By Injury In Round Steel Tubing Stability Limit Bearing Capacity Analysis

Round steel tube members now have been widely used in space grid structures, reticulated shell structures, power transformation structures and ocean platforms, etc. Most of the above-mentioned space structures are multiply hyperstatic structures under complicated stress condition. Although strict design calculations are made to guarantee the members have sufficient strength in their work life, yet dash and improper loads may damage them during construction and in service. These damages include elastic-plastic bending and local dent in the walls of the tube. In addition, corrosive medium such as atmosphere and contaminated water can also bring corrosion damage in the walls of the tube. All these forms of damages will cause the depressing of the member's load carrying capacity as well as the whole structure's load carrying capacity and service life. The capacity and condition of some members of the structure will change apparently because of the damages. Thus preliminary designs and calculations will not reflect the structural security condition after a time in service. Hence, the security of the in active service structures, especially the damaged members should be reappraised, thus right decision can be made whether the damaged members should be repaired or replaced at once or continue in service at some definite restrictive condition. Furthermore, the studies on damaged members not only relative to person wealth security but also possess prodigious economic value. This article studies round steel tube members, which are widely used in power transformation structures and the changing of their ultimate bearing capacities as well as stability qualities under general damaged conditions.There are many non-linear manners when the elements losing the stability under static loads. And there are also many classifications based on different theories and different emphasis to the problem. When the element studied lost the stability during the elastic-plastic period, the stability balance equation turn to the special coefficient differential equation, and the analytic value cannot be got. Therefore, it is needed to get the result through the numerical value method to most instances. The most used numerical value methods in the member analysis are divided into two sorts. One is to get the value directly. The Other is to get the value through the stationary value principle of general potential energy or other similitude method with correlation energy. This article studies on damaged round steel tube members and at the same time both material nonlinearity and geometric nonlinearity are considered in calculation. Numerical integration method is planed to be adopted to analyses the ultimate bearing capacity of damaged round steel tube members. According to the theory of numerical integration calculation programs are complied to calculate the ultimate bearing capacity of damaged round steel tube members. Thus the impacts of different damage notch depths and different damage zone lengths on round steel tube members' stability ultimate bearing capacity can be discussed.There are many sorts of the numerical integral approaches. The method adopted inthis thesis is the Tailor progression method. The basal theory of this method is to found the relation of M-P-Φ of any section of the element, then get the elemental limit load through the balance of the inner and the outer force, the deformation correspondence and the relation between the inner force and the deformation of the section. The progress of this method can be divided into two steps. One is found the relations of the moment, compression force and the curvature on the base of the balance of the internal force. The other step is to found the relation of the flexibility, corner and the curvature through the elemental deformation curve. Generally, there are three distributing sorts of the stress when having the section analyzing, respectively are the elastic distributing, single section plastic distributing and double sections plastic distributing. When calculat...