Rib Slab Design Examplehpexample.pdf
This document was uploaded by user and they confirmed that they have the permission to share it. If you are author or own the copyright of this book, please report to us by using this DMCA report form. Report DMCA
Overview
Download & View Rib Slab Design Examplehpexample.pdf as PDF for free.
More details
- Words: 893
- Pages: 5
Design of Hollow Pot Slab Project : Regional Office for CWA at Pamplemousses.
01 0635 AS 5/10/2001
Page Job No. Made by Date
Project Sub-Title : First Floor Slab
Sketch and Plan on Hollow Pot Slab
Sketch
Rib
Plan
Lx
Ly Plan view of a Hollow Pot
Slab Dimensions
Hollow pot slab width, b
=
3.00
m
Hollow Block Dimensions & Thickness of Topping H 205 457 Hollow blocks have same length (L=457mm) and width (W=205mm) but their heights , H varies. Hollow blocks have a minimum crushing strength of 3.50N/mm 2 on gross area. Height of hollow block, H
=
mm
Topping to be placed on top of hollow blocks, t
=
mm
Design of Hollow Pot Slab Project : Regional Office for CWA at Pamplemousses.
02 0635 HM 5/10/2001
Page Job No. Made by Date
Project Sub-Title : First Floor Slab
Exposure Conditions (Cl 3.3.4; BS8110;Part1;1997) Exposure condition, (Table 3.2: BS8110;Part1;1997) Lowest grade of concrete to be used, C30 Nominal cover to all reinforcement including links to meet durability requirements, c d (Table 3.3;BS8110;Part1;1997)
Period of fire resistance, t Nominal cover to all reinforcement including links to meet specified periods of fire resistance, c f (Table 3.4:BS8110;Part1:1997)
Effective cover , ce
= 30 =
=
mm
Cover as Fire Protection (Cl 3.3.6;BS8110;Part1;1997) h
=
=
N/mm2
mm
0
Note
Effective cover mm
Ribbed Dimension
The width of the reinforced concrete rib should be greater or equal to that given in table 3.2;BS8110;Part1;1997 Rib width, b =
The total rib height will be equal to the sum of the topping thickness and the hollow block height, h
=
mm
0
mm
Effective depth , d = h-ce-θl-θm/2 where ce = effective cover θl = Diameter of links θm = Diameter of main steel Links diameter, θl
=
6
mm
Main bar diameter, θm Therefore, effective depth of Rib, d
= =
16
mm mm
Design of Hollow Pot Slab Project : Regional Office for CWA at Pamplemousses.
Page Job No. Made by Date
Project Sub-Title : First Floor Slab
03 0635 HM 5/10/2001
Self weight of hollow pot slab = Superimposed Dead load (Screed, plaster and finishes), =
1.00
Dead load kN/m2 2 kN/m
Live Load (BS6399:Part1:1996),
=
2.50
Live load 2 kN/m
LOAD AT ULTIMATE LIMIT STATE = 1.4 Gk + 1.6 Qk
=
Ultimate design load 2 kN/m 5.4
Distance between center line of two consecutive ribs Load resisted by each rib , wr
= =
0.0
mm kN/m
Moment and Reinforcement Calculations Since the ribs span in one direction , maximum moment will 2 occur at mid-span and will be equal to w rl /8 Maximum moment Mmax
=
kNm
Reinforcement Calculations (Cl 3.4.4.4;BS8110;Part1;1997) Moment coefficient K = M/(bfd2fcu) = Since K< 0.156, therefore no compression reinforcement is required. Lever arm , Z = d[.5+sqrt{(.25-(K/.9)}]
=
mm
=
mm
2
Minimum reinforcement A s min is equal to .15%bh and is less than that required. Area of steel provided, A s prov =
mm
2
Since d-z =(357-339)=18 < hf/2, Neutral Axis lies within flange and beam is designed with b=b f Area of steel required, As req = M/0.95*fy*z where fy = 425N/mm2
Design of Hollow Pot Slab Project : Regional Office for CWA at Pamplemousses.
04 0635 HM 5/10/2001
Page Job No. Made by Date
Project Sub-Title : First Floor Slab
Deflection Check (Cl 3.4.6;BS8110;Part1;1997) Basic span to effective depth ratio for a flanged rib beam, simply supported is obtained from Table 3.9 of BS8110;Part1;1997 bw/b
=
For bw/b less or equal to 0.3, the basic l/d ratio for a simply supported flanged beam = Modification factor (Cl 3.4.6.6 BS8110;Part1;1997) The design service stress in tension reinforcement in a member may be obtained from the equation given below fs = 2*fy*As req/(3*As prov )
=
Modification factor , M.F. is obtained from the formula given below 2 MF = .55 + (477-fs)/[120+(.9+M/bd )] =
Permissible span to effective depth ratio is equal to the basic span to effective ratio multiplied by the modification factor Therefore, Permissible l/d = Actual span to effective depth ratio,
=
Since Permissible span to effective depth ratio is greater than actual span to effective depth ratio, therefore beam satisfies deflection criteria
N/mm
2
Design of Hollow Pot Slab Project : Regional Office for CWA at Pamplemousses.
Page Job No. Made by Date
Project Sub-Title : First Floor Slab
Design shear force V = wl/2 Design shear stress, v = V/bd
= =
05 0635 HM 5/10/2001
Shear Check (Cl 3.6.4; BS8110;Part1;1997) kN N/mm2
Note The calculated design shear stress must be less than 2 0.8sqrtfcu = 4.4 N/mm (Cl 3.6.4; BS8110;Part1;1997) (100As/bd)
1/3
(400/d)1/4 1/3 (fcu/25)
= = =
Note 100As/bd should not be taken as greater than 3 400/d should not be taken as less than 1
Design concrete shear stress is obtained from the formula 1/3 1/4 1/3] given vc= 0.79*[(100As/bd) *(400/d) *(fcu/25) /γm
=
N/mm
=
mm2
2
where γm = 1.25 From table 3.7;BS8110;Part1;1997 it is seen that 0.5vc < v < vc+.4 , hence minimum links for the whole length of beam is to be provided as calculated from the formula given below; (Asv/Sv)*(.95*fyv) = 0.4b Links to be provided : R06-150 which is equivalent to 82mm2
Transverse steel As trans = .15%bh
=
Area of steel provided
=
Topping Reinforcement 2 mm /m 2
mm /m
01 0635 AS 5/10/2001
Page Job No. Made by Date
Project Sub-Title : First Floor Slab
Sketch and Plan on Hollow Pot Slab
Sketch
Rib
Plan
Lx
Ly Plan view of a Hollow Pot
Slab Dimensions
Hollow pot slab width, b
=
3.00
m
Hollow Block Dimensions & Thickness of Topping H 205 457 Hollow blocks have same length (L=457mm) and width (W=205mm) but their heights , H varies. Hollow blocks have a minimum crushing strength of 3.50N/mm 2 on gross area. Height of hollow block, H
=
mm
Topping to be placed on top of hollow blocks, t
=
mm
Design of Hollow Pot Slab Project : Regional Office for CWA at Pamplemousses.
02 0635 HM 5/10/2001
Page Job No. Made by Date
Project Sub-Title : First Floor Slab
Exposure Conditions (Cl 3.3.4; BS8110;Part1;1997) Exposure condition, (Table 3.2: BS8110;Part1;1997) Lowest grade of concrete to be used, C30 Nominal cover to all reinforcement including links to meet durability requirements, c d (Table 3.3;BS8110;Part1;1997)
Period of fire resistance, t Nominal cover to all reinforcement including links to meet specified periods of fire resistance, c f (Table 3.4:BS8110;Part1:1997)
Effective cover , ce
= 30 =
=
mm
Cover as Fire Protection (Cl 3.3.6;BS8110;Part1;1997) h
=
=
N/mm2
mm
0
Note
Effective cover mm
Ribbed Dimension
The width of the reinforced concrete rib should be greater or equal to that given in table 3.2;BS8110;Part1;1997 Rib width, b =
The total rib height will be equal to the sum of the topping thickness and the hollow block height, h
=
mm
0
mm
Effective depth , d = h-ce-θl-θm/2 where ce = effective cover θl = Diameter of links θm = Diameter of main steel Links diameter, θl
=
6
mm
Main bar diameter, θm Therefore, effective depth of Rib, d
= =
16
mm mm
Design of Hollow Pot Slab Project : Regional Office for CWA at Pamplemousses.
Page Job No. Made by Date
Project Sub-Title : First Floor Slab
03 0635 HM 5/10/2001
Self weight of hollow pot slab = Superimposed Dead load (Screed, plaster and finishes), =
1.00
Dead load kN/m2 2 kN/m
Live Load (BS6399:Part1:1996),
=
2.50
Live load 2 kN/m
LOAD AT ULTIMATE LIMIT STATE = 1.4 Gk + 1.6 Qk
=
Ultimate design load 2 kN/m 5.4
Distance between center line of two consecutive ribs Load resisted by each rib , wr
= =
0.0
mm kN/m
Moment and Reinforcement Calculations Since the ribs span in one direction , maximum moment will 2 occur at mid-span and will be equal to w rl /8 Maximum moment Mmax
=
kNm
Reinforcement Calculations (Cl 3.4.4.4;BS8110;Part1;1997) Moment coefficient K = M/(bfd2fcu) = Since K< 0.156, therefore no compression reinforcement is required. Lever arm , Z = d[.5+sqrt{(.25-(K/.9)}]
=
mm
=
mm
2
Minimum reinforcement A s min is equal to .15%bh and is less than that required. Area of steel provided, A s prov =
mm
2
Since d-z =(357-339)=18 < hf/2, Neutral Axis lies within flange and beam is designed with b=b f Area of steel required, As req = M/0.95*fy*z where fy = 425N/mm2
Design of Hollow Pot Slab Project : Regional Office for CWA at Pamplemousses.
04 0635 HM 5/10/2001
Page Job No. Made by Date
Project Sub-Title : First Floor Slab
Deflection Check (Cl 3.4.6;BS8110;Part1;1997) Basic span to effective depth ratio for a flanged rib beam, simply supported is obtained from Table 3.9 of BS8110;Part1;1997 bw/b
=
For bw/b less or equal to 0.3, the basic l/d ratio for a simply supported flanged beam = Modification factor (Cl 3.4.6.6 BS8110;Part1;1997) The design service stress in tension reinforcement in a member may be obtained from the equation given below fs = 2*fy*As req/(3*As prov )
=
Modification factor , M.F. is obtained from the formula given below 2 MF = .55 + (477-fs)/[120+(.9+M/bd )] =
Permissible span to effective depth ratio is equal to the basic span to effective ratio multiplied by the modification factor Therefore, Permissible l/d = Actual span to effective depth ratio,
=
Since Permissible span to effective depth ratio is greater than actual span to effective depth ratio, therefore beam satisfies deflection criteria
N/mm
2
Design of Hollow Pot Slab Project : Regional Office for CWA at Pamplemousses.
Page Job No. Made by Date
Project Sub-Title : First Floor Slab
Design shear force V = wl/2 Design shear stress, v = V/bd
= =
05 0635 HM 5/10/2001
Shear Check (Cl 3.6.4; BS8110;Part1;1997) kN N/mm2
Note The calculated design shear stress must be less than 2 0.8sqrtfcu = 4.4 N/mm (Cl 3.6.4; BS8110;Part1;1997) (100As/bd)
1/3
(400/d)1/4 1/3 (fcu/25)
= = =
Note 100As/bd should not be taken as greater than 3 400/d should not be taken as less than 1
Design concrete shear stress is obtained from the formula 1/3 1/4 1/3] given vc= 0.79*[(100As/bd) *(400/d) *(fcu/25) /γm
=
N/mm
=
mm2
2
where γm = 1.25 From table 3.7;BS8110;Part1;1997 it is seen that 0.5vc < v < vc+.4 , hence minimum links for the whole length of beam is to be provided as calculated from the formula given below; (Asv/Sv)*(.95*fyv) = 0.4b Links to be provided : R06-150 which is equivalent to 82mm2
Transverse steel As trans = .15%bh
=
Area of steel provided
=
Topping Reinforcement 2 mm /m 2
mm /m
Related Documents
Rib Slab Design Examplehpexample.pdf
October 2019 12
Precast Rib Slab Design
April 2020 8
Slab Design
May 2020 24
Top Circular Slab Design
April 2020 7
Precast Rib Beam Design
April 2020 9
Flat Slab Design
May 2020 14More Documents from ""