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 threedimensional 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.
ELPLA is a powerful tool for analyzing piledraft 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 C71 appears to define the pile diameter. Pile diameter is required for design of the slab for punching shear.
Figure C71 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 C72.
Figure C72 Defining pile groups for Winkler’s Model
Pile groups for Isotropic Elastic HalfSpace and Layered soil Models
When pile groups are required to define for one of these two soil models, the following Dialog box of Figure C73 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 C73 Defining pile groups for HalfSpace and Layered soil Models
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 (Free)
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:
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 halfspace soil medium (Isotopic elastic halfspace 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 halfspace soil medium and layered soil medium  Continuum model)
9) Modulus of compressibility method for flexible raft (Isotopic elastic halfspace 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.
It is possible to consider raft with any arbitrary shape including holes (Figure A1). Also it is possible to consider raft with variable thickness (Figure A2). 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 A3).
Figure A1 Arbitrary shape of raft with hole
Figure A2 Variable slab thickness
Figure A3 Arbitrary type of loads
It is possible to define elastic or fixed rotations and displacements on the raft (Figure A4). Also transitional or rotational springs may be defined.
The soil is defined by a number of borings each boring has multilayers with different soil material (Figure A5). Also variable thickness and discontinuous soil strata can be considered (Figure A6). Loading and reloading of the soil modulus can be taken into account by the analysis (Figure A7). Three different methods are used to determine the flexibility coefficients or the modulus of subgrade reaction:
1 HandDivision 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 A5 The soil is defined by a number of borings
Figure A6 Variable thickness soil strata
Figure A7 Loading and reloading soil modulus are considered
You can display, plot and print data and results graphically using the sub program ELPLAGraphic. 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 A8 to Figure A14).
The results and data can be presented graphically as follows:
The graphical drawing, if desired, can be saved as WMFFiles format. In which can be exported into other Windows applications to prepare reports, slide presentations, or add further information to the drawing.
Figure A8 Results can be tabulated on the mesh
Figure A9 Results can be contoured
Figure A10 Moment distribution on the raft can be plotted
Figure A11 Principal moments as streaks
Figure A12 Raft deformation can be plotted as a deformed mesh
Figure A13 Results can be plotted in isometric shape
Figure A14 Results can be plotted as circular diagram
Further more, you can display, plot and print results at specified sections graphically using the sub program ELPLASection. It is possible to draw settlements, contact pressures, deformation, internal forces, modulus of subgrade reaction and reinforcement (Figure A15 to Figure A17). It is also possible to determine extreme values of the results from many load cases. The results can be presented graphically as follows:
Also, drawing sections, if desired, can be saved as WMFFormat 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 A15 Results can be plotted at specified section
Figure A16 Results from many projects can be plotted together
Figure A17 Max. and Min. values can be calculated and plotted together
You can list data and results using the sub program ELPLAList. Listing the data and results can be displayed first on the screen, and then can be sent to the printer (Figure A18 to Figure A20). The results and data can be listed as follows:
The listed results and data, if desired, can be saved as ASCIIformat Files. In which can be exported to other Windows applications to prepare reports or add further information.
Figure A18 Data can be tabulated
Figure A19 Results can be tabulated
Figure A20 Data can be imported to another text editor applications
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 B2):
  German Standard 
  Euro Code 
  Egyptian code 
  Terzaghi 
  Meyerhof 
Figure B2 Menu "Bearing capacity factors"
Enhancements in ELPLA 9.0 
New separate program ELPLABoring is developed. By the program, the user can define boring logs graphically and draw limit depths (Figure B94).
Figure B94 ELPLABoring
Enhancements in ELPLA 8.0 
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 
The SelfAdaptive 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 selfadaptive 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 Gridbased generation (Figure 1).
 SelfAdaptive Mesh Wizard 1.0 is included in ELPLA 9.2 (MUI)

bAdaptive mesh (Delaunay generation)


cAdaptive mesh (Gridbased generation)

Figure 1 Two types of adaptive mesh generation: Delaunay generation and Gridbased generation
Beside the following tutorial and verification examples, ELPLA solves different civil engineering 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 ACI, EC 2, DIN 1045 and ECP codes.
 Determining the stress in soil.
GEOTEC Office Applications with Multilingual User Interface
The new Englishlanguage versions of GEOTEC Office applications with Multilingual User Interface (MUI) are now available. The Multilingual User Interface Pack is a set of language XML resource files that can be added to the English version of GEOTEC Office applications. MUI Pack allows the user interface language to be changed according to the preferences of individual users to one of the available supported languages. MUI Pack provides a single version of GEOTEC Office applications to which users can add one or more MUI Packs providing localized user interface and help files. Now, three languages are already available in ELPLA 9.1; English, German and Arabic.
The major benefits of the new MUI Pack are:
 Allows user interface switching between languages
 Easy to update with new languages
 Languagespecific updates do not affect all languages
 Languages are XML based resources that make it easier to users to add their own languages.
TwoDimensional Frame Problems
The analysis of TwoDimensional frame problems is now available in ELPLA.
Design for punching
It is possible to design the floor slab or raft foundation for punching due to concentrated loads and reactions from columns, piles or supports. The design for punching is carried out according to 4 different codes: ACI, DIN 1054, EC2 and ECP.
Flexibility coefficients for interior nodes
For rigid and elastic rafts, it is convenient to determine the flexibility coefficient of interior node at the characteristic point of the loaded area on that node. While for flexible foundation, it is real to determine the flexibility coefficient of interior node at that node.
Now it is possible to determine the flexibility coefficient of the interior node due to a uniform load at that node
 at the characteristic point of the loaded area, where rigid settlement equal to flexible settlement
 at the midpoint of the loaded area, where maximum settlement occurs
 at the interior node on the loaded area.
Flexibility coefficients for exterior nodes
Earlier versions of ELPLA determine flexibility coefficients for both interior and exterior nodes by assuming uniform loaded areas on these nodes. This assumption uses the principle of superposition for determining the flexibility coefficients. Now it is possible to convert the loaded areas on exterior nodes to point loads, Figure B3. By this way the program doesn't need to use the principle of superposition in the analysis, making it much faster than the old analysis. The new way of analysis is consequently faster and more efficient for problems that contain a large finite element mesh.
GEOTEC Software is providing universities and consulting companies by the right tools for the last 20 years. We also assist our clients on various geostructural projects. From basic to advanced problems, GEOTEC Software can provide you with the right technical assistant.