What is section modulus (Z)?

Section modulus is a measure of a beam's resistance to bending. It is calculated as Z = I/c, where I is the second moment of area and c is the distance from the neutral axis to the extreme fiber. For a rectangular section: Z = b×h²/6.

What does the safety factor mean?

The safety factor is the ratio of yield strength to actual stress (fy/σ). A safety factor > 1.5 is typically required for structural designs under static loading. Values <1.0 indicate overstress.

When is the design critical?

A design becomes critical when the utilization ratio exceeds 100%, meaning the actual stress surpasses the allowable stress (fy/γM). This requires redesign with a larger section or stronger material.

How are different materials compared?

Different materials have different yield strengths: steel ≈250 MPa, aluminum ≈240 MPa, concrete ≈30 MPa, timber ≈10 MPa. Selection depends on availability, cost, weight, and environmental conditions.

Can I use this for dynamic loads?

This calculator assumes static loading. Dynamic loads require fatigue analysis and higher safety factors. Consult a structural engineer for dynamic applications.

Bending Stress Calculator

Free bending stress calculator for structural design. Enter bending moment (kN·m) and section modulus (cm³) to calculate maximum stress (MPa), safety factor, and utilization ratio for steel, aluminum, concrete, or timber.

Calculate maximum bending stress, safety factor, and material utilization from bending moment and section modulus.