Morihisa Fujimoto

ON WIND-PROOF PERFORMANCE OF LATTICED STEEL TOWERS

SYNOPSIS The wind-proof performance of latticed steel towers has been investigated through full-scale and model tests. The tower tested is fabricated with structural angle steel and the shape of cross section is square, which is most common among various types of microwave telecommunication towers of Nippon Telegraph and Telephone Public Corporation. Together with the experiments presented is an approximate analysis for the buffeting of such structures based on stationary random process, which comes out to agree well with the experimental results. As a consequence of this study, design formulas are proposed from a viewpoint of practical application for wind loads on latticed steel towers considering for dynamic effects of winds.

Effects of various factors on Charpy impact characteristics of reinforcing steel bars.

The reinforcing steel bars which are one of the structural rolled steels for construction can be classified into two types as blast furnace reinforcing steel bars and electric furnace reinforcing steel bars. Electric furnace reinforcing steel bars are utilized for about 85 per cent of all reinforcing steel bars at present.In this study, firstly, the Charpy impact characteristics of the above-mentioned two types of material SD35 were investigated.Secondly, the correlations between the Charpy impact characteristics and various factors such as chemical compositions, rolling conditions, and optical microstructures were studied using the multiple regression analysis method.As a result, the apparent differences in Charpy impact characteristics were found between the two types of bars. That is to say, the electric furnace steel bars had energy transition curves or fracture transition curves with more gentle slopes, lower shelf energies (vEshelf), and higher energy ransition temperatures (vErE) or higher fracture transition temperatures (vTrs) than the blast furnace steel bars. Therefore, it has been realized that these differences in characteristics depend on Mn, Cr and N Contents as well as on reduction ratio. It has also been realized that vTrE and vTrs shift to lower temperatures as the ferrite perlite structures become lamellar.