Scribd
Upload
1K views4 pages

Structural Design for Engineers

This document specifies the design of a simply supported one-way reinforced concrete slab with an effective span of 3600mm. The slab thickness is designed to be 150mm thick to satisfy minimum thickness requirements for fire resistance of 80mm and deflection control of 138mm. Reinforcement details are specified, with main reinforcement of H12 bars at 250mm spacing and secondary reinforcement of H12 bars at 300mm spacing. Shear, bending moment, deflection, and cracking checks are performed and the design is verified to meet all requirements.

Uploaded by

fyqae
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
1K views4 pages

Structural Design for Engineers

This document specifies the design of a simply supported one-way reinforced concrete slab with an effective span of 3600mm. The slab thickness is designed to be 150mm thick to satisfy minimum thickness requirements for fire resistance of 80mm and deflection control of 138mm. Reinforcement details are specified, with main reinforcement of H12 bars at 250mm spacing and secondary reinforcement of H12 bars at 300mm spacing. Shear, bending moment, deflection, and cracking checks are performed and the design is verified to meet all requirements.

Uploaded by

fyqae
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
You are on page 1/ 4

SIMPLY SUPPORTED ONE WAY SLAB

SPECIFICATION
3600

Effective span, L = 3600mm


Characteristic Action :
Permanent, gk = 1.0 kN/m2 (Excluding selfweight)
Variable, qk = 3.0 kN/m2
Design life = 50 years
Fire resistance = R60
Exposure clases = XC3
Materials :
Characteristic strenght of concrete, fck = 30 N/mm2
Characteristic strenght of steel, fyk = 500 N/mm2
Unit weight of reinforced concrete = 25 kN/m3
Assumed bar = 12mm
SLAB THICKNESS
Minimum thickness for fire resistance = 80 mm
Estimated thickness considering deflection control
h = L / 26 = 3600 / 26 = 138
mm

Use : 150

DURABILITY, FIRE AND REQUIREMENTS


Min. cover with regard to bond, C min,b = bar = 12 mm
Min. cover with regard to durability, C min,dur = 25 mm
Min. required axis distance for R60 fire resistance, a = 20 mm
Min. concrete cover regard to fire, C min = a bar / 2 = 20 (12/2) = 14mm
Allowance in design for deviation,

C dev = 10mm

Nominal cover, Cnom = C min + C dev = 14 + 10 = 24mm


30mm
ACTION AND ANALYSIS
Slab selfweight = h x 25 = 0.150 x 25 = 3.75 kN/m2
Permanent load (excluding selfweight) = 1.00 kN/m2
Characteristic permanent action, gk

= 4.75 kN/m2

Characteristic variable action, qk

= 3.00 kN/m2

Design action, nd = 1.35gk + 1.5qk

= 10.91 kN/m2

Shear Force
V = wd L / 2
= 10.91 (3.60 / 2)
= 19.64 kN
Bending moment
m = wd L2 / 8
= 10.91 ( 3.602 / 8)
= 17.67 kNm
MAIN REINFORCEMENT
Effective depth
d = h Cnom 0.5 bar = 150 30 (0.5x12) = 114mm
Design moment, MEd = 17.67 kNm
K = M / bd2 fck
= 17.67 x 106 / (1000 x 1142 x 30)
= 0.045 < K bal = 0.167 (Compression reinforcement is not required)

Use :

Z = d ( 0.5 + 0.25 K / 1.134 )


= d ( 0.5 + 0.25 0.045 / 1.134 )
= 0.96 d > 0.95 d
As = M / 0.87 fyk z
= 17.67 x 106 / (0.87 x 500 x 0.96 x 114)
= 371.17 mm2/m
Main bar : H 12 250 (452 mm2 / m)
Min and max reinforcement area
As, min = 0.26 (fctm / fyk) bd
= 0.26 ( 2.9 / 500) (1000 x 114)
= 171.91 mm2/m
Secondary bar : H 12 300 ( 377 mm2 / m)
As, max = 0.04 bh = 0.04 x 1000 x 150 = 6000 mm2/m
SHEAR
Design shear force, VEd = 19.64 kN
Design shear resistance, V Rd,c = [ 0.12 K (100 p1 fck)1/3 ] bd
k = 1 + ( 200 /d ) < 2.0
= 1 + ( 200 / 114 ) = 2.32

Use : 2.0

p1 = As / bd < 0.02
= 452 / (1000 x 114) = 0.004

Use :

0.004
V Rd,c = [ 0.12 (2.0) (100 x 0.004 x 30)1/3 ] x 1000 x 114
= 62638.76 N = 62.6 kN
Vmin = [ 0.035k 3/2 fck ] bd
= [ 0.035(2.0) 3/2 x 30 ] x 1000 x 114
= 61812.81 N = 61.8 kN
So, V Rd,c = 62.6 kN > VEd = 19.64 kN

OK!

DEFLECTION
Percentage of required tension reinforcement
p = As req / bd
= 372 / 1000 x 114 = 0.0033
Reference reinforcementt ratio
po = (fck) x 10-3 = (30)1/2 x 10-3 = 0.0055
Faktor for structural system k = 1.0
p > po
l/d = k [ 11 + 1.5 fck

po
fck
p + 3.2

po
p

- 1 ) 3/2

= 1.0 ( 11 + 13.7 + 9.54 ) = 34.24


Modification factor for span less than 7m
= 1.00
Modification factor for steel area provided
= As prov / As. Req = 452 / 372 = 1.22 < 1.5
Therefore allowable span affective depth ratio
( l/d) allowable 34.24 x 1.00 x 1.22 = 41.77
Actual span effective depth
(l/d) actual = 3600 / 114 = 31.58
(l/d) actual = 31.58 < ( l/d) allowable = 41.77
Ok !

CRACKING
h = 150mm < 200mm
main bar : Smax, slab = 3h = 450 > 400mm

Ok !
= 400mm

max, bar spacing = 250 < Smax, slabs


secondary bar = Smax, slab = 3.5h = 525 > 450mm

Ok !
= 450mm

max. Bar spacing = 300 mm < Smax, slab

Ok !

You might also like