Effect of eccentric loading on foundation
A foundation can be subjected to eccentric loads and or to inclined loads eccentric or
concentric if a vertical load acts on a rectangular foundation as in figure (a) of width B
and L such that the load has eccentricities eB and eL to answer this kind of arrangement
we imagine an artificial concept of effective foundation width and length. The effective
foundation is that foundation plan that is symmetrical about the point of application of the
load where the effective length is L1 =L - 2eL and effective width B1 = B - 2eB
For strip footing with width B subjected to a line load with an eccentricity e the B1 = B-
2e
For such an arrangement the ultimate load is computed as
qu = CNc + ꙋZNq+ 0.5ꙋBNꙋ
qu = CNc Sc Ic Dc+ꙋZ Nq Sq Iq Dq +0.5ꙋ B Nꙋ Sꙋ Iꙋ Dꙋ
where Sc Sq Sꙋ are shape factors
Ic Iq Iꙋ are inclination factors
Dc Dq Dꙋ are depth factors
The values of Nc and Nq used in these equations are obtained from Meyerholf
equation(1963)
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, Inclined loading on foundation
For the inclined load as shown in figure (b) the approach is to determine the
horizon and vertical component of the load P as PH and PV and then followed
by taking moments to eccentricity e in order that the effective width of the
foundation B1 can be determine from the formula
B1 = B – 2e
The ultimate bearing capacity of the strip foundation of width B is then
computed as to be equal to a strip foundation of width B1 subjected to a
concentric load P inclined at to the vertical
qu = CNc Sc Ic Dc+ꙋZ Nq Sq Iq Dq +0.5ꙋ B Nꙋ Sꙋ Iꙋ
Dꙋ Ic = Iq = ( 1 - / 900 )2
Iꙋ = (1 - /ø )2
Foundation design example 1
Sand on a proposed construction site has the following particulars
i) Sand internal angle of shearing resistance ø =360
ii) Unit weight =19KN/m3
iii) Factor of safety
This study source was downloaded by 100000856941565 from CourseHero.com on 12-03-2022 17:24:35 GMT -06:00
https://www.coursehero.com/file/171560737/EECI-4271-Foundation-Engineering-Effect-of-eccentric-loading-on-foundation-Lecture-4pdf/
A foundation can be subjected to eccentric loads and or to inclined loads eccentric or
concentric if a vertical load acts on a rectangular foundation as in figure (a) of width B
and L such that the load has eccentricities eB and eL to answer this kind of arrangement
we imagine an artificial concept of effective foundation width and length. The effective
foundation is that foundation plan that is symmetrical about the point of application of the
load where the effective length is L1 =L - 2eL and effective width B1 = B - 2eB
For strip footing with width B subjected to a line load with an eccentricity e the B1 = B-
2e
For such an arrangement the ultimate load is computed as
qu = CNc + ꙋZNq+ 0.5ꙋBNꙋ
qu = CNc Sc Ic Dc+ꙋZ Nq Sq Iq Dq +0.5ꙋ B Nꙋ Sꙋ Iꙋ Dꙋ
where Sc Sq Sꙋ are shape factors
Ic Iq Iꙋ are inclination factors
Dc Dq Dꙋ are depth factors
The values of Nc and Nq used in these equations are obtained from Meyerholf
equation(1963)
This study source was downloaded by 100000856941565 from CourseHero.com on 12-03-2022 17:24:35 GMT -06:00
https://www.coursehero.com/file/171560737/EECI-4271-Foundation-Engineering-Effect-of-eccentric-loading-on-foundation-Lecture-4pdf/
, Inclined loading on foundation
For the inclined load as shown in figure (b) the approach is to determine the
horizon and vertical component of the load P as PH and PV and then followed
by taking moments to eccentricity e in order that the effective width of the
foundation B1 can be determine from the formula
B1 = B – 2e
The ultimate bearing capacity of the strip foundation of width B is then
computed as to be equal to a strip foundation of width B1 subjected to a
concentric load P inclined at to the vertical
qu = CNc Sc Ic Dc+ꙋZ Nq Sq Iq Dq +0.5ꙋ B Nꙋ Sꙋ Iꙋ
Dꙋ Ic = Iq = ( 1 - / 900 )2
Iꙋ = (1 - /ø )2
Foundation design example 1
Sand on a proposed construction site has the following particulars
i) Sand internal angle of shearing resistance ø =360
ii) Unit weight =19KN/m3
iii) Factor of safety
This study source was downloaded by 100000856941565 from CourseHero.com on 12-03-2022 17:24:35 GMT -06:00
https://www.coursehero.com/file/171560737/EECI-4271-Foundation-Engineering-Effect-of-eccentric-loading-on-foundation-Lecture-4pdf/
