CE6501 – STRUCTURAL ANALYSIS
UNIT – I
TWO MARKS QUESTIONS AND ANSWERS
Why it is necessary to compute deflections in structures?
Computation of deflection of structures is necessary for the following
(i) If the deflection of a structure is more than the permissible, the structure will
not look aesthetic and will cause psychological upsetting of thje occupants.
(ii) Excessive deflection may cause cracking in the materials attached to the
structure. For example, if the deflection of a floor beam is excessive, the floor finishes
and partition walls supported on the beam may get cracked and unserviceable.
What is meant by ‘cambering technique, in structures?
Cambering is a technique applied on site, in which a slight upward
curve is made in the structure / beams during construction, so that it will straighten out
and attain the straight shape during loading. This will considerably reduce the
downward deflection that may occur at later stages.
Name any four methods used for the computation of deflections in
(i) Virtual work method – Dummy unit load method
(ii) Strain energy method
(iii) Willot Mohr diagram method
(iv) Method of elastic weights
State the difference between strain energy method and unit load method in
the determination of deflection of structures.
In strain energy method, an imaginary load P is applied at the point
where the deflection is desired to be determined. P is equated to Zero in the final step
and the deflection is obtained.
In unit load method, an unit load (instead of P) is applied at the point
where the deflection is desired.
What are the assumptions made in the unit load method?
Assumptions made in unit load method are
1. The external and internal forces are in equilibrium
2. Supports are rigid and no movement is possible.
3. The material is strained well within elastic limit.
Give the equation that is used for the determination of deflection at a given
point i in beams and frames.
Deflection at a point i is given by,
M x m x dx
DEPARTMENT OF CIVIL ENGINEERING/ FMCET