Yukio Ueda

Elasto-Plastic Large Deflection Analysis of Beam-Columns and Rectangular Plates

The authors research group developed Plastic Node Method (P. N. M.) and has demonstrated the efficiency of this method in analyzing the material nonlinear behavior of many kinds of structures, such as ships, offshore structures. While, for analysis of elastic large deflection (geometrical nonlinear behavior) of structural elements, such as beam-columns, rectangular plates, some analytical methods are effective.In this paper, these two methods are combined for an accurate and efficient analysis of elasto-plastic large deflection of these elements. The work of this paper will be summarized as follows.1) The original plastic node method is modified in such a way that condensed nodal plastic displacements are redistributed in the element for evaluation of elasto-plastic stiffness with large deflection.By this treatment, an accurate analysis becomes possible for elasto-plastic large deflection of the elements, including at post-ultimate strength state.2) A simple and accurate deformation function for each type of the elements is selected.3) Appropriate locations and number of checking points for plasticity are proposed. To take account of intermediate state between initial plasticity and full plasticity, an appropriate size of plastic zone at each checking point is assumed.This method is applied to several examples, and its usefulness and validity is demonstrated by comparing with the results of the finite element analysis. Necessary computer time for the example analysis by this new method was found to be 1/601/100 by F. E. M.

Ultimate Strength of Transverse Girders Under Bending

When structures are constructed by welding, structural members are usually accompanied by welding distortions. In this paper, the ultimate strength of transverse girders in ship structures with initial deflections under bending are investigated.First, the entire behavior, elastic-plastic large deflection, of these girders are theoretically analysed by the strip element method. A series of experiments are carried out on model girders subjected to bending moment with respect to their strong axes. Comparison is made between the test results and theoretical one and good agreement is observed between them. By these studies, a great deal of valuable information is obtained on the ultimate strength of the girders.An approximate model is also proposed to exhibit the influence of initial deflection on the ultimate strength of girders. It is found that the proposed approximate method of analysis is very useful for prediction of the ultimate strength.

Strength of Welded Connections (Repoert 1)

Recently, steel structures are in a trend to be designed with consideration of their reserved strength in the plastic range. Accordingly, the strengths of welded connections are also to be discussed from this point of view. There are only few papers which dealt with elastic-plastic behavior of welded connections and consequently, present conventional design formulae of welded connections seem to be based on the simple elastic analysis or the experimental results on the fracture strength.In order-to clarify the elastic-plastic behavior of welded connections, a series of experiments was conducted on cruciform connections with fillet weld under uniaxial forces, pure bending, and pure shear, and their combination. From the results, it was found that the connection showed a sudden reduction of regidity at general yielding and reached its ultimate strength after a large amount of plastic deformation. Therefore, it is very reasonable to discuss the strength of welded connection in terms of the above two points, i.e., yield and ultimate strength.Theoretical analysis was also made on the above mentioned strength with the aid of plastic analysis method. The results of the analysis well coincide with those of the experiment and locate well the actual sections in which general yielding and ultimate strength are attained. Based on the results of the investigation, design fomulae are proposed for the yield and ultimate strength of welded connection.