Enhancement of Characteristic Strengths with Impulsive Loading
Characteristic strengths can be enhanced when the rate of changing the strain very high. For example, consider a column subjected to a blast loading. The load application time is very small. It is normally less than the response time of the structure.
When we talk about blast loading, time is in milliseconds. The duration of application of loading on the structure is less than one second in most of the time. Everything happens in a very shorter period of time.
Different researches have been carried out on these subjects. There are thousands of technical papers published on this subject. If we search on google we can find almost everything about the designs. However, very limited information is available on the internet or books.
The book “Blast Effects on Buildings by G C Mays and P D Smith” states about the enhancement of characteristic strengths of concrete and the steels. They have introduced a factor called dynamic increase factor (DIF) which is multiplied by relevant characteristic strength.
The dynamic increase factor is to be used to design reinforced concrete and structural steel elements depending on the deformation or damage limit imposed.
Above the table is extracted from the book Blast Effects on Buildings by G C Mays and P D Smith. According to the above table and deformation or damage limits imposed, multiplication can be done. It is advisable to refer to the above book for more information.
To learn more about material strengths and design characteristic strengths refer to the following article.
Characteristic Strength