Stress intensification factor


Maximum stresses calculated according to traditional strength equations are nominal stresses. Peak stresses are omitted. It is fine presented in academic example of plate with the hole. Stress calculated using equation (1) is exactly this nominal stress.

 Peak stress


tensile stress                    (1)

 , where t - plate thickness


For constructions designed from many years suitable stress intensification factors (SIF) are defined. They are defined also for pressure parts. In case of piping, equations for calculating SIF are presented in table H.1 of Appendix H (EN 13480-3:2012). In chapter 12.3 which concerns flexibility analysis SIF denoted as "i" appears at moments "M" in such loads like:

- sustained load

where MA - resultant moment from the sustained mechanical load


- sustained and occasional or exceptional loads

where MB - resultant moment from the occasional or exceptional loads


- thermal expansion and alternating loads

where MC - range of resultant moment due to thermal expansion and alternating loads


- creep


- single non-repeated support movement


where MD - resultant moment from a single non-repeated anchor/restraint movement


American equivalent of EN 13480-3 is standard B31.1-2010. Actually in "Download" section is available program for calculating SIF to piping elements according to EN 13480-3:2012. It calculates SIF for general cases. It is possible to calculate SIF also for particular cases of in-plane and out of plane bending. Actually B31.1 and particular cases are out of consideration in program. Such works are planned in the future.