Learning / bridge engineering
crossmember
Floor beam action
Lesson review: expert verification remains open
This lesson has received a full-context editorial review and a check of its technical explanations. Selected arithmetic has been checked separately. This is not independent engineering sign-off.
Checks needed for project use
- Bridge component studies and adjustable examples still need an independent bridge-engineering review, including applicability, load models and detailing guidance.
- Specialist review remains for: A transverse beam shows bending between longitudinal girders. A three-dimensional frame captures torsion and bracing action; connection eccentricities can introduce secondary stresses. The cross calculation is a local idealisation; it does not verify the displayed bridge or applicable design requirements.
These are educational models and exercises. Check their assumptions before using the results. The full technical content and every diagram have not yet been independently verified.
Concrete and steel calculations retain their stated first-generation Eurocode teaching basis. Use the standards and amendments specified for your project; do not mix generations without an appropriate design basis.
Read the lesson register and outstanding review notesLoads and actions
Cross-members distribute differential girder loading, deliver restraint forces and stabilise girders during erection. End diaphragms may also transmit bearing forces and support jacks.
Choose a model
A transverse beam shows bending between longitudinal girders. A three-dimensional frame captures torsion and bracing action; connection eccentricities can introduce secondary stresses.
Design considerations
Choose solid cross-girders, cross-frames or diaphragms to suit erection and final restraint. Design connections for the forces generated by differential deflection and verify the claimed restraint stiffness.
Durability and maintenance
Inspect weld toes, bolt groups and connections where adjacent girders deflect differently. Allow coating access between crossing plates.
Floor beam action
Local idealisation. Bracing forces, torsion and connection eccentricity are additional effects.
A 4 m simply supported cross-member: M = PL/4; each end reaction = P/2.
M = 200.0 kN·m; R = 100.0 kN at each end