Study of fatigue strength assessment methods of welded structures based on nominal stress;

The fatigue strength of duplex stainless steel welded jointing with longitudinal fillet welded gusset and with longitudinal flat side gusset welded on plate were evaluated by hot spot stress,and the hot spot stress S-N curves were obtained and compared with the nominal stress S-N curves.

On the basis of calculation results,fatigue life was estimated by nominal stress approach.

The nominal stress approach and the accumulative damage theory are adopted in order to analyze the buried pipeline fixing sector.

The life prediction methods of notched specimen are reviewed,especially on nominal stress approach,local stress-strain method and stress field intensity approach.

Two pieces of improvement on the crack width control method using nominal tensile stress for prestressed concrete flexural member;

Finally a modified nominal tensile stress was proposed.

Secondly, on the basis of research results, through calculation analysis, creates a simplified method of the width control of cracking in BUPC structures by nominal tensile stress and provides the recommendation of cracking -control and checking calculation in BUPC structures.

A factor of friction power is considered during fatigue,and a new model for predicting fretting fatigue life under low cycle load is presented based on a nominal stress method.

According to the working features of port crane,safe life prediction process of crane metal structure based on nominal stress method is introduced in this paper.

The conclusion showed that local stress-strain method is more accurate and reliable than nominal stress method and we used the example to prove the correctness of the conclusion.