. EJ EF .
3.1. (. 3.14, ).
. 3.14
. (3.17) Mp (. 3.14, ) `Mi , (. 3.14, ).
(3.17) . [0 ,l ] Mp , , `Mi [0 ,l ] . : [0, l /2] [ l /2, l ], `Mi (x) . :
v max = D ip = 2 (w1× yc 1)/ EJ = 2 [(2/3)×(l /2)×(ql 2/8)]×[(5/8)×(l /4)] = 5 ql 4/384 EJ.
, q0.
[0 ,l ] (3.21) , Mp `Mi , :
v max = (l /6 EJ)×4(ql 2/8)×(l /4) = ql 4/48 EJ.
, [0 ,l ] f (x) = Mp (x) × `Mi (x) , .
3.2. A - , (. 3.15, ).
P =1 |
M =1 |
P =1 |
. 3.15
. Mp `Mi , A (. 3.15, ).
, Mp `M :
D = (Mp ´ `M ) = (1/ EJ) w1× y 1 + (1/2 EJ) w2× y 2 = (1/ EJ)[(1/3)× l ×(ql 2/2)]×(3/4) l +
+ (1/2 EJ) [ l ×(ql 2/2)]× l = (3/8)(ql 4/ EJ).
:
D = (Mp ´ `M ) = (1/2 EJ) [ l ×(ql 2/2)]×(l /2) = (1/8)(ql 4/ EJ).
:
___________ __
D = Ö (D)2 + (D)2 = (Ö10 ql 4)/8 EJ.
:
q = (Mp ´ `M ) = (1/ EJ) w1×1 + + (1/2 EJ) w2×1 = (1/ EJ)[(1/3)× l ×(ql 2/2)]×1 +
+ (1/2 EJ) [ l ×(ql 2/2)]×1 = (5 ql 3/12 EJ).
, : , .
|
|
3.3. , 2.5, EJ = const (. 2.9, ).
Mi =1 |
. 3.16
. Mp (. 2.9, ) (. 3.16, ), `Mi (. 3.16, ). Mp w = (1/2) × l ×(ql 2/4), `Mi.
Mp w : w1 w2 (. 3.16, ).
, . , , :
q = (Mp ´ Mi) = (1/ EJ) [(3) w× y w× y ] = (1/ EJ) [3w × y +w1 × y 1+
+w2 × y 2] = (1/ EJ) {3 [(1/2) × l ×(ql 2/4) ] × [(2/3)×(1/2)] + [(2/3) × l ×(ql 2/8)] ×
× [(1/2)(1/2+1)] + [(1/2) l (ql 2/4) ] × [(2/3)(1/2) + (1/3) × 1]} = (11 ql 3) / (48 EJ).
3.4. EJ = const, i j , , (. 3.17, ).
. i j .
MP (. 3.17, ), `Mi `Mj , ij (. 3.17, -), Δ i Δ j . i j Δ ij = Δ i Δ j.
, MP `Mij Δ , , `Mij Δ `Mi `Mj (. 3.17, ).
θ ij, MP `Mij θ , i j (. 3.17, ).
, :
Δ ij = (MP ´ `Mij Δ) = (1/ EJ) [ (1/2) ×(l /2)×(Pl /4)] × [(1/3) × ()/4] =
= (1/ EJ) ×(Pl 2/16) × ()/12 = (1/ EJ) ×(Pl 3 )/192;
θ ij = (MP ´ `Mij θ) = (1/ EJ) × ((1/2) ×(l /2)×(Pl /4)) × 1 = (1/ EJ) × (Pl 2/16).
, .
-, , , , .
P |
j |
Pi =1 |
j |
i |
) |
`Mi |
) |
`Mj |
Pj =1 |
i |
) |
Pi =1 |
i |
Pj =1 |
j |
`Mij Δ |
) |
Mi =1 |
j |
Mj =1 |
i |
`Mij θ |
Mk =1 |
´ |
θB |
P |
Ml =1 |
l |
) |
k |
`Mkl θ |
) |
ΔB |
j |
P |
) |
i |
MP |
Pl/ 4 |
) |
j |
i |
l/ 2 |
l/ 2 |
|
|
. 3.17
-, , , , . , , k l, (. 3.17, ). k l , `Mkl θ , θ kl = (M ´ `Mkl θ) .
, j, Δ iP θ iP B (. 3.17, ).