Foundation Design For residential Houses

EPCM ENGINEERS LIMITEDLINE HEATER FOUNDATION DESIGN

DESIGN CODECRITERIA FOR SELECTION AND DESIGN OF RESIDENTIAL SLABS-ON-GROUND: BRAB REPORT #33

VARIABLE SYMBOL

CONCENTRATED LOAD

PLASTICITY INDEX PI

ALLOWABLE SOIL BEARING PRESSURE

CLIMATIC RATINGSLAB LENGTH L

SLAB WIDTH L'

STEP 1: DETERMINE TOTAL AVERAGE LOADVARIABLE SYMBOL

TOTAL SLAB AREA

ESTIMATED DEAD WEIGHT OF SLAB

w

STEP 2: ESTABLISH CONTROLLING SOIL PROPERTIESVARIABLE SYMBOL

NOTE: (2.5<qu/w<7.5) THE SOIL IS COMPRESSIBLE, qu/W>7.5 THE SOIL IS EXPANSIVE AND qu/w<2.5 THE FOUNDATION NEEDS PILES.

STEP 3: DETERMINE SUPPORT INDEXVARIABLE SYMBOL

SUPPORT INDEX C

STEP 4: ASCERTAIN THE DEFLECTION RATIOVARIABLE SYMBOL

DEFLECTION RATION ∆/L

TOTAL WEIGHT OF SUPERSTRUCTURE (ALL DEAD AND LIVE WEIGHT) WS

WC

ULTIMATE STRENGTH OF CONCRETE AFTER 28 DAYS

fY

ULTIMATE STRENGTH OF CONCRETE AFTER 28 DAYS

fC'

MAXIMUM ALLOWABLE SHEAR STRESS IN CONCRETE

VC

qU

CW

ASLAB

SUPERSTRUCTURE LOAD PER SQUARE FOOT OF SLAB AREA

wS

wd

TOTAL SUPERSTRUCTURE AND SLAB DEAD LOAD

RATIO OF SOIL BEARING PRESSURE TO TOTAL LOAD

qu/w

STEP 5: DETERMINE OUTSIDE SLAB DIMENSIONSVARIABLE SYMBOL

LONG DIRECTION(LENGTH) LSHORT DIRECTION(WIDTH) L'

STEP 6: DETERMINE EFFECTIVE LOAD FOR SLABVARIABLE SYMBOL

ϕ

STEP 7: DEVELOP LAYOUT OF STIFFENING BEAMSVARIABLE SYMBOL

DESIGN OF SLAB

VARIABLE SYMBOL

ASSUMED LENGTH TO DIAMETER RATIOL/d

BEAM DEPTH d

B

B'

STEP 9: EXECUTE RECOMMENDED DESIGN COMPUTATIONSVARIABLE SYMBOL

DEPTH RATIO IN THE LONG DIRECTION L/d

DEPTH RATIO IN THE SHORT DIRECTIONL'/d

LOAD INDEX IN THE LONG DIRECTIONLOAD INDEX IN THE SHORT DIRECTION

COEFFICIENT ϕ FOR THE LONG DIRECTION

EFFECTIVE LOADS FOR SLAB IN THE SHORT DIRECTION

EFFECTIVE LOADS FOR SLAB IN THE LONG DIRECTION

NUMBER OF WEB OF STIFFENING BEAMS ON THE LONG DIRECTION

nL

NUMBER OF WEB OF STIFFENING BEAMS ON THE SHORT DIRECTION

nS

STEP 8: SELECT/TEST TENTATIVE DESIGN VALVES FOR d, bS, B, AND B'

WIDTH OF WEB OF STIFFENING BEAM IN THE LONG DIRECTION

bs

WIDTH OF WEB OF STIFFENING BEAM IN THE SHORT DIRECTION

bs

SUM OF WIDTHS OF ALL BEAMS RUNNING PARALLEL TO THE LONG DIRECTION(L) OF SLAB

SUM OF WIDTHS OF ALL BEAMS RUNNING PARALLEL TO THE SHORT DIRECTION(L') OF SLAB

v

v

p

p

z

z

THEREFORE, THE STEEL RATIO IN THE SHORT DIRECTION IS p=

2 No. 10mm

2 No. 10mm

2 No. 10mm

2 No. 10mm

STEP 10: CHECK SLAB DEAD LOADVARIABLE SYMBOL

TOP SLAB DESIGN THICKNESS t

ADJUSTED BEAM DEPTH

VOLUME OF CONCRETE IN THE BEAMS

SLAB AREA

SHEAR CRITERION IN THE LONG DIRECTION

SHEAR CRITERION IN THE SHORT DIRECTION

MOMENT CRITERION IN THE LONG DIRECTION

MOMENT CRITERION IN THE SHORT DIRECTION

DEFLECTION CRITERION IN THE LONG DIRECTION

NOTE: FROM FIG. 17, FOR Z, p1 =

COMPARING p1 AND p

THEREFORE, THE STEEL RATIO IN THE LONG DIRECTION IS p = p1

DEFLECTION CRITERION IN THE SHORT DIRECTION


COMPARING p1 AND p

REINFORCING REQUIRED PER BEAM IN THE LONG DIRECTION: BOTTOM STEEL AS

REINFORCING REQUIRED PER BEAM IN THE LONG DIRECTION: TOP STEEL A'S

REINFORCING REQUIRED PER BEAM IN THE SHORT DIRECTION: BOTTOM STEEL AS

REINFORCING REQUIRED PER BEAM IN THE SHORT DIRECTION: TOP STEEL A'S

LINEAL FEET OF BEAM IN THE LONG DIRECTION

LF

LINEAL FEET OF BEAM IN THE SHORT DIRECTION

L'F

ddepth

VCON

ASLAB

SLAB THICKNESS EQUIVALENT TO BEAM VOLUME

tBV

EQUIVALENT UNIFORM SLAB THICKNESS

AVERAGE SLAB LOADESTIMATED TOTAL AVREAGE LOAD w

ACTUAL TOTAL AVREAGE LOAD

tUNI

wAV

wT

RATIO OF ESTIMATED LOAD TO ACTUAL LOAD

EPCM ENGINEERS LIMITEDLINE HEATER FOUNDATION DESIGN

DESIGN CODECRITERIA FOR SELECTION AND DESIGN OF RESIDENTIAL SLABS-ON-GROUND: BRAB REPORT #33

VALUE UNIT

52.91 kips

0 kips

60000 psi

4000 psi

75 psi

292500 psf

2526.25 ft8000 mm6.56 ft2000 mm

STEP 1: DETERMINE TOTAL AVERAGE LOADCALCULATION VALUE UNIT

172.222566667356

307.2187404 psf

82.49343832021 psf

389.71217872021 psf

STEP 2: ESTABLISH CONTROLLING SOIL PROPERTIESCALCULATION VALUE UNIT

6.41499069443978

NOTE: (2.5<qu/w<7.5) THE SOIL IS COMPRESSIBLE, qu/W>7.5 THE SOIL IS EXPANSIVE AND qu/w<2.5 THE FOUNDATION NEEDS PILES.

STEP 3: DETERMINE SUPPORT INDEXCALCULATION VALUE UNIT

0.89

STEP 4: ASCERTAIN THE DEFLECTION RATIOCALCULATION VALUE UNIT

REF TO TABLE III 0.0027777777777778

ft2

REF TO FIG. 6(USING CW AND PI)

STEP 5: DETERMINE OUTSIDE SLAB DIMENSIONSCALCULATION VALUE UNIT

SAME AS ABOVE 26.246719160105 ftSAME AS ABOVE 6.56167979002625 ft

STEP 6: DETERMINE EFFECTIVE LOAD FOR SLABCALCULATION VALUE UNIT

0.5

63.1647239984986 psf

31.5823619992493 psf

STEP 7: DEVELOP LAYOUT OF STIFFENING BEAMSCALCULATION VALUE UNIT

REF TO THE DRAWING

REF TO THE DRAWING 2

REF TO THE DRAWING 3

CALCULATION VALUE UNIT

REF TO STEP 8 ON THE CHART TAB(USING w G) 10.6654

29.5310658691901 in750.089073077428 mm

9.05511811023622 in

230 mm

9.05511811023622 in

230 mm

18.1102362204724 in

27.1653543307087 in

STEP 9: EXECUTE RECOMMENDED DESIGN COMPUTATIONSCALCULATION VALUE UNIT

10.6654

2.66635

137.314617388041 psf732.34462606955 psf

STEP 8: SELECT/TEST TENTATIVE DESIGN VALVES FOR d, bS, B, AND B'

1464.51532029041 psf

1952.68709372054 psf

0.0007809820848513

0.0002603273616171

0.002897212635747

-0.00036864787634

-0.0011496299611913

0.0007809820848513

0.0002414343863123

-0.0008379140688585

-0.0010982414304756

THEREFORE, THE STEEL RATIO IN THE SHORT DIRECTION IS p= 0.0002603273616171

0.208840302354017

134.735409466717

0

USE IN ADDITION TO THE STEEL BAR ON THE SLAB 0

0.0696134341180056

44.9118031555725

0

USE IN ADDITION TO THE STEEL BAR ON THE SLAB 0

STEP 10: CHECK SLAB DEAD LOADCALCULATION VALUE UNIT

10mm at 12in o.c. Each way placed 1/3 of the slab thickness 9.80392156862745 in250 mm

52.49343832021 ft

15.1574803149606 ft

22.7271443005626 ft

96.6830171899724

172.222566667356

6.73660965999052 in


THEREFORE, THE STEEL RATIO IN THE LONG DIRECTION IS p = p1


in2

mm2

in2

mm2

in2

mm2

in2

mm2

ft3

ft2

16.540531228618 in

113.707107724292 psfAS GIVEN ABOVE 389.71217872021 psf

420.925848124292 psf

1.0800941595066

0

COMPRESSIBLE SOIL

TRUELONG DIRECTION

SHORT DIRECTION

WC/w

If C > 0.65 - wc/w

IF C <= 0.65 - wC/w

FALSE

C = Cr IN THE SHORT DIRECTION WHEN THE SOIL IS COMPRESSIBLE

C = Cr IN THE LONG DIRECTION WHEN THE SOIL IS COMPRESSIBLE

SELECT A BEAM SPACING NOT GREATER THAN 15FEET, NOR SMALLER THAN 8 FEET-PREFERABLE 9-12FEET. SELECT A BEAM WIDTH BETWEEN 8 AND 14 INCHES, PREFERABLE 8 TO 10 INCHES.


MUST BE < 21,600 psf

MUST BE < 21,600 psf

This value is compared with the value of P obtained for the moment criterion. If P1 > P and P1 does not exceed P by more than 0.0015, P1 is the controlling steel ratio or else P. If P1 > P and P1-P >0.0015, a considerable percentage of steel is needed to impart stiffness rather than strength to the beam. This means that the dimensions of the beam must be increased in order to reduce p1-p. Therefore, a wider beam is needed in the long direction.


4 No. 12mm No. of Steel:

steel thickness (Diameter in millimeter):

2 No. 12mm AREA:

2 No. 12mm

1 No. 12mm

since all squares of the top slab have spans smaller than 12 feet.

82.49343832021

MUST BE GREATER THAN 0.95

MUST BE < wd

0.83791955333

0.83791955333

0.89





2

10 mmsteel sizes readily available are: 6,8,10,12,16,20,25,32mm

157.079632679 mm2




This value is compared with the value of P obtained for the moment criterion. If P1 > P and P1 does not exceed P by more than 0.0015, P1 is the controlling steel ratio or else P. If P1 > P and P1-P >0.0015, a considerable percentage of steel is needed to impart stiffness rather than strength to the beam. This means that the dimensions of the beam must be increased in order to reduce p1-p. Therefore, a wider beam is needed in the long direction. INITAL VALUE OF C INITAL VALUE OF C DIFFERENCE

LONG DIRECTION

BOTTOM 91.44 134.73

TOP 0 43.29

SHORT DIRECTION

BOTTOM 30.48 44.91

TOP 0 14.43

NO

TE: NO

ADD

ITION

TOP REIN

FORCM

ENT

WILL BE N

EEDED

IF THE D

IFFERENCE IS ZERO

O

R LESS, WH

EREAS AN AD

DITIO

NAL

REINFO

RCEMEN

T WILL BE N

EEDED

IF THE

DIFFEREN

CE IS POSITIVE





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Foundation Design For residential Houses