Alcan Structural Engineering

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Determine basic l/d and K from Figure 7

i

' i

i

To determine stress in the reinforcement (os), calculate the ratio Gk/Qk, read up the graph to the appropriate curve and read across to determine osu.

os can be calculated from the expression: os = osu ( As,req ) (—)

Figure 7

Basic span-to-effective-depth ratios

36 34 32 30 28

IT 26

c ro

0.40% 0.60% 0.80% 1.00% 1.20% 1.40% 1.60% Percentage of tension reinforcement (ASireq'd/bd)

Notes

1 This graph assumes simply supported span condition (K = 1.0).

K =1.5 for interior span condition K =1.3 for end span condition K = 0.4 for cantilevers.

2 Compression reinforcement, p, has been taken as 0.

3 Curves based on the following expressions:

Figure 11

Procedure for determining flexural capacity of flanged beams

START

Carry out analysis of beam to determine design moments, M (see Table 3)

Determine lo (see Figure 9) and beff from: beff = (bw+ beff1 + beff2) where beffi = (0.2bi + 0.1 lo) < 0.2 lo < bi beff2 = (0.2b2 + 0.1 lo) < 0.2 lo < b2 Note: The flange width at the support will be different from that at mid-span. For symbols refer to Figures 9 and 10

Determine K from K =

where b = bw at support b = beff in span bd2 fck

Determine K' from Table 4 or K' = 0.60 d - 0.18 ô2 - 0.21 where d < 1.0

Neutral axis in flange. Design as rectangular section (Figure 2) and then check longitudinal shear (Figure 14)

Neutral axis in web Calculate moment capacity of flange from:

Figure 9

Definition of lo, for calculation of effective flange width

l0 = 0.85 l1	l0 = 0.15 (li + I2 )		l0 = 0.7 I2	l0 = 0.15 I2 + I3
					Effective flange width parameters Figure 10 Effective flange width parameters Figure 12 Placing of tension reinforcement in flanged cross section Figure 12 Placing of tension reinforcement in flanged cross section Figure 13 Notations for the connection between flange and web Figure 13 Notations for the connection between flange and web the interface of the fiange and web can be resisted by the transverse reinforcement in the fiange. The position of the neutral axis should be determined, and then the area of reinforcement can be calculated depending whether it lies in the flange or web (see Figure 11). At supports the tension reinforcement to resist hogging moments should be distributed across the full width of the effective flange as shown in Figure 12.The span-to-depth deflection checks using ratio of tension reinforcement should be based on area of concrete above centre of tension steel.