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C C C C P C C C TIE PROVISION - horizontal ties

P - Peripheral tie Int. - Internal tie C -Column (external) tie W -Wall (external) tie

Figure 2.1 Structural details

2.3 Floor slab

2.3.1 Idealization of structure

Consider as a one-way continuous slab on knife-edge supports and design a typical 5 m interior span where

2.3.2 Cover for durability and fire resistance

Nominal cover for exposure class 1 (internal) is 20 mm.

Cover should not be less than the bar size when 20 mm maximum aggregate size is used.

175 mm slab with 20 mm cover will give 1.5 hours fire resistance. . . . OK

Use 20 mm nominal cover bottom and top

2.3.3 Loading

Self-weight of slab = 0.175 x 24 = 4.2 kN/m2 Finishes = 0.5 kN/m2

Characteristic permanent load (gk) = 4.7 kN/m2 Characteristic variable load (q ) = 4.0 kN/m2

NAD 6.1(a) & BS 8110 Table 3.5 & Figure 3.2

Design permanent load =

= 1.35 x 4.7

= 6.35 kN/m2

Design variable load

= 1.5 x 4.0

Table 2.2

2.3.4 Design moments and shears

Moments have been obtained using moment coefficients given in Reynolds and Steedman's Reinforced concrete designer's handbook, Table 33.

Support moment = 0.079 x 6.35 x 52 + 0.106 x 6.0 x 52

Span moment = 0.046 x 6.35 x 52 + 0.086 x 6.0 x 52 = 20.2 kNm/m

Design shear force = 0.5 x 6.35 x 5 + 0.6 x 6.0 x 5 = 33.9 kN/m

2.3.5 Reinforcement 2.3.5.1 Support

Assume effective depth M

For zero redistribution, x/d should be less than 0.45 OK 2.5.3.4.2(5)

Minimum area of reinforcement 0.6 bp

0 0

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