, , , :
;
, , .
2.4. M, Q, N (. 2.5, ).
. (. 2.5, ). RB (. 2.5, ), BC:
S MC ( BC ) = 0; _ RB = ql /2.
(. 2.5, ):
S X ( BC )= 0; _ XC = ql /2;
S Y ( BC ) = 0; _ YC = ql.
3-2 , 2, XC, YC ( 5-3 2.3 . 2.5, ).
AC BC, : XC = X¢C ; YC = Y ¢ C. 3-4 4-5 , 1-2 2-3 2.3 (. 2.5, ).
, C 2-3 3-4 qy, M Q, qx, N = const.
. 2.5
(. 2.5, ) , (. 2.5, ).
, , , , 2.4. , , .
2.5. (. 2.6, ).
. (. 2.6, ):
S MB = 0; _ YA = ql /4;
S MC ( A ) = 0; _ XA = ql /4;
S X = 0; _ XB = 3 ql /4;
S Y = 0; _ YB = ql /4.
:
S MC ( ) = XB × l YB × l ql × l /2 = 3 ql 2/4 ql 2/4 ql 2/2 = 0.
. 2.6
1-2 , 2. . , M , M = ql 2/4 C, 4.
M , 4 XB, YB. , 4- ( . 2.6, ) .
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Q N (. 2.6, , ).
(. 2.6, ).
, , ( ) .
, , .
, - : M = 0, Q = 0, N ¹ 0.
, , N.
.
: , , : , .
, , .
, :
S M 1 = 0; S M 2 = 0; S M 3 = 0,
, , , :
S M 1 = 0; S M 2 = 0; S Y = 0,
Oy .
, , , , - .
, .
2.6. (. 2.7, ).
3 P |
3 P |
. 2.7
. :
S M = 0; _ RB = 2 P;
S MB = 0; _ RA = P.
:
S Y = RA + RB - 3 P = 0.
N 2-3 N 2-4 I-I (. 2.7, ) , . RA : N 2-4, N 2-3 N 1-3 (. 2.7, ).
N 2-4 S M 3() =0, , N 2-3 N 1-3:
- RA × d - N 2-4 × d = 0; _ N 2-4 = - RA = - P.
2-4 3-5 , N 2-3 :
S Y () = RA - N 2-3 = 0; _ N 2-3 = RA = P.
3-4 II-II, (. 2.7, ) , (. 2.7, ):
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S Y () = RA + N 3-4×sin45 = 0; _ N 3-4 = - RA / sin45 = - P × .
, , :
S Y () = R - 3 P + N 4-3×sin45 = 0; _ N 4-3 = N 3-4 = - P × .
: , .
:
S X = 0, S Y = 0,
, .
, , , .
2.7. (. 2.7, ), .
. 1- , RA, N 1-2 N 1-3 , (. 2.7, , ):
S Y = RA + N 1-2 ×sin45 = 0; _ N 1-2 = - P × ;
S X = N 1-2 ×cos45 + N 1-3 = 0; _ N 1-3 = P.
2- , N 2-4 N 2-3 N 2-1 = N 1-2 (. 2.7, ):
S X = - N 2-1 ×cos45 + N 2-4 = 0; _ N 2-4 = - P;
, , 3- , N 3-1 = N 1-3 N 3-2 = N 2-3, N 3-4 N 3-5 (. 2.7, ), :
S Y = N 3-2 + N 3-4×sin45 = 0; _ N 3-4 = - P × .
N 2-4, N 2-3 N 3-4 , 2.6. N 3-5:
S X = - N 3-1 + N 3-4×cos45+ N 3-5 = 0; _ N 3-5 = 2 P.
, 4 5, N 4-5, N 4-6 N 5-6.
, 5- N 5-6 , , 6- , , :
S X = - N 6-4 ×cos45 - N 6-5 = 0;
S Y = N 6-4 ×sin45 + R = 0.
, .
. , . (1.3):
W * = 2Ӗ = 0,
- , , - , .
, , .
1. , .
2. .
3. , .
4. , , , , .
4. , , , , .
5. , . , .
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1. , , .
2. , .
3. , .
, .
2.7. (. 2.8, ).
. 2.8
. , , (1.2.4). :
S M = 0; _ VA = /2;
S MB = 0; _ V = - /2;
S MC ( AC ) = 0; _ HA = /2;
S X = 0; _ HB = /2.
, .
, 3- , , N 2-3 = 0 ( 3), 3. N 2-1 = N 2-4 = 0 ( 1) .
, 5- , , N 5-6 = 0 ( 3), 5. N 6-7 = 0, 4-6 6- 4- . , 1-4 4-7, 4, (. 2.8, ). 4- , :
N 4-1 = - ( × )/2;
N 4-7 = ( × )/2.
, N 4-2 = N 2-4 = 0, N 4-3 = N 4-1 = - ( × )/2.
, , (. 2.9, ).
, , , .
l , f, .
, , , (. 2.9, ).
( 2.5) ( 2.7):
S M = 0; _ V = (1/ l) S Pi ai ;
S M = 0; _ V =(1/ l) S Pi (l - ai);
S X = 0; _ HA = HB = H;
S MC ( A ) = 0; _ H = HA = (1/ f)[ V ×(l /2) -S Pi (l /2 - ai)].
, , , (. 2.9, ). , :
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V = V; V = V,
:
H = M / f , (2.1)
M = [ V ×(l /2) -S Pi ×(l /2 - ai)] - , x = l /2 .
, , .
, (. 2.9, ) y = f (x) , . .
.2.9
t N n Q, j , t . ( 2.2.1) , , , . .
:
S MC ( A ) = 0; _ M (x) = [ V × x -S Pi (x - ai)] - H × f (x),
:
M (x) = M () - H × f (x), (2.2)
M () = [ V × x -S Pi ×(x - ai)] - x.
, H × f (x), . 2.9, , .
. , , 1/100. , .
:
S n() = 0;_ Q (x) = (V -S Pi)×cosj - H ×sinj,
,
Q (x) = Q (x)×cosj - H ×sinj, (2.3)
Q (x) = V -S Pi - .
, .
:
S t() = 0;_ N (x) = - [(V -S Pi)× sinj + H ×cosj].
:
N (x) = - [ Q (x)×sinj + H ×cosj]. (2.4)
, , , (2.1), fC / l.
, , , : M, Q N.
(2.2) , , .
. , .
l fC q (x).
, (2.2). M (x) = 0, :
M () - H × f (x) = 0,
:
y = f (x) = M ()/ H.
, :
M () = (ql /2)× x - qx 2/2,
, (2.1) H = / f = (ql 2)/(8 f), , :
y = f (x) = (4 f / l 2)×(xl - x 2).
, .
1. , , , 1.3, , (1.10), . , , .
.
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2. , , , .
3. , s. , , , .