1_ increasing the slab thickness
2- using drop panel
3- using shear reinforcement
4- increasing the concrete compressive strength:
All of the options listed could help. I will only add increasing area of the base, if that is required based on your calculation of the critical area and perimeter for punching shear.
dear Joseph
drop panel is the same concept of increasing the area of the base.
best regards,
Dear Joseph,
The drop panel is the same concept of increasing the area of the base.
Best regards,
Agreed Salam, but area had to be mentioned for completeness. It is always expected to consider all possible options to help in arriving at the most appropriate design option.
Dear Salam
The gentlemen before me gave good advices.
Increasing the slab depth helps for sure, since there is a linear correlation between slab depth and punching shear resistance.
Lower concrete compressive strength has a clear negative effect on punching shear resistance. Still, PS resistance cannot be increased indefinitely by only increasing the concrete compressive strength.
I suggest you to concentrate on the governing mechanism to observe the problem area. Is the failure within or outside the punching shear reinforced zone? Or Is it the resistance of concrete struts? That way you can find an optimum solution.
For example, additional stirrups will not help if the governing failure (under consideration of stirrups of course) is the failure of concrete struts.
Experience shows placing stirrups around the support area would increase the punching shear resistance by a factor around 1.40 (until the concrete strut will be the governing failure mode).
If you need more than that you can consider steel shearhead for example, offering a wide support area which can be considered as a close-to-rigid body. They are quite popular especially in presence of higher loads.
Best regards,
Safak
Both above will help. Increasing grade of concrete can be in addition.
Yes Mr. Dhirendra I referred to grade of concrete as compressive strength.
Increase slab thickness and use drop panels are the most effeceint steps in my opinion
All methods above could help. in my opinion, increasing slab thickness could increase the punching shear, but self-wight of concrete will be increased simultaneously. this could be a negative point.
increasing shear reinforcement is good idea, but it's constrained to specific limit.
In my humble opinion, using drop panel and increasing compressive of concrete could be the most appropriate method to use practically and economically sometimes.
regards,,
Actually, all the options above contribute in increasing the punching shear of slab. In my opinio, the efficive way is providng shear reinforcement
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