Study on the Brittle Fracture of Welded Beam-to-Column Connections of Heavy Steel : COD Testing

It was reported that the brittle fracture in plastic range at room temperature took place in the full scale tests of wide flange beam-to-column connections of which the thickness of column flanges were from 40mm to 60mm. It is very important to analyze this phenomenon, because the wide flange of heavy steel section is generally used in the construction of multi-story buildings. In general, the following factors seem to have influence upon brittle fracture; (1) material properties (grade of steel, change of material properties by welding, anisotropy of rolled steel, etc.) (2) temperature (transition temperature) (3) constraint intensity of plastic deformation (plane strain, dimensions of members, etc.) (4) residual stresses (by rolling and welding, etc) The brittle fracture is caused by superposition of these factors, and it is necessary to make clear how these factors affect on the brittle fracture. The former two factors can be estimated by the test of small specimen, but the latter two cannot be done by it, and they should be estimated by the test of large scale specimen. Therefore the authors examine the fracture toughness of welded beam-to-column connections of heavy steel section. At first stage we focused our attention on the former two factors, that is, (1) material properties and (2) temperature, and carried out the COD testing of small scale specimen which is little affected by the latter two factors.