Allowable Stress Design is a unique design practice that is adopted by civil engineers while they work on their building projects. It is a practice which entails the designer ensuring that the stresses imposed on the structures owing to the service load don’t exceed the elastic limit.
What is Allowable Stress Design or Permissible Stress Design?
Alternately known as the Permissible Stress Design, ASD has been globally replaced by Limit State Design. This particular phenomenon is anintegral part of Structural Engineering. As far as the replacement of the ASD by Limit State Design is concerned, it must be stated that the United States of America is definitely an exception. In the USA, Allowable Strength Design is not totally replaced by Limit State Design except in cases of Suspension Bridges. It was way back in the 1960s when limit stress design had already been deployed for Suspension Bridges in place of ASD.
The difference between ASD and Load and Factor Design and the usage of ASD in the construction industry
While engineers are working on timber or steel designs, they are required to zero in on a particular design of their choice. When it comes to steel construction, let us tell you that though there has been a shift from ASD to the LRFD (Load and Factor Design), LRFD was not readily accepted as a mainstream methodology by professionals even when the universities had actually started teaching the LRFD specifications. The professionals themselves were not really ready to accept LRFD initially though the safety offered by LRFD was already an established factor.
Now, there are obvious differences between ASD and LRFD. Allowable Stress Design compares actual and allowable stresses whereas LRFD compares required to actual strengths. It should be remembered that the ultimate loads cannot really be compared with service loads. At least, these two factors can never be compared directly. Either the ultimate loads must be unfactored or the service loads must be factored, when it comes to this particular comparison.
When it comes to timber construction, LRFD remains a relatively new introduction as well.
Do you want to know more?
Are you willing to find out more about the usage of ASD, LRFD and LSD in the construction industry? If yes, then we would suggest that you educate yourself more about their nuances. Hope this particular post has been of help. Please make sure you’re actually turning to other reliable sources as well in order to be duly guided in this regard.