Test: General Design Requirements - Civil Engineering (CE) MCQ

Structure should be designed such that it fulfils it intended purpose during its lifetime and be adequately safe in terms of strength, stability and structural integrity and have adequate serviceability. Structure should also be economically viable, aesthetically pleasing and environment friendly.

Serviceability is related to utility of structure. The structure should perform satisfactorily under service loads, without discomfort to user due to excessive deflection, cracking, vibration, etc. Other considerations of serviceability are durability, impermeability, acoustic and thermal insulation etc.

Analysis refers to determination of axial forces, bending moment, shear force, torsional moments etc. acting on different members of structure due to applied loads and their combinations.

When the static equilibrium equations are insufficient for determining internal forces and reactions on that structure, the structure is said to be statically indeterminate. Analysis of these structures is complex and cannot be analysed only by using laws of statics, various analytical methods like slope deflection method, moment distribution method, etc.

Code suggests the use of any of the following methods for steel structures : (i) elastic analysis, (ii) plastic analysis, (iii) advanced analysis, (iv) dynamic analysis.

Steel structures and their elements are normally designed by limit state method. When limit state method cannot be conveniently adopted, working stress method may be used.

IS 800:2007 is the code of practice for general construction in steel. It is issued by Bureau of Indian Standards.

Permissible Stress = Yield Stress / Factor of Safety. Permissible Stress is the amount of stress that will not cause failure. It is a fraction of yield stress. It takes care of overload or other unknown factors.

In Working Stress Method, Working Stress ≤ Permissible Stress. Each member is checked for number of different combinations of loadings.

In working stress method, the factor of safety for the above are as follows : (i) for tension members = 1.67, (ii) for long column = 1.92, (iii) for short columns = 1.67, (iv) for connections = 2.5-3.