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Unformatted text preview: CIVL 232 Design of Structural Concrete
Assignment 2: Singly reinforced sections in bending; moment redistribution
Assigned: Thursday, 2 March 2006
Due date: Thursday, 9 March 2006
2.1 (a) Describe the failure characteristics of underreinforced and overreinforced
beams.
(b) Derive the formula for the design of a singly reinforced rectangular section in
bending:
M
As =
0.95 f y z ( ) where z = d 0.5 + 0.25 − K / 0.9 , and K = M
.
f cu bd 2 2.2 A reinforced concrete beam of 300 mm wide and 600 mm deep is required to span 6
m, as shown in Fig. 2.2. The beam carries dead and imposed loads of 25 kN/m and
19 kN/m, respectively. Design the beam section for bending. fcu = 30 N/mm2, fy =
460 N/mm2, d = (h – 50) mm. 600 Gk = k2525kN/m, Qk= 19kN/m
G = kN/m, Qk = 19 kN/m
As
As 6000 300 Fig. 2.2 500
5 00 2.3 A simply supported RC beam with fcu = 30 N/mm2, fy = 460 N/mm2 contains 4T25, as
shown in Fig. 2.3. If the span is 7m, determine the maximum imposed load that the
beam can carry. Assume that the load is: (a) a uniformly distributed load, and (b) a
point load at midspan. 44T25
T25
300
300 Fig. 2.3
1 2.4 Determine the moment of resistance for the beam crosssection shown in Fig 2.4. fcu
= 30 N/mm2, fy = 460 N/mm2, and As = 1960 mm2.
200 200 Ass
A 200 700 200 600 Fig. 2.4
2.5 A fixedend beam shown in Fig. 2.5 is subjected to an increasing uniformly
distributed load of w/unit length. By design, the ultimate bending strength at span is
80% of that at supports. If w is the load to cause the first plastic hinge, determine
(a) The collapse load that the beam may carry with moment redistribution;
(b) The moment redistribution ratio at sections A and C. =
= ( w + wa ) L2
12 wL2
12 ⎛ wL2 wa L2 ⎞
+
⎜
⎟
⎜ 24
8⎟
⎝
⎠ Fig. 2.5 2 ...
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This note was uploaded on 12/24/2011 for the course CIVL 232 taught by Professor Jskuang during the Spring '06 term at HKUST.
 Spring '06
 JSKUANG

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