www.sefindia.org

STRUCTURAL ENGINEERING FORUM OF INDIA [SEFI]

 Forum SubscriptionsSubscriptions DigestDigest Preferences   FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups  RegisterRegister FAQSecurity Tips FAQDonate
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log in to websiteLog in to websiteLog in to websiteLog in to forum 
Warning: Make sure you scan the downloaded attachment with updated antivirus tools  before opening them. They may contain viruses.
Use online scanners
here and here to upload downloaded attachment to check for safety.

Raft foundation design
Goto page Previous  1, 2, 3, 4, 5, 6, 7, 8, 9, 10  Next
 
Post new topicReply to topic Thank Post    www.sefindia.org Forum Index -> SEFI General Discussion
View previous topic :: View next topic  
Author Message
es_jayakumar
General Sponsor
General Sponsor


Joined: 24 Nov 2011
Posts: 1406
Location: Cochin

PostPosted: Sun Jan 31, 2016 3:07 pm    Post subject: Reply with quote

A small Excel sheet prepared to verify the adequacy of the thickness of the raft provided for a slab type raft foundation, based on punching shear criterion, is enclosed.


E S Jayakumar



Warning: Make sure you scan the downloaded attachment with updated antivirus tools  before opening them. They may contain viruses.
Use online scanners
here and here to upload downloaded attachment to check for safety.
Design of Raft Thickness.xls
 Description:

Download
 Filename:  Design of Raft Thickness.xls
 Filesize:  113 KB
 Downloaded:  1240 Time(s)

Back to top
View user's profile Send private message
SADATCHARAMOURTHY
SEFI Member
SEFI Member


Joined: 20 Jun 2009
Posts: 4

PostPosted: Thu Feb 25, 2016 5:19 am    Post subject: Reply with quote

Dear mohd_arastu

It's my humble request to send me your Excel sheet of Raft design on my below mail ID.

My Email ID is sadatcharamourthy@yahoo.com
Back to top
View user's profile Send private message
ynagaraju
SEFI Member
SEFI Member


Joined: 25 Apr 2016
Posts: 2

PostPosted: Mon Apr 25, 2016 2:57 pm    Post subject: Re: Excel sheet of Raft design Reply with quote

Dear mohd_arastu

It's my humble request to send me your Excel sheet of Raft design on my below mail ID.

My Email ID is archiedesigners1@gmail.com
Back to top
View user's profile Send private message
monikabothra
SEFI Member
SEFI Member


Joined: 31 Jan 2016
Posts: 2

PostPosted: Sat Apr 30, 2016 12:17 pm    Post subject: Raft / Strap Design Reply with quote

Dear mohd_arastu

It's my humble request to send me your Excel sheet of Raft design on my below mail ID.

My Email ID is monikabothra@ymail.com
Back to top
View user's profile Send private message
prash1730
SEFI Member
SEFI Member


Joined: 02 Jul 2008
Posts: 3

PostPosted: Sat Nov 07, 2020 2:45 pm    Post subject: Reply with quote

Dear mohd_arastu,
Thanks a lot for preparing a spreadsheet spreadsheet for raft design. Request you to send a copy of the same to prash1730@gmail.com


Best regards,
PNP
Back to top
View user's profile Send private message
VPandya
General Sponsor
General Sponsor


Joined: 09 Nov 2009
Posts: 834

PostPosted: Tue Nov 10, 2020 5:04 am    Post subject: STAAD/PRO RAFT FOUNDATION WITH PLATE ELEMENT EXAMPLE Reply with quote

Dear Sefi Friends ,

I have used  STAAD/PRO  PLATE ELEMENTS WITH WINKLER SPRINGS, (MODULUS OF SUBGRADE REACTION , SOIL SPRINGS) FOR  HIGH RISE BUILDING WITH MANY COLUMNS,  RAFT FOUNDATION . DESIGNED WITH ACI 318-08 Code . I am giving here a Link from STAAD/PRO on RAFT FOUNDATION EXAMPLE :

Link:  



https://youtube.com/watch?v=_KvR3tYRvjA  

Note :  Link will tell  you how to create STAAD/PRO model .  If does not work contact STAAD/PRO HELP .



Regards.

Vasudeo Pandya  P.E.
Structural Engineer
Back to top
View user's profile Send private message
Moosewala
SEFI Member
SEFI Member


Joined: 06 Aug 2020
Posts: 7

PostPosted: Mon Jan 03, 2022 12:47 pm    Post subject: Reply with quote

Sir,


Can we use the emperical formulas as given by E. Bowles using bearing capacity https://snaptube.cam/ of soil to calculate modulas of subgrade reaction? if yes, To what extent the values should be assumed to be appropriate ?


Regards.
Back to top
View user's profile Send private message
vikram.jeet
General Sponsor
General Sponsor


Joined: 26 Jan 2003
Posts: 3469

PostPosted: Tue Jan 04, 2022 5:42 am    Post subject: Reply with quote

STRUCTURE AND GEOTECHNICAL COMBINE

MODULUS OF SUBGRADE REACTION
The modulus of subgrade reaction is very important soil/rock parameter.

MODULUS K = (LOAD/AREA) /( CORRESPONDING SETTLEMENT)

Generally for field tests on 75cm  circular plate , pressure for 1.25mm Settlement is taken .
Then  K = p/0.125  MPA/cm =  10p / 0.125   kg/cm2/cm
P is the pressure for a settlement of 1.25mm on plate

REFER IS 9214 FOR DETERMINATION OF K VALUE


USEFUL SOIL DATA (AS PER SP-7, NBC OF INDIA)

COHESION LESS SOIL

LOOSE SOIL
RELATIVE DENSITY  < 20%
SPT N VALUE (BLOWS/30CM)   < 10
MODULUS OF SUBGRADE REACTION K   15000KN/m3(DRY,MOIST)
MOD OF SUBGRADE REACTION K   9000 kN/m3 (Submerged state)

MEDIUM SOILS
RD 20% TO 70%
SPT N VALUE    10 TO 30
K (DRY/MOIST) -  15000  - 47000 KN/m3
K (Submerged state) -  9000 - 29000 kN/m3

DENSE SOILS
RD> 70%
SPT N VALUE >30
K (DRY/MOIST) -  47000 - 180000 kN/m3
K (Submerged)  29000 - 108000  kN/m3

ALL ABOVE DATA IS FOR COHESION LESS SOILS



USEFUL SOIL DATA (AS PER SP-7 )

COHESIVE SOILS

SOFT TO VERY SOFT SOILS
SPT N VALUE  < 4

UNCONFINED COMPRESSIVE STRENGTH - NOT GIVEN , MUST BE SMALL
MODULUS OF SUBGRADE REACTION K - NOT GIVEN



MEDIUM SOILS
SPT N VALUE   4  TO  8

UNCONFINED COMPRESSIVE STRENGTH  Not given , but seems < 100 kN/m2 , since stiff values are given in range 100 - 200 kN/m2.

K  value - not given , but seem  < 27000 kN/m3 looking at range of stiff values


STIFF SOILS
SPT N VALUE  8  TO  15
UCS  100  -  200 KN/m2
Modulus of subgrade reaction K value    27000 kN/m3


VERY STIFF SOILS
SPT N VALUE  >  15
UCS   200 - 400 KN/m2
Mod of subgrade reaction K value  27000 to 54000 kN/m3


HARD SOILS
SPT N VALUE  > 15
UCS  > 400 KN/m2
Mod of subgrade reaction K   54000 to 108000 kN/m3

UCS VALUES AND K VALUES ARE ON SQ PLATE 300X300MM
AV LOAD INTENSITY TO BE LESS THAN (ULTIMATE BC/2)


FOR MORE INFO REFER SP7 CHAPTER 6 ANNEXURE B
Back to top
View user's profile Send private message
vikram.jeet
General Sponsor
General Sponsor


Joined: 26 Jan 2003
Posts: 3469

PostPosted: Tue Jan 04, 2022 5:45 am    Post subject: Reply with quote

MODULUS OF SUBGRADE REACTION

EMPIRICAL FORMULA FOR CALCULATING MODULUS K

K= 0.65 {(Es*B^4)/(E I)}^(1/12) *  Es/(1 - u^2)  * 1/B

Approximately K can be taken as
K = 0.65 * Es/(1 - u^2)  * 1/B
(1/12 the power term taken as nearly unity)

Es - Modulus of Elasticity of soil
E - Young's modulus of foundation material
u - Poisson ratio of soil
B - Foundations width
Back to top
View user's profile Send private message
vikram.jeet
General Sponsor
General Sponsor


Joined: 26 Jan 2003
Posts: 3469

PostPosted: Tue Jan 04, 2022 5:47 am    Post subject: Reply with quote

MODULUS OF SUBGRADE REACTION

FOR RIGID FOUNDATIONS :
MODULUS K = ( Average contact pressure)/(average settlement )

The ultimate BC  = SBC* FOS


MODULUS K =( SBC * FOS) /(PERMISSIBLE SETTLEMENT)

The formula given by Foundation Design book by BOWELS is based on this.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topicReply to topic Thank Post    www.sefindia.org Forum Index -> SEFI General Discussion All times are GMT
Goto page Previous  1, 2, 3, 4, 5, 6, 7, 8, 9, 10  Next
Page 9 of 10

 

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


© 2003, 2008 SEFINDIA, Indian Domain Registration
Publishing or acceptance of an advertisement is neither a guarantee nor endorsement of the advertiser's product or service. advertisement policy