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Geotechnical Software - Shallow Foundation
Beam foundation is adopted in the case of combined footing supporting two or more columns. The combined footing is modelled structurally as a beam foundation resting on the soil. The sub soil may be modelled in several ways. Two common models for the subsoil are:
(a) Discrete spring-bed model using modulus of subgrade reaction (also known as “beams on elastic foundation” or “Winkler beam theory”). The soil parameter used for this analysis is the modulus of subgrade reaction.
(b) Elastic half–space model where the subsoil model is replaced by elastic, homogeneous, isotropic semi-infinite continuum. The soil parameters used are elastic modulus and Poisson ratio.
The “Beam Foundations” software consists of two modules incorporating the above two commonly used models of analysis.Key Features
Discrete
spring-bed model
This model is based on subgrade reaction
theory. The analysis of the foundation beam is based on the
solution of the differential equation
where k=k_s×B, EI=Flexural rigidity of foundation beam,
k_s=Modulus of subgrade reaction, B=width of foundation beam. The foundation base is assumed to be smooth and the soil pressure is assumed uniform across the width. The solution of this differential equation is complicated and cumbersome except for very simple problems. For practical problems where the loads are in the form of several concentrated loads, moments and UD loads it becomes necessary to resort to numerical solutions. The software module uses finite element solution of the problem using the exact displacement function and therefore gives exact solution to the problem.
Elastic
half-space model
In this approach the subsoil is
modelled by a homogeneous, isotropic elastic half-space
characterised by an elastic modulus and a Poisson ratio. This
model has the merit of accounting for the continuous nature of
the soil medium. The discrete spring bed model does not account
for the soil continuity. The solution is based on the vertical
displacement due to a distributed surface loading on an elastic
half-space (given by “Boussinesq”). Again numerical solution of
the problem is essential for tackling practical problems as no
analytical solution is available for finite beams. The software
module for Elastic half-space model is based on finite element
formulation assuming a smooth base and uniform soil pressure
across the width.
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