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If end supports of continuous beam is fixed then B.M. will ___________ at the supports.
Produced
Maximum
Not produced
Minimum
Produced
In a continuous beam, if the end supports are fixed, the rotation at these supports is restricted to zero. Consequently, internal bending moments are generated at these fixed ends to resist the rotational forces.
In a continuous beam, if the end supports are fixed, the rotation at these supports is restricted to zero. Consequently, internal bending moments are generated at these fixed ends to resist the rotational forces.
MfтАЛ=12wL2тАЛ тАФ Fixed end moment for a uniformly distributed load
╬╕=0 тАФ Boundary condition at fixed support
According to the principle of structural mechanics, a support that prevents rotation (a fixed support or 'encastr├й') induces a reactive moment, denoted as MfтАЛ. For a fixed-end beam with a uniformly distributed load w over length L, this moment is calculated as MfтАЛ=12wL2тАЛ. This moment counteracts the rotation that would otherwise be caused by external loading.
Fixed supports are characterized by zero displacement and zero slope (rotation).
Statically indeterminate structures like fixed beams require compatibility equations to solve for support moments.
The presence of fixed supports increases the overall stiffness of the structural system.
Reduces mid-span deflection compared to simply supported beams.
Provides higher structural redundancy.
Sensitive to support settlement, which can significantly alter the internal moment distribution.
Requires more robust detailing and reinforcement at the joints.
Monolithic reinforced concrete building frames.
Continuous bridges where piers are rigidly connected to the superstructure.
If the end were simply supported (pinned), the bending moment at the end would be zero.
Option B (Maximum) is incorrect because the moment is generally highest at the internal supports or mid-span depending on the load configuration, not necessarily the fixed ends.
A is correct тАФ A fixed support constrains rotation, thereby producing a reactive bending moment at the support.
Always remember that in structural analysis, 'Fixed' means restraint against both translation and rotation, directly leading to the development of reaction moments.