Field note / structural beams
Reaction balance is the first check.
A full-span UDL contributes wL and acts at midspan. An off-centre point load contributes P and acts at its selected distance a. Taking moments about either support gives the two vertical reactions.
The point load changes the shear diagram.
Under the UDL, shear decreases linearly with distance. At the point load it changes suddenly by P. That jump is why the tool checks the shear immediately before and after the point load as well as the support values.
Maximum moment may not be at the point load.
The tool evaluates the supports, point-load location, and zero-shear positions within each UDL segment. The largest positive candidate is reported with its distance from the left support.
What still needs a design check
- Self-weight, factored combinations, load width, support stiffness, and restraint.
- Shear capacity, flexural resistance, lateral-torsional buckling, connections, and bearing.
- Deflection, vibration, cracking, fatigue, fire, durability, and code-specific serviceability criteria.