In a fixed beam, what is the bending moment at the supports?
Analysis & Theory
In a fixed beam, bending moments at the supports are generally negative and at their maximum magnitude.
A fixed beam resists rotation at the supports. What does this imply?
A
It acts like a simply supported beam
B
It has no bending moment
C
It develops fixed end moments
D
It cannot carry any load
Analysis & Theory
Fixed beams develop fixed end moments because rotation is restricted at the supports.
For a fixed beam under a central point load P over span L, the maximum bending moment occurs at:
D
Ends and center equally
Analysis & Theory
The maximum (negative) moment occurs at the fixed supports, not mid-span.
What is the typical shape of the BMD for a fixed beam under central point load?
D
A mix of positive and negative curves
Analysis & Theory
The BMD shows negative moment at ends and a smaller positive moment at the center.
The maximum positive bending moment in a fixed beam under central point load is:
Analysis & Theory
Maximum positive bending moment = PL/12 at mid-span for fixed beam with central point load.
For a fixed beam carrying UDL (w) over full span L, the fixed end moment at each support is:
Analysis & Theory
Each fixed end moment = -wL²/12 (negative sign due to hogging moment at supports).
Fixed beams are more efficient than simply supported beams because:
A
They require less material
B
They distribute moments more evenly
C
They develop higher positive moment
D
They allow more deflection
Analysis & Theory
Fixed beams develop both positive and negative moments, reducing maximum moment and deflection.
Compared to a simply supported beam, the fixed beam under the same load:
Analysis & Theory
Fixed beams have lower maximum bending moment and deflection compared to simply supported beams.
In fixed beams, the BMD contains:
C
Both positive and negative moments
D
Constant moment throughout
Analysis & Theory
Fixed beams show both hogging (negative) and sagging (positive) moments in their BMD.
What happens to fixed end moments if a fixed beam is symmetrically loaded?
A
They are equal and opposite
B
Only one end has moment
Analysis & Theory
In symmetric loading, both fixed end moments are equal in magnitude and opposite in direction.