Column Punching Checks with Finite Elements (ACI318 and IS456)

ProtaStructure 2025 introduces enhanced support for punching shear checks for flat slabs and raft foundations in compliance with both the ACI318 American and IS456 Indian Codes (and other similar codes including NSR10, NTE030, Dominican Republic, Indonesia, Philippines and Thailand).

This latest version can automatically calculate the out-of-plane shear forces, V13 and V23, around the punching perimeter and incorporate them into the punching shear analysis.

Additionally, ProtaStructure 2025 can evaluate consecutive punching perimeters, ensuring a comprehensive assessment of potential failure zones.

The software also facilitates the calculation of necessary punching reinforcement, streamlining the design process and enhancing the accuracy and safety of structural designs.

For detail help on functions of the punching dialog, kindly refer to : Column Punching Check

For guidance on flat slab analysis & design : Working with Flat Slabs

Inclusion of Column Outlines

To increase the accuracy & optimum results for punching shear checks with finite element results, the column outlines will always be cropped out of the finite element mesh for flat slabs and raft foundations.  The details are as follows : 

1. All column outlines are automatically included in the FE mesh unless there are connecting beams or wall. 
   
2. In other words, “Include Column Outlines” option only controls the columns with connecting beams.
   
3. Section outlines are not included in FE mesh for columns with column drops.
   
4. Section outlines are not included in FE mesh for columns inside (or at the corners of) shearwalls. 
   

Figure above : FE Model  of flat slab floor, where slabs are meshed to the outline / perimeter of column

The Methodology

The maximum value of shear stress is obtained by collecting results from the punching perimeter which can be rectangular, circular or irregular depending on the column and slab geometry.

Results are collected for each combination and the envelope value is used.

      

Figures above : V23 shear contours and punching station points for envelope combinations in analysis post-processor.

  
Figures above : Column drop panels, punching perimeters and shear contours shown simultaneously on physical floor plan

The methodology and formulation are different for different design codes, but in principle, if the concrete tensile strength is solely enough to counteract the punching stresses around the punching perimeter, then no additional punching reinforcement is calculated.

However, if the punching stress is larger than concrete tensile strength then the punching reinforcement is calculated by ProtaStructure.

Existing slab reinforcement and additional patch reinforcement (if any) will be considered as punching reinforcement.

Figure above : Column Punching dialog

Figure above : Consecutive punching perimeters, V13 contours, column drops, patch regions, patch reinforcement and slab base reinforcement shown on the plan at the same time

Figure above : Punching shear check report for consecutive punching perimeters.

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