- Van IOC gio toi han Kiem tra :
CHUONG 2 MO HINH HOA VA PHAN TICH DAO DONG
CAU DAY VANG THEO PHI/ONG PHAP PHAN TLTHLX HAN
2.1. Gidi thieu chung
Trong phan tfch tmh va dgng luc ket cau cfiu day vang, can thiei phai ly tudns hoa ket cau thue te theo mot each thue md hinh nao đ, ggi chung la md hinh hoa ket caụ Xay dung md hinh ket cau rdi rac phan nhd ket cau thanh cac phdn lu nhd cae niit, cac phuang trinh can bang luc va ehuyen vi xae dinh tai cae niit phan ehiạ Trone cac phuang phap md hinh rdi rac hoa thudng dung trong tfnh loan ket cau thi phuang phap phan tu hCrii han (f^HHj duge ap dung pho bien. rung rai nhai trong tfnh loan kei eau do Ihfch hgp vai lap irinh tren may tfnh, thuan Igi va hieu qua trong giai quyet cae bai loan phan tfch iTnh va dgng lire, kel cau Idn vdi nhieu an sd va lam vice phuc lap.
Md hinh ket cau cau day vang phai phu hgp vai su lam vice cua ket cau thue te, cii the la can bao ton cac dae diem hinh hgc va ca hgc ciia ket cau thue lẹ Co hai dang
md hinh: md hinh tdng the va md hinh cue bg. Vdi mo hinh long the ihdng ihirdng co
hai each xa>' dimg md hinh la md hinh phang va md hinh khdng gian. Trong xay dimg md hinh ket cau cau day vang thudng ap dung cac loai phan tu nhu phan tu thanh khdng gian. [•)han tir dam, phan tii dan va phfin lu Uim ban, xac dinh ehu\ en \ i mil \ a luc nut ciia cac loai phan tu tren the hien tren hinh 2.1.
Trong ehuong nay se trinh ba\' ve each thue md hinh hoa kei cau can day vang theo phirong phap I^FIH phuc vu phan tfch dao dgng rieng ciia kei eau eau da> vang. Vice mo hinh hoa ket cau eau dav \'ang can thiet dua tren nghien emi \e eau tao \a su
lam \'iee eiia eae bd phan kei caụ Chirane na\ eune se nehien euu co so Iv ihu\et phan
ifeh dao dong rieng iheo phuong phap PTMH de ed the sir dung eae kel qua dao dgng
2.2. Cau tao so bd cac bd phan cau day vang
Sa do kit cau: Ket cau cau day vang rat da dang ve cau tao tii bd trf so đ ket
cau (hai nhip, ba nhip hay nhieu nhip, đi xiing hay khong đi xung), each bd tri dav tren col thap (bd tri day đng quy, bd trf song song hay bd tri re quat), .so lugne mat phang day (bd trf mot mat phang hay hai mat phang day) (hinh 2.2).
Can too dam círng: Dam cung la bg phan cau lao rat quan trgng cua kei cau cau
day vang. Cau tao dam cung phu thugc nhieu vao sd lugng mat phdng day, chieu rone mat caụ Phan biet cau lao dam cung theo vat lieu be tdng hoae thep hoae vat lieu hdn hgp thep - be tong. Theo cau tao cd cac dang dam cirng pho bien nhu sau: dane dam ban. dang dam I thep, dang dam ehu n , dang dam dam hop, dang dan ciimg (hinh 2.3).
Cau tao cot thap: Cau tao va hinh dang cua cot thap phu thugc vao sd lugne mat
phang day, eau lao lien kel vdi dam, chi6u eao ciia col thap va anh hudng Kin ldi do cirng chung ciia ca he ihdng. Theo cau tao cd cae dang cot thap pho bien nhu sau: dang cot thap dan, dang cot thap hinh chiJ H, dang col thap hinh ehu A va dang egi thap hinh chfr Y ngirgc (hinh 2.4).
Cau tao day rang: Cac bd day vang thudng cau lao d hai dang pho bien sau: bd
cap sai dat sone sone, bd cap tao dat sone sonẹ Ve dae trune co hoc vat lieu, cd the* xem cac bd cap cau day vang chi cd kha nang ehiu keo, khdng ehiu nen \ a udn.
Cau tao lien ket va ^oi: Lien ket bien tai vi trf cot thap thudne cd cae dane: lien
O . . . I s — . ^
ket cirne eiCra cot va dam, edi di đne, edi cd dinh, khdne cd edi, trone khi lien ket edi eiia dam tai md cau va cac Iru neo thudng la cd cau tao chong nhd.
2.3. .Mo hinh ket cau cau day vang theo phúong phap PTHH 2.3.1. Md hinh dam ciirng
Md hinh dam cung theo cac phan lir thanh khdng gian dan hdị Cae diem mil tren mo hinh xae dinh phan tu la eae diein dae trung tren dani nhu eae mil treo day
25
vang. cac mil lien kel, cac mil cd sir thay doi dae trung liet dien... Tuv theo dane cau tao cua dam cCmg va yeu cau tfnh loan, cd nhieu each xay dung mo hinh tdne thé cua dam
Ph;in tu thanh dJn Phan lij Ihanh dam 5
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Phan lif ihanh kh6ng gian Phan lii tam
Hinh 2.1. Mdi sd loai phan tu thanh thudne dune trone md hinh boa eau dav \ani:
K c i cau c^u d^y v,ing 3 nhip
d.U dong quy
KOt cau c;Ui da\ dav soni! sonc
KOt cau »;.iu dav \An<2 ?• nhip
d.^y re ijuat
O . i i i ^ J J in hítp J i i n - C l u flJi C h j > | Q u j n g N m h )
Í).iiig J.I111 hi^p n h i i i u n g . i n - C J U C u n T h ^
ninh 2.3. Cau lao dam eirne eau dav vane
( 0 1 I M i • I . '
- 2 7 -
cung ph6 bien nhu sau: mo hinh phang chap hay md hinh phdng khdng chap, md hinh khong gian mgl true dam trung tam, md hinh khong gian hai triic dam. md hinh khone gian mang dam phdng va mo hinh khdng gian chi tiet (hinh 2.5) [34], [35], [36 ]
Cac dae trung vat lieu va hinh hgc bao gdm md dun dan hdi udn (E), mo dun cat (G) va dae trung hinh hgc cua cac nhdm phan tu gdm dien iich cua liet dien (A), dien
lich cat cd hieu ciia tiet dien(A2, A3), md men quan tfnh udn (L., lyy), hang sd xodn [i)
xac dinh theo cac eong thue thong thudng. Tuy nhien su phue tap la viec xac dinh đ ciimg xoan ciia tiet dien. Do cung xodn phu thugc cau tao hinh dang ciia mat edl dam va dam ehiu tac diing cua dang xoan nao: xoan thuan tuy (xodn St Vemanl). dang xodn eudng bue hay xoan bien dang. Mot sd eong thue riit ggn tfnh loan hdng sd xodn tuong duane (J,,) ) vdi mot so dang mat edl dugc trinh bay trong [34], [36].
Uanihui^ui
Dundi/r^a O j n i t h / ^
nsiiiUoilid Clfiiihuhi Ufiuhahu
i i i \ viuTai
Riui tu djs \'ait:
N b hinh true dim irupi! lam
F h f i i i /
R u n i a
lien kLi ^citei
Nb hinh lhL"o hu dini
RVui [\J
i h i n h k h T ^ a . i n
fhuru
Nb hinh iheo rruns dini
di\ v.ut;
Riiniu
Hinh 2.5. Cach thire mo hinh tone the dam cung
2.3.2. M d hinh cot thap
Cot thap diroe md hinh ihanh nhieu phan lU thanh khdng gian dan hdị eae diem
mil ndi, cae nut cd su thay doi liet dien mat cdt ngang va cac mil bien lien ket... Cac dae trung vat lieu gdm md dun dan hdi udn (E), mo dun cat (G) va dae trung hinh hgc eiia cac nhdm phan tu gdm dien tfch (A), dien tfch cdt (A2, Â ), mo men quan tfnh udn (Ị.. I33), hdng sd xodn (J) xac dinh theo cac eong thiic theo dang mat cdt tiet dien.
2.3.3, Mo hinh day vang
Mo hinh sir lam viec cua cac day vang nhu phan tu dan dan hdi xac dinh qua hai mil: nut tren cot thap va mil tai dam. Cac dae trung ciia cac phan tu day vang gdm md dun dan hdi (E) va dien tfch tiet dien (A). Khi xet tdi anh hudng cua do vong ciia cac day vang va luc cang trong cac day vang tdi mo dun dan hdi Young, cd the dua vao tfnh loan vai md dun dan hdi tuong duang ciia cap vang ( md dun dan hdi Ernst )[]]. [3]. Mo dun dan hdi tuong ducmg ciia cap vang phu thugc vao chieu dai day, lire cang trong day, trgng lucmg ban than eiia day vang.
Md dun dan hdi luang duong theo tiep luyen
1 1 y f-
TC
Etj.. E 1 2 a ;
(2.3.3.0
Md dun dan hdi tuone duone theo cat lu\en