RAFT FOUNDATION
 
INTRO & LIMITATIONS

 

The software performs Analysis, Design, Estimation, Costing & AutoCAD Drawing of RCC Rigid Raft Foundation. Refer IS : 2950 - PART 1 - 1981.

The Software basically requires a User to enter Raft data for Joints, Columns, Beams, Slabs, Point loads & Continuity. The rest of the things are taken care of by the software.

The results are displayed in the form of BM & SF, Raft Beam & Slab Schedule, Quantities, Cost & Approximate Bar bending Schedule for Beams.

Graphics option are available for display and tabular Format is available for Editing and Deleting Data.

A User should Delete / Edit Input-Data through the various Program Options only. If any editing is done outside the design environment than Data files may become corrupted. All Data should be Strictly "Entered" as explained in following steps.

Extensive Printing options are available under each display. Printing is straight forward with default set of values ( Arial Font, 8 mm Thick, Bold, Portrait ).
Only Beam Schedule will be Printed in Landscape Orientation.

The best way to go about the software is to Mark on the Foundation Plan, Joint, Beam, Column and Slab Numbers. A Joint represents a Column location or an intersection between 2 Raft Beams. The Beams are represented by its location in the form of Right Hand Side (RHS) & Left Hand Side (LHS) Joint numbers. The Slabs are represented by LEFT BOTTOM & RIGHT TOP joint numbers. All Joints will have X & Y Co-Ordinates, Top Left corner is taken as origin (0, 0). Joint / Beam / Column / Slab numbers should start with " 1 " and should not be repeated.

The Program will generate automatic Joint, Beam, Column & Slab Numbers from the information given in Project File. Some of these Numbers / Members may not be required & shall be deleted in a systematic manner as explained in the following chapters. The Final Plan Graphics should look exactly as the Raft Foundation Plan.
Cantilever Raft beams / slabs cannot be analyzed.
Beams / Columns / Slabs shall be along two mutually perpendicular axis (X and Y). Polygonal (Multi-sided) slabs cannot be analyzed.
Analyze the Structure, assuming Raft Top (Column Base) as Hinged. Hence there shall be no Moments on Raft Top. Raft Beam shall Carry Moments due to DL + LL and also Due to Wind and Seismic Shear. Structure shall be Analyzed in Either direction. Hence User shall enter 3 Column Load Cases, i.e.

● DL + LL

DL + LL + Wind / Seismic Load in Ton (From X-X Direction)

DL + LL + Wind / Seismic Load in Ton (From Y-Y Direction)

End Column Reactions on Raft Beams (DL + LL + Wind or Seismic) are obtained by running 2-D or 3-D Portal Frame Analysis programs separately. User may use our 2-D Frame Analysis software for calculation of End Reactions.
 
Only three (3) Load Cases can be analyzed per File for Each Raft Beam, viz :

● DL + LL (Due to Upward Soil Pressure, Calculated by Program Automatically)

● { DL + LL + Wind Or Seismic End Moment (WL1). } * 0.80

Wind Or Seismic End Moment shall be entered by the user on individual beams having Columns supports.

● { DL + LL + Wind Or Seismic End Moment (WL2).  } * 0.80

Whatever will the value of WL1, the program will reverse its sign (Multiply it by
 - 1) and use it as the default 3rd Case.

● Multiplication Factor of 0.80 will be applied within the Program by default.

End Moments on Raft Beams (Wind or Seismic) are obtained by running 2-D or 3-D Portal Frame Analysis programs separately. User may use our 2-D Frame Analysis software for calculation of End Moments.

More cases can be obtained by manipulating initial values as given in the project file or individual Beam and Slab files. For example Analysis option can be re-run with LL decreased by 0.8 (0.5* 0.8 = 0.4 T/M2).  However a designer has to 1st copy the original file in to another file (using Copy Option) & do the above mentioned modifications.
Provide 300 x 300 MM Haunch between All Raft Slabs & Beams.
In absence of 300 x 300 MM Haunch, Raft Slab may not be safe in Shear.
Export to Excel :

When the " Analysis Result -> Bending Moment & Reaction " option is Run, a Text file is automatically created. This File will open in Any Text Editor. You can also Open this Text File in EXCEL.
Start Excel -> File -> Open -> Delimited ->Next : Delimiters -> Comma ->Next -> Finish.
Now you will notice that Complete Data is displayed in Excel Spread Sheet.
If more than One File is Created, Corresponding to Each of Load Cases, than Open Excel Sheet for Each File (Load Case). In Excel Sheet Editing, Deleting, Sorting, Printing & Merging of Data/Files/Excel Sheets is Extremely Easy. This way any no. of Load Cases can be Manipulated.

Similar Text files are created in " Shear Corrected BM & SF " (Design BM & SF),
" Raft Beam Schedule " and  " Raft Slab Schedule option for Exporting Results to Excel Spread Sheet & its subsequent Manipulation.
 
Intersecting Joints between two Beams (Main & Secondary) is assumed as Hinged. Hence no Moment transfer is envisaged.
Connection between End Column and Beam is considered as Hinged. Hence no Moment transfer is envisaged between Column and Beam. However End Moments can be applied at Raft Beam joints as mentioned above under Load Case { DL + LL + Wind Or Seismic End Moment (WL1). }
After data input, the user has to switch over to graphic option for visual checking of joints / columns / beams / slab nos. When the data is error free the user can  run the Analysis, Design and Quantity options. The various results are also available through display or print options.
Analysis, Design and Quantity options should be run in strict order, else program will give unexpected results.
Program creates automatic Joint numbers as per nos. of Horizontal & Vertical Grids. Here Grids means Beams coming along Column center lines  as well as all  Internal Beams not aligned with columns. A user has to input Information regarding Horizontal & Vertical Grids while creating Project File.
A user can delete the Joints not required by using Joint Option.
Joints will be automatically re-numbered when "UPDATE" button is clicked or at "EXIT".
Remember to Delete / Edit Corresponding Beam / Column / Slab Member, whose Joint has been deleted.
Always delete Beam / Column / Slab member from the "END" to facilitate further Editing. After Deleting press "UPDATE" button for re-numbering of members.
After Deleting corresponding Beam / Column / Slab Member & Updating, edit the required Joint Numbers of affected Beam / Column / Slab Members.
Go through the "READ ME" Button for better understanding of that particular Option.
Raft Beam & Slab Design is as per IS 456 - 2000. Refer IS 2950 : Part 1 - 1981 / 1965 For Rigid Raft Design / Relative Stiffness Factor.
Beam Width / Depth < 150 mm not permitted.
Beam Width / Depth > 3500 mm not permitted.
Links (Stirrups) Area > 44.8 cm2 for Beams is not permitted.
Beam Reinforcement > 4 % not permitted.
Age factor is considered as 1.1 .
skin reinforcement is provided when web depth is more than 750 mm.
All Columns are placed Centrally with respect to Beams in either direction. There is no provision to offset the column in either direction. If the offset is large than user should re-workout the Beam Span. 
Minimum Computer RAM memory of 1 GB, Pentium 4 + or Eqv.  is recommended.
Use Laser OR Ink Jet Printer.