Design Guide of Slab on Grade

TATA CONSULTING ENGINEERS

SECTION:

TCE.M6-CV-064

DESIGN GUIDE FOR SLABS ON GRADE

SHEET

i

TITLE

OF

iii


TATA CONSULTING ENGINEERS 1-10-60/3, SURYODAYA BEGUMPET HYDERABAD - 500 016

FILE: M6-CV-064(R1)

VALID UPTO: 2003-03-29

M6-CV-064(R1)-1.jpg , M6-CV-064(R1)-1.jpg, M6-CV-064(R1)-4.jpg,, M6-CV-064(R1)-4.jpg

REV.NO

M6-CV-064(R1)-2.jpg , M6-CV-064(R1)-2.jpg, M6-CV-064(R1)-5.jpg,, M6-CV-064(R1)-5.jpg

R0 INITIALS

R1

ISSUE

SIGN

INITIALS

SIGN

PPD.BY

DVSBNR

SD/-

MVRR

SD/-

CKD.BY

SBK

SD/-

VVSS

SD/-

APP.BY

RBG

SD/-

MGK

SD/-

DATE

M6-CV-064(R1)-3.jpg , M6-CV-064(R1)-3.jpg, M6-CV-064(R1)-6.jpg

1996-07-29

2000-03-30

INITIALS

SIGN

INITIALS

SIGN

R1

TATA CONSULTING ENGINEERS TCE.M6-CV-064


SECTION:REV.STAT.

SHEET

ii OF iii

REVISION STATUS SHEET Rev. No.

R1

Date

Description

2000-03-30 2000-03- 30

Definition of grade slab added. Document revised as per Latest ACI 360R-92 code. Detail guide lines for selection of sub base and safety factor in design has been included. Table 1 expanded by giving giving the values of allowable load for K= 100 pci and k= 200 pci along with necessary notes. PCA design charts for Post loads have been added for k= 100 and 200 pci also. Table III & Cl 6.3 deleted as source of information not available. Cl 6.4 renumbered as Cl 6.3. Guide lines for minimum and maximum reinforcement added. All charts have been incorporated into the Computerised document by scanning. Scanned files are kept in JPEG format separately to reduce file size. Revised matter is kept under bold format. Document Revised and Revalidated.

ISSUE R1 FORM NO. 120 R1


SECTION:CONTENTS

TCE.M6-CV-064

SHEET iii


OF iii

CONTENTS

SL.NO.

TITLE

SHEET NO.

1.0

INTRODUCTION

1

2.0

SCOPE

1

3.0

APPLICABLE STANDARDS AND CODES OF PRACTICE

1

4.0

DEFINITIONS AND GENERAL NOTATIONS

1

5.0

GUIDELINES FOR THICKNESS OF SUB-BASE

2

6.0

DESIGN OF SLAB

5

7.0

JOINTING PRACTICES

10

TABLE-I

13

TABLE-II

16

APPENDIX-1

FIGURES

17



SLABS ON GRADE

1.0

SECTION: WRITE-UP

SHEET

1

OF 17

INTRODUCTION

With the rapid industrialisation, the amount of expenditure incurred on industrial buildings has been considerably increased. One of the important elements of such industrial buildings is the flooring to meet the requirements of the various types of movements within the building. Flooring essentially consists of the top finish, grade slab, sub base and sub grade (See Fig.No.1). Many times, the floor cost contributes as large as 10% of the building cost. Hence, it is very essential to give sufficient attention to design the grade slab in such a way to reduce its costs and at the same time satisfy the basic requirements of the industry. 2.0

SCOPE

This design guide covers different design methods being practised to arrive at the optimum grade slab thickness for the required design loads. It also covers guidelines for sub base thickness and joint practices. In general this guide can be used to arrive at the thickness of the grade slab in the buildings used for industrial purposes. 3.0

APPLICABLE STANDARDS AND CODES OF PRACTICE ACI:360R-92 Design of Slabs on Grade

ACI: 302.1

Guide for Concrete Floor and Slab Construction

IRC:58

Guidelines for the design of rigid pavements for highways.

IS:1834

Specification for hot applied sealing compounds for joints in concrete

IS:1838

Pre formed fillers for expansion joints in concrete non extruding and resilient type (Bitumen impregnated fibre)

4.0

DEFINITIONS OF GENERAL TERMS AND NOTATIONS

4.1

DEFINITIONS

Grade slab: It is a slab, continuously supported by ground whose total loading when uniformly distributed would impart a pressure to the grade ISSUE R1

FORM NO. 120 R1


SECTION: WRITE-UP

SHEET

SLABS ON GRADE

2

OF 17

or soil that is less than 50 percent of the allowable bearing capacity thereof. The slab may be uniform or variable thickness and it may include stiffening elements such as ribs or beams. The slab may be plain, reinforced or pre-stressed concrete. The reinforcement or pre-stressing steel may be provided for the effects of shrinkage and temperature or for structural loading. Sub-grade: This is the naturally occurring ground excavated down to formation level or imported fill material on made up ground.

This is selected material imported to form a level, smooth Sub-base : working platform on which slab is to be laid. Usually, granular materials with low plasticity index are selected as sub-base materials. Wearing Surface: This may be the upper surface of the slab suitably finished, or an applied topping or covering material. 4.2

NOTATIONS

Kips : 1000 lbs Psi : Pounds per square inch. Pci : Pounds per cubic inch.

5.0

in

: inches

L

: Distance in meters between free transverse or free longitudinal joints

f

: Coeff. of friction between pavement (slab) and sub grade.

W

: Weight of slab in kg/m

S

: Allowable working stress in steel in kg/cm

2

2

GUIDELINES FOR SELECTION OF SUB-BASE The soil support system for a grade slab usually consists of a “Base”, a “sub base” and a “Sub grade”. If the existing soil has the required strength and properties to support the slab, the slab may be placed directly on the existing sub grade. However normally the existing grade

ISSUE R1

FORM NO. 120 R1


SLABS ON GRADE

SECTION: WRITE-UP

SHEET

3

OF 17

will not be normally at correct elevation or slope. Therefore some cut or fill is required with the best of site selections. The nature of the soil must be identified in order to determine its suitability either as a base, as a sub base or as a sub grade material. Design methods use the modulus of sub grade reaction to account for the soil properties. It is a spring constant that depends on the kind of soil, the degree of compaction and the moisture content. The Standard Modulus of Sub grade reaction is the one which uses a 30inch diameter plate for the test. It is suggested to refer to this value wherever a reference is made as modulus of sub grade reaction. Recently a modified modulus of sub grade reaction based on 12-inch diameter plate test is also being adopted. This test is less expensive and the value for a given soil is twice that of the Standard Modulus. Hence if this modified value if furnished then half of it is to be taken as Standard Modulus before using in the design. Fig 9.0 shows the general relation ship between soil classification and the range of values for the modulus of sub grade reaction. It also shows the general relationship between California Bearing Ration (CBR) and modified modulus of sub grade reaction and standard modulus of sub grade reaction, which is the basis for slab on grade design. Normally there is a wide range of soils across the site. The soil support system is rarely uniform. Therefore, some soil work is generally required to provide a more uniform surface to support the slab. The extent of this work such as the degree of compaction or the addition of a sand-gravel base is generally a problem of economics. Selection of soils in the well graded gravel (GW) and poorly graded gravel (GP) groups, as a base material may appear costly. However the selection of these materials has distinct advantages. Not only do they provide a superior modulus of sub grade reaction but they also tend to speed construction during inclement weather. Certainly not all projects will require the detail soil classification. On projects where the slab performance is not so critical, engineering judgement should be exercised to reduce costs. A prime pre requisite for the proper design of grade slab is soil identification to arrive at the modulus of sub grade reaction. In the absence of detail soil classification which is expensive a lower value of modulus may be considered and add a selected thickness of crushed stone to improve factor of safety.

ISSUE R1

FORM NO. 120 R1


SLABS ON GRADE

SECTION: WRITE-UP

SHEET

4

OF 17

For weak sub grades of soil types, such as clay, silt and sandy silty clay with water table within 600 mm of formation level, a sub-base of 150 mm thickness is recommended. In case of normal sub grades of soil types comprising of well-graded and drained sand or sandy gravel, 80-mm thick sub-base is recommended. These recommendations apply to sub-bases under roof cover, and hold good in situations where the construction traffic consists only of small dampers and possibly trunk mixers. Where the sub-base is exposed to the weather and to heavy construction traffic, it is recommended that the above sub base thickness is increased by 75 mm. In case of expansive soils such as Black cotton soils proper care shall be exercised in consultation with the Geo technical specialists. These are prone to significant volume changes. In the absence of detail recommendations at least the top 600mm of such soil shall be replaced totally with a suitable base material. Provision of a vapour barrier such as thick polyethylene sheet shall be considered on the base. Vapour barriers in direct contact with the slab are discouraged. The barriers shall be covered with about 100 to 150 mm of fine granular material to provide a permeable and absorptive base directly under the slab.

Where the ground is very unstable or where considerable depths of fill have been used and high settlements are expected, the floor may be designed as a suspended slab on pile foundations.

5.1

RECOMMENDED GRADE OF CONCRETE AND TOPPING THICKNESS

Normally, for good abrasive resistance under the action of moving wheels, dragging of heavy castings and such other metal equipment, fork lifts with iron2 typed wheels, etc. Concrete with a cube-crushing strength of 40 N/mm at 28 days, (grade M40) is recommended. Under normal loading conditions grade M20 is generally adequate. Specify workable concrete with the largest practical maximum size of coarse aggregate. It is also worth while to consider using 60 or 90-day strengths in slab thickness design to permit use of concrete with lower shrinkage than could be achieved with the same strength at 28 days if permitted otherwise.

Thus the topping may be about 50 mm for integral construction and about 75 mm for bonded construction. ISSUE R1

FORM NO. 120 R1


SLABS ON GRADE

5.2

SECTION: WRITE-UP

SHEET

5

OF 17

BAY LAYOUT

From practical considerations, preferably the bay width should not exceed about 4.5 m. If the slab is not reinforced, joints should be formed at intervals not exceeding 6 m. Floors are usually constructed as follows. Long-strip Construction : The floor pattern is usually in long stretches lengthwise, 25 m to 30 m long between expansion joints in between control joints are so planned that the resulting bays are approximately square. The strips are divided into smaller bays by means of induced transverse control joints either formed in the green concrete or by sawing shallow grooves in the surface two or three days after the concrete has hardened. Chequer Board Construction : In fill bays are usually laid after 7 days or more in an attempt to eliminate shrinkage contraction movement.

It is recommended that preference be given to long-strip construction.

6.0

DESIGN OF SLAB

Various design methods have been evolved for calculating the thickness of slabs on grade, such as PCA (Portland Cement Association) method, WRI (Wire Reinforcement Institute) method, PTI (Post-Tensioning Institute) methods etc. There is no single or unique design technique that can be recommended for all applications. However, PCA method can be used for most of the general applications. 6.1

FACTOR OF SAFETY

The Factor of safety for a slab on grade is selected based on experience and also considering the number of allowable load repetitions. This Value generally varies between 1.4 and 2.0. A factor of safety of 2.0 pertains to unlimited number of stress repetitions i.e. more than 4,00,000 cycles of allowable load repetitions. Factor of safety of 1.4 is the lower limit and corresponds to approximately 1500 allowable load repetitions. Generally a Factor of safety of 1.7 is recommended for use. This corresponds to allowable load repetitions of approximately 42000 cycles. Compounding safety factors is a common error. Inclusion of safety factors in the modulus of sub grade reaction, applied loads, the compressive strength, flexural strength of concrete and also in the number ISSUE R1

FORM NO. 120 R1


SLABS ON GRADE

SECTION: WRITE-UP

SHEET

6

OF 17

of load repetitions will produce an expensive design. The Safety Factor is applied to the flexural strength of concrete only and is a function of number of allowable load repetitions. 6.2

DESIGN PROCEDURE BY PCA METHOD

Portland Cement Association has studied the pavement theory and developed thickness design charts for floors on grade. Portland Cement Association also publishes the design methods. The method is also applicable to slabs on ground for outdoor storage and material handling areas. The factors involved in determining the required floor slab thickness is: i.

Strength of sub-grade and sub-base

ii. Strength of concrete iii. Location and frequency of imposed loads Grade slabs are generally subjected to Vehicle wheel loads, Concentrated loads such as Rack storage Leg loads and Uniform loads including strip loads. For grade slabs intended for industrial loading a minimum thickness of 125mm (5 inches) is suggested.

6.2.1

For Vehicle Loads( Refer Fig 2.0)

Following factors are required to arrive at the thickness of the grade slab. i.

Maximum axle loads

ii. Number of load repetitions iii. Wheel contact area (tyre data) iv. Spacing between wheels on the heaviest axle v. Sub grade strength ( Standard modulus of sub grade reaction) vi. Flexural strength of concrete If the tyre data is not available, the contact area can be estimated for pneumatic tyres by dividing wheel load by inflation pressure. Tyre inflation pressure for pneumatic tyres range from 80 to 100 psi. Steel cord tire pressure ranges up to 120 psi. ISSUE R1

FORM NO. 120 R1


SLABS ON GRADE

SECTION: WRITE-UP

SHEET

7

OF 17

Thickness Design Example:

For single wheel axle loads (one wheel on each side of axle) Data for lift truck

Axle loads = 25 kips (single wheel axle) = 25000 lbs Wheel spacing S = 37" No. of wheels = 2 Tyre inflation pressure = 110 psi 25000 / 2 Tyre contact area = = 114 sq.inches. 110 Sub-grade modulus, K = 100 pci Concrete flexural strength, r = 640 psi Select safety factor permitting unlimited stress repetitions = 2.0 Procedure

Concrete working stress =

640 2

= 320 psi

Slab stress per 1000 lb of axle load =

320 25

= 12.8 psi

Refer Fig.2.0, locate the point left hand side vertical axis corresponds to stress 12.8 psi, move right to contact area of 114 sq.inches, down to wheel spacing of 37 inches taken right to read a slab thickness of 7.9 inches on the line for sub grade modulus k of 100 psi. Hence, use 8 inches thick slab. In case of axles having Dual tires/ wheels on either side of axle it is suggested to consider as a single equivalent wheel on either side and contact area can be considered accordingly as a conservative estimate. After that the same Fig 2.0 can be applied. 6.2.2

For High Rack Storage Leg Loads

When loads on rack legs exceed the wheel loads of vehicles operating in the wear house, leg loads will control the thickness of slab. When a correct size of the base plate is used, concrete bearing and punching shear stresses will remain within acceptable limits. The design factors are same as used for vehicle loads except that a higher safety factor is selected. Safety factors in ISSUE R1

FORM NO. 120 R1


SLABS ON GRADE

SECTION: WRITE-UP

SHEET

8

OF 17

the range of 3.9 to 4.8 will satisfy building code requirements when the rack leg is regarded as a supporting column and the slab is regarded as a non-reinforced spread footing.

Thickness Design Example Data

Spacing of wheels in width direction, X = 50 in Spacing of wheels in length direction, Y = 60 in Max. expected load on leg = 8 kips Effective contact area = 50 sq.in Sub-grade modulus K = 50 pci Concrete flexural strength, r = 640 psi Select safety factor = 4.0 Procedure

Concrete working stress = 640/4 = 160 psi Slab stress per 1000 lb of post load = 160/8 = 20 psi Refer Fig.3.0 (A), locate the point on left hand side corresponds to effective contact area of 50 sq. inches and a stress of 20 psi, move right to Yspacing of 60 inches, up to X-spacing of 50 inches taken right to read a slab thickness of 11.4 inches. Hence, use 11.5 inches thick slab. Similarly Fig 3.0 (B) corresponds to a modulus of sub grade reaction of 100 pci and Fig 3.0 (C) corresponds to a modulus of sub grade reaction of 200 pci. 6.2.3 Uniform Loads

Uniform loads are defined as loads distributed over a large area. For most wear houses and industrial floors, concentrated loads are the controlling design factor since distributed loads do not usually produce stresses of the same magnitude. Design for distributed loads has two objects:

ISSUE R1

FORM NO. 120 R1


SECTION: WRITE-UP

TCE.M6-CV-064

SHEET

SLABS ON GRADE

i.

9

OF 17

to prevent cracks in the aisle ways or unloaded areas due to excessive negative moment and

ii. to avoid objectionable settlement due to consideration of the foundation soils. The allowable distributed loads for different thickness for uniform and non-uniform loading is shown in Table-I & II respectively.

6.3

DESIGN OF REINFORCEMENT

Reinforcing steel will enhance the performance of the slab on grade. reinforcement will help in preventing the formation of cracks.

Steel

There are two aspects to give attention in the use of reinforcement for industrial floors. One is the quantity of the reinforcement. The second is the placement of the steel within slab. Reinforcement in concrete grade slabs is designed to counteract the tensile stresses caused by shrinkage and contraction due to temperature or moisture changes. The amount of longitudinal and transverse steel required per metre width or length of slab is computed by the following formula: Area of steel A = Where L = f

=

Lfw

2

cm /m width or length

2S Dist. in 'm' between free transverse or free longitudinal joints

Coeff. of friction between pavement and sub grade (usually 1.5)

W = Weight of slab in kg/m S =

2

2

Allowable working stress in steel in kg/cm (usually taken as 50 to 60% of the yield stress of steel)

Where cracking due to temperature and shrinkage stresses has to be controlled and there is likelihood of appreciable bulking of the sub grade due to fluctuations in water table, reinforcement should be provided to ISSUE R1

FORM NO. 120 R1


SLABS ON GRADE

SECTION: WRITE-UP

SHEET

10 OF 17

help transfer the load evenly over the sub grade. The minimum reinforcement required is 0.15% in each direction in case of High yield strength deformed bars. In case of plain mild steel bars the minimum reinforcement shall be 0.20% in each direction. The maximum reinforcement shall be restricted to 0.6% in both the cases. Spacing shall not exceed 3 times the effective thickness of the slab or 450mm whichever is less. It is suggested to go for spacing in the range of 150 to 200mm and also equally in both the directions.

7.0

Since reinforcement in grade slab is not intended to contribute towards its flexural strength, it shall be placed slightly above the mid depth. The general preference is for the placing of reinforcement about 50 mm below the top surface. JOINTING PRACTICES Good jointing practice is one way of ensuring crack-free floors. Most cracks in concrete floors are the result of three actions i.e. volumetric change due to drying shrinkage, direct stress due to applied loads and flexural stress due to bending. Cracks can be the net result of the three. Drying shrinkage is an unavoidable, inherent property of concrete, so the possibility of cracking exists. Control measures are taken to allow concrete to crack in predictable and straight-line pattern by proper jointing. Three kinds of joints are used :i.

Isolation joints/Expansion joints : To allow movement between the floor and other fixed parts of the building such as columns, walls and machinery bases.

ii. Control joints/contraction joints : To induce locations.

cracking at pre selected

iii. construction joints - to provide stopping places during construction. Typical joint layout is shown in Fig.4.0.

7.1

ISOLATION JOINTS

Isolation joints are placed as shown in Fig.5.0 & Fig.6.0 wherever complete separation between the floor and adjoining concrete is needed to allow them to move independently without damage. Isolation joint permits horizontal and vertical movement between the abutting faces of the floor slab and other parts of the building because there is no keyway, bond or mechanical connection ISSUE R1

FORM NO. 120 R1


SLABS ON GRADE

SECTION: WRITE-UP

SHEET

11 OF 17

across the joint. It is important that the entire surface of each isolation joint be covered with joint material as shown in Fig.5.0 conforming to IS:1838 to be sure that there is no concrete-to-concrete contact because such contact is likely to cause spalling at the joint. 7.2

EXPANSION JOINTS

These joints are meant to accommodate expansion and are provided with a clear gap for the full depth between adjacent slabs. They are spaced at 25 m to 30 m along the slab length and are filled with expansion joint filler , which is compressible enough to accommodate the expansion of the adjacent slabs. For this purpose, it is required to use filler confirming to IS:1838. Dowel bars may be omitted for slabs less than 150 mm thick. Expansion joints may be provided with load transfer devices which are generally dowel bars cantilevering out 450 mm on either side of the joint or tongue-and-groove joints. Load transfer devices transfer the load from one panel to the other at the expansion joint. It is not possible to have a load transfer device at the entrance; the base slab thickness may therefore be locally increased by 50 percent. 7.3

CONTRACTION JOINTS (OR) CONTROL JOINTS:

Control joints act to relieve stress and with proper spacing they eliminate the cause of uncontrolled random cracking. They allow horizontal movement of the slab. Control joints in industrial and commercial floors are usually cut with a saw. They should be cut to a depth of generally 1/4 the slab thickness. The objective is to form a plane of weakness in the slab so that the crack will occur along that line to avoid random cracking and curling. In case of thick slabs a crack induced is anchored to the sub grade immediately below the joint. Load transfer across a control joint is provided by the interlocking of the jagged face formed at the crack. For long joint spacing or heavily loaded slabs, dowel bars are used as load transfer devices. The above-discussed varieties of control joints are shown in Fig.7.0. The steel must be discontinued at all control joints. In general spacing of joints shall be 2 to 3 times slab thickness in inches expressed in feet. ISSUE R1

FORM NO. 120 R1


SLABS ON GRADE

7.3.1

SECTION: WRITE-UP

SHEET

12 OF 17

Longitudinal Control Joints :

These are the main construction joints to be provided at not more than 4.5 m apart. Tie bars, 12 mm dia, 900 mm long at 600 mm centre to centre at every fourth longitudinal joint should be de-bonded to permit contraction movement. 7.3.2

Transverse Control Joint :

These joints limit the concrete tensile stresses to control cracking. Control joints are spaced at 5 m to 6 m intervals and are formed by providing a continuous, crack inducing dummy groove or saw cut in the upper portion of the base slab. In case sawed joints are adopted, the depth of the saw cut should not be less than the diameter of the largest-size coarse aggregate. The width of the dummy groove should be 5 to 10mm and its depth one fifth of the slab thickness with a minimum of 25 mm and a maximum of 50 mm. In slabs thicker than 200 mm, the lower crack induced reduces the depth of the surface groove. The closer joint spacing in non reinforced slabs can limit the crack width and eliminate the tying. A free contraction joint is normally used only for slabs thicker than 225 mm, subject to heavy wheel loads over 5t. The grooves should be filled with hot applied sealing compounds confirming to IS:1834. 7.4

CONSTRUCTION JOINTS :

Construction joints usually form the edges at the end of each day's work. They are located to confirm to the floor-jointing pattern. Where there is no control or isolation joint, a butt-type construction joint is satisfactory for thin floors. For thick and more heavily loaded floors, a tongue and groove joint is used or dowels are added to the butt joint. A bonded construction joint in a plain slab is a butt type construction joint with tie bars when concrete placement is interrupted for 30 minutes. Different varieties of construction joints are shown in Fig.8.0.

ISSUE R1

FORM NO. 120 R1


SECTION:

TCE.M6-CV-064

SHEET


WRITEUP

13 OF 17

TABLE - I ALLOWABLE DISTRIBUTED LOADS, UNJOINTED AISLE (UNIFORM LOAD, VARIABLE LAYOUT)

Notes: 1) K of Sub Grade : Disregard increase in k due to sub base. 2) Critical aisle width equals 2.209 times the radius of relative stiffness 3) Relative stiffness= l =

sub grade and

µ

Eh 4

3

12(1 − µ 2 )k

where h is thickness, k is modulus of

is poisons ratio.

4) Assumed load width = 300 in; Allowable load varies only slightly for other load widths. 5) Allowable stress = 0.5 * Flexural strength

Slab Thickness

Working Stress Psi

Inches

Critical Aisle Width Ft

t criTical aisle width

Allowable load , psf At other aisle widths 6-ft 8 - ft 10 -ft 12 -ft aisle aisle aisle aisle

14-ft aisle

Sub grade k = 50 pci 5

300 350 400

5.6 5.6 5.6

610 710 815

615 715 820

670 785 895

815 950 1,085

1,050 1,225 1,400

1,215 1,420 1,620

6

300 350 400

6.4 6.4 6.4

670 785 895

675 785 895

695 810 925

780 910 1,040

945 1,100 1,260

1,175 1,370 1,570

8

300 350 400

8.0 8.0 8.0

770 900 1,025

800 935 1,070

770 900 1,025

800 935 1,065

880 1,025 1,175

1,010 1,180 1,350

10

300 350 400

9.4 9.4 9.4

845 985 1,130

930 1,085 1,240

855 1,000 1,145

850 990 1,135

885 1,035 1,185

960 1,120 1,285

12

300 350 400

10.8 10.8 10.8

915 1,065 1,220

1,065 1,240 1,420

955 1,115 1,270

915 1,070 1,220

925 1,080 1,230

965 1,125 1,290

14

300 350 400

12.1 12.1 12.1

980 1,145 1,310

1,225 1,430 1,630

1,070 1,245 1,425

1,000 1,170 1,335

980 1,145 1,310

995 1,160 1,330



SECTION:

TCE.M6-CV-064

SHEET


WRITEUP

14 OF 17

TABLE – I (Contd) Slab-

Working

Critical

Thickness

Stress

Aisle

Inches

Width Ft

Psi

t Critical Aisle width

Allowable load , psf At other aisle widths 6-ft aisle

8 - ft aisle

10 -ft aisle

12 –ft aisle

14-ft aisle

Sub grade k = 100 pci 5

300 350 400

4.7 4.7 4.7

865 1,010 1,155

900 1,050 1,200

1,090 1,270 1,455

1,470 1,715 1,955

1,745 2,035 2,325

1,810 2,115 2,415

6

300 350 400

5.4 5.4 5.4

950 1,105 1,265

955 1,115 1,275

1,065 1,245 1,420

1,320 1,540 1,760

1,700 1,985 2,270

1,925 2,245 2,565

8

300 350 400

6.7 6.7 6.7

1,095 1,280 1,460

1,105 1,285 1,470

1,120 1,305 1,495

1,240 1,445 1,650

1,465 1,705 1,950

1,815 2,120 2,420

10

300 350 400

7.9 7.9 7.9

1,215 1,420 1,625

1,265 1,475 1,645

1,215 1,420 1,625

1,270 1,480 1,690

1,395 1,630 1,860

1,610 1,880 2,150

12

300 350 400

9.1 9.1 9.1

1,320 1,540 1,755

1,425 1,665 1,900

1,325 1,545 1,770

1,330 1,550 1,770

1,400 1,635 1,865

1,535 1,795 2,050

14

300 350 400

10.2 10.2 10.2

1,405 1,640 1,875

1,590 1,855 2,120

1,445 1,685 1,925

1,405 1,640 1,875

1,435 1,675 1,915

1,525 1,775 2,030



SECTION:

TCE.M6-CV-064

SHEET


WRITEUP

15 OF 17

TABLE – I (Contd) Slab

Working

Critical

Thickness

Stress

Aisle

inches

At Critical

Psi

Width Ft Sub grade k = 200 pci

Aisle width

Allowable load , psf At other aisle widths 6-ft aisle

8 - ft aisle

10 -ft aisle

12 –ft

aisle

14-ft aisle

5

300 350 400

4.0 4.0 4.0

1,225 1,425 1,630

1,400 1,630 1,865

1,930 2,255 2,575

2,450 2,860 3,270

2,565 2,990 3,420

2,520 2,940 3,360

6

300 350 400

4.5 4.5 4.5

1,340 1,565 1,785

1,415 1,650 1,890

1,755 2,050 2,345

2,395 2,800 3,190

2,740 3,200 3,655

2,810 3,275 3,745

8

300 350 400

5.6 5.6 5.6

1,550 1,810 2,065

1,550 1,810 2,070

1,695 1,980 2,615

2,045 2,385 2,730

2,635 3,075 3,515

3,070 3,580 4,095

10

300 350 400

6.6 6.6 6.6

1,730 2,020 2,310

1,745 2,035 2,325

1,775 2,070 2,365

1,965 2,290 2,620

2,330 2,715 3,105

2,895 3,300 3,860

12

300 350 400

7.6 7.6 7.6

1,890 2,205 2,520

1,945 2,270 2,595

1,895 2,210 2,525

1,995 2,330 2,660

2,230 2,600 2,972

2,610 3,045 3,480

14

300 350 400

8.6 8.6 8.6

2,025 2,360 2,700

2,150 2,510 2,870

2,030 2,365 2,705

2,065 2,405 2,750

2,210 2,580 2,950

2,480 2,890 3,305




SECTION:

SHEET

WRITEUP

16 OF 17

TABLE-II

ALLOWABLE DISTRIBUTED LOADS, UNJOINTED AISLE (NONUNIFORM LOADING, VARIABLE LAYOUT)

Slab Thickness in 5

Sub grade k pci

Allowable load, psf

550

Concrete flexural strength, psi 600 650

700

50 100 200

535 760 1,075

585 830 1,175

635 900 1,270

685 965 1,370

6

50 100 200

585 830 1,175

640 905 1,280

695 980 1,390

750 1,055 1,495

8

50 100 200

680 960 1,355

740 1,045 1,480

800 1,135 1,603

865 1,220 1,725

10

50 100 200

760 1,070 1,515

830 1,170 1,655

895 1,265 1,790

965 1,365 1,930

12

50 100 200

830 1,175 1,660

905 1,280 1,810

980 1,390 1,965

1,055 1,495 2,115

14

50 100 200

895 1,270 1,795

980 1,385 1,960

1,060 1,500 2,120

1,140 1,615 2,285

Notes: 1) K of Sub Grade : Disregard increase in k due to sub base. 2) Allowable stress = 0.5 * Flexural strength 3) Based on aisle and load widths giving maximum stress




SECTION:

SHEET

WRITEUP

17 OF 17

FIGURES

The following figures (Graphs & Charts) are enclosed in the Appendix 1. In soft copy format these figures are kept in separate “ JPEG” files. SLAB1.JPEG:

FIG 1 :

The elements of a concrete floor

FIG 2 :

PCA design chart for axles with single wheels

SLAB2.JPEG:

FIG 3 A :

PCA Design chart for Post loads where sub grade modulus is 50 pci

SLAB3.JPEG:

FIG 3 B :

PCA Design chart for Post loads where sub grade modulus is 100pci

FIG 3 C :

PCA Design chart for Post loads where sub grade modulus is 200 pci

SLAB4.JPEG:

FIG 4 TO 7 : ISOLATION JOINTS SLAB5.JPEG:

FIG 8 :

CONSTRUCTION JOINTS

SLAB6.JPEG:

FIG 9 :

Inter relationship of soil classifications and strengths


Design Guide of Slab on Grade

Recommend Documents