One-way Joist Slab

Reinforced Concrete II

Hashemite University

The Hashemite University Department of Civil Engineering

Lecture 2 – One One--way Joist Slab System Dr Hazim Dwairi Dr.

Dr. Hazim Dwairi

The Hashemite University


One--way Joist Floor System One

Dr. Hazim Dwairi

Dr. Hazim Dwairi



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One--way Joist Floor System One

Dr. Hazim Dwairi



One-way Joist OneFloor System General G l fframing i layout of the pan joist system

Dr. Hazim Dwairi

Dr. Hazim Dwairi



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General framing layout of the pan joist system

Dr. Hazim Dwairi



ACI Code Recommendations • ACI 8.13.1: Joist construction consists of a monolithic combination of regularly spaced ribs and a top slab arranged to span in one direction or two orthogonal directions. Solid Slab, hs = larger of hs

S

Slope 1:12

Min. b=100mm Dr. Hazim Dwairi

Dr. Hazim Dwairi

50mm without filler 40mm with filler (1/12) S

Max. = (3.5)b

Max. 750mm



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Minimum Slab System Depth • Based on deflection control. use table 9.5(a) in the ACI code to check minimum thickness required.

Dr. Hazim Dwairi



Distribution Rib (Cross Rib) Distribution Ribs • Placed p perpendicular p to jjoists* • Spans < 6.0 m: Use None • Spans 6.0 6.0--9.0 m: Provided at midspan • Spans > 9.0 m: Provided at thirdthirdpoints • At least l t one continuous ti φ12 b bar iis provided at top and bottom of distribution rib. *Note: not required by ACI Code, but typically used in construction Dr. Hazim Dwairi

Dr. Hazim Dwairi



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Dead Load Calculations • Permanent loads such as fixed machines or furniture • Weight of the structural elements (R.C. unit weight = 25 kN kN/m /m3) • Weight g of fixed attachments such as tiles, mortar, false ceiling …etc.

Dr. Hazim Dwairi



Typical One One--way Joist Slab

Typical Cross-Section Dr. Hazim Dwairi

Dr. Hazim Dwairi



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Load Calculations • Slab Loads: – – – –

Tiles Mortar Sand Fill Solid Slab

= (0.025) (22) = (0.025) (22) = (0.100) (13) = (0.070) (25)

Total

= 0.55 kN kN/m /m2 = 0.55 kN kN/m /m2 = 1.30 kN kN/m /m2 = 1.75 kN kN/m /m2

= 4.15 kN/m kN/m2

• Rib Loads: – Joist Web – 5 Blocks/m – Plaster

= (0.18) (0.135) (25)= (25)= 0.61 kN kN/m /m = 5 (0.18 kN kN/Block) /Block) = 0.90 kN kN/m /m = (0.52) (0.025)(22) = 0.29 kN kN/m /m

Total Dr. Hazim Dwairi

= 1.80 kN/m kN/m



Load Calculations • Total Ultimate Rib Load – Dead Load from Slab = (0.52) (0 52) (4.15) (4 15) = 2.16 2 16 kN kN/m /m – Live Load from Slab = (0.52) (2.0) = 1.04 kN kN/m /m

wu = 1.2 (1.80 + 2.16) + 1.6 (1.04) = 6.42 kN kN/m /m • Total Ultimate Load on Slab: wu = 6.42/0.52 = 12.34 kN kN/m /m2

Dr. Hazim Dwairi

Dr. Hazim Dwairi



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Cases of Loading (Pattern Loads) • Using influence lines to determine pattern loads • Largest moments in a continuous beam or frame occur when some spans are loaded and others are not. • Influence lines are used to determine which spans to load and which spans not to load.

Dr. Hazim Dwairi



Qualitative Influence Lines The Mueller Mueller--Breslau principle can be stated as follows: If a function at a point on a structure, such as reaction, or shear, or moment is allowed to act without restraint, the deflected shape of the structure, to some scale, represents the influence line of the function function.

Dr. Hazim Dwairi

Dr. Hazim Dwairi



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Qualitative Influence Lines

Dr. Hazim Dwairi



One-way Joist Slab OneDesign Example • Design a typical joist and solid slab for the floor system shown below. • Floor system is part of residential building.

Dr. Hazim Dwairi

Dr. Hazim Dwairi



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One-way Joist Slab OneDesign Example 4400mm

4400mm

• Clear Span ln = 4400 – 400 = 4000 mm • Min. thickness hmin = 4000/18.5 = 216 mm • Use typical slab thickness h = 250 mm.

Dr. Hazim Dwairi



One-way Joist Slab OneDesign Example • Recall: – Ultimate rib load wu = 6.42 6 42 kN kN/m /m – Ultimate slab load wu = 12.34 kN/m kN/m2

• ACI moment and shear envelopes Cm = -1/9 if only two spans

Cm =

-1/24

1/14

-1/10

-1/11

1/16

-1/11

-1/11

Cv =

1.0

Eq. 1

1.15

1.0

Eq. 1

1.0

1.0

(c) Discontinuous end integral with support where support is spandrel beam Dr. Hazim Dwairi

Dr. Hazim Dwairi



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One-way Joist Slab OneDesign Example • Typical Rib Flexure Design – – – –

wu = 6.42 6 42 kN kN/m /m ln = 4000 mm d = 250 – 20 – 10 – 10/2 = 215 mm As,min = 0.0033 (120) (215) = 85.14 mm2

Moment

Coeff.

Mu –ve*

wuln

Mu –ve*

wuln2/9

Mu +ve**

Dr. Hazim Dwairi

wuln

2/24

2/14

kN.m

a (mm)

As (mm2)

Bar size

4.28

7.88

54.4

2φ10

11.41

21.74

150.0

2φ10

7.34

3.09

92.3

2φ10

*Rectangular Section ** T-Section The Hashemite University


One-way Joist Slab OneDesign Example • Typical Rib Shear Design Vu = 1.15 1 15 (6 (6.42)(4.0/2) 42)(4 0/2) = 14 14.77 77 kN φVn = 1.1 x 0.75 x √28/6 x 120 x 215 = 18.77 kN φVn > Vu O.K.

• Solid Slab Design – – – – – Dr. Hazim Dwairi

Dr. Hazim Dwairi

ln = 400 – 2(15) = 370mm Mu = 12.34 12 34 (0.37) (0 37)2/12 = 0 0.141 141 kN.m kN m As = 8.7 mm2 (b=1000mm, d=70d=70-20 20--10/2=45mm) As,min = 0.0018(1000)(70) = 126 mm2 Use φ10/block or welded wire mesh The Hashemite University


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Reinforcement Details 0.25 of ln1

0.30 of ln1 or ln2

2φ10

2φ10

2φ10

2φ10

2φ10

Typical 150mm

At least one bar continuous or spliced a class A splice

ln1

Dr. Hazim Dwairi

Dr. Hazim Dwairi

ln2



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One-way Joist Slab

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