PAD FOOTING ANALYSIS AND DESIGN (BS8110-1:1997)

Project

Pad footing analysis and design (BS8110-1:1997)

Section

Civil & Geotechnical Engineering

GEODOMISI Ltd. - Dr. Costas Sachpazis Civil & Geotechnical Engineering Consulting Company for Structural Engineering, Soil Mechanics, Rock Mechanics,

Foundation Engineering & Retaining Structures.

Tel.: (+30) 210 5238127, 210 5711263 - Fax.:+30 210 5711461 Mobile: (+30) 6936425722 & (+44) 7585939944, costas@

Calc. by

Dr.C.Sach pazis

Date

23/05/2013

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Job Ref.

Sheet no./rev.

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PAD FOOTING ANALYSIS AND DESIGN (BS8110-1:1997)

1100

1100

2500

Pad footing details Length of pad footing; Width of pad footing; Area of pad footing; Depth of pad footing; Depth of soil over pad footing; Density of concrete;

Column details Column base length; Column base width; Column eccentricity in x; Column eccentricity in y;

Soil details Dense, moderately graded, sub-angular, gravel Mobilisation factor; Density of soil; Design shear strength; Design base friction; Allowable bearing pressure;

Axial loading on column Dead axial load on column;

L = 2500 mm B = 1500 mm A = L ? B = 3.750 m2 h = 400 mm hsoil = 200 mm conc = 23.6 kN/m3

lA = 300 mm bA = 300 mm ePxA = 0 mm ePyA = 0 mm

m= ;1.5; soil = 20.0 kN/m3 ' = 25.0 deg = 19.3 deg Pbearing = 200 kN/m2

PGA = 200.0 kN

Project

Pad footing analysis and design (BS8110-1:1997)

Job Ref.

Section

Civil & Geotechnical Engineering

GEODOMISI Ltd. - Dr. Costas Sachpazis Civil & Geotechnical Engineering Consulting Company for Structural Engineering, Soil Mechanics, Rock Mechanics,

Foundation Engineering & Retaining Structures.

Tel.: (+30) 210 5238127, 210 5711263 - Fax.:+30 210 5711461 Mobile: (+30) 6936425722 & (+44) 7585939944, costas@

Calc. by

Dr.C.Sach pazis

Imposed axial load on column;

Date

23/05/2013

Wind axial load on column;

Total axial load on column;

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PQA = 165.0 kN PWA = 0.0 kN PA = 365.0 kN

Date

Sheet no./rev.

1

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Foundation loads Dead surcharge load; Imposed surcharge load; Pad footing self weight; Soil self weight; Total foundation load;

FGsur = 0.000 kN/m2 FQsur = 0.000 kN/m2 Fswt = h ? conc = 9.440 kN/m2 Fsoil = hsoil ? soil = 4.000 kN/m2 F = A ? (FGsur + FQsur + Fswt + Fsoil) = 50.4 kN

Horizontal loading on column base Dead horizontal load in x direction; Imposed horizontal load in x direction; Wind horizontal load in x direction; Total horizontal load in x direction; Dead horizontal load in y direction; Imposed horizontal load in y direction; Wind horizontal load in y direction; Total horizontal load in y direction;

HGxA = 20.0 kN HQxA = 15.0 kN HWxA = 0.0 kN HxA = 35.0 kN HGyA = 5.0 kN HQyA = 5.0 kN HWyA = 0.0 kN HyA = 10.0 kN

Moment on column base Dead moment on column in x direction; Imposed moment on column in x direction; Wind moment on column in x direction; Total moment on column in x direction; Dead moment on column in y direction; Imposed moment on column in y direction; Wind moment on column in y direction; Total moment on column in y direction;

MGxA = 15.000 kNm MQxA = 10.000 kNm MWxA = 0.000 kNm MxA = 25.000 kNm MGyA = 25.000 kNm MQyA = 30.000 kNm MWyA = 0.000 kNm MyA = 55.000 kNm

Check stability against sliding

Resistance to sliding due to base friction

Passive pressure coefficient;

Hfriction = max([PGA + (FGsur + Fswt + Fsoil) ? A], 0 kN) ? tan() = 87.7 kN Kp = (1 + sin(')) / (1 - sin(')) = 2.464

Stability against sliding in x direction

Passive resistance of soil in x direction;

Hxpas = 0.5 ? Kp ? (h2 + 2 ? h ? hsoil) ? B ? soil =

11.8 kN

Total resistance to sliding in x direction;

Hxres = Hfriction + Hxpas = 99.5 kN

PASS - Resistance to sliding is greater than horizontal load in x direction

Stability against sliding in y direction Passive resistance of soil in y direction; 19.7 kN Total resistance to sliding in y direction;

Hypas = 0.5 ? Kp ? (h2 + 2 ? h ? hsoil) ? L ? soil = Hyres = Hfriction + Hypas = 107.4 kN

Project

Pad footing analysis and design (BS8110-1:1997)

Job Ref.

Section

Civil & Geotechnical Engineering

Sheet no./rev.

1

GEODOMISI Ltd. - Dr. Costas Sachpazis Civil & Geotechnical Engineering Consulting Company for Structural Engineering, Soil Mechanics, Rock Mechanics,

Foundation Engineering & Retaining Structures.

Tel.: (+30) 210 5238127, 210 5711263 - Fax.:+30 210 5711461 Mobile: (+30) 6936425722 & (+44) 7585939944, costas@

Calc. by

Dr.C.Sach pazis

Date

23/05/2013

Chk'd by

-

Date

App'd by

Date

PASS - Resistance to sliding is greater than horizontal load in y direction

Check stability against overturning in x direction

Total overturning moment;

MxOT = MxA + HxA ? h = 39.000 kNm

Restoring moment in x direction

Foundation loading;

Mxsur = A ? (FGsur + Fswt + Fsoil) ? L / 2 = 63.000

kNm

Axial loading on column;

Mxaxial = (PGA) ? (L / 2 - ePxA) = 250.000 kNm

Total restoring moment;

Mxres = Mxsur + Mxaxial = 313.000 kNm

PASS - Restoring moment is greater than overturning moment in x direction

Check stability against overturning in y direction

Total overturning moment;

MyOT = MyA + HyA ? h = 59.000 kNm

Restoring moment in y direction

Foundation loading;

Mysur = A ? (FGsur + Fswt + Fsoil) ? B / 2 = 37.800

kNm

Axial loading on column;

Myaxial = (PGA) ? (B / 2 - ePyA) = 150.000 kNm

Total restoring moment;

Myres = Mysur + Myaxial = 187.800 kNm

PASS - Restoring moment is greater than overturning moment in y direction

Calculate pad base reaction Total base reaction; Eccentricity of base reaction in x; Eccentricity of base reaction in y;

T = F + PA = 415.4 kN eTx = (PA ? ePxA + MxA + HxA ? h) / T = 94 mm eTy = (PA ? ePyA + MyA + HyA ? h) / T = 142 mm

Check pad base reaction eccentricity

abs(eTx) / L + abs(eTy) / B = 0.132 Base reaction acts within combined middle third of base

Calculate pad base pressures

A) = 22.880 kN/m2

q1 = T / A - 6 ? T ? eTx / (L ? A) - 6 ? T ? eTy / (B ?

A) = 148.747 kN/m2

q2 = T / A - 6 ? T ? eTx / (L ? A) + 6 ? T ? eTy / (B ?

A) = 72.800 kN/m2

q3 = T / A + 6 ? T ? eTx / (L ? A) - 6 ? T ? eTy / (B ?

A) = 198.667 kN/m2 Minimum base pressure; Maximum base pressure;

q4 = T / A + 6 ? T ? eTx / (L ? A) + 6 ? T ? eTy / (B ?

qmin = min(q1, q2, q3, q4) = 22.880 kN/m2 qmax = max(q1, q2, q3, q4) = 198.667 kN/m2

PASS - Maximum base pressure is less than allowable bearing pressure

Project

Pad footing analysis and design (BS8110-1:1997)

Section

Civil & Geotechnical Engineering

GEODOMISI Ltd. - Dr. Costas Sachpazis Civil & Geotechnical Engineering Consulting Company for Structural Engineering, Soil Mechanics, Rock Mechanics,

Foundation Engineering & Retaining Structures.

Tel.: (+30) 210 5238127, 210 5711263 - Fax.:+30 210 5711461 Mobile: (+30) 6936425722 & (+44) 7585939944, costas@

Calc. by

Dr.C.Sach pazis

Date

23/05/2013

Chk'd by

-

Date

Job Ref.

Sheet no./rev.

1

App'd by

Date

148.7 kN/m 2

198.7 kN/m 2

22.9 kN/m 2

72.8 kN/m 2

Partial safety factors for loads Partial safety factor for dead loads; Partial safety factor for imposed loads; Partial safety factor for wind loads;

Ultimate axial loading on column Ultimate axial load on column;

Ultimate foundation loads Ultimate foundation load; 70.6 kN

Ultimate horizontal loading on column Ultimate horizontal load in x direction; kN Ultimate horizontal load in y direction; kN

Ultimate moment on column Ultimate moment on column in x direction; 37.000 kNm Ultimate moment on column in y direction; 83.000 kNm

fG = 1.40 fQ = 1.60 fW = 0.00 PuA = PGA ? fG + PQA ? fQ + PWA ? fW = 544.0 kN Fu = A ? [(FGsur + Fswt + Fsoil) ? fG + FQsur ? fQ] =

HxuA = HGxA ? fG + HQxA ? fQ + HWxA ? fW = 52.0 HyuA = HGyA ? fG + HQyA ? fQ + HWyA ? fW = 15.0

MxuA = MGxA ? fG + MQxA ? fQ + MWxA ? fW = MyuA = MGyA ? fG + MQyA ? fQ + MWyA ? fW =

Project

Pad footing analysis and design (BS8110-1:1997)

Job Ref.

Section

Civil & Geotechnical Engineering

Sheet no./rev.

1

GEODOMISI Ltd. - Dr. Costas Sachpazis Civil & Geotechnical Engineering Consulting Company for Structural Engineering, Soil Mechanics, Rock Mechanics,

Foundation Engineering & Retaining Structures.

Tel.: (+30) 210 5238127, 210 5711263 - Fax.:+30 210 5711461 Mobile: (+30) 6936425722 & (+44) 7585939944, costas@

Calc. by

Dr.C.Sach pazis

Date

23/05/2013

Calculate ultimate pad base reaction

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Ultimate base reaction; Eccentricity of ultimate base reaction in x; Eccentricity of ultimate base reaction in y;

Tu = Fu + PuA = 614.6 kN eTxu = (PuA ? ePxA + MxuA + HxuA ? h) / Tu = 94 mm eTyu = (PuA ? ePyA + MyuA + HyuA ? h) / Tu = 145 mm

Date

Calculate ultimate pad base pressures

31.957 kN/m2

221.824 kN/m2

105.941 kN/m2

295.808 kN/m2 Minimum ultimate base pressure; Maximum ultimate base pressure;

q1u = Tu/A - 6?Tu?eTxu/(L?A) - 6?Tu?eTyu/(B?A) = q2u = Tu/A - 6?Tu?eTxu/(L?A) + 6?Tu? eTyu/(B?A) = q3u = Tu/A + 6?Tu?eTxu/(L?A) - 6?Tu?eTyu/(B?A) = q4u = Tu/A + 6?Tu?eTxu/(L?A) + 6?Tu?eTyu/(B?A) = qminu = min(q1u, q2u, q3u, q4u) = 31.957 kN/m2 qmaxu = max(q1u, q2u, q3u, q4u) = 295.808 kN/m2

Calculate rate of change of base pressure in x direction

Left hand base reaction;

fuL = (q1u + q2u) ? B / 2 = 190.336 kN/m

Right hand base reaction;

fuR = (q3u + q4u) ? B / 2 = 301.312 kN/m

Length of base reaction;

Lx = L = 2500 mm

Rate of change of base pressure;

Cx = (fuR - fuL) / Lx = 44.390 kN/m/m

Calculate pad lengths in x direction Left hand length; Right hand length;

LL = L / 2 + ePxA = 1250 mm LR = L / 2 - ePxA = 1250 mm

Calculate ultimate moments in x direction Ultimate moment in x direction; = 198.900 kNm

Mx = fuL?LL2/2+Cx?LL3/6-Fu?LL2/(2?L)+HxuA?h+MxuA

Calculate rate of change of base pressure in y direction

Top edge base reaction;

fuT = (q2u + q4u) ? L / 2 = 647.040 kN/m

Bottom edge base reaction;

fuB = (q1u + q3u) ? L / 2 = 172.373 kN/m

Length of base reaction;

Ly = B = 1500 mm

Rate of change of base pressure;

Cy = (fuB - fuT) / Ly = -316.444 kN/m/m

Calculate pad lengths in y direction Top length; Bottom length;

LT = B / 2 - ePyA = 750 mm LB = B / 2 + ePyA = 750 mm

Calculate ultimate moments in y direction Ultimate moment in y direction; kNm

My = fuT?LT2/2+Cy?LT3/6-Fu?LT2/(2?B) = 146.500

Material details Characteristic strength of concrete;

fcu = 30 N/mm2

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