Design of Simple RC Substructure

[xkybb]

Hello!

I am designing a simple rectangular RC structure (8x8m) with 2 stories (A superstructure and substructure of 4m height respectively).

1.The structure consists of 4 columns (400x400mm) in 4 corners extending to the raft foundation.
2. The ground floor slab (200mm) and top slab (200mm) are supported by beams (300x400mm) connecting the columns in the corners.
3. Between the columns and under the beams there are wall (200mm thk.)

In order to simplify the structure and allow verification by manual calculation, I planned to detail the connection between the walls and the columns NOT as fixed (see attached dwg.). I designed the RC frame (column+beam) seperately which can be verified by stiffness matrix method, and I planned to design the wall (mainly for substructure) as earth retaining wall fixed to the raft footing (eg. like a L shape retainning wall).

My questions are:
1. Is such detailing practical and common?
2. Will there be a weak zone at the connection between wall and column as rotation is allow? Is that weak zone and crack wont appear if the deflection of the wall is checked to satisfy the SLS requirement for deflection?

 

[SteynvW]

I am assuming that this is a concrete wall with a basement and the retaining wall
base and the slab on grade is one element (retaining wall with no heel),
normally in term of design it is designed with the end conditions as
you described (conservative design).
but I will detail build the wall into the columns.

Another note, I would adjust the detailing of the concrete
retaining wall.

 

[xkybb]

Reply to SteynW,

Thx for your answer.

I am wondering if I design the connection as "free", while I detail and build it as fixed into the columns, whether it would arouse unexpected and not designed forces/moment transferred to the column from the wall, and endanger the structural safety of the columns?

I try to seperate the wall and columns mainly because I dont know how to determine by manual calculation the resultant forces and moment transferred from wall to the columns if the connection is fixed. Therefore, I try to detail and design the wall as a L shape retaining wall which is only fixed to the raft foundation.

 

[CBSE]

If you design as "free" and detail as "fixed" you are going to get different forces in your connections.

 

[xkybb]

Reply to CBSE,

If I design and detail it as "free", will the be any weak zone of cracking between the wall-column connection as the wall bend inward when subjected to soil pressure? Or it wont happen as long as I check that the wall satisfy the SLS deflection requirement?