Question

what is the comparison between ultimate strength design method and allowable stress method

Answer 1

Hai khan,Ultimate design method means we have to take failure load for design.so that structure will be used as optimum.but  some disadvantages are  there.In allowable stress method we have to use the allowable load for design that means we will take the yield strength of materials for design.so it will be more safer than that method...now a days we are not using that two methods.Limit State Design method is now adays wr are doing in India.

Answer 2

the first one is design based on ultimate limit of failure of structure and the other one is based on higher factor of safety so that the stucture will not fail even due to anticipated expected load on the structure...ultimate method is the least and most economocal way of design sturctures like building are based on this method while structures like chimney,dam which are heavy and typical is design on allowable stress method...
in ultimate strength method a partial factor of safety is applied both to material strength and design load ...while in allowable stress method the factor of safety is applied to material strength only  thus curtailing stresses and hence is known as allowable stress method.