Grade Beam Design for Buildings 3

• Nov 4, 1999

1
• #2

legner

Structural

Mar 24, 1999

40

US

Please clarify - do you mean grade beam as in concrete beam spanning between caissons or grade beam as in combined footing supporting multiple columns?

 

Upvote 0 Downvote

• Nov 6, 1999

1
• Thread starter
• #3

RNP

Structural

Nov 2, 1999

4

US

Grade Beam supporting a masonry wall and supported at it's endes by buttress walls! I think analizing as a combined footing sounds the most accurate. What do you think?

 

Upvote 0 Downvote

• Mar 13, 2000

• #4

legner

Structural

Mar 24, 1999

40

US

We typically design grade beams without considering any soil support. However, what you are talking about sounds more like a continuous footing with unusual end supports. I would recommend designing it as a beam on elastic foundation, either by the classical formulas while ignoring the end supports, or with an analysis program. Either way, you will need the subgrade modulus.

 

Upvote 0 Downvote

• Mar 14, 2000

• #5

RUSSRASCAL

Structural

Apr 1, 1999

14

US

THE POST-TENSIONING INSTITUTE HAS A LINE LOAD ANALYSIS FOR GRADE BEAMS IN THE SLAB ON GROUND PROGRAM. PERSONALLY, FOR THE LAST FORTY YEARS I'VE BEEN DESIGNING THEM LIKE A WALL FOOTING. THE PROOF IS IN THE PUDDING. SO FAR SO GOOD.

 

Upvote 0 Downvote

• Mar 21, 2000

• Thread starter
• #6

RNP

Structural

Nov 2, 1999

4

US

To:Legner, your solution was interesting.In my situation, I considered the grade beam to span between buttress walls that are supporting masonry walls above them. The grade beams were designed to limit deflection to 1/8 in. This was to prevent cracking in the masonry walls. I ignored the soil all together because, I was not sure if the the soil was totally activated in bearing.

 

Upvote 0 Downvote

• Apr 17, 2000

• #7

zhol

Structural

Apr 15, 2000

5

SD

you must also consider wheather the soil is expansive or not because if it is then it is better to isolate the beam's sofit than to support it directly on soil

 

Upvote 0 Downvote

• May 17, 2000

• #8

DENIRO

Structural

May 10, 2000

22

EG

we always design it as a beam on elastic foundation...<br>using any FEA sofware...

 

Upvote 0 Downvote

• Oct 17, 2000

1
• #9

zbolf

Structural

Apr 22, 1999

2

US

I would say that if the grade beam is supported at the ends then it should be designed as the framed beam without the help of the soil below. The settlement in the soil is something very difficult to estimate. The beam might in couple of years end up with the gap betwwen the bottom of the beam and the grade. Thus using the soil to reduce the beam size and/or reinforcement may result in under-designed beam.
The other option is to design the continuous footing under the load. In this case you can use Winkler model to assess the forces and the deformation.

[sig][/sig]

 

Upvote 0 Downvote

• Jun 19, 2001

• #10

Inquisitive

Automotive

May 16, 2003

2

GB

I would like to know the sanctity of having a grade beam resting on the ground without any excavation and supporting RC wall and roof. I would analyse the beam with the Winkler model. Would that be correct? I would like to specify that this type of structure is to be set up in an earthquake prone area.

 

Upvote 0 Downvote

• Jun 21, 2001

• #11

IJR

Structural

Dec 23, 2000

774

TR

Inquisitive

You are probably talking about a very light structure. To my knowledge statics is only one part of foundation engineering and though I am not an expert here, I know that the other side of the story is protection of your foundation. So placing a footing on level 0.00 (vegetation)grade is not healthy. Please check out stuff like snow depth, vegetation soils, expansive soils etc.

Since your proposition is completely out of question for a large building, where earthquakes hit better and foundations play a significant role, then I will not attempt to comment on placement of foundation at level 0.00

good luck.
IJr

 

Upvote 0 Downvote