. + Cch 1: btd xc dinh theo = 300+ Cch 2: btd xc dinh tu diu kin cn bng p luc: N = (p - hm).b = z.btd , m z = (p - hm).k btd = kbtung tu di voi mng don, bFtd =kl . b, bit ty s l/b btd( k- h s tra bng phu thucbz,bl trong bang tratnh ung sut ) 12zbtzglh1hmbm Kim tra diu kin:2h . p2 zbt2 z 2R pm + = hay 2 q q2RFNp = Trung hp tng qut (mt dt khng phng, nn nhiu lop, khng du, tai trong theo phuong ngang v m men lon ). Thuong dng cc phuong php gia thit mt truot nhumt truot tru trn, mt truot phng, gy khc...d dnh gi n dinh nn. D n dinh cuacng trnh voi nn duoc dnh gi qua h s n dinh hay h s an ton Kmin = lucgiu divoimt truot gia thit [ K ], Fs = luc tip giu di voi mt truot gt [Fs] luc gy truot di voi mt truot gt Share-connect.blogspot.com 5Ts.nguyn nh tin B mn c hc t nn mng HXD - TTGH 2 (hoc goi l tnh ton v bin dang): ni dung tnh ton l [S] hay Sgh [S]-ccbindangchophpcuacngtrnhdttrnnn,thuong duocxcdinhtheo cc tiu chun xy dung S-bindangdubo(-dln,chnhln,vntcln,chuynvingang,dvng...) voi t hop tai trong co ban v ti tiu chun.* Nu mt dt phng, dng nht, tai trong phn b du, c th tnh S = pgl. b. .0E201 * Truong hop tong qut du bo S theo phuong php cong ln tung lop.Dlnmilopmongchiudyhiduoctnhtheocngthuccuabitonmtchiu-khng no ngang- nhu sau: Si=1i 2 i 1h .ei 1e e+(nu c kt qua th nghim nn p) Si = hi . .Eglzii 0i(nu khng c kt qua th nghim nn p ) (xem lai phuong php cng ln trong gio trnh Co Hoc Dt)12btzglhiV.Trnh t thit k nn mng: Buc 1: Thu thp xu l ti liu bao gm:- Ti liu v cng trnh: Mtbng,mtct,ccyucucngnng,so dktcu,bangthoptaitrong(Noi, Moi, Qoi) tc dung ln mng. (Cc loai tai trong, t hop tai trong ging nhuphn kt cu bn trn) - Ti liu v nn dt bao gm:+Mangluoivphuongphpkhaost.Mangluoikhaostcgng 3dim:don gian: 100 - 150m / dim, trung bnh: 50 - 30m / dim, phuc tap < 30m / dimShare-connect.blogspot.com 6Ts.nguyn nh tin B mn c hc t nn mng HXD + Ti liu v cng trnh ln cn, mi truong xy dung.Tu d - Dnh gi diu kin xy dung (lm co so cho buoc 2)-7 -Mt Bng nh V H KHOAN + D su khao st: Mng bng hks 3B Mng b hks 1,5B Mng su hks 3m tu d su dt mng du kin+ Phuong php khao st:- Gin tip: do h, khoanly mu nguyn dang, ph hoai i th nghim trong phng- Truc tip: Th nghim bn nn E0 Th nghim nn ngang EnTh nghim xuyn tinh CPT qC dia tng, E0, c, ... Th nghim xuyn tiu chun SPT N dia tng, E0, c, ... Th nghim Ct cnh Cu.. + Lt ct dia cht: D thy duoc su thay di cua dia tngmt ct a cht cng trnh tuyn II-II + Cc kt qua th nghim v cc chi tiu vt l co hoc cua tung lop dt + Dia cht thuy vn: cao d nuoc ngm (hin tai v muc nuoc cao nht c th), tnh chtnuoc ngm,Share-connect.blogspot.com 7Ts.nguyn nh tin B mn c hc t nn mng HXD St St phaCt pha Bn888 888888888888 888Hu c888CtCui , sig)423bn1e)a) yu b)f)tth)h1 lnyu tttt)yu ttttttyu c)h2 lnCGia cngmi mi C - Xc dinh cc tiu chun xy dung:[S],((

LS, h s an ton... Buc 2: D xut phuong n nn mng kha thi: phuong n kha thi theo nghia rng:- V vt liu- Loai mng theo dang kt cu co ban, d cung, hnh dang mng...- Phung php thi cng - D su dt mng: nng v su - Giai php gia cTrong thuc t nguoi thit k thuong rt quan tm dn cc phuong n v d su mng (mng nng v mng su) k hiu l Hm (hm)Hm phu thuc vo: - Tai cng trnh: d lon, d lch tm, tai ngang, dng- tinh. Ni chung cng trnh lon v chiulucphuctapthmngcxuhuongcngsu.Taitrong dngcungthuongdng mng su. - D quan trong cua cng trnh (cp cng trnh)...- Cng trnh ln cn. - Dc bit l diu kin dia cht khu vuc xy dung.a) Lop dt bn trn khng tt, b dy lon, b) Lop dt bn trn tt, b dy lonc) Lop yu nm giua cc lop tt, d) Lop yu nm trn b mte) Xen kep khng du f) San lpg) Mi dth) Muc nuoc ngm cao.Cc k hiu Buc 3: Thit k so b cc phuong n kha thi Sau khi d xut cc phuong n nn mng nguoi ta thit kso b cc phuong n d ( theo cc nguyn tc co ban d trnh by) Share-connect.blogspot.com 8Ts.nguyn nh tin B mn c hc t nn mng HXD Nhc lai: Nguyn tc co ban trong thit k ni chung v nn mng ni ring - Thoa mn cc diu kin k thutMng+ Diu kin cuong d+ Bin dang, nutNn + Diu kin v truot, lt+ Diu kin v ln, lch, nghing, xoay ... - Thi cng: C kha nng don gian, nhanh (co gioi ho) - Kinh t.Buc 4:So snh ( cc chi tiu kinh t, d tin cy). - So snh cc chi tiu kinh t, d tin cy cua cc phuong n s b- Chon phuong n ti uu d thit k k thutBuc 5: Thit k k thut, thi cng phuong n nn mng duoc chon( Gioi thiu o cc phn mng nng v mng coc ... ) Buc 6: Ban vShare-connect.blogspot.com 9Ts.nguyn nh tin B mn c hc t nn mng HXD S trnh t thit k nn mng ni chung Ti liu Ti liuCng trnh Ti liu a cht Cc tiu chunqui phm xutccphngnkh thi (ch v chiu su mng) Phng n 1 Thitksb ccphngn xut Phng n 3 Phng n 2 Sosnhvchn phngnk thut Thitkkthut phng n c chn Bn v thit k Share-connect.blogspot.com 10Ts.nguyn nh tin B mn c hc t nn mng HXD Luyn tp-chng m u 1) Phn loai mng v nn.Nu pham vi ung dung cua mi loai.2) Cc nguyn nhn thuong gy cho cng trnh ln nhiu, ln lch lonNu cc bin php han ch ln v lch.3) Cc nguyn nhn thuong gp v ph hoai nn cng trnh, khi dt dp.Nu cc bin php chng truot, lt.4) Khi thit k nn mng, cn thu thp cc ti liu g? Cho v du.5) Thit k cng trnh di voi phn nn dt gm nhung ni dung tnh ton g?Hy nu cc diu kin k thut trong mi ni dung tnh ton d.Hy phn tch cc yu t anh huong dn vic lua chon phuong n chiu su mng. Share-connect.blogspot.com 11T.S. Nguyn nh tin b mn c hoc t nn mng > 150a: lp bo v > 80b tng 150#aGing b tngB > 0,5mh > 50050:100hbchng I - mng nng I - mng nng trn nn t nhin Khicngtrinhdtlnnndttunhintaidsuhmnho,anhhuongcuadttrnday mong toi cac mt tip xuc la nho, ta noi do la mong nng trn nn tu nhin. Trong Co hoc dt,mongcobrngb,dsuhm,nuhm/b0,5(theoBerezansev)thikhidtduoi mong bi pha hoai dt bi dy tri, ta coi hm do la nng Trong thuc t nhung mong co hm 3m co th coi la nng. - Pham vi ung dung: Tai trong khng lon, cng trinh nho, Q0 nho Lop dt bng phng co suc chiu tai phu hop, co chiu day du lon. Ngay ca khi lop dt trn co suc chiu tai khng lon nhung co th giai quyt bng cach giam tai cng trinh trn din tich mong lon (bng giao nhau, be) I.1 - Phn loi v cc yu cu cu to mng. - Phn loai (xem trang 2) - Cu tao cac mong bng vt liu gach, da, b tng, b tng da hc thuong xy duoi cac tuong gach, da, dang bng, git cp tuy vao goc cung vt liu. - Mong b tng ct thep rt ph bin va da dang: Mong don duoi ct, tru, thap nho, ct thep Bng doc ngang: dung duoi tuong, vach cung, duoi hang ct Mong be: duoi nha cao tng, b, u tu, thuyn, mt duong cung, sn bi, bn Kich thuoc va d cung tng tu mong don bng be, hp, vo cho phep chiu tai tac dung lon hon, suc chiu tai cua nn lon hon va kha nng bin dang giam. Share-connect.blogspot.com 12T.S. Nguyn nh tin b mn c hoc t nn mng- Yu cu cu to chung di vi mng BTCT:+ B tng 150# ( thuong 200#).+ Thp thuong dng thp gai, ko thng, dai dng ct tron+ Lt: b tng gach v, b tng ngho (100# ) dy 50mm + Lop bao v 30 mm (c lop lt) Cu to mng n Mng don dui ct tr (xem 147 - 149 BTCT II ) >B/10200>3cmbctlneo (thung >=15d)BLShare-connect.blogspot.com 13T.S. Nguyn nh tin b mn c hoc t nn mng Cu to mng bng di tng Cu to Mng bng di hng ct a-bng giao nhau b- bng don c- tit din Bng duoi hng cotThp dt theo yu cau doi voi dam lin tucnn goi l mng dam (giao nhau) Share-connect.blogspot.com 14T.S. Nguyn nh tin b mn c hoc t nn mng Cu to mng b, hp, v Mt s dang mong hp Ct thep trong ban mong cu tao theo cac yu cu di voi ban ngam, k, con trong suon theo nguyn tc dang dm don hay giao nhau. CU TAO GIANG MNG:+ Thuong cu tao nhm tng d cung cng trinh, giam chnh lun kt hop voi d tuong bao,Faging5cm2,hgingchontheokinhnghim(nguynlydm)tuythucvaodiu kin dia cht, tinh cht tai trong va luoi ct. Share-connect.blogspot.com 15T.S. Nguyn nh tin b mn c hoc t nn mng I.2. Thit k mng nng cng. - Ni dung co ban trong thit k la xac dinh cac dc trung cua mong gm: + Vt liu + D su mong + Kich thuoc mong l(L) x b(B) x h(h0) + Sao cho thoa mn cac yu cu k thut, thi cng va kinh t. Trinh tu thit k co th nhu sau: Ti liu - Cng trnh- Nn- Cc tiu chun thit k Bc 1 Phng nH mng nng- Nn- Cngmm - n, bng, b ... Bc 2 Bc 3 Vt liu mng- #, thp Rn, Rk, Fa...- Lt lp bo v ao Bc 4 su mng hm (xem phn 4 chng m u) Chn kch thc mng b x h (bng di tng)b x l x h (n) B x L x h (b) Bc 5 ng sut di mng - pBc 6- p0(khng k TLBT)(Thng b qua Q0)- pgl = ptc - hm Bc 7Kim tra kch thc y 1- Kh nng chu ti: trt, lt v iu kin kinh t v bxl. 2- Bin dng SSgh Bc 8Kim tra chiu cao mng v Fa Tnhtoncngvtliumngdotitrngcng trnh v p0 gy ra v iu kin kinh t v h,Fa. Vd: trt ngang, lt, c kt chm Bc 9 Cc kim tra khc Bc 10 Cu to v Bn v Share-connect.blogspot.com 16T.S. Nguyn nh tin b mn c hoc t nn mng -Mongcunglamongcodcunglonduoitacdungcuataitrongcngtrinhmong bin dang nho co th bo qua ung sut duoi mong p co th coi la tuyn tinh. + Mong bng duoi tuong, vach. + Mongbngduoihangct,mongbenhungdcungmongrtlon(hlonvah suon day). + Mong don duoi ct, tru.la nhung loai mong cung: - p lc tnh ton dui dy mng: + FNP = FN0 + tb . hm(tb = 20KN/m3 ) + Pmax, min = WMP N = N0 + trng lng mng + t ph lpM = M0 + M (N0) +0M (Q0) +0M (p lc t)M0+M(N0)(nuQ0nhvmngchn su, kt cu khng gian cng). - Trong tinh toan gia thit bo qua tai trong ngang, sau co th kim tra diu kin truot phng lt o buoc 9. - p lc tnh ton phn b di y mng khng k trng lng bn thn mng v t ph: P p =0 - tb . hm (khng k trong luong ban thn mong va dt phu) tuc la FNp00=- p lc tiu chun phn b di y mng: tcP Pgl = - tc . hm mtt'.h. 1.15P 2 1- Cc bc tnh ton: Bc 1:Thu thp va xu ly tai liu (xem lai phn trn) xac dinh gia tri Sgh([S]), FS. V d- Nha khung va nha tuong chiu luc Sgh = 8 - 10cm, (LS)gh = 0,2 0,4% Bc 2: Chon h mong:Don duoict co gingBng duoi tuong trn nn... Bc 3:Chon vt liu mong: BTCT ( 200# ) Thep ( AI, AII ) gai Lot, lop bao v a0 3cmNu dung khi xy: gach chi dc vua xi mng cat vang 75# Bc 4:Chon d su dt mong hm (xem phn truoc) Bc 5: Chon kich thuoc mong (theo kinh nghim nao do).Day mong b x l (don), b (bng duoi tuong). Chiu cao mong, bc mong h, hb h0, h0b(h0 h - a0) NoMoP minPmaxABShare-connect.blogspot.com 17T.S. Nguyn nh tin b mn c hoc t nn mng Pgh Bc 6:Xac dinh ung sut duoi mong p, pmax (d kim tra suc chiu tai, kha nng truot, lt) p0, p0max (tinh toan kim tra cuong d vt liu mong) pgl ( tinh d lun cua nn dt ) Bc 7:Kim tra kich thuoc day mong b x l, b va chon b x l, b hop ly. Day mongphai du lon (thich hop) d p du nho nhm: Nn dt du kha nng chiu tai chng truot, lt ( TTGH 1 cua nn ) D lun, chnh cho phep( S Sgh ))n tp:1- Nu m}t dt phng, dng nht th diu kin nn du ch|u tai: + p < R + pmax 1,2R Trong R = SghFp = SmFCc h BbA + + '2 + FS h s an ton chn tu cp v loi cng trnh V d nh thng ly 2 - 3 ( 2 khi no?3 khi no? ) + A = N . n . m . i+ B =Nq . nq . mq . iq

+ C = Nc . nc .mc . ic Trong N, Nq,Nc - h s sc chu ti ca nn, ph thuc vo gc ma st trong ca t (tra ph lc trang 20) Cc ni ,mi,ii- h s hiu chnh hnh dng, nghing mt t, lch ti. )`cqnnn= 1 i vi mng bng )`+ == =lb2 , 0 1 n1 nlb2 , 0 1 ncqi vi mng n, b Cc h s hiu chnh mt dc ca b mt t hoc lp t phn lp = 0 - 50 mi ( m, mq, mc ) = 1; > 50 th m = mq = ( 1- 2)tgtg; mc = m - tg Nmc.1+ i , iq , ic : l cc s hiu chnh v lch ca ti trng c tnh theo cng thc: i = (1 - )3 ; iq = (1-0,7)3 ; ic = iq - 1 Ni 1qq(Trng hp = 0 th cc cc h s i ; iq ; icbng1)- Nu nn phn lop dang nhu sau thi cn kim tra kh nng chiu tai cua lop dt (2): + p2 = ) ' ( hm pZbZo o+2 2hoc) .(

mqh h FNp + =1 1 2 + pmax 1,2.R2

- Truong hop mt dt dc, nn phn lop phuc tap thi dung cac phuong phap gia thit mt truot (vi du mt truot tru tron) d kim tra kha nng truot. Share-connect.blogspot.com 18T.S. Nguyn nh tin b mn c hoc t nn mng 2- iu kin: S Sgh (Sgh c bc 1 ): Si - tnh ton d bo iiiLSS + Nu nn t phng, ng nhtSi = Pgl. b. . 0201E + Tng qut phng php cng ln tng lp (iukinkinhtthhin p R.(pmax1,2R hay p2 R2) Nu b x l (b) cha ph hp th tr li bc 3 hay 5. Bc 8: Kim tra chiu cao mong va tinh ct thep trong mong. Ni dung: TTGH1: Tinh toan cuong d vt liu mong TTGH 2: Bin dang va nut (thuong khng tinh ma dam bao bng cu tao) Nhu vy o buoc nay cn tinh cuong d mong. a. Trng thi lm vic ca mng bng di tng:+ Phia trn chiu tai trn din hep bt, d cung theo phuong doc tuong la 'v cung lon. Phia duoi tai (p0) phn b tai trong trn din lon b d cung trn phuong ngang mong la huu han Mong lam vic ging nhu kt cu conson ngam tai mep tuong (kt cu chiu un) 2 kha nng pha hoai cuong d a.1.Phhoitheom}txin:(tuongdmthungmong). Gia thit mt dm thung nghing 450tao thanh hinh thap dm thung (hinh bn), hoc nut v phia lch tm do ung sut keo chinh gy ra diu kin Q Qb (Di voi cu kin chiu un khng co ct xin, dai va bo quanh huong cua ct doc)Coirng chi v mt phia lch Q Pdt 0,75.Rk. h0 ( hay Pdt k.Rk. h0 ) trong do Pdt p dt. bdt h0 p dt. bdt / (0,75. Rk) Rk - cuong d chiu keo cua b tng a.2. Ph hoi theo tit din thng ng:Tai mep tuong thuong chi dt ct don khng dt ct xin va kep.Diu kin:- Khng ph hoi dn ( trang 37 KC BTCT1 ) NoMo450P > 00minP0maxP0tP0t450btkc k RP0maxP0tP0th1hmp2b x l12yu hn bqxq30o30oShare-connect.blogspot.com 19T.S. Nguyn nh tin b mn c hoc t nn mng 0 ngp0 maxpbbth0 nngRM4 0,(thng khng cn tnh iu kin ny) - Din tch ct thp yu cu vi h0 theo phng b rng Fa 09 , 0 h RMangchn n?Trong Mng =2 22max ng o ongbxP P + saochobcctthpa100 200hockimtrahm lng = 0ahthc F= 0,15 0,4% Ghi ch: Kh nng ct theo chu vi tng rt t xy rab. Trng thi lm vic v cc iu kin kim tra i vi mng n di ct.- Phia trn mong tai phn b hep duoi din Fc bc. lc. Phia duoi phan luc dt p tac dung trn din rng hon nhiu b x l.Cu kin ban chiu un hai kha nng pha hoai cuong d mong:+ Pha hoai tit din nghing: hinh thap hoc pha hoai mt nghing 450 v phia lch + Pha hoai tit din dung: coi gn dung la tit din qua mep ct. b.1. Kim tra cng trn tit din nghing:Ct dm thung mong tao thanh dang thap 4 mt hay coi gn dung 1 mt xin 450. Trong moitruonghoptinhantoanlatruonghop mtmtxin450 v phia lchtmvoicng thuc: Pt 0,75. Rk.h0.btb, trong : Pt = P0t + P0max.lt.b (hop luc phan luc dt trong pham vi gach cheo trn hinh duoi dy)2 btb - Canh trung binh cua thap dm thung. NoMohmc lc bbP0maxP0tP0ttb bNoMo lnhmP0maxP0tP0t45P0min0(M ln) 0h0 h0bngLtShare-connect.blogspot.com 20T.S. Nguyn nh tin b mn c hoc t nn mng NoMohmc lc bb0nglnglbngh00maxp pbtb = bc + h0 ( nu bc + 2h0 b ) hoc = 2b bc + ( nu bc + 2h0 > b ) b.2. Tnh ton cng trn tit din ng:Githitsphng:Bnmnglbnconson ngm ti mp ct (c lp theo hai phng). -iukinphhoidncabtngvngchu nn: h0trb .nR 4 , 0ngM (t xy ra thng khng cn tnh iu kin ny) - Tnh ton ct thp vng chu ko: + Theo phng l chiu di conson l lng 22max 01.2.2.2ngng ongnngl bpbl P PM =+= 09 0 haRlngMlaF, + Theo phng b, tng t : 0 a2ng0 abng bah R 9 , 02 / b . l . ph R 9 , 0 MF = =Chn thp, b tr v kim tra hm lng trong khong hp l. = 0h baF.thc = 0,15 0,4% (hay theo kinh nghim a = 70 200) Bc 9: Cac tinh toan khac nhu kim tra kha nng truot ngang, n dinh tng th, tinhtoan c kt cua nn tuy tung truong hop moi phai kim tra cac diu kin nay. Bc 10: Cu to mng- B tr ct thp, bc mng (nu c). - Ct ch. - Ging (nu c). - Khe ln (nu c). Bc 11: Bn v, bao gm:- Mt bng mng nng. - Cc chi tit mng nng. - Thng k vt liu. - Cc ghi ch cn thit. Share-connect.blogspot.com 21T.S. Nguyn nh tin b mn c hoc t nn mng + Trt ngang: Kim tra theo mt trt gi thit hbl0 Q 0 MN0I.3.Cc loi mng tnh theo nguyn l mng cng. I.3.1- Mng khe ln: - Ti trng tnh ton ti y mng: M = M0 + M(N0) M(N0) = N0. e0- C hai trng hp xy ra: +P0min > 0 tnh ton nh phn trn gii thiu. +P0min1 )H s gia mng xy hoc mng b tng vi t Tn t t st cng 0.30 t st do 0.20 t ct t m 0.55 t ct m 0.45 t st cng 0.45 t st do 0.25 t ct cng 0.50 t ct do 0.35 0.75NoMoMNP > 0a)PP < 0b)PP = 0minc)P =+maxNFMWmaxmaxminminPmaxebxoShare-connect.blogspot.com 22T.S. Nguyn nh tin b mn c hoc t nn mng Ko= Tgi x n1 ( n1 [ K ] T ph hoi x n2 (n2>1 )Vi: [K]- h s n nh cho php f - H s ma st t v mng ( xem bng) (Ch : khi tnh p, p0, pgl vn gi thit b qua Q0) + Kim tra lt: Ko= Mgi i vi tm lt gi thit > [K] Mlt I.3.3-Mng tng chn, tng hm: a. Tng chn trng lc: phi k n p lc t ln phn tng (phng php gn ng)- S tnh: Coi tng lm vic nh conson ng. Ni lc N, Q, M c tnh t gi thit bi ton phng. - Phn thn tuong duoc tinh toan theo nguyn ly cu kin nen lch tm. -Phnmongtinhtoantheonguynlymong cungduoituongdnoitrnvoichuykimtra truot ngang va lt (xem phn trn). - Trong do tai trong tac dung gm: Trong luong ban thn tuong. ap luc dt chu dng theo phung ngang. TrongluongcuakhidtGdtheophuong thng dung. b. Tng tng hm chu lc: vic k dn anh huong cua su lam vic khng gian la rtkho gia thit tinh tuong dc lp hay khung kin trong bai toan phng nhu hinh v sau. H1H2H1H2NoMoNoMoTng hmPSn tng hmSn tng trtSn tng trtSn tng hmTng hmBng di tng hay di ctMng bH'/32H'/3H'- Trong giai on thi cng: tu vo phng php thi cng, bin php chng , bo v tngmcstnhphhpviplctltnhhaychng.(xemphntng trong t). GGPPShare-connect.blogspot.com 23T.S. Nguyn nh tin b mn c hoc t nn mng NoG GNu hm tng i cng Thay hm hmt = 2 13132h h +khi tnh sc chu ti ca nn Rv p l p lc tnh. Lc s tnh l tng conson hay tng gi cc v tr chng v ngm ti mng - Trong giai on s dng: s tnh tng l tng gi hoc ngm ti sn trt v ngm ti mng chu p lc t v ti trng s dng. Trng hp tng hm l tng chn khung chu lc th tnh ton tng chu p lc t theo s gn ng l dm lin tc c b rng 1m ti 3 v tr (H/3, 2H/3, H - xem hnh v trn) v gi ti v tr cc ct. Sau b tr thp theo kt qu tnh ton cho 3 on tng H/3. Trng hp c nhiu tng hm th phng ng ca tng c tnh ton theo s gi ln cc sn trung gian ca tng hm. Nhiu trng hp phng n tng hm kt hpmng b c hiu qu kinh t ln, ngay c khi ti trng cng trnh ln. I.3.4. Mng chu ko Tnh ton gn ng coi rng mt trt ( do ko ln) nghing i vi phng thng ng gc = 0 . V d vi = 0 + Lc gi:G , G , C ms = ..z.tg Tms = 2(1+b).hm.ms(z = hm/2) + Lc ko: N0 h s an ton chu ko k = lckogi lc>[K] I.3.5. Mng di nhiu ct -Vigithitmngcng,titrngtnhtonti y mng: N = N01 + N02 + trng lng mng + t ph lp M = N01.e1+ N02.e2 + M01 + M02 p lc di y mng: FNFNpni =10 + tb.hm pmax,min = WMp Cacbuoctinhtoansaudogingmongduoict,tuong.Khikimtrachiucaovact thep trong mong thi cn cu vao cu tao vi tri cac ct ma co so d tinh toan phu hop. No1Mo1NMNM1 2bLe1 e2hmNo2Mo2Share-connect.blogspot.com 24T.S. Nguyn nh tin b mn c hoc t nn mng V d o hnh trn c 2 ct 1 v 2 - Theo phuong b rng b: So d tinh vn la ban conson ngam tai mep ct (s ly gia tri Mng lon d tinh Fa ) - Theo phuong dai l: dm don gian co mut thua, gi ln 2 ct. Mgi, Mnhip Fa (co th b tri 1 hoc 2 lop luoi thep) hmNu Mnhp , L' nhhmNu Mnhp , L' lnM giM nhpb.Pmaxb.PminAAL'A-AA-AShare-connect.blogspot.com 25T.S. Nguyn nh tin b mn c hoc t nn mng Luyn tp-chng 1 Mng nng cng A. Phn l thuyt. 1 Phn bit mong nng cung va mm (yu cu v hinh minh hoa). Tu do cho bit ni dung tinh toan khac nhau o buoc nao? 2 Cac yu cu cu tao co ban di voi mong nng loai cung duoi tuong, ct (yu cu v hinh). Giai thich tai sao co cac yu cu do. 3 Trinh bay cac tai liu cn thit trong thit k nn va mong. 4a/Trinhbaynidungkimtrakichthuocdaymongbngduoituong,trongtruong hop tai trong ngang nho. b/ tuong tu nhu trn voi mong don duoi ct. 5Trinhbaynidungkimtrakichthuocdaymongnngcungtrongtruonghoptai trong ngang lon. 6Nhu trn trong truong hop lch tm dang k. 7a/Trinhbaynidungtinhtoankimtrachiucao,cttheptrongmongnngduoi tuong. b/ Nhu trn di voi mong don duoi ct 8 Trinh bay ni dung tinh toan n dinh cua tuong chn dt (trong giai doan su dung). B. Phn bi tp: 1) Chn su chn mng hm v xc nh kch thc y mng hp l ca mng bngdi tng (di 20m), chu lc N0 =30 T/m, M0 = 2,5 Tm/m, Q0 = 0,5T/m. Cho bit: ln cho php Sgh = 10cmNn t gm 2 lp: -Lp trn l loi st pha c st B=1,18, =1,75 T/m3, dy 1,6m -Lp di l ct nh c cng khng xuyn trung bnh l qc = 560T/m2 v h s n ngang 0 = 0,3. (T chn s an ton). 2) Chnchiusuchnmngvxcnhkchthcymngbnghpltheoiukinscchuticalpt2vihsantonl2.Chobit:Titrngditng N0=30 T/m, M=2,5Tm/m, Q=0,5 T/m. Nn gm 2 lp: Lptrn:dy3,4mtloidnhWnh=48%,Wd=22%,W=26%,=1,82T/m3,=20o, C=2,8 T/m2. Lp di: Wnh=32%, Wd=26%, W=30%, =14o, C=2,8 T/m2, =1,76T/m3 3) Kim tra kch thc chiu cao v ct thp trong mng bng di tng chu lc b tngct thp. Bit: -Tng dy 20cm, chu ti N0=30 T, M0=2,5 Tm, Q0=0,5 T. -Mng: + Mc btng 250 Share-connect.blogspot.com 26T.S. Nguyn nh tin b mn c hoc t nn mng + b x h = 2 x 0,4m, chiu di L = 20m. + Ct thp (Fa) gm 1012/m, Ra = 27000T/m2. + Lp bo v ct thp dy mng 5cm. 4) - Xc nh chiu cao v ct thp hp l cho mng n di ct (20x20cm), chu ti N0= 60 T/m, M0 = 8 Tm/m, Q0 = 3 T/m. Bit: + Mng chn su 1,5m.+ Mc btn 250.+ Lp lt bng btn ngho 100# dy 100mm.+ Lp bo v ct y: 5,0cm.+ Kch thc y mng 1,5 x2,0m.- Hy v chi tit cu to mng. Share-connect.blogspot.com 27T.S. Nguyn nh tin b mn c hoc t nn mng I.4- Mng mm I.4.1.Khi nim, phn loi:- Cc mng c cng hu hn di tc dng ca ti trng bin dng mng ng k ng sut di y mng khc tuyn tnh. Khi cng ca mng i vi t t = ( )1h . E2l. E3b30>hay t =1h . EB . L . E3b20>th coi l mng dm, bn mm Trong : Eb - m un n hi ca b tng E0 - m un bin dng ca t- C th gp:+ Mng bng di hng ct ( bng dc hay giao nhau ) + Mng bn di hng ct, y b, u tu, thuyn ... l cc loi mng mm. - Phn loi:+ Mng dng dm n ) 7 ( bl:i) Dm di, ngn ii) Dm cng, mm+ Mng dm giao nhau gm bng dc + ngang + Mng dng bn) 7 (