- Bi~u db giarn ap h,rc do "tac d\ffig" h,rc dinh C clla ddt gay ra: Bi~u db co dl;\llgchCinh~t va co trj s6 am (chi~u ap h,rc di ra kh6i tuOng) (Hinh 3.11 c). chCinh~t va co trj s6 am (chi~u ap h,rc di ra kh6i tuOng) (Hinh 3.11 c).
- Bi~u db ap h,rc do tac d\lng clla tai tn;mg q gay ra co dl;lng chCi nh~t (Hinh3.11b). 3.11b).
- Bi~u db ap h,rc t6ng co th~ co dl;lng hinh thang hay tam giac nhu hinh (3.lle)ho~c (3. 11g). ho~c (3. 11g).
N~u q =0 thi tl;lid(l sau He tinh theo cong thuc (3.35) bi~u db ap h,rc t6ng se co trj s6 b~ng khong.
,,,,, ,,,, "" " Ho~e ., e,q~q1..., ~ a- b- e- d- e- g-
Hinh 3.11. Bi8u db lip h!e ddt eM d(ing eua ddt dfnh co tiii tr9ng phiin b6 d@uben tren
Cuemg d(l phan b6 cua ap h,rc do C (ecc) vii q (ecq) gay ra tinh theo cac cong thuc sau:
ecc=2C Pc ecq = /"cq
Pc - H~ s6 ap h,rc d<ltcM d(lng do anh huemg cua l\ic dinh C
(3-34)(3-35) (3-35)
(3-36)
Ngoili ra co th~ dung phuang phap c(lng c(lt d<ltd~ ve bi~u dbap h,rc (Xem Hinh 3.12). --- ---t--- :i' ---~~~----~ ---) , 0 1 --- ---r--- ~ q -::r: :\ ::c , " ...7 I\ yA"Hn I 1 ,I y1...,Htt I a - Khi Hq>H, b - Khi H,>Hq
(3-37)- Bi~n d6i tac dl,mg cua IlJc diOO C cua dih thimh mQt tAng ddt co cling y, <pvai - Bi~n d6i tac dl,mg cua IlJc diOO C cua dih thimh mQt tAng ddt co cling y, <pvai ddt thlJc b~ng cach: Tu6ng tuQ'l1gboc di ffiQt lap ddt co chi~u day He. He duqc tiOO theo c6ng thuc: H, = 2C tg(450 +<r» y. 2 b . ... a- b- c-
Hinh 3.13. Bibu db ap h,rc d,llxongang do tai tn,mg t~p trung P tac dung len tuimg ch~n dfrt
(3-39)
O,lP
epmax. = b
- Bi~n d6i tac dl,mg cua IlJc q thaOO mQt lap ddt d~p them ben tren ding cocung y,<p vai ddt thlJc b~ng cach: Tu6ng tuQ'l1gd~p them mQt lap ddt co chi~u day cung y,<p vai ddt thlJc b~ng cach: Tu6ng tuQ'l1gd~p them mQt lap ddt co chi~u day Hq. Hq duqc tiOOtheo c6ng thuc (3-38).
H =.9. (3-38)
q y
- TiOOchi~u day lap ddt tinh toan cu6i cling H,,: H" =H +Hq -HeKhi co H" ta ti~n haOOve bi~u db OOuve bi~u db v6i ddt riJi Khi co H" ta ti~n haOOve bi~u db OOuve bi~u db v6i ddt riJi
Khi H" :<; H, mc Hq< He thi bi~u db co d1;lngtam giac (HiOO 3.12b), Khi H" >
H,tuc Hq>He thi bi~u db co d1;lnghiOOthang (HiOO 3.12a)Khi q = 0 thi Hq = 0, khi ddt la ddt rai thi He = 0 Khi q = 0 thi Hq = 0, khi ddt la ddt rai thi He = 0
* Ap lyc xo ngang len tuimg chan do ted tr9ng tqp trung P tren mgt ddt
Khi co tai tn:mg t~p trung P tren m~t ddt va cach mep tuang mQt do::m b (HiOO 3.13). Bi~u db phiin b6 ap IlJc do P tac dl,lng len lung
tuang theo thlJc nghi~m co d1;lng
duang cong (HiOO 3J3b), OOung d~ :c
don gian co th~ xem la d1;lngduang th~ng (HiOO 3.13c).
Tri s6 16n OOdt cua bi~u db (epmax) la t1;livi tri z =b va duqc tiOO gAn dung theo c6ng thuc sau:
5. Tinh toan ap h,rc ddt hi d6ng (Eb)
Bi~u db ap h,re bi dQng ella diit dinh eo d~g, eong thUe tinh eae tri s6 ap h,re tuang 1\I bi~u db ap Ive ehu dQng, no la t6ng eua 3 bi~u db: Bi~u db ap IVe do diit fai, bi~u db do tae d\ffig eua Ive dinh C va bi~u db do tae d\ffigeua tai tn;mg q (Hinh 3.14).
N~udUng bi~u db ap Ive dftt ehu dQng d~ ve bi~u db ap Ive dftt bi dQng thi ehi dn thay 2 di~rn sau:
- Bi~u db ap Ive do tae d\ffig eua h,redinh C eua ap Ive ehu dQng eo dftu am eon eua ap IVe dfttbi dQng eo dftu duang, tue ehi~u di vao phia tuang, nen ta ehi dn dbi ehi~u eua eeese thanh ebe'Cong thue tinh ap Ive t6ng thay dftu eua tri s6 eectir dftu tm thanh dftu eQng se thanh ebc'
q
'.
..
ebq=qAb eb,=2CI'J, y,,"H qAb+2C[3,,+y,,"H
+-++-+ I I I I
a- b- c- d- e-
Hinh 3.14. Bibu db liph,rcdil bi d(ingcua dil dinhcoIii Ir9ng philn b6 dbu ben Iren
- Thay eae h~ s6 Ac,~e b~ng Ab,~btrong tftt ea eae eong thue tinh toan Clfang dQ phan b6 eua eae ap Ive thanh phftn.
eb~=YAbZ (3-40)
ebe=2C ~b (3-41)
ebq= Abq (3-42)
Ab- H~ s6 ap Ive dfttbi dQngdo anh huang eua goe rna sat trong <p
~b - H~ s6 ap Ive dftt bi dQngdo anh huang eua Ive dinh C CaeMs6 Ab,~btinh theo eae eong thue sau:
(3-44)
Bi6u d6 t6ng ap h,re bi d(\ng eua d~t rai vii co q =0 co d(lng tam giae. Con I(li tM eil cae dl;mgkhae, bi6u d6 t6ng ap h,re bi d(\ng baa gia cling co d(lilg hinh thang.
Ta cling co th6 dung phuang philp e(\ng e(\t d~t d6 tinh toan eho ap h,re d~t bi d(\ng.
3,2.5. Lvc dQng
* Tr<;mgluqng tieu ehu~n xe hO'icae cfrp Iii H-8, H-IO, H-13 ...(eae 568, 10, 13... chi trong luqng xe tinh b~ng T~n).
* Trong luqng tieu ehu~n cae 10(lixe cO' gi6i eh(lY b~g banh hO'i Iii T-80 ... hay eh(lY b~ng day xieh Iii T-30, T-60 ...
* Sue n(ing tieu ehu~n b(\ hilnh:
Ll)'e d(\ng b(\ hanh Iii 300 kg/m2 phan b6 trang ph(lm vi 16i di eua nguai. Sue d~y eua nguai vila Ian can Iii75 kg/m.
3.2.6. Trqng luqng ban thiin
Caeh xae dinh trong luqng bim than nhu 5au: Tri 56: P=Yv' V
Trang do:
Yv - Trong Iuqng rieng eua v~t li~u.