Design of Stiffened Slab Foundations on Reactive Soils Using 3D Numerical Modeling
Publication: International Journal of Geomechanics
Volume 20, Issue 7
Abstract
Over the past decades, stiffened slab foundations have been assessed as the most successful foundation system for structures that are susceptible to risks from reactive soils. However, most existing design methods simplify the complex three-dimensional (3D) moisture flow into a two-dimensional (2D) problem, which poses inevitable deformation incompatibility between soil mounds and footings. This paper proposes a design method based on advanced 3D finite-element (FE) coupled flow-deformation and stress analysis using a realistic seepage process, thereby mitigating the significant limitations associated with the available design methods. The paper presents the basic assumptions and necessary procedures of the proposed design method, along with detailed calibration and validation via an example that was also solved using a popular method, for comparison. The paper also uses the 3D modeling process to perform a comprehensive parametric study and produce a design tool based on a sophisticated artificial intelligence (AI) analysis using the evolutionary polynomial regression (EPR) technique.
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Acknowledgments
The authors would like to acknowledge the contribution of the Australian Government Research Training Program Scholarship in supporting this research.
Notation
The following symbols are used in this paper:
- aj
- constant;
- B
- width of slab foundation;
- Bw
- minimum breadth of stiffening beam (web width);
- bf
- effective flange width (for T-sections);
- e
- edge distance;
- ES
- is the matrix of exponents;
- E1
- extremely reactive clay sites, which may experience extreme ground movement (75 mm < ys ≤ 100 mm);
- E2
- extremely reactive clay sites, which may experience extreme ground movement (100 mm < ys ≤ 120 mm);
- F
- a function constructed by the process;
- f
- a function selected by the user;
- concrete grade;
- fy
- reinforcement steel yield stress;
- H1
- highly reactive clay sites, which may experience high ground movement;
- H2
- highly reactive clay sites, which may experience very high ground movement;
- Icr
- cracking transformed moment of inertia;
- Ieff
- effective moment of inertia;
- Ig
- gross moment of inertia;
- k
- candidate inputs;
- L
- length of slab foundation;
- Ld
- diagonal length (from corner to corner) of slab foundation;
- M
- moderately reactive clay sites, which may experience moderate ground movement;
- M
- maximum service moment;
- Mcr
- cracking moment;
- Ml
- bending moment in the long direction;
- Ms
- bending moment in the short direction;
- Mu
- ultimate moment;
- m
- the number of terms of the target expression;
- N
- 500 MPa (fy) steel grade;
- r
- coefficient of correlation;
- S
- slightly reactive clay sites, which may experience slight ground movement;
- Tb
- depth of the stiffening beam;
- Teq
- equivalent slab thickness;
- Vl
- shear force in the long direction;
- Vs
- shear force in the short direction;
- X
- matrix of input variables;
- Xi
- vector(s);
- vector of target values;
- y
- estimated vector of output of the process;
- ym
- maximum soil mound differential movement;
- ys
- characteristic surface heave; and
- Δall
- allowable slab foundation differential movement.
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Published In
International Journal of Geomechanics
Volume 20 • Issue 7 • July 2020
Copyright
© 2020 American Society of Civil Engineers.
History
Received: Feb 27, 2019
Accepted: Oct 8, 2019
Published online: Apr 29, 2020
Published in print: Jul 1, 2020
Discussion open until: Sep 29, 2020
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