Practical Punching Shear Review
Punching shear is a local slab failure mode. It can occur around columns, pedestals, piles, or concentrated supports. The slab may look strong in flexure. Yet a small zone near the support can control the design. This calculator gives a clear example workflow. It compares factored shear demand with two way concrete shear capacity. It also allows shear reinforcement input, perimeter loss, and demand magnification.
Why This Check Matters
A flat slab transfers load directly into a column. Load spreads through a short depth. High stress can form around the column face. The critical section is normally placed at a distance of one half effective depth from the column face. The perimeter at that section is called b zero. A larger column, deeper slab, or stronger concrete usually increases resistance. Openings near the column can reduce the useful perimeter. Edge and corner columns often have less perimeter available.
Using the Results
The result shows gross perimeter, effective perimeter, shear stress, concrete capacity, design capacity, and demand ratio. A ratio below one suggests the selected inputs pass the simplified check. A ratio above one suggests more depth, a larger column, shear reinforcement, or a revised layout may be needed. The required shear reinforcement value shows the extra nominal strength needed after concrete resistance is counted.
Good Input Practice
Use factored load effects from the structural load combination. Use the effective depth to tensile reinforcement, not the full slab thickness. Enter the concrete strength used for design. Keep units consistent. The tool uses metric units. Force is entered in kN. Dimensions are entered in mm. Strength is entered in MPa.
Engineering Notes
This page is intended for learning, planning, and quick examples. It does not replace a licensed structural review. Building codes can change. Project rules may require special checks for transfer slabs, drop panels, capitals, prestressing, seismic design, openings, and unbalanced moment transfer. Always verify final design values with the governing code and project drawings.
Example Benefits
The example table helps users compare common cases. It shows how load, depth, column size, and edge condition change the result. Small input changes can move the ratio quickly. This makes early design review easier and more transparent for teams.