Anchorage Zone Stress Calculator

Calculator Inputs

Prestressing force P (kN)

Jacking or effective tendon force at the anchorage.

Bearing plate width (mm)

Plate dimension along member width (b-direction).

Bearing plate depth a (mm)

Plate dimension along member depth (h-direction).

Member width b (mm)

Overall width of the end block / web.

Member depth h (mm)

Overall depth of the end block.

Eccentricity e (mm)

Distance from centroidal axis (0 for concentric).

Dispersion distance x (mm)

Distance from plate to assumed supporting area.

Dispersion angle (deg)

45° is a common simplified assumption.

Concrete strength f'c (MPa)

Cylinder strength used for bearing limit estimate.

Steel yield strength fy (MPa)

Used to estimate required bursting reinforcement area.

Bursting force method

Choose eccentric if e > 0 and anchorage is offset.

Reset

Case	P (kN)	Plate (mm)	Member b×h (mm)	e (mm)	f'c (MPa)	σb (MPa)	Fbst (kN)
A	900	180×180	300×800	0	35	27.78	19.69
B	1200	200×200	300×900	0	40	30.00	16.67
C	1500	220×220	350×1000	50	45	30.99	20.70

These examples are for illustration only. Always confirm assumptions with project specifications and governing design standards.

Bearing area: A1 = (plate width) × (plate depth)
Supporting area (simplified): w2 = w1 + 2x·tan(θ), h2 = h1 + 2x·tan(θ), bounded by member size; A2 = w2·h2
Bearing stress: σb = P / A1 (P in kN, A in mm² → MPa)
Allowable bearing stress (basic enhanced limit): σallow = 0.85·f'c·min(√(A2/A1), 2.0)
Bursting tensile force (basic):
- Concentric: Fbst = 0.25·P·(1 − a/h)
- Eccentric: Fbst = 0.30·P·(1 − a/(h − 2e))
Average transverse stress (basic): σt,avg = Fbst / (b · (heff − a))
Estimated bursting steel: As,req = Fbst / (0.87·fy)

Enter the tendon force at the anchorage (P) and plate size.
Provide member width (b) and depth (h) for the end block.
If the anchorage is offset, enter eccentricity (e) and select the eccentric method.
Set a dispersion distance (x) and angle (θ) to estimate supporting area A2.
Enter concrete strength and steel yield strength for basic checks.
Click Calculate to see results above the form.
Use the CSV/PDF buttons to export your latest result.