Introd. Ã s pontes de concreto - Engenhariaconcursos.com.br
Introd. Ã s pontes de concreto - Engenhariaconcursos.com.br
Introd. Ã s pontes de concreto - Engenhariaconcursos.com.br
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42<<strong>br</strong> />
Cap. 2 Ações nas Pontes<<strong>br</strong> />
T 0 ε 0<<strong>br</strong> />
T(y)<<strong>br</strong> />
T<<strong>br</strong> />
y<<strong>br</strong> />
h<<strong>br</strong> />
Δ ε(y)<<strong>br</strong> />
ε<<strong>br</strong> />
T u<<strong>br</strong> />
ΔT<<strong>br</strong> />
ε<<strong>br</strong> />
u<<strong>br</strong> />
Temperatura Deformação<<strong>br</strong> />
Fig. 2.21 Linearização da temperatura e das <strong>de</strong>formações.<<strong>br</strong> />
Como não existe força normal e momento fletor aplicados, as tensões normais são autoequili<strong>br</strong>adas,<<strong>br</strong> />
<strong>com</strong>o indica as expressões 2.8 e 2.9.<<strong>br</strong> />
N = ∫ σT (y).dA = 0<<strong>br</strong> />
(2.8)<<strong>br</strong> />
M = ∫ σT (y).y.dA = 0<<strong>br</strong> />
(2.9)<<strong>br</strong> />
Com base no esquema da Fig. 2.21, po<strong>de</strong>-se colocar as <strong>de</strong>formações na seguinte forma:<<strong>br</strong> />
ε0 = α.T 0<<strong>br</strong> />
(2.10)<<strong>br</strong> />
εu<<strong>br</strong> />
= α. Tu (2.11)<<strong>br</strong> />
⎡ ⎛ ΔT<<strong>br</strong> />
⎞⎤<<strong>br</strong> />
Δε( y) = −α⎢T(y)<<strong>br</strong> />
− ⎜Tu + y⎟⎥<<strong>br</strong> />
(2.12)<<strong>br</strong> />
⎣ ⎝ h ⎠⎦<<strong>br</strong> />
sendo: ΔT = T0<<strong>br</strong> />
−T u<<strong>br</strong> />
α=coeficiente <strong>de</strong> dilatação térmica<<strong>br</strong> />
A partir da lei <strong>de</strong> Hooke, tem-se:<<strong>br</strong> />
⎡⎛<<strong>br</strong> />
ΔT<<strong>br</strong> />
⎞ ⎤<<strong>br</strong> />
σ<<strong>br</strong> />
T<<strong>br</strong> />
( y) = Δε(y).E<<strong>br</strong> />
= ⎢⎜Tu<<strong>br</strong> />
+ y⎟ − T(y) . α.E<<strong>br</strong> />
h ⎥ (2.13)<<strong>br</strong> />
⎣⎝<<strong>br</strong> />
⎠ ⎦<<strong>br</strong> />
sendo:<<strong>br</strong> />
E =<<strong>br</strong> />
módulo <strong>de</strong> elasticida<strong>de</strong><<strong>br</strong> />
Substituindo a expressão (2.13) nas expressões (2.8) e (2.9), resulta:<<strong>br</strong> />
1<<strong>br</strong> />
T u<<strong>br</strong> />
= ∫T<<strong>br</strong> />
∫ y .y. dA<<strong>br</strong> />
(2.14)<<strong>br</strong> />
A I<<strong>br</strong> />
y<<strong>br</strong> />
( y) .dA − T( )