, . . 3.1.
. 3.1.
, :
q = p * lp + g * lp + g = 2600*1 + 0,011*7850*1 + 30 = 2716,4 /;
q ;
lp , (lp = 1 );
g (g = t * γ);
γ (γ = 7850 /3);
g ( g = 30 /).
q = p * lp * γf + γf * (g * lp + g) = 2600*1*1,1 + 1,05*(0,011*7850*1 + 30) = 2982,2 /;
q ;
γf .
Mmax Qmax:
Mmax = q * l2 / 8 = 2982,2 * 3,52 / 8 = 4566,5 *;
Qmax = q * l / 2 = 2982,2 * 3,5 / 2 = 5218,9 .
Wx:
Wx = Mmax / (Ry * γc) = 4566,5 / (25*106*1) = 182,7 10-63 = 182,7 3;
Ru (Ru=25*106 /2);
γc (γc=1).
20 8239-89: h=20 , b=10, s=0,52 , t=0,84 , r1=0,95 , r2=0,4 , =26,8 2, =21 /, I=1840 4, W=184 3, S=104 3.
, :
q = p * lp + g * lp + g = 2600*1 + 0,011*7850*1 + 21 = 2707,4 /;
q = p * lp * γf + γf * (g * lp + g) = 2600*1*1,1 + 1,05*(0,011*7850*1 + 21) = 2972,7 /.
Mmax Qmax:
Mmax = q * l2 / 8 = 2972,7 * 3,52 / 8 = 4551,9 *;
Qmax = q * l / 2 = 2972,7 * 3,5 / 2 = 5202,2 .
I II :
σmax = Mmax / Wx ≤ Ry * γc;
σmax ;
Wx - ;
σmax = 4551,9 / 184*10-6 = 24,7*106 ≤ 25*106*1 = 25*106 /2;
.
τmax = Qmax * S / (I * δ) ≤ R * γc;
τmax ;
S ;
I ;
δ ;
R (Ru=14,5*106 /2);
τmax = 5202,2 * 104*10-6 / (1840*10-8 * 0,52*10-2) = 5,65*106 ≤ 14,5*106*1 = 14,5*106 /2;
.
. , .
. .
:
fmax = 5/384 * q * l4 / (E * I) ≤ [f] = l / 250;
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fmax ;
E (E=21*109 /2);
[f] ;
f = 5/384 * 2707,4 * 3,54 / (21*109 * 1840*10-8) = 0,0137 ≤ 3,5/250 = 0,014 ;
.