a) materials behave linearly
b) yielding effects can be ignored
c) member instability effects cannot be ignored
d) frame instability effects can be ignored

Answer: c
Explanation: The following are the assumptions of first order elastic analysis of rigid jointed frame : (i) materials behave linearly, (ii) yielding effects can be ignored, (iii) member instability effects such as those caused by axial compression can ignored, (iv) frame behaves linearly frame instability effects such as those caused by moments due to horizontal frame deflection, etc can be ignored.