Design grid line C

Effective depth, d d = 300 - 30 - 20 / 2 = 260 mm Flexure: column strip and middle strip, sagging

K = MEd / bd2fck = 140.5 x 106 / (1000 x 2602 x 30) = 0.069 z / d = 0.94 z = 0.94 x 260 =244 mm

As = MEd / fydz = 140.5 x 106 / (244 x 500 / 1.15) = 1324 mm2 / m

Deflection: column strip and middle strip,

F2 = 1.0 (no brittle partitions'1"") F3 = 310 / (7s where

where

(Tsn = (500/ 1.15) x (85 + 0.3 x 40) /16.6 = 254 MPa (or « 253 MPa (From Concise EC2 Figure 15.3 for Gk / Qk = 2.1, y/2 = 0.3 and yg = 1.25)

^ = redistribution ratio = 1.03 « 253 x (1324 / 1570) / 1.03 = 207 F3 = 310 / 207 = 1.50** . Allowable l / d = 20.3 x 1.2 x 1.50 = 36.5

<Concise EC2 Table 15.5>

<Concise EC2 Table 15.10> <Concise EC2 Table 15.11> <Concise EC2 Table 15.12> <Concise EC2 Table 15.13>

<Concise EC2 Fig. 15.3> <Concise EC2 Table 15.14> <Concise EC2 Fig. 15.3>

* As punching shear force (rather than a beam shear force) 'effective' span is not appropriate.

Cladding and strip of slab beyond centre of support. ftt Otherwise for flat slabs 8.5 / 9.5 = 0.89 as span > 8.5 m. <7.4.2(2)>

^ In line with Note 5 to Table NA.5, 1.50 is considered to be a maximum for 310 / <rs.

§§§ Note: Continuity into columns will reduce sagging moments and criticality of deflection check (see Section 3.5.14).

**** Note requirement for at least 2 bars in bottom layer to carry through column <9.4.1(3)>

Flexure: column strip, hogging: MEd = 222.3 kNm / m

K = MEd / bd2fck = 222.3 x 106 / (1000 x 2602 x 30) = 0.109

As = MEd / fydz = 222.3 x 106 / (231 x 500 / 1.15) = 2213 mm2 / m

Flexure: middle strip, hogging: MEd = 95.3 kNm / m

K = MEd / bd2fck = 95.3 x 106 / (1000 x 2602 x 30) = 0.069

As = MEd / fydz = 95.3 x 106 / (247 x 500 / 1.15) = 887 mm2 / m

Requirements:

There is a requirement to place 50% of At within a width equal to <9.4.1(2)>

0.125 of the panel width on either side of the column. Area required = (3 x 2213 + 3 x 887) / 2 mm2

1.e. require 4650 / 1.5 = 3100 mm2 / m for 750 mm either side of the column centreline.

Use H20 @ 100 T2 (3140 mm2 / m) 750 mm either side of centre of support

In column strip, outside middle 1500 mm, requirement is for Area required = 3.0 x 2213 - 16 x 314 mm2 = 1615 mm2

Within = in 3000 - 2 x 750 mm = 1500 mm i.e. 1077 mm2 / m

Use H20 @ 250 T1 (1256 mm2 / m) in remainder of column strip

Perpendicular to edge of slab at edge column:

Design transfer moment to column Mt = 0.17 bed2fck <9.4.2(1), I.1.2(5)> where be = cz + y = 400 + 400 = 800 mm <Fig. 9.9>

K = MEd / bd2fck = 275.8 x 106 / (800 x 2602 x 30) = 0.170

As = MEd / fydz = 275.8 x 106 / (213 x 500 / 1.15) = 2978 mm2 / m

++++ The hogging moment could have been considered at face of support to reduce the amount of reinforcement required.

This reinforcement to be placed within cx + 2cy = 1100 mm <SMDSC>

Try 10 no. H20 T1 N-bars in pairs @ 200 (.3140 mm2) local to column

(max. 200 mm from column)

Note:

Where a 200 x 200 hole occurs on face of column, be becomes 600 mm and pro rata, As required becomes 2233 mm2 i.e. use 4 no. H20 each side of hole (2512 mm2).

Perpendicular to edge of slab generally

Assuming that there is partial fixity along the edge of the slab, top reinforcement capable of resisting 25% of the moment in the adjacent span should be provided

Check minimum area of reinforcement

4.min = 0.26 (frtm / fyk) M ^ 0.0013 btd where bt = width of tension zone

Asmin = 0.26 x 0.30 x 300666 x 1000 x 260 / 500 = 390 mm2 / m

(p = 0.15%) Use H12 @ 200 (565 mm2 / m) The reinforcement should extend 0.2h from edge = 600 mm <9.3.1.4(2)>

Greener Homes for You

Greener Homes for You

Get All The Support And Guidance You Need To Be A Success At Living Green. This Book Is One Of The Most Valuable Resources In The World When It Comes To Great Tips on Buying, Designing and Building an Eco-friendly Home.

Get My Free Ebook


Post a comment