For a simply supported beam under a uniform load, what is the essential check to confirm strength?

For a simply supported beam under a uniform load, what is the essential check to confirm strength?

• A. Compute the bending moment capacity and compare with factored moment using the cross-section properties.
• B. Check only deflection.
• C. Check only shear.
• D. Ignore material properties.

Answer: (A)

In strength design, you confirm the member can actually resist the loads by comparing what the cross-section can hold in bending to what the loads demand. For a simply supported beam under a uniform load, the worst internal bending moment occurs at midspan and is M = wL^2/8. The essential check is to compute the beam’s bending capacity from the cross-section properties and the material strength, then compare that capacity to the factored moment demanded by the load. If the capacity meets or exceeds the factored moment, the beam passes the strength check. Deflection and shear are important but address different concerns: deflection relates to serviceability (how the beam deforms under load in normal use), and shear is another potential failure mode that may govern in some designs. However, the fundamental strength check centers on bending capacity versus factored moment, using the cross-section geometry and material properties. Ignoring material properties would make the check meaningless, since capacity depends on those strengths.

In strength design, you confirm the member can actually resist the loads by comparing what the cross-section can hold in bending to what the loads demand. For a simply supported beam under a uniform load, the worst internal bending moment occurs at midspan and is M = wL^2/8. The essential check is to compute the beam’s bending capacity from the cross-section properties and the material strength, then compare that capacity to the factored moment demanded by the load. If the capacity meets or exceeds the factored moment, the beam passes the strength check.

Deflection and shear are important but address different concerns: deflection relates to serviceability (how the beam deforms under load in normal use), and shear is another potential failure mode that may govern in some designs. However, the fundamental strength check centers on bending capacity versus factored moment, using the cross-section geometry and material properties. Ignoring material properties would make the check meaningless, since capacity depends on those strengths.