Finite Dif Tut B
Finite Dif Tut B
Finite Dif Tut B
1.
For the beam shown in Fig. 1 find the slope and deflection at mid-span of the beam. Use four divisions
and five nodes. The flexural rigidity of the beam is EI.
2p
p
Fig. 1
2.
The stepped cantilever beam in Fig. 2 is of length L. Find the deflection of the free end using four
divisions and five nodes. Compare your answer with the exact value: 3PL3/16EI.
NOTE At an abrupt change of cross-section the effective flexural rigidity (EI)eff is given by
1/(EI)eff = 0.5{1/(EI)left + 1/(EI)right}. This is because the curvature 1/R = M/EI must be the same. Using
the average flexural rigidity 0.5{(EI)left + (EI)right} does not guarantee this.
P
2EI EI
Fig. 2
3.
Determine the deflection, bending moment and end support reactions for the beam of fexural rigidity
EI below. The beam sits on an elastic foundation beteen simple supports. The foundation modulus k is
equal to 0.1024EI/4 where = L/4. Use four equal divisions and symmetry to reduce the amount of
work.
Ans. The mid-span deflection and bending moment are 0.0102qL4/EI and 0.0978qL2 respectively. The
end reaction is 0.414qL.
4.
Find the deflection upward of the simply-supported beam of flexural rigidity EI shown below. Use five
equal divisions. Compare your answer with the exact values: y 1 = 0 y2 = 320L2/EI y 3 = 560L2/EI
y 4 = 640L2/EI y5 = 480L2/EI y6 = 0 all multiplied by 10-4.
1
Fig.4
L
5.
Find the rotation at end A of the beam of flexural rigidity EI shown below. Use four equal divisions.
Compare your answer with the exact value L/4EI.
1
A B Fig.5
6.
Find the deflection and bending moment at midspan of the beam-column of flexural rigidity EI shown
below. The magnitude of the axial load P is 0.3PE where PE is the critical buckling load. Use six equal
divisions. Compare your answer with the exact values: y3 = 1.420WL3/(48EI) M3 = 1.350WL/(4EI)
W
P = = P Fig.6
7.
Using four equal divisions find the end-moment at B in the beam-column shown in Fig. & below.
Ans. MB = 0.342PL
9EI A B
P= Fig.7
L2 EI 1.5EI
L/2 L/2