one way shear check for a pile cap
one way shear check for a pile cap
(OP)
Hello,
I have a circular bin supported by 8 columns. Bin dia is 12m. we are using a octagonal pilecap with 56 piles. I am using 1.5m deep pilecap. otagone has 17m dia. To check the one way shear at d from the face of column, I am having 30 piles contribute to that section. shear capacity of 1.5m mat with 30Mpa concrete is far less with 17m width. Even I am reducing shear by column loads in that section. I cannot increase the depth otherwise my piles will be overstrsed.
I can not put more piles due 3d spacing requirement.
1. Should i check one way shear based on pile capacity or actual reactions from various load combinations.
2. Is it normal to provide shear ties in a pile cap with scattered column on the top.
any reference material related to large pilecap is greatly appreciated.
All useful thougths are welcome.
Thanks in advance.
I have a circular bin supported by 8 columns. Bin dia is 12m. we are using a octagonal pilecap with 56 piles. I am using 1.5m deep pilecap. otagone has 17m dia. To check the one way shear at d from the face of column, I am having 30 piles contribute to that section. shear capacity of 1.5m mat with 30Mpa concrete is far less with 17m width. Even I am reducing shear by column loads in that section. I cannot increase the depth otherwise my piles will be overstrsed.
I can not put more piles due 3d spacing requirement.
1. Should i check one way shear based on pile capacity or actual reactions from various load combinations.
2. Is it normal to provide shear ties in a pile cap with scattered column on the top.
any reference material related to large pilecap is greatly appreciated.
All useful thougths are welcome.
Thanks in advance.






RE: one way shear check for a pile cap
RE: one way shear check for a pile cap
We can not use more than 30Mpa. if I use 2.5d, my piles capacity will be reduced by 25%, which i can not afford.
However to increase the depth, i need more piles which means greater footprint. How do i justify this against shear capacity. However I can increase shear capacity by using shear ties and lesser depth.
RE: one way shear check for a pile cap
RE: one way shear check for a pile cap
Even I designed it as strut and tie method, i still need to check oneway shear as per code.According to this all piles outside the d face of column will contribute to shear. My question is why we do not recomend to use shear ties in footing. is it due to cost of labour or material.
I mean if we have option to use shear ties to overcome this problem. I discuss with many colleagues, but all of them in opinion of increase depth to overcome shear. but my problem is that my piles would be overstressed.
RE: one way shear check for a pile cap
But there is nothing inherently wrong with using shear reinforcement in a big footing like this. Shear reinforcement is used all the time in mat foundation slabs supported on piles for high rise buildings.
RE: one way shear check for a pile cap