ECMAT - Mat Foundation Design

This part of user manual describes how to use ECMAT for the design of Mat Foundations with single or multiple pedestals. ECPlus applications are designed as wizard type which is a step by step guided input procedure. If you are new to ECPlus applications, click here for general guidance.

Prerequisites: The user is expected to have a basic understanding of foundation design concepts.
The minimum input data required to use this application is as follows:

• ❶ Soil data such as Safe Bearing Capacity and ground water table.
• ❷ Allowable stability factors
• ❸ Concrete and Reinforcement Grades
• ❹ Pedestal Dimensions
• ❺ Foundation Loads

Technical reference for ECMat can be found here.

Following sections are presented with various input pages of ECMAT application with descriptions:

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Design Options

This page allows to select the foundation support system, i.e. soil or pile, design standard and unit.

Foundation System

Select if the foundation is supported on Soil or Pile

Design Standard

Select the National Standard for the design. Available Standards: ☉British, ☉European and ☉American.

Unit

Displays the active design unit. The unit   Change   button is displayed when ☉American Standard is selected.

British or European Standard can not be selected when Imperial unit is active.

Change

Click this button to open the unit change pop-up dialog.

☐  Reset all Input Data
Check this option to reset the input data for the new unit. This option is recommended if the job is new and no input data has been entered before.

☐  Convert Dimensions and Properties
Check this option to convert all the previously entered input data except Load data to the new unit.

☐  Convert Loads
Check this option to convert previously entered load data to the new unit.

Note: Both Convert Dimensions and Properties and Convert Loads options can be used simultaneously to convert all the previously entered input values to the new unit.

Incorrect option selection leads to out of range errors and should be manually corrected.

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Foundation

This page allows the input of foundation data such as depth of the foundation and depth of the water table below the ground level.

Depth of Foundation

Enter the depth of the foundation pad below the finished ground level. Blinding concrete thickness should not be included in this depth.
↔ Range: 0 to 5000 mm (0 to 200 inches)

☐   Consider Water Table

Check this option to consider water table.

Depth of the Water Table below GL

Enter the depth of the water table from the ground level. Presence of water table induces buoyancy effect and affects the stability of the foundation.
↔ Range: 0 to 5000 mm (0 to 200 inches)

Extend of Minimum Soil Cover

Select the option from Nil, Full and Partial
▽ Nil: Select this option if the soil cover above pad is likely to be zero due to any adjacent excavation.
▽ Full: Select this option if the soil cover above pad is to be considered as full up to the ground level.
▽ Partial: Select this option to specify a partial soil cover.

Minimum Soil Cover above Pad

Enter the minimum soil cover to be considered above Pad. This input is enabled when 'Extend of Minimum Soil cover' is selected with the option Partial. Any soil cover specified excess of available depth is ignored.

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Pad and Pedestal

This page allows to enter the Pad and Pedestal Dimensions and the locations of Pedestals on the Pad. Graphical Edit can also be used to enter the pad size and pedestal locations visually.

Pad

Length of the Pad (X-Dir) - L_f
Enter the dimension of the Pad in X direction.
↔ Range: 300 to 100000 mm (10 to 4000 inches)

Breadth of the Pad (Z-Dir) - B_f
Enter the dimension of the Pad in Z direction.
↔ Range: 300 to 100000 mm (10 to 4000 inches)

Thickness of the Pad - T_f
↔ Range: 100 to 10000 mm (4 to 400 inches)

Move pedestals to pad CG

Click on this button to move pedestals in accordance with CG of the pad.

Pedestal

The buttons   Define Pedestal Types   and   Define Pedestal Locations   are provided in this section.

Define Pedestal Types

Click this button to open the pop-up dialog and define the pedestal types and its dimensions. This is a spreadsheet type input dialog - right click on the spreadsheet to add or delete rows. Alternatively, the user can copy and paste data from an external source such as Microsoft Excel.

Type

▽ Pedestal: Select this option when pedestal load is applied at a height above the ground level such as pedestal supporting a steel column.
▽ Loaded Area Top: Select this option when pedestal load is applied at the top of the Pad such as a concrete column supporting roof beams.
▽ Loaded Area Bot: Select this option when pedestal load is applied at the bottom of the Pad such as a concrete column supporting roof beams.

Shape

Select the shape of the pedestal from the available options Rectangle, Square, Circle, Octagon or Wall.

Length of the Pedestal (L)

Enter the length of the pedestal for the selected shape as defined in the picture.
↔ Range: 100 to 3000 mm (4 to 120 inches)
↔ Range: 100 to 12000 mm (4 to 480 inches) for walls

Breadth of the Pedestal (B)

Enter the breadth of the pedestal for the selected shape as defined in the picture.
↔ Range: 100 to 3000 mm (4 to 120 inches)

Top Of Ground level (TOG)

Enter the height of the pedestal above Ground Level. Not applicable for 'Loaded Area' Pedestal Type.
↔ Range: 0 to 6000 mm (0 to 240 inches)

Used at

Displays the pedestal locations on the pad where the pedestal type is used (Information only)

Pedestal Locations

Click this button to open the pop-up dialog and define the pedestal locations with reference to the top left corner of the pad. This is a spreadsheet type input dialog - right click to add or delete rows. Alternatively, the user can copy and paste data from an external source such as Microsoft Excel.

X / Y / Rotation (deg)

Enter the x and y co-ordinates to locate the pedestal on the pad and the angle at which the pedestal is rotated with respect to X axis as shown in the picture.

Pedestal Type

Choose the pedestal type from the list of pedestal types defined in Define Pedestal Types pop-up.

Pedestal locations can also be defined conveniently by Graphical Edit mode.

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Reinforcement

This page allows to enter the clear cover to the rebars of Pad and Pedestals and define the reinforcement details.

Clear Cover to Pedestal - C_ped
Enter the clear cover for the Pedestal.
↔ Range: 15 to 150 mm (0.5 to 6 inches)

Clear Cover to Pad - C_pad
Enter the clear cover for the Pad.
↔ Range: 15 to 150 mm (0.5 to 6 inches)

Two buttons for  Pad Reinforcement   and  Pedestal Reinforcement   for each pedestal type defined in Define Pedestal Types pop-up are provided in this page.

Pad Reinforcement

click this button to open the pad reinforcement pop-up as follows:

• ☐   Check Reinforcement

  Check this option if the pad reinforcement design is required.

• ☐   Top Reinforcement

  Check this option if the pad is provided with reinforcement at top.

• ☐   Near Layer X dir

  Check this option if the rebars provided in the X direction is the first layer (near to the surface).

• Bottom Reinforcement / Top Reinforcement

  Select the rebar diameter and enter spacing as required for each layer of reinforcement in both directions.

Pedestal Reinforcement

Click this button to open the pedestal reinforcement pop-up for the selected pedestal type as follows:

☐   Pedestal Reinforcement
Check this option if the pedestal reinforcement design is required. If the pedestal type is Loaded Area, reinforcement can not be defined.

Main Reinforcement / Ties
Reinforcement for main longitudinal bars and ties can be defined according to the shape of the pedestal.

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Loads and Combinations

This page allows to define the load cases, SLS and ULS combinations. Allowable factor of safety for stability conditions, percentage of increase in safe bearing capacity for each combination are also defined in this page. Pedestal loads can be applied to according to the load convention of different structural analysis software.

The following buttons are provided for pop-up dialog for the input data:

• STAAD Import of L&C
• Define Load Cases
• Service Load Combinations
• Allowable Load Factors
• Ultimate Load Combinations
• Pedestal Loads

Load Input Convention Options ☉STAAD Reactions (Y up), ☉STAAD Forces (Y up) and ☉Standard Convention are provided to facilitate the load import from various structural analysis software according to their convention.

STAAD Import of L&C

Click this button to open the pop-up dialog to import load cases and combinations from STAAD Input File. This is an optional import feature. User can skip this and define load cases and load combinations directly.

To import the load cases and combinations, follow the steps as below

1. Paste the load cases from STAAD with load case numbers
2. Select the Dead Load No, from the list box above
3. Click Next button
4. Paste the SLS load combinations from STAAD Input file
5. Click Next button
6. Paste the ULS load combinations from STAAD Input file
7. Click Next button
8. Click Finish button to complete the STAAD Import.

STAAD Imported load cases and combinations can be modified if required.

Define Load Cases

Click this button to open the load cases pop-up dialog. This is a spreadsheet type input dialog - right click to add or delete rows. Alternatively, the user can copy and paste the data from external source such as Microsoft Excel.

In this pop-up, n - number of load cases and its type can be defined.

Description

Enter the description of the load case. Do not duplicate the load case description since it is used as a reference to define the load combinations. This field can not be left blank and the special character '#' can not be used.

Type

Select the load type Dead, Live, Wind, Seismic, or Other. First load case type should be 'Dead'

Service Load Combinations

Click this button to open the Service Load Combinations pop-up dialog. This is a spreadsheet type input dialog - right click to add or delete rows. Alternatively, the user can copy and paste the data from an external source such as Microsoft Excel.

In this pop-up, n - number of Service Load Combinations (SLS) can be added with factors for each load case defined earlier.

Load Cases Factors

Load Case Description is displayed in each spreadsheet column. Enter the load factor for every load case and for each load combination.
↔ Range: -10 to 10

Allowable Factors (SLS)

Click this button to open the allowable factors for Service Load Combinations pop-up dialog. This is a spreadsheet type input dialog but rows can not be deleted or added. The user can copy and paste the data from an external source such as Microsoft Excel.

The first column header displays the service load combination according to the load factors defined in the service load combinations.

SBC Inc (%):

Enter the percentage of increase / decrease of safe bearing capacity for each service load combination. Negative value indicates decrease in allowable value.
↔ Range: -100 to 200

Overturning / Sliding / Uplift

Enter the allowable factor of safety for the stability type.
↔ Range: 1 to 10

Crack Width

Select if crack width is to be checked for each combination. If the crack width check option is not selected in Design Settings, no crack width check is carried out for any combination.

Ultimate Load Combinations

click this button to open the Ultimate load Combinations pop-up dialog. This is a spreadsheet type input dialog - right click to add or delete rows. Alternatively, the user can copy and paste the data from an external source such as Microsoft Excel.

In this pop-up, n - number of Ultimate Load Combinations (ULS) can be added with factors for each load case defined earlier.

Load Cases Factors

Load Case Description is displayed in each spreadsheet column. Enter the load factor for every load case and for each load combination.
↔ Range: -10 to 10

Load Batch (Total x)

Select the batch for which the pedestal loads are to be applied. To add or delete more batch loads use the button (1).

Pedestal Loads

Select the pedestal location for which the loads are to be applied.

Click the button (shown as 3) to import the pedestal loads from an excel file (accepted formats .xls and .xlsx). This will allow the user to conveninently import the loads for all pedestal locations at once. The template for importing the loads from the excel file is available to download (shown as 4). The excel file to be imported shall have two sheets namely 'Locations' and 'Reactions'. The sheet 'Locations' defines the mapping of pedestal locations to the nodes for various batches. The sheet 'Reactions' shall have the reactions or foundation loads to be imported. The user must verify if the loads are propertly imported.

Pedestal Loads

Click the button (shown as 2) to open the Pedestal Loads pop-up dialog for the selected Load Batch and selected Pedestal Location. This is a spreadsheet type input dialog but rows can not be deleted or added. Alternatively, the user can copy and paste the data from an external source such as Microsoft Excel.

Load Components

Enter the loads Fx, Fy, Fz, Mx, My and Mz for the selected pedestal location for each load case according to the selected load convention.
↔ Range: -100000 to 100000

A picture is presented to indicate the active load convention (STAAD Reactions (Y Up), STAAD Forces (Y Up) or Standard Convention)

Pedestal is not design checked for torsion.

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Graphical Mode:

The foundation size and the pedestal locations can also be modeled visually in Graphical Mode. Graphical Edit mode is invoked by clicking the right bottom picture of the input page.

Click the pedestal locations on the picture to select and make the modification using the buttons given on the left side.

Buttons are provided for group selection, copying, rotating the pedestals and pad.

The   Fit Pedestals   button is to get the pad to the size encompassing all the pedestals with the margin specified.

The size of pad can be conveniently modified using the options Extend, Trim and Move and applying on sides of the pad   L   Left   R   Right   B   Bottom   A   All

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Design Setting

Setting for various Design Data such as Soil, Concrete, Passive Resistance and Material and Safety Factors are presented in this section. This setting pop-up can be accessed by clicking the bottom panel below the left navigation.

Soil

Allowable Net Bearing Pressure - SBC
↔ Range: 25 to 1000 kN/m² (0.5 to 20 ksf)

Contact Percentage - C_p
Enter the percentage of minimum soil bearing area.
↔ Range: 10 to 100

Density of Soil - γ_soil
↔ Range: 10 to 40 kN/m³ (60 to 250 pcf)

Density of Ground Water - γ_w
↔ Range: 5 to 15 kN/m³ (30 to 100 pcf)

Angle of Internal Friction - Φ
↔ Range: 0 to 60 deg

Coefficient of Friction - μ
Enter the coefficient of friction between the bottom of the pad and soil or any underlying media.
↔ Range: 0 to 1.5

Pile

Pile properties and parameters such are dimension, spacing, working load, density are provided in this section.

Pile Size - P_size

↔ Range: 100 to 3000 mm (4 to 120 inch)

Working Load Compression / Tension / Lateral - P_alc / P_alt / P_all

↔ Range: 10 to 100000 kN (2 to 22500 kips)

Density of Soil - γ_soil

↔ Range: 10 to 40 kN/m³ (60 to 250 pcf)

Density of Ground Water - γ_w

↔ Range: 5 to 15 kN/m³ (30 to 100 pcf)

Reinforced Concrete Properties (BS 8110)

Enter the reinforcement concrete properties on selection of British Standard from Design Option.

Density of Concrete - γ_conc
↔ Range: 10 to 40 kN/m³

Strength of Concrete - f_cu
Enter characteristic strength of concrete.
↔ Range: 15 to 100 N/mm²

Strength of Reinforcement - f_y
Enter characteristic strength of main reinforcement for pad and pedestal.
↔ Range: 150 to 2000 N/mm²

Strength of Links - f_yv
Enter characteristic strength of links for pedestal.
↔ Range: 150 to 2000 N/mm²

Modulus of Elasticity of Steel - E_s
↔ Range: 50 to 300 kN/m²

Reinforced Concrete Properties (BS EN 1992-1-1)

Enter the reinforcement concrete properties on selection of European Standard from Design Option.

Density of Concrete - γ_conc
↔ Range: 10 to 40 kN/m³

Compressive Cylinder Strength - f_ck
↔ Range: 15 to 100 N/mm²

Main Reinforcement Grade - f_yk
Enter grade of main reinforcement for pad and pedestal.
↔ Range: 150 to 2000 N/mm²

Shear Reinforcement Grade - f_yv
Enter grade of shear reinforcement for pedestal.
↔ Range: 150 to 2000 N/mm²

Modulus of Elasticity of Steel - E_s
↔ Range: 50 to 300 kN/mm²

Cement Type - C_type
Select the cement class S, R or N

Reinforced Concrete Properties (ACI 318)

Enter the reinforcement concrete properties on selection of American Standard and Design Unit from Design Option.

Density of Concrete - γ_conc
↔ Range: 10 to 40 kN/m³ (60 to 250 pcf)

Compressive Strength of Concrete - f'_c
↔ Range: 15 to 100 N/mm² (1 to 4 ksi)

Yield Strength of Reinforcement - f_y
Enter yield strength of reinforcement for pad and pedestal.
↔ Range: 150 to 2000 N/mm² (20 to 300 ksi)

Concrete Modification Factor - λ
↔ Range: 0.75 to 1

Modulus of Elasticity of Steel - E_s
↔ Range: 50 to 300 kN/mm² (7000 to 45000 ksi)

Passive Resistance

Passive Resistance

☐   Include Passive Resistance: Select if passive resistance is to be considered. Other options in the following have no effect if this is not selected.

Pedestal Resistance

☉ None: Select this option if passive resistance is not to be considered on pedestals.
☉ Unshielded Pedestals: Select this option if passive resistance is to be considered on pedestals which are fully or partially exposed to soil passive pressure without being shielded by others pedestals ahead in the direction of the shear force.


P1 - Fully unshielded pedestal
P2, p3 - Partially unshielded pedestals
P4 - Fully shielded pedestal

☉ All Pedestals: Select this option if passive Resistance is to be considered on pedestals irrespective of the shielding condition from other pedestals. User can select this option if it is presumed that all pedestals are fully effective in offering the passive resistance.

Other

☐   Passive Resistance on Overturning: Select this option if passive resistance is to be considered in resisting overturning. (By default only sliding is considered)
☐   Mobilized Passive Pressure for Design: Select this option if pedestals are to be designed for mobilized passive forces (Passive force generated due to applied shear forces).

Material Partial Safety Factors

Enter the material safety factors on selection of British or European Standard and Design Unit from Design Option.

Flexure/Compression, Concrete in Shear, Reinforcement
γ_mc, γ_mcs, γ_ms
↔ Range: 1 to 2

Stability Safety Factors

☐   Same for Full and Minimum Soil: Check this option to consider same allowable factors for both full and minimum soil conditions.

☐   Passive Resistance for Min. Soil: Check this option to consider passive resistance for minimum Soil condition.

Sliding, Overturning, Uplift
γ_slide, γ_over, γ_up
Enter the default factors of safety for these stability conditions. However, actual value for each load combination can be changed in Load Combination page.
↔ Range: 1 to 10

☐   Apply to all Combinations: Check this option to apply these factors to all SLS combinations.

Crack Width

☐   Crack Width
Check this option if crack width is to be considered for Pad Design. However, for each load combination, this option can be changed in Load Combination page.

Allowable Crack Width - W_c
Enter the allowable crack width for the pad design.
↔ Range: 0.05 to 0.6 mm (0.002 to 0.024 in)

Torsional Stability Check

☐   Check for Torsional Stability
Check this option if torsional stability is to be considered for the foundation.

National Annex

Select the National Annex after selecting the European Standard in Design Option.

Nation
Select the National Annex option for the relevant factors to be considered in the design.

α_cc
Enter the value for the User Defined National Annex option. For other options, this is not editable.
↔ Range: 0.7 to 1.2

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Error Handling

Errors and Warnings are generated to prevent any inadvertent error in the input data. This section describes how to handle the errors and warnings. These errors are displayed at the bottom of the input page when the data in one or more input fields invalidate each other. Calculation can not be run if there is any error in the input data.