Research area and topicality of the work. Large equipment such as pressure vessels, mining equipment, heat exchangers, steam generators and other structures are provided with bolted closures for the purpose of in-service inspection and maintenance of internal components. The serious stress concentrations existing at the thread roots often cause danger of low cycle fatigue failure of the connectors. The load distribution along the threads has a direct influence on the stress at the thread roots. Load distribution in thread is so very unequal that some turns may be over the plastic yield limit but other turns are only in an elastic state. It is very useful to find the load distribution laws within threaded connection for elasto-plastic state of turns because it gives primary data for predicting low cycle durability of whole connection. Up to now low cycle fatigue calculating methods directly do not use data of the load distribution in thread. Instead of it the influence of some structural features to the low cycle durability somewhere approximately are evaluated by constant factors. That is insufficient because many structural parameters of threaded connections which influence to load distribution are designed in wide range of dimensions. Trustworthy way for more exact calculation of the stress at the thread roots is direct use of load distribution data. It is unavoidable when in order to increase thread connections fatigue life advanced techniques for improvement of load... [to full text]