Pseudo-Dynamic Bearing Capacity of Shallow Strip Footing Resting on c-Φ Soil Considering Composite Failure Surface

2015 ◽  
Vol 6 (2) ◽  
pp. 12-34 ◽  
Author(s):  
Arijit Saha ◽  
Sima Ghosh
Keyword(s):  
Bearing Capacity ◽  
Failure Mechanism ◽  
Limit Equilibrium ◽  
Failure Surface ◽  
Friction Angle ◽  
Strip Footing ◽  
Unit Weight ◽  
Composite Failure ◽  
Seismic Accelerations ◽  
Seismic Bearing Capacity

The evaluation of bearing capacity of shallow strip footing under seismic loading condition is an important phenomenon. This paper presents a pseudo-dynamic approach to evaluate the seismic bearing capacity of shallow strip footing resting on c-F soil using limit equilibrium method considering the composite failure mechanism. A single seismic bearing capacity coefficient (N?e) presents here for the simultaneous resistance of unit weight, surcharge and cohesion, which is more practical to simulate the failure mechanism. The effect of soil friction angle(F), soil cohesion(c), shear wave and primary wave velocity(Vs, Vp) and horizontal and vertical seismic accelerations(kh, kv) are taken into account to evaluate the seismic bearing capacity of foundation. The results obtained from the present analysis are presented in both tabular and graphical non-dimensional form. Results are thoroughly compared with the existing values in the literature and the significance of the present methodology for designing the shallow strip footing is discussed.

Seismic Bearing Capacity Factor Considering Composite Failure Mechanism

2018 ◽  
Vol 9 (1) ◽  
pp. 65-77
Author(s):  
Swetha S Kurup ◽  
Sreevalsa Kolathayar
Keyword(s):  
Bearing Capacity ◽  
Failure Mechanism ◽  
Static Analysis ◽  
Limit Equilibrium ◽  
Failure Surface ◽  
Shallow Foundation ◽  
Capacity Factor ◽  
Composite Failure ◽  
Seismic Bearing Capacity ◽  
Bearing Capacity Factor

This article describes how the design of shallow foundation needs complete knowledge about bearing capacity. During earthquakes additional lateral force acts at the foundation bed which reduces the bearing capacity. Most of the literature present either the pseudo static analysis or assume a planar failure surface to estimate seismic bearing capacity factors. Here, a pseudo dynamic approach that considers the time dependent effect of earthquake loading is employed. A composite failure surface has been considered for a more realistic estimation of seismic bearing capacity. New expressions were formulated to arrive at the seismic bearing capacity factor, considering the forces acting on the failure wedge based on the limit equilibrium approach. The effect of soil friction angles and the seismic peak of horizontal ground accelerations on the seismic bearing capacity were studied using the proposed method. It was observed that present pseudo-dynamic analysis with a composite failure mechanism gives lower values of seismic bearing capacity factors when compared to pseud- static analysis.

GENERALIZED SOLUTION FOR SEISMIC UPLIFT CAPACITY OF STRIP ANCHORS USING PSEUDO-STATIC APPROACH

2007 ◽  
Vol 01 (04) ◽  
pp. 311-328 ◽  
Author(s):  
DEEPANKAR CHOUDHURY ◽  
K. S. SUBBA RAO
Keyword(s):  
Limit Equilibrium ◽  
Failure Surface ◽  
Friction Angle ◽  
Present Theory ◽  
Generalized Solutions ◽  
Unit Weight ◽  
Uplift Capacity ◽  
Principle Of Superposition ◽  
Seismic Acceleration ◽  
Acceleration Coefficient

Generalized solutions for uplift capacity of inclined shallow strip anchors embedded in general c–ϕ soils with inclined slope carrying a uniform surcharge is developed in this paper for seismic condition. The individual effects of unit weight, surcharge and cohesion components on the computation of uplift capacity of anchors are considered. Limit equilibrium method with logspiral failure surface is adopted in the analysis and the effects of seismic forces are considered as pseudo-static forces. The results have been presented in the form of seismic uplift capacity factors as functions of anchor inclination, ground inclination, embedment ratio, soil friction angle and seismic acceleration coefficients both in the horizontal and vertical directions. Both the seismic accelerations change significantly the uplift capacity of anchors. Effect of the vertical seismic acceleration coefficient has been found to always reduce the uplift capacity whereas the effect of horizontal seismic acceleration coefficient has been found to reduce the uplift capacity in most of the cases. Results are presented in graphical and tabular forms. Estimation of error while using the principle of superposition to compute the seismic uplift capacity is also conducted. A comparative study between the present theory and available results in literature shows the merits and requirement of the present analysis.

Bearing Capacity of Strip Footings in Two Layered Cohesive-friction Soils

1974 ◽  
Vol 11 (1) ◽  
pp. 32-45 ◽  
Author(s):  
P. Purushothamaraj ◽  
B. K. Ramiah ◽  
K. N. Venkatakrishna Rao
Keyword(s):  
Bearing Capacity ◽  
Failure Mechanism ◽  
Friction Angle ◽  
Unit Weight ◽  
Layered Soils ◽  
Strip Footings

A method has been formulated for bearing capacity of footings on two layered soils with varying cohesion, friction, and unit weight based on the second theorem of Drucker and Prager (kinematical consideration). The failure mechanism considered was fundamentally similar to that of Prandtl–Terzaghi but with different wedge angles. The critical wedge angles were found in each case. Bearing capacity charts for footings are presented by varying cohesion in layers, with the same friction angle and unit weight. The charts are readily usable for any combination of c2/c1, d/b, φ, and γ.

scholarly journals Evaluation of Bearing Capacity of Strip Footing Using Random Layers Concept

2015 ◽  
Vol 37 (3) ◽  
pp. 31-39 ◽  
Author(s):  
Marek Kawa ◽  
Dariusz Łydżba
Keyword(s):  
Monte Carlo ◽  
Bearing Capacity ◽  
Failure Mechanism ◽  
Design Theory ◽  
Cohesive Soil ◽  
Probability Of Failure ◽  
Mean Value ◽  
Strip Footing ◽  
Random Field Theory ◽  
The Mean

Abstract The paper deals with evaluation of bearing capacity of strip foundation on random purely cohesive soil. The approach proposed combines random field theory in the form of random layers with classical limit analysis and Monte Carlo simulation. For given realization of random the bearing capacity of strip footing is evaluated by employing the kinematic approach of yield design theory. The results in the form of histograms for both bearing capacity of footing as well as optimal depth of failure mechanism are obtained for different thickness of random layers. For zero and infinite thickness of random layer the values of depth of failure mechanism as well as bearing capacity assessment are derived in a closed form. Finally based on a sequence of Monte Carlo simulations the bearing capacity of strip footing corresponding to a certain probability of failure is estimated. While the mean value of the foundation bearing capacity increases with the thickness of the random layers, the ultimate load corresponding to a certain probability of failure appears to be a decreasing function of random layers thickness.

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