Download pdf - 2015.03.11 - Concrete Slabs on Grade

Concrete Slabs on Grade Analysis, Design, and Detailing

By Otto J. Schwarz, P.E., S.E.

Ryan Biggs | Clark Davis Engineering and Surveying, P.C.

SE University, March, 2015 www.LearnWithSEU.com


I. Slabs on Grade and the Building Code

II. Types of Slabs on Grade

III. Design Parameters

IV. Methods of Analysis

V. Crack-Control, Vapor Retarders, and Subgrade

Preparation

2

Concrete Slabs on Grade Referenced Codes / Texts

2009 International Building Code

ACI 318 08 Building Code Requirements for Structural Concrete

ACI 360R 06 (2010 ACI MCP)

Designing Floor Slabs on Grade, Ringo, Boyd C., and Anderson,

Robert B., 1992

Concrete Floors on Ground, PCA, 2001. (2008 expanded available)

ARMY TM 5-809-12, Concrete Floor Slabs on Grade Subjected to

Heavy Loads, Departments of the Army and the Air force Technical

Manual, 1987

Wire Reinforcement Institute, 1989.

3

ACI 360 Definition:

A slab, supported by ground, whose main purpose is to support the applied loads by bearing on the ground.

(1992 whose total loading when uniformly distributed would impart a

pressure to the grade or soil that is less than 50% of the allowable bearing capacity thereof.)

A Slab on Grade is

4

Concrete Slabs on Grade Type 1 Engineering

Sufficient for light duty projects. Offices, light commercial, residential, etc. Slab on grade is primarily a walking surface.

Standard concrete specification and a note on the building plan.

Type 2 Engineering Projects where grade slabs perform heavy lifting

Industrial applications (forklifts, machinery loads, etc.) Warehouses (critical joint detailing, storage racks, etc.) Expansive soils / significant frost depths Exterior / Aggressive Environments Brittle low-crack-tolerance flooring

5

Concrete Slabs on Grade First Project Questions

What should the concrete strength be? What thickness of slab should I specify? How do I determine the required slab strength? How should the slab be reinforced? Where do I place contraction / control joints?

6

Occupancy** Min. Slab Thickness

Reinforcement

Sub-Slabs under other slabs 2 None

Domestic or light commercial (loaded less than 100 psf)

4 One layer 6x6 W1.4xW1.4 WWF, min. ideal conditions; 6x6 W2.1xW2.1 WWF for avg. conditions

Commercial institutional barns (loaded 100-200 psf)

5 One layer 6x6 W2.1xW2.1 WWF or one layer 6x6 W2.9xW2.9 WWF

Industrial (loaded not over 400-500 psf) and pavements for industrial plants, gas stations, and garages

6 One layer 6x6 W2.9xW2.9 WWF or one layer 6x6 W4xW4 WWF

Industrial (loaded not over 600-800 psf) and heavy pavements for industrial plants, gas stations, and garages

7 Two layers 6x6 W2.9xW2.9 WWF or two layers 6x6 W4xW4 WWF

Industrial (loaded 1500 psf) 8 Two mats of bars (one each, T & B) each of #4 bars @ 12 c/c, E.W.

Industrial (loaded 2500 psf) 9 Two mats of bars (one each, T & B) each of #5 bars @ 12 c/c, E.W.

Industrial (loaded 3000-3500 psf) 10 Two mats of bars (one each, T & B) each of #5 bars @ 8 to 12 c/c, E.W.

7

Notes on General Guidelines

** For loads in excess of 500 psf, use at least 3000 psi quality controlled concrete, and investigate subsoil conditions with extra care. Fill material and compaction should be equivalent to ordinary highway practice. If laboratory control of compaction is available, the load capacities can be increased in the ratio of the actual compaction coefficient, k, to 100.

For loads in excess of 1500 psf, the subsoil conditions should be investigated

with extra care and subbase should provide k 200. Place first layer 2 inches below top of slab; second layer 2 inches above

bottom of slab. Information taken from Concrete Reinforcing Steel Institute Handbook

(CRSI), 1984, pg 13-61.

8

Concrete Slabs on Grade confession

I was a successful Type 1 Engineer for many years.

Stable subgrade materials Uniform loading criteria Light service point loads (< 500lb) Tolerant Floor Coverings

Carpet Vinyl Tile

General Guidelines and Rules of Thumb Worked!

9

International Building Code What Applies?

non-structural and structural concrete

Non-structural the design and construction of slabs on grade shall not be governed by this chapter except Section 1910 Minimum Slab Provisions Section 1904 Durability Structural Slabs on Grade: transmitting vertical loads or lateral

forces from other parts of the structure to the soil.

Structural concrete shall be designed and constructed in accordance with IBC Chapter 19 Concrete ACI 318 as amended by section 1908.

10

International Building Code Section 1910 Minimum Slab Provisions

Thickness not less than 3.5 inches, and

Either 6-mil minimum polyethylene vapor retarder

Joints lapped 6 inches Between base course or subgrade and floor slab

Or Other approved equivalent method or materials to

control vapor transmission

Type 1 Engineering check!

11

International Building Code Section 1904 Durability Requirements

Concrete Strength and W/C Ratio Must Conform to ACI 318 Based on Exposure

Exposure to Freeze/Thaw in moist condition or deicers Exposure to Sulfates in water or soil Exposure to water when low permeability is required Exposure to chlorides when concrete is reinforced:

Deicing chemicals Salt Saltwater Brackish water Seawater

No Problem for most Type 1 projects! 12

This Code does not govern design and construction of slabs-

on-ground, unless the slab transmits vertical loads or lateral

forces from other portions of the structure to the soil.

and additionally

13

ACI 318 Section 1.1.7

IBC 2009 The Construction Documents for structural concrete construction shall include:

A statement if slab on grade is designed as a structural diaphragm for structures assigned to Seismic Design Category D, E, or F.

and

ACI 318 - Drawings, Details, and specifications shall show: Statement if slab-on-ground is designed as a structural

diaphragm (21.12.3.4)

14

The Construction Documents Concrete Slabs on Grade - Seismic

Although not mandated by the code, indication of slab-on-grade function on drawings and details for: Structural bracing for basement or retaining walls, Transmission of lateral forces at bases of shear walls

and frames for MWFRS and Low Seismic Zones, Support of posts, racks, machinery, or vehicles. Others

The Construction Documents Concrete Slabs on Grade

15

ACI 360 The Slab on Grade...

May be of uniform or variable thickness,

May include stiffening elements such as ribs or beams,

May be constructed of plain unreinforced concrete,

May be conventionally reinforced or prestressed for

the effects of shrinkage and temperature and/or

structural loadings.

(The slab on grade may be all of these things; Structural or Non-Structural.)

16

Slabs on Grade Types ACI 360 A Plain (unreinforced) concrete slabs B Reinforced to limit crack widths due to Shrinkage,

Temperature, and Applied Loads Mild Steel Bars Wire Reinforcement (WWR or WWF) Fiber Reinforcement

C Reinforced to prevent cracking due to Shrinkage,

Temperature, and Applied Loads Shrinkage compensating concrete Post Tensioned

D Structural Slabs (ACI 318) (Inclusive of all types!)

17

18

Type A the Plain Concrete Slab

No Reinforcement Simple to Construct Designed to Remain Uncracked in Service Cement Type I or II Close Joint Spacing (2 to 3 per inch thick at limited aspect ratio.)

More opportunity for curling and joint deterioration Flatness and Levelness may decrease over time

Subgrade Uniformity and Drying Shrinkage Extremely Critical

Type B Reinforced to Limit Cracking Thickness Design Can be the Same as for Unreinforced

Slabs

Reinforcing Does Not Add Significantly to the Load Carrying Capacity of the Type B Slab

Reinforcement (Bars or WWF) Placed in Upper of Slab

Thickness Nominal reinforcement to limit crack widths between joints Reinforced for structural capacity at a cracked section

Assumed to Remain Uncracked in Service May have many, closely spaced, fine cracks.

Cement Type I or II

Joint Spacing Greater than Type A. Based on Thickness and Subgrade Computed using Subgrade Drag Equation

19

Type C Reinforced to Prevent Cracking

Shrinkage Compensating Concrete (ACI 223)

ASTM C 845 Type K Cement or Separate Expansive Admixture

Reinforcement of 0.15% to 0.2% in Upper of Thickness of

Slab to Limit Initial Slab Expansion and to Restrain the Subsequent Drying Shrinkage

Detailed to be isolated from fixed portions of the structure for

both initial expansion and drying / temperature shrinkage Wider Construction Joint Spacing than Type A Slab (40 to

150 feet)

20

21

Type C Reinforced to Prevent Cracking Post Tensioned Control Cracking with Minimum

Precompression, or Provide Active Prestress to resist

Structural Loadings (Type D) Consider Short and Long Term Force

Loss Subgrade drag loss Restraint at fixed portions of structure Elastic Shortening Creep

Widely Spaced (100 to 500 feet!) or Non-Existent Control Joints.

Construction Joints to Limit Tendon Lengths and Losses.

Type D Structural Slab on Grade loads from other portions of the structure to the soil

22

P P P

Type D Structural Slab on Grade Designed for Code Defined Factored Loads

Design Governed by ACI 318 Reinforced with mild steel or post-tensioning tendons

Cracked Section for mild steel design.

PT design as cracked or uncracked. (minimum mild steel?)

Designed per Chapter 22 Plain Structural Concrete

Uncracked Section

Position and Detailing of Reinforcement Important

Joint Spacing Typically for Construction Process Reinforcing index typically higher; thus smaller well distributed cracks.

23

Design Parameters Effecting Slab Design / Type

Use: Loading (uniform, concentrated, rack, wheel, vibration) Exposure

Materials and Subgrade: Concrete Mix Design: Strength / Curing Subgrade: Strength and Uniformity Placement of Vapor Retarder (if any)

Safety Factors Analysis Technique

Code Requirements

24

Use: Loading and Exposure

Residential and Commercial Expansive Soils (PTSOG) Wall Loads (Vertical) Diaphragm Loads Stair Stringers

Industrial Point Loads (Posts and

Racks) Forklifts Wear Surface Durability

Floor Finish Rigid (joint layout) Flexible (concealing)

Tolerance of Owner for Imperfections

25

Materials and Subgrade Concrete Slab

Strength (fc >/= 2,500 psi) Mix Design Placement and Curing

Sub-grade Modulus (k) Pounds per Square Inch per Inch

Deflection (PCI) from estimate or Geotechnical Engineer

Allowable Bearing Pressure Pounds per Square Foot (PSF)

allowable from Geotechnical Engineer

Radius of Relative Stiffness Function of thickness, subgrade

modulus, and concrete modulus of elasticity

26

cffr '5.7=

ACI 318 - 08 (eqn. 9-10) Empirically

27

Subgrade Modulus k

Simplified engineering variable based on the assumption of homogeneous linear elastic subgrade behavior. Subgrade load / deformation relationship is:

Non-linear Not a fundamental soil property

k will vary based on Type of soil structure (density, moisture content, etc.) Prior loading Width and shape of loaded area Depth of subgrade Magnitude of load Duration of load

28

Subgrade Modulus k nevertheless, field determination

ASTM D1196 Plate Load Field Test 30 diameter bearing plate Several tests over project

area to obtain representative k.

29

30 * From Ringo, Boyd C., and Anderson, Robert B., Designing Floor Slabs on Grade, pg 143, 1992

Radius of Relative Stiffness,l

31

42

3

))(1(12)(

ktEl c

=Ec = Concrete Modulus t = slab thickness = Poisson's ratio k = subgrade modulus

Factors on the Factor of Safety

Ratio of r to t (safety factor) Subgrade Preparation Shrinkage Stress (function of concrete mix and curing) Load Repetition Fatigue and Impact Client Perception

32

Typical Factors of Safety

Load Type Commonly Used F.S.

Occasionally Used F.S.

Moving Wheel Loads 1.7 to 2.0 1.4 to 2.0+

Concentrated Rack and Post Loads

1.7 to 2.0 Higher under special circumstances

Uniform Loads 1.7 to 2.0 1.4 lower limit

Line and Strip Loads 1.7 2.0 conservative upper limit

Construction Loads 1.4 to 2.0

33

Methods of Analysis/Design

PCA (Portland Cement Association) WRI (Wire Reinforcing Institute) COE (Corps of Engineers) PTI (Post Tensioning Institute)

Numerical Solution (Ringo) Various Finite Element Solutions

PCA Mats Ram Concept / Elements RISA

34

PCA Method (Portland Cement Association)

Chart Form Solution for Wheel, Rack, and Post Loadings Solutions based on slab analyzed with a load layout on an area

of slab having a dimension equivalent to 3 times the radius of relative stiffness, l Joints should be reinforced (continuity)

Reinforcement for Shrinkage and Temperature effects only.

Based on limiting tension on bottom of the slab.

Charts developed for each value of subgrade modulus, interpolation between charts allowed.

35

PCA Method Example 1 Post Load

(PCA Axle Load Charts)

Given: Service Load = 12,000 lbs (equivalent to 24k axle load) Base Plate = 12 x 12 Subgrade Modulus = 150 pci Fc = 3,000 psi Safety Factor = 2.0 Poissons Ratio, = 0.15

36

Calculated Variables: Modulus of Rupture, fr = 411 psi Allowable Stress = 205 psi Stress/1000lb axle = 205/24 = 8.5 psi / 1 k axle (set wheel spacing to 3l, iterative process)

37

Iterative Solution: Thickness = 8.5

Explanation: s > 3l check at 8.5, l = 32.3 3l = 96.9 OK Selection of small s will yield a large t, corresponding to a larger 3l, and require iteration.

WRI Method (Wire Reinforcement Institute)

Nomographs Utilized to Solve for Slab Thickness

Developed based on a discrete element computer modeling of a slab continuum on a Winkler foundation (soil as linear springs).

3 step iterative process

1st solves for relative stiffness of system based on material and subgrade properties and assumed slab thickness

2nd uses stiffness parameter and loading geometry to solve for slab moment

3rd uses slab moment and Modulus of Rupture/Safety Factor to give required slab thickness

38

WRI Method Example 2 Post Load (single axle wheel charts)

39

Given: (same for comparison) Service Load = 12,000 lbs Base Plate = 12 x 12 Subgrade Modulus = 150 pci Fc = 3,000 psi Safety Factor = 2.0 Poissons Ratio, = 0.15

Calculated Variables: Modulus of Rupture, f r = 411 psi Allowable Stress = 205 psi Ec = 57,000 sqrt(fc) = 3122 ksi Set s = 96 based on l from Example 1

Step 1 Assume Thickness, D/k = 12x105 Plate area = 144 in2 Eq. Circle dia. = 13.5

40

41

s=96 0 add. moment.

Step 2 M = 212 inlb / in / kip (ftlb / ft / kip) Step 3 I8.5 = 614.1 in4 S = 144.5 in3 so, = 212(12)(12)/144.5 = 211 psi 205 psi OK

Radius of Relative Stiffness Examples 1 and 2

42

3

42

3

)150)(15.01(12)5.8(3122000

))(1(12)(

3122000300057000'57000

=

=

===

ktEl

cfE

c

Radius of relative stiffness, l = 32.3 Verify no other loads, joints, or edges within 3l = 8-0 Use 8.5 slab, size reinforcing based on preferred method to

allow joint spacing of approximately 16. Ok at 2 to 3 per inch for Type A Slab

42

COE Method (Corps of Engineers / ARMY TM)

Chart Form Solution for Required Slab Thickness

Developed based on Westergaards (c.1920) formula for edge stresses in a concrete slab.

PRESET design variables:

Impact factor of 1.25 Concrete Modulus of Elasticity, Ec = 4000 ksi (fc 4,900 psi) Factor of Safety, F.S. 2.0

2 step solution

Determine design index category from Table based on nature of loading.

Determine thickness based on k and r from chart. 43

COE Method

44

Begin with Assumed Flexural Strength fr

If Ec = 4,000 ksi, fr 530 psi

PTI Method (Post Tensioning Institute)

Slab thicknesses solution based on allowable slab tension considering pre-compression from post-tensioning and calculated slab design moments induced by shrinking or swelling soils.

Post tensioning force based on desired minimum residual prestress, length between joints, and subgrade drag.

Design for Edge Lift and Center Lift Conditions

45

Numerical Solution Example 3 - Post Load

Equation Solution from Ringo and Anderson, 1996 Design Parameters / Variables

Factored Point Load, Ps = 12k, or Pu Ps(SF)=24k Subgrade Modulus, k = 150 pci Square Base plate Dimension, b = 12 in fc = 3000 psi Poissons Ratio, = 0.15 Safety Factor = 2.0

46

Numerical Solution (Ringo) Example 3

41047.53000

03.0'

03.0 === xcf

A

47

614,116,503000000,915'000,915 === xcfxB

400,110,3)12(150)( 44 === bkC

7400,110,3

)(614,116,50log)1047.5)(000,24(3

42

=

=

t

txt

=

CtBAPt u

)(log)(3

2

Where,

and

and

Therefore,

inches

Numerical Solution Example 3

Punching Shear Check ACI 318 Chapter 22 7 Slab

kkVchbcfVc

so

and

bhb

where

hbcfhbcfVc

o

o

oo

2438))((')66.2(6.0

0.1

"62)125.3(4)2

(4

))(('66.2))(('38

34

>=

=

=

=+=+=

+=

48

Finite Element Modeling - FEM

Finite Element Modeling Solution Slab moments, Bearing pressures Deflections

Shear must be calculated by hand (typically) Element size and Model Area from

Radius of relative stiffness Nature of loading Actual slab geometry

Capable of considering complicated loading Slab geometry changes / steps / joints

49

FEM Software Example 4 Post Load

Factored load entered as surface load on 3 square elements Pu = 24.0 kips Ps = 12.0 kips (SF = LF = 2.0 for comparison with previous examples)

Capacity Analyzed per ACI318 Chap. 22 Subgrade Modulus, k= 150 pci = 259 kcf

Spring Constant = 5.4 k/inch on 6x6 grid Thickness of slab set to 8.5 Modeled area = 3l = 8 ft x 8 ft

50

51

FEM Software Example 4 Post Load

Calculate Stress Example 4

ksiI

Mc 248.0

12)5.8(12

)25.4)(12(99.23 ==

52

ftkftkftMu /99.2'5.5

44.16 ==

Moments averaged over 2X the radius of Relative Stiffness, therefore,

Design Moment from Analysis,

ACI 318 Chapter 22 Example 4

ftkft

ftkftMn

ScfMn

99.298.1)5.144(3000)5(6.0

'5

Analysis / Design Summary PCA, WRI

Limited by Published Tables, Non-Structural Loads Quick Solution for Rack and Wheel, Can Adapt for Post Loads and Wall Loads

COE Limited by Published Tables, Non-Structural Loads Difficult to Modify Hard Wired Design Variables Limited to Wheel Loadings and Load Classes

FEM Most Versatile modeling of multiple loadings and geometries Requires Understanding of meshing and calculated stress

distribution (Experience) Most Time Consuming

54

Detailing Joints and Vapor Retarders

55

Allowable tensile stress is meaningless if the slab is already cracked.

Control Joints & Vapor Retarders Crack Control Control Joint Spacing &

Layout Guidelines Details & Conditions

Shrinkage Crack Control Subgrade Drag

Equation & Example

56

Vapor Retarders Location based on ACI

Flowchart Types of Vapor Retarders

Control Joint Spacing & Layout

Spacing 2-3 times the slab thickness in feet Type A Plain Concrete Slabs Increase for W.W.F. and Bar Reinforcing (Subgrade Drag Equation) Increase for Post Tensioning

Layout on Regular Grid No Joint Offsets unless

Construction Joint Pour Strip

Release from Restraint Columns Walls Turn-Downs

57

Control Joint Spacing & Layout considerations

Maximum control joint spacing for a given project: Type of Use/Occupancy

Parking Garage Commercial Light Manufacturing Churches, Schools, Office Buildings Etc.

Concrete Specifications How tight is the specification in regards to required strength,

water/cement ratios, & slump? (curling, shrinkage) Vapor Retarder Location

Curling Drag

Project Type Exposure and Risk: Is this a high risk project (condominium!) where

every little concrete crack is going to be scrutinized?

58


59

Placed at slab discontinuities column, bearing wall, slab step,

elevator pit, loading dock, etc.

Cut in a timely manner. Random shrinkage cracks will

develop within 12 to 16 hours of slab placement.

Create weakened planes to attract shrinkage cracks.

Cut the slab into approximate

rectangles w/ aspect ratios < 1.25 preferably,

(1.5 to 2 max.)


60

Control joints must be continuous or must be terminated at a construction joint.

Otherwise: Random cracks may appear!

OR


61

Re-entrant corners Place a construction joint to

separate the slab pieces. (Best Choice)

Extend two control joints at 90 from corner.


62

Thickened edges (turndowns) Crack may wander due to

increased stiffness of thickened section.


Reinforced Joints / Dowels Resists Curling at Control and Construction Joints

Shear Transfer Across Control and Construction Joints

Enhanced performance over keyed joints after shrinkage

Explicitly Designed Based on: Bearing on Concrete Concrete Breakout (ACI 318 Appendix D as a guide.) Bending and Shear of Dowel of Plate Shear Friction (Saw-cut joints reinforcing cut only)

63

Control Joint Spacing & Layout reinforced joints / dowels

Continued Slab Reinforcing Reinforcing Bar or WWF Steel Area Reduced at Joint Weakened Plane to Attract Crack

Smooth Dowels Round or Square Bonded on one side of joint only Eliminates Restraint Longitudinally

64

Control Joint Spacing & Layout reinforced joints / dowels

65

Plates Diamond or Tapered Rectangular Bonded on one side of joint only Eliminates Restraint Longitudinally AND Transversely


Field preparation problems: Even if the Drawings are Perfect!

Saw cut not in the right location Concrete not up to specifications

Too Wet Overworked Surface Inadequate Curing Too Hot / Exposed to Direct Sun

Control Joints not cut in time.

66

Shrinkage Crack Control

The presence of reinforcing steel will not prevent conventional Portland cement concrete from cracking due to shrinkage of the concrete as it hydrates, dries out, and hardens.

Shrinkage cracking is caused by the restraint to shrinkage which is predominantly related to the materials of the concrete mix, the roughness of the base upon which the slab is placed, and the effectiveness of the curing process.

The steel, while not preventing such cracking, will hold the cracks tight (hairline), maintaining aggregate interlock, and mitigating faulting of the slab.

67


ss f

FLwA2

=

68

Subgrade Drag Equation Used to select adequate area of

steel reinforcing to be used for shrinkage crack control.

AS = area of reinforcing steel (in2/lf) F = coefficient of friction L = slab length between free ends (joints) (ft) w = weight of concrete slab (psf) fS = allowable steel stress (psi) (usually 2/3 Fy)

Subgrade Drag Equation Coefficients of Friction

Polyethylene Sheeting 0.5-0.6 (Vapor Retarder placed above subbase stone)

Sand Layer 1.0 Granular Subbase 1.5

Blended Sand & Gravel 1.8 Plastic Soils 2.0

69

Subgrade Drag Example

)60000(322

25.106)25(5.1

psi

psfftAs

=

70

Given: Slab thickness, t = 8.5 Slab length, L = 25 Fy = 60 ksi

Deformed Bars & WWF WWF may have higher

yield strengths.

Solutions: #3 @ 26 O.C.

Spacing Limited to 3 x t 6x6-W2.9xW2.9 WWF 14 Minimum Spacing

Recommended for Constructability!

ftinAs /05.02=


Specify / Control Largest practical aggregate size. Minimize aggregate gap-grading. 90 day strengths (where possible). Lowest fc for application. Reduce Portland Cement content. Breathable low moisture subgrade.

71

Vapor Retarders Proper moisture protection is desirable for any slab on grade where the floor will be covered by tile, wood, carpet, impermeable floor coatings, or where the floor will be in contact with any moisture-sensitive equipment or products.

ACI Committee Report 302.1-99

72

Vapor Retarders Location based on ACI Flow-chart Recommendations Types of Retarders/Barriers

Polyethylene Sheeting Highly susceptible to punctures & tears

Extruded or Premolded Stego Wrap, etc.

Sensitive Floor Coverings VCT, Glue Applied Carpet

Critically Sensitive Floor Coverings Rubber, Vinyl, Epoxy, Wood, Linoleum

73

Vapor Retarders Flow Chart Does the slab have a vapor-sensitive

covering or in a humidity-controlled area?

YES

NO

See Figure 1

Vapor retarder/barrier is required

Slabs in humidity-controlled area Slabs with vapor- sensitive coverings

See Figure 2 (2) Will the slabs and base material be placed in weatherproof environment (under roof)? (1)

See Figure 2 (2) See Figure 3

YES NO (1) If granular material is subjected to future moisture infiltration, use Figure 2.

(2) Reduced Joint Spacing, Low Shrinkage Design, or other measures likely needed. 74

Vapor Retarders Figures

75

Subgrade Preparation drawings

Essential to Provide the Engineering Parameters Governing the Design. Explicitly indicate or performance specify what is required in the field. To be Verified in the field by the project Geotechnical Engineer.

Geotechnical Report is Not a contract document and is not typically

included in the project manual. Report is typically referenced as provided by the owner for information only.

Indicate:

Recommendations of Geotechnical Report, or Assumed Quantities to be Verified in the Field

Limit Risk (Ringo): Due to lack of specific geotechnical information, this slab has been designed using a subgrade modulus of k =____ pci and design loading of __________. The designer is not responsible for differential settlement, slab cracking, or other future defects resulting from unreported conditions mitigating the above assumptions.

76

Concrete Slabs on Grade Summary

I. Building Code I. Non-structural II. Structural

II. Types of Slabs on Grade I. Plain (Type A) II. Reinforced Shrinkage and Temperature (Types B and C) III. Structural (Type D)

III. Design Parameters I. Use II. Exposure III. Materials (Concrete and Subgrade)

IV. Methods of Analysis I. Allowable Tension Stress II. LRFD Design

V. Crack-Control, Vapor Retarders, and Subgrade Preparation

77


QUESTIONS?

SE University, March, 2015 www.LearnWithSEU.com

CHALLENGE QUESTION:

Which Slab on Grade Reference Code/Text is the answer to this sessions Challenge Question?

A. IBC 2009 B. ACI 318 08 C. ACI 360R 06 D. Designing Floor Slabs on Grade

Please circle the answer that is announced so that you can use the information to complete your quiz (NY) or form (FL) for PDH.

Slide Number 1Concrete Slabs on GradeAnalysis, Design, and DetailingConcrete Slabs on GradeReferenced Codes / TextsACI 360 Definition:Concrete Slabs on GradeConcrete Slabs on GradeFirst Project QuestionsSlide Number 7Notes on General Guidelines Concrete Slabs on GradeconfessionInternational Building CodeWhat Applies?non-structural and structural concreteInternational Building CodeSection 1910 Minimum Slab ProvisionsInternational Building CodeSection 1904 Durability RequirementsACI 318Section 1.1.7The Construction DocumentsConcrete Slabs on Grade - SeismicThe Construction DocumentsConcrete Slabs on GradeACI 360 The Slab on Grade...Slabs on Grade Types ACI 360Slide Number 18Slide Number 19Slide Number 20Slide Number 21Type D Structural Slab on Gradeloads from other portions of the structure to the soilSlide Number 23Design ParametersEffecting Slab Design / TypeUse: Loading and ExposureMaterials and SubgradeSubgrade Modulus kSubgrade Modulus knevertheless, field determinationSlide Number 30Radius of Relative Stiffness,lFactors on the Factor of SafetyTypical Factors of SafetyMethods of Analysis/DesignPCA Method(Portland Cement Association)PCA MethodExample 1 Post Load(PCA Axle Load Charts)Slide Number 37WRI Method(Wire Reinforcement Institute)WRI MethodExample 2 Post Load(single axle wheel charts)Slide Number 40Slide Number 41Radius of Relative StiffnessExamples 1 and 2COE Method(Corps of Engineers / ARMY TM)COE MethodPTI Method(Post Tensioning Institute)Numerical SolutionExample 3 - Post LoadNumerical Solution (Ringo)Example 3Numerical SolutionExample 3Finite Element Modeling - FEMFEM SoftwareExample 4 Post LoadSlide Number 51Calculate StressExample 4ACI 318 Chapter 22Example 4Analysis / Design SummaryDetailingJoints and Vapor RetardersControl Joints & Vapor RetardersControl Joint Spacing & LayoutControl Joint Spacing & LayoutconsiderationsControl Joint Spacing & LayoutControl Joint Spacing & LayoutControl Joint Spacing & LayoutControl Joint Spacing & LayoutControl Joint Spacing & LayoutControl Joint Spacing & Layoutreinforced joints / dowelsControl Joint Spacing & Layoutreinforced joints / dowelsControl Joint Spacing & LayoutShrinkage Crack ControlShrinkage Crack ControlSubgrade Drag EquationCoefficients of Friction Subgrade Drag ExampleShrinkage Crack ControlVapor RetardersVapor RetardersVapor Retarders Flow ChartVapor Retarders FiguresSubgrade PreparationdrawingsConcrete Slabs on GradeSummarySlide Number 78Slide Number 79