Eccentric Footing e>L/6, Formula for Moment calculation? 5

[ak.t]

Hi All,

The footing size is (1.4 x 1.75)m (Fig. attached) & the SBC is 110 kN/m2

I get e> L/6 condition, Hence, I applied the 2P/BL' to calculate pressure max;
where L' is the bearing length = 3* (0.5L-e)

Thus, Qu = 2P/BL' = 102.6 kNm2

L' = 1.55 m ; P = 111.6 kN(Factored, Calculated) ;
M = 39.856 kNm (Factored, Calculated)
L = 1.75 m ; e = 0.357 m


How do I calculate moment for reinforcement from this triangular pressure profile ?
In report i found that Moment is 4.62 kNm. But I could not get the same.
Thank you.

 

[r13]

Also, I think it is important to check and design for the construction case, which may govern the flexural design (especially bottom of slab).

Loadings - Weight of wall + Weight of slab + Wind (in both directions)

 

[r13]

I think I found mistake in the report.

When sum moment about center of the base, they included the wind (M=24.91), but forgot moment caused by the wall (P=42.3).
With the arm from center of wall to center of the base x = 0.725, for un-factored load case M_CL = 24.91 + 42.3*0.725 = 24.91 + 30.67 = 55.8 (24.91 reported), P = 89.47 (ignore w₄), e = 55.8/89.47 = 0.624m >> 0.27m (0.27mm in report)

For factored load case:

P_u = 1.2*89.47 = 107.36
M_u = 1.2*24.91+1.6*30.67 = 78.96 (39.856 reported)
e = 78.96/107.36 = 0.736m > distance x = 0.725m ----> Resultant force near outer wall face

Check my calculation, see if there is mistake.

 

[ak.t]

Yes. The moment caused by the wall shall be included too due to eccentricity.
P/A + M/Z = 114.36 kN/m2 that exceeds the allowable bearing pressure (110 kN/m2) now. Subsequently, all the following design steps shall be revised. Shear check is not done.
This project'd executed long back ago.can't be revised. But I will revise my cals for my self study and will include shear check also.

And regarding the moment calculation, thank you so much for the detailed way of explaining. I am clear now. so, the query started with moment calculation. But I learned the concepts well now by all answers, especially you. Thank you so much

 

[r13]

Actually, there is no need to check shear, since the wall possess the heaviest weight. But don't forget the step in your next assignment.

A simple sketch can tell thousand words, reminder of our own task/act, and easier for anybody else to understand.

At this junction, If I am you, I'll discuss with a close higher up to seek advice and direction. Usually a thorough evaluation is required. Good luck.

 

[ak.t]

I dn't know how do they react, if I notify the missing cals of moment caused by wall. Seniors are not very approachable.
Thank you retired13 for the wishes.

 

[r13]

Yes, I understand, this is a difficult situation for a new hire. I might consider send my direct supervisor an email with the finding stated. I don't know how the company will react, but you shall be safe if you don't talk too much about this incident. Keep looking for other better opportunity though. A good company shouldn't let this happen.

 

[ak.t]

True..Thanks Again

 

[ak.t]

Dear All,

This is regarding the concrete column to concrete wall panel connections that to be established by L-angle (weld). For the same structure that're discussed in this tread require this connection. Both column and wall panel are precast members. I would require to check whether this connection shown in this attached Fig. is adequate or not.

I would require to check whether this connection shown in this attached Fig. is adequate or not.

Thank you

 

[r13]

Akshikas,

It is better to open a new thread, this thread is too long for people to browse. Unless you need to reference back to the calculation.

 

[ak.t]

Dear retired13,

Posted as new thread Link. Thank you.