In this study, tensile tests of notched flat plates are conducted. The purpose of this experiment is to reveal the relationship between stress concentration factor α 3.5-9.3 and fracture critical stress of notched tensile specimens of spheroidal graphite cast iron and the relationship between maximum first principal stress and stress concentration factor α in spheroidal graphite cast iron. Table 1 shows stress-concentration factor α of previous and this studies. Stress-concentration factor α is calculated from equation (1). Stress-concentration factor α of previous studies only 2 and 10. This study, considering α between 3.5 and 9.3. Notched tensile specimens are made of the castings shown in Fig. 1 by cutting. Fig. 3 presents the notched tensile test specimen and clip gauges mounting position. It is measured notch displacement of specimens. The shape of notched tensile specimens are indicated in the Table 2. Notched tensile specimen has 8 different shape notches. All of these specimens, length is 550mm, width is 90mm, thickness is 20mm, notch depth c is 5mm and 10mm, and notch bottom radius ρ is 0.25mm, 0.5mm, 1mm, and 2mm.

 Specimens of round bar tensile tests is shown in the Fig. 4. The results are indicated in the Table 3 and Fig. 5. Fig. 5 is stress-strain relationships of notched tensile specimens.

 Fig. 6 shows the load-displacement relationships. The list of notched tensile test results are indicated in the Table 4. Notch round bar tensile test was conducted to calculate fracture critical stress. The test specimen and analysis model are shown in the Fig. 8 and Fig. 9. The list of notch round bar tensile test is shown in the table 5 and Fig. 10.

 Fig. 11 shows the analysis model of notched tensile specimen. As indicated in the Fig. 12, the load-deformation relationships are relative to experimental results. The difference between the maximum first principal stress of tensile analysis and fracture critical stress was under 13%. It is shown in the Table 6. Fig. 13 shows eccentricity analysis of 10-0.5(1).

 Fig. 15 shows the relationship between the maximum first principal stress of tensile analysis _Pσ and stress- concentration factor α. It is the linear relationships.

 From the results of test and analysis, following findings were obtained.

 (1) The difference between the maximum first principal stress of tensile analysis and fracture critical stress was under 13%. Therefore, in the scope of this study, fracture critical stress is relative to brittle fracture of spheroidal graphite cast iron.

 (2) By analysis imitating eccentricity, fracture critical stress is applicable to brittle fracture of spheroidal graphite cast iron when the eccentricity of difference is 1.2 of left _dσ/right _dσ in elastic range, as same as nothing eccentricity.

 (3) Including this study and previous studies, the relationship between the maximum first principal stress of tensile analysis _Pσ and stress-concentration factor α is linear in stress-concentration factor α 2.2~10.8.

 (4) By the results of notched specimen tensile test, the larger stress-concentration factorα, the smaller the displacement of fracture. Specimens with smaller stress-concentration factors tend to vary in maximum displacement comparing specimens of the same shape.

 In this study, T shaped tensile tests and 3-point tensile tests are conducted. The purpose of these experiments is to reveal the relationships between brittle fracture of spheroidal graphite cast iron and fracture critical stress in various stress conditions. Fig. 1 shows the application method of fracture critical stress for brittle fracture. Bending specimens are made of the T shaped castings shown in Fig. 2 by cutting. Specimens of round bar tensile tests is shown in the Fig. 3. The results are indicated in the Table1 and Fig. 4. Fig. 4 is Stress-strain relationships of T shaped castings.

 Fig. 5 presents the T-shaped tensile bending test specimen and displacement measuring position. It is measured vertical displacement of the end of specimen, and calculated the deformation angle of the end. Fig. 6 presents the specimen case of three-point bending. PR shaped specimen has the protuberance. It is 5 mm. PL shaped specimen has no protuberances. All of these shaped specimens are composed of width 35 mm and 125 mm. The narrow width specimens are supposed to be plane stress condition, and the wide width specimens are supposed to be plane strain conditions.

 Fig. 7 shows the Lord-deformation relationships and Bending stress-deformation relationships. Bending stress was calculated by the formula (1) and (2). The wide width specimens broke earlier deformation angle than the narrow width specimen. The list of bending test results are indicated in the table2.

 Notch round bar tensile test was conducted to calculate fracture critical stress. The test specimen and analysis model are shown in the Fig. 9 and Fig. 10. The list of notch round bar tensile test is shown in the table3.

 Fig. 12 shows the analysis model of T shaped specimen. As indicated in the Fig. 13, the Lord-deformation relationships are relative to experimental results. The difference between the maximum first principal stress of bending analysis and fracture critical stress was under 15%. It is shown in the Table4.

 From the results of test and analysis, following findings were obtained.

 (1) The wide width specimens were broken smaller deformation than the narrow width ones. That is because the wide width specimen is likely plane strain. This is why, when the same deformation with narrow width specimens, the wide ones has higher stress.

 (2) The difference between the maximum first principal stress of bending analysis and fracture critical stress was under 15%. Therefore, in the various stress conditions, fracture critical stress is relative to brittle fracture of spheroidal graphite cast iron. It is necessary to set the safety factor of fracture critical stress when fracture critical stress is applied to actual structures.

 (3) CS specimens (the tensile side is casting surface) were broken earlier than MS specimens (the tensile side is machining surface). However, it is necessary to consider the effects of cast iron surface for fracture, because the number of CS and MS specimens are not enough.

The purpose of this study is to clarify the influence of scallop details on fracture and deformation capacity of beam-to-column joints. This paper presents the results of full-scale tests of welded beam-to-column joints using SN490B with some type of the scallop details (snip-cut method, non-scallop method and scallop method by using reinforcement welding) on field and shop. Based on the test results, snip-cut of field welding beam-to-column joint have large deformation capacity which is equal or higher than that of shop welding beam-to-column joints.