Commercial Building Inspector B2Structural SystemsMedium
A structural engineer is designing a connection for a steel wide-flange beam to a column in a moment frame. The connection must be designed to resist significant bending moments and shear forces. Which of the following connection types is generally preferred for achieving a fully restrained (FR) or moment-resisting connection in steel construction?
- AWelded Flange Plate Connection
- BDouble Angle Shear Connection
- CSeated Connection
- DShear Tab (Single Plate) Connection
Show answer & explanationAnswer & explanation
Correct answer: A. Welded Flange Plate Connection
Welded flange plate connections (or directly welded flange connections) are designed to transfer both flexural moments and shear forces between members. By welding plates to the beam flanges and then to the column, or directly welding the beam flanges to the column, the connection provides significant rotational restraint, classifying it as a fully restrained (moment-resisting) connection.
Why the other options are wrong
- B. Double angle shear connections are also primarily designed for shear transfer and offer minimal rotational restraint, classifying them as simple connections.
- C. Seated connections are typically simple connections designed to primarily support gravity loads and transfer shear, offering little to no moment resistance.
- D. Shear tab connections are primarily designed to transfer shear forces and are typically considered simple (shear-only) connections.
Fully Restrained (FR) Moment Connection
A steel connection designed to transfer both moment and shear forces between connected members, providing sufficient rotational stiffness to maintain the original angle between the members.
- Crucial for moment frames in resisting lateral loads (wind, seismic).
- Examples: welded flange plate, welded direct flange, extended end plate.
- AISC classifies connections as FR, PR (Partially Restrained), or Simple.
Memory trick: Steel connections: simple for shear, moment for bending.