ELPLA (ELASTIC PLATE) is a program for analyzing raft foundations of arbitrary shape with the real subsoil model. The mathematical solution of the raft is based on the finite element method. The program can analyze different types of subsoil models, especially the three-dimensional Continuum model that considers any number of irregular layers. A good advantage of this program is the capability to handle the three analyses of flexible, elastic and rigid foundations. In addition, the mesh of the rigid and flexible foundations can be constructed to be analogous to the finite elements mesh of the elastic foundation. Therefore, the three analyses can be compared easily and correctly. ELPLA can also be used to represent the effect of external loads, neighboring foundations, tunneling and the influence of the temperature difference on the raft.

## Piled Raft Foundation

ELPLA is a powerful tool for analyzing piled-raft foundations. ELPLA has models for analyzing single pile, pile groups, piled raft and friction piles in clay soil.

Analysis of Piled Raft

Multiple Models to Meet Design Requirements

Practical Examples

Digital book and practical examples are provided with the software package

In ELPLA, there are different calculation methods to analysis of the raft on piles. Therefore, the pile group for each method are required to define according to the used soil model as described in the next paragraphs.

Pile groups for Simple Assumption Model

In this model all forces acting on the raft will be transmit linearly on the piles. When the "Pile groups" command is chosen for this model, the following Table in Figure C-71 appears to define the pile diameter. Pile diameter is required for design of the slab for punching shear.

Figure C-71  Defining pile groups for Simple Assumption Model

Pile groups for Winkler’s Model

For the two methods of Constant and Variable Modulus of Subgrade Reaction (methods 2 and 3), when the modulus of subgrade reaction is required to define by the user, pile groups in this case will be the pile diameter and the pile stiffness, Figure C-72.

Figure C-72  Defining pile groups for Winkler’s Model

Pile groups for Isotropic Elastic Half-Space and Layered soil Models

When pile groups are required to define for one of these two soil models, the following Dialog box of Figure C-73 appears. The soil data around and under the pile are required to define. Soil data are used to determine the pile stiffness due to the soil type by ELPLA.

Figure C-73  Defining pile groups for Half-Space and Layered soil Models

## ELPLA Editions

ELPLA is available in two editions, each geared to meet a specific set of user requirements. The features available to you depend on which product you have.

ELPLA Lite Edition

ELPLA Lite edition allows users to easily create projects for analysis and design floor slab or raft foundation. It includes all the ELPLA standard functions except that the node number is limited to 300 nodes.

Full documentation is provided with ELPLA Lite edition.

Documentation provided with ELPLA includes the "ELPLA reinforced concrete design" book plus ELPLA User’s Guide containing full documentation of ELPLA theory with illustrated examples.

ELPLA Professional Edition

The professional edition provides professional users with all methods for analysis and design floor slab, isolated raft or system of rafts. It includes all the features of the ELPLA theory.

The following table shows the difference among ELPLA editions:

 Lite Professional Max. number of nodes 300 Unlimited Analysis of system of many foundations - x Calculation methods: 1-Linear Contact Pressure x x 2- Constant Modulus of Subgrade Reaction x x 3- Variable Modulus of Subgrade Reaction x x 4- Modification of Modulus of Subgrade Reaction by Iteration - x 5- Isotropic Elastic Half Space - x 6- Modulus of Compressibility (Iteration) x x 7- Modulus of Compressibility (Elimination) - x 8- Rigid Slab x x 9- Flexible foundation - x System Symmetry: Symmetrical system about x-axis - x Symmetrical system about y-axis - x Double-symmetrical system - x Anti-symmetrical system in x-axis - x Special Cases: Influence of temperature change - x Influence of additional settlements - x Influence of external foundation - x

## Calculation methods

In ELPLA, different numerical methods with 3 soil models are considered for analyzing raft foundations as follows:

1) Linear contact pressure (Simple assumption model)

2) Constant modulus of subgrade reaction (Winkler's model)

3) Variable modulus of subgrade reaction (Winkler's model)

4) Modification of modulus of subgrade reaction by iteration (Winkle's model/ Continuum model)

5) Modulus of compressibility method for elastic raft on half-space soil medium (Isotopic elastic half-space soil medium - Continuum model)

6) Modulus of compressibility method for elastic raft on layered soil medium (Solving system of  linear equations by iteration) (Layered soil medium - Continuum model)

7) Modulus of compressibility method for elastic raft on layered soil medium (Solving system of linear equations by elimination) (Layered soil medium - Continuum model)

8) Modulus of compressibility method for rigid raft (Isotopic elastic half-space soil medium and layered soil medium - Continuum model)

9) Modulus of compressibility method for flexible raft (Isotopic elastic half-space soil medium and layered soil medium- Continuum model)

Beside the 9 main methods stated above, ELPLA can also be used to analyze system of flexible, elastic or rigid foundations. Further more, ELPLA can be used to analyze many other structural problems such as floor slabs, grids, plane frame and plane stress.

## Geometry and Loads

It is possible to consider raft with any arbitrary shape including holes (Figure A-1). Also it is possible to consider raft with variable thickness (Figure A-2). Loads on the raft can be applied independently on the mesh at any position. Loads may be defined in different types such as point loads, line loads and polygon uniform loads (Figure A-3).

Figure A-1 Arbitrary shape of raft with hole

Figure A-2 Variable slab thickness

Figure A-3 Arbitrary type of loads

## Boundary conditions

It is possible to define elastic or fixed rotations and displacements on the raft (Figure A-4). Also transitional or rotational springs may be defined.

Figure A-4 Fixed displacements

## Soil

The soil is defined by a number of borings each boring has multi-layers with different soil material (Figure A-5). Also variable thickness and discontinuous soil strata can be considered (Figure A-6). Loading and reloading of the soil modulus can be taken into account by the analysis (Figure A-7). Three different methods are used to determine the flexibility coefficients or the modulus of subgrade reaction:

1- Hand-Division of boring logs to nodes

2- Subareas method

3- Interpolation method

It is possible to draw soil layers by different symbols according to the German Standard DIN 4023 for easy identification. Also the limit depth of soil layers can be determined. Variable foundation levels can be considered in the analysis.

Figure A-5 The soil is defined by a number of borings

Figure A-6 Variable thickness soil strata

## Graphical drawing of data and results

You can display, plot and print data and results graphically using the sub program ELPLA-Graphic. It is possible to draw raft geometry, boring locations, soil profiles, loading, boundary conditions, settlement, deformation, contact pressure, moment, shear, modulus of subgrade reaction and reinforcement (Figure A-8 to Figure A-14).

The results and data can be presented graphically as follows:

• Data in the plan
• Data in isometric view
• Boring locations
• Boring logs
• Limit depth
• Arrangement of rafts including neighbor foundations
• Result values in the plan
• Distribution of results in the plan
• Results as contour lines
• Results in isometric view
• Results as circular diagrams
• Principal moments as streaks
• Support reactions as arrows
• Deformation
• Girders

The graphical drawing, if desired, can be saved as WMF-Files format. In which can be exported into other Windows applications to prepare reports, slide presentations, or add further information to the drawing.

Figure A-8 Results can be tabulated on the mesh

Figure A-9 Results can be contoured

Figure A-10 Moment distribution on the raft can be plotted

Figure A-11 Principal moments as streaks

Figure A-12 Raft deformation can be plotted as a deformed mesh

Figure A-13 Results can be plotted in isometric shape

Figure A-14 Results can be plotted as circular diagram

## Drawing sections

Further more, you can display, plot and print results at specified sections graphically using the sub program ELPLA-Section. It is possible to draw settlements, contact pressures, deformation, internal forces, modulus of subgrade reaction and reinforcement (Figure A-15 to Figure A-17). It is also possible to determine extreme values of the results from many load cases. The results can be presented graphically as follows:

1- Section in x-direction
2- Max./ Min. values in x-direction
3- Overlapping in x-direction
4- Section in y-direction
5- Max./ Min. values in y-direction
6- Overlapping in y-direction
7- Arbitrary section

Also, drawing sections, if desired, can be saved as WMF-Format files. In which can be exported to other Windows applications such as Word, WordPerfect and AutoCAD to prepare reports, slide presentations, or add further information.

Figure A-15 Results can be plotted at specified section

Figure A-16 Results from many projects can be plotted together

Figure A-17 Max. and Min. values can be calculated and plotted together

## Tabulating data and results

You can list data and results using the sub program ELPLA-List. Listing the data and results can be displayed first on the screen, and then can be sent to the printer (Figure A-18 to Figure A-20). The results and data can be listed as follows:

1- Display tables of data
2- Print tables of data
3- List tables of data through Text-Editor
4- Display tables of results
5- Print tables of results
6- List tables of results through Text-Editor

The listed results and data, if desired, can be saved as ASCII-format Files. In which can be exported to other Windows applications to prepare reports or add further information.

Figure A-18 Data can be tabulated

Figure A-19 Results can be tabulated

Figure A-20 Data can be imported to another text editor applications

## Bearing capacity factors

The bearing capacity factors used to determine the ultimate bearing capacity can optionally be defined according to different codes and authors. These factors are required to carry out the nonlinear analysis of the soil. The bearing capacity factors are defined according to (Figure B-2):

 - German Standard - Euro Code - Egyptian code - Terzaghi - Meyerhof

Figure B-2 Menu "Bearing capacity factors"

## Boring log

New separate program ELPLA-Boring is developed. By the program, the user can define boring logs graphically and draw limit depths (Figure B-94).

Figure B-94 ELPLA-Boring

## Design of the slab

The design of the slab for determining reinforcement and punching stress can be carried out according to the following design codes:

 EC2 European Committee for Standardization, Design of Concrete Structures - Eurocode 2 DIN 1045 German Institute for Standardization, Design and Construction of Reinforced Concrete ACI American Concrete Institute Building Code Requirements for Structural Concrete ECP Egyptian Code of Practice for Design and Construction of Reinforced Concrete Structures

## Self-Adaptive Mesh Wizard

The Self-Adaptive Mesh Wizard is a tool that helps the user for generating finite element mesh with better element/ node distributions. The wizard is used to regenerate the finite element mesh for slab floor and raft problems. The new mesh will be generated based on the strain energy distribution. The self-adaptive technique used in this wizard reduces general system error besides enhances stress distributions. Adaptive mesh is generated either by using Delaunay generation or by using Grid-based generation (Figure 1).

- Self-Adaptive Mesh Wizard 1.0 is included in ELPLA 9.2 (MUI)

 a-Original Mesh
b-Adaptive mesh (Delaunay generation)
c-Adaptive mesh (Grid-based generation)

Figure 1 Two types of adaptive mesh generation: Delaunay generation and Grid-based generation

### Subcategories

Beside the following tutorial and verification examples, ELPLA solves different civil engineering problems.

- Soil-structure interaction problems.

- Analysis and design of rafts.
- Analysis of rigid rafts.
- Analysis of flexible foundations.
- Analysis and design of floor slabs.
- Determining the consolidation settlements.
- Analysis and design of pile caps.
- Determining forces on piles due to structure loads.
- Settlement calculation of surface foundations.
- Determining the settlement due to surcharge fills or surcharge concentrated loads.
- Determining the surface settlement around rafts.
- Determining the constant or variable modulus of subgrade reaction.
- Effect of external loads or neighboring foundations.
- Effect of temperature difference.
- Effect of tunnelling.
- Analysis of system of flexible, elastic or rigid foundations.
- Analysis of beams or grids by FE method.
- Simulation of excavations and construction of embankments.
- Determining the ultimate bearing capacity of the soil.
- Determining the limit depth.
- Eliminating negative contact pressure.
- Design of slabs according to ACIEC 2, DIN 1045 and ECP codes.
- Determining the stress in soil.

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