How to verify punching shear in pile caps
While creating the design of pile cap, special attention should be given on the Punching Shear Checks. Punching Shear stands for a concentrated load that leads to a shear stress on the section close to the load and this load should be countered with the structural member from where the concentrated load or the reaction is restored.
In punching shear considerations, there should be two checks to observe in the design of pile caps. First one should be the punching shear strength of pile cap because of the concentrated load of the column and the second should be the shear strength of pile caps because of the reactions of a pile or group of piles.
Punching shear checks should be treated seriously since structural failures caused by punching prior to it happen leave a least warning or distinctively no warning at all.
After the geometrical assumptions, the design should be validated with software or manual calculations. As part of verifications, it is required to verify that sufficient design thickness is maintained to withstand the concentrated load or reactions, if not the thickness should be raised or supplementary shear reinforcements should be arranged.
But, generally, the first vital thing should be is increasing the thickness in spite of arranging the shear reinforcements, particularly when a pile cap is being designed.
Punching Shear Check with SAFE model
The article sheds light on how to accomplish a Punching Shear Checks in Pile Caps. It will focus on how to perform the punching shear checks with the SAFE program and the punching shear capacity checks as per the ACI code.
The Punching Shear Check is considered as the final step to take into consideration for making the design of pile cap. Assume, there is a SAFE model of pile cap that already accomplished the run analysis.
For the member to be sufficient in punching shear, the proportion of the actual shear stress divided by the capacity of shear stress should be below one. If the result is produced as otherwise then, assumed thickness is not sufficient and an increase in thickness is essential.
In the SAFE interface, click the Display>Show Punching Shear Design and the Punching Shear Capacity Ratios/Shear Reinforcement is shown. Suppose, there is 2500mm thick pile cap supported with 5 numbers of piles. The capacity ratios because of pile reactions and column loads are below 1 then assumed thickness is sufficient in punching shear.
To get information on punching shear capacity check as per ACI code, go through the following link thestructuralworld.com