High performance steel (HPS) are steel which exhibit improved strength, weld ability, ductility and energy absorption. These enhanced properties compared to conventional steel may give HPS protective properties against extreme loads that may occur in earthquakes. For high-rise building in Taiwan, HPS has many further practical applications. However, the cause of brittle failure in box columns-beams welded joints still exits such as fracture at column and diaphragm electro gas welding (EGW) cause of the effect of high heat input welding and welding defects. Furthermore, the impact of this effectiveness in the intersection area will be more serious under seismic loading because the swing of beam establishes the forces which directly go through column beam joint welded. In order to ensure the structural stability and ductility requirement, the damage should not occur at the junction and make beam getting to plastic period. In this study, the structural characteristics of welded joint area were investigated through experimental and analytical procedures, including (a) behavior of jumbo specimen under series of loading test, (c) analytical model studying stress intensity factor of welding joint.

1. Barson, J.M. and Rolfe, S.T., “Fracture and Fatigue Control in Structural - Applications of Fracture Mechanics”, Prentive-Hall, New Jersey, (1977)
2. Broek, D., “Element Engineering Fracture Mechanics”, 4th Ed. Martinus Nijhoff Publishers, 1986
3. Hertzberg, R.W., “Deformation and fracture mechanics of engineering materials”, 2nd ed. John Wiley and Sons, New York, 1983.
4. Sheng-Jin Chen, Hsin-Yi Lin, “Stress concentration and fracture of steel beam-to-column moment connection”, The Chinese journal of mechanics, Vol.6, No.2, December 1990.
5. Chen Cheng-Chih, Lai Chien-lin, Lin Ker-chun, Lin Nan-jiao, “Finite element analysis of Electro-Slag Weld defects on Fracture of steel box column plate”, Progress in steel building structures, Vol. 13. No. 4, Aug. 2011.
6. J. Zhang, P. Dong, “Residual stresses in welded moment frames and implications for structural performance”, Journal of structural engineering, March 2000.
7. Takeshi Mori, “Evaluation formula for fatigue strength of crucirom welded joints failing from weld roots under Bi-axial Loading”, International journal of Steel structures, Vol.8, No.3, Sep. 2008.
8. Elena Mele, Luis Calado, Antonello De Luca, “Cyclic behavior of beam-to-column welded connections”, Steel and Composite Structures, Vol. 1, No. 3 (2001), PP. 269-282.
9. H. Kuwamura, “Classification of material and welding in fracture consideration of seismic steel frames”, Engineering structures, 25 (2003) 547-563.
10. Le-Wu Lu, James M. Ricles, Changshi Mao, John W. Fisher, “Critical issues in achieving ductile behavior of welded moment connections”, Journal of Constructional Steel Research, 55 (2000) 325-341.
11. Le-Wu Lu, James M. Ricles, Changshi Mao, John W. Fisher, “Ductile details for welded unreinforced moment connections subject to inelastic cyclic loading”, Journal of Constructional Steel Research, 25 (2000) 667-680.
12. Le-Wu Lu, James M. Ricles, John W. Fisher, E.J. Kaufmann “Development of improved welded moment connections for earthquake-resistant design”, Journal of Constructional Steel Research, 58 (2002) 565-604.
13. Jun Iyama, James M. Ricles, M.ASCE, “Prediction of Fatigue life of welded beam –to-column connections under Earthquake Loading”, Journal of structural engineering,Vol.135, No.12. Dec. 2009.
14. Frank, K.H., and Fihser, J., “Fatigue Strength of Fillet Welded Cruciform Joints”, Journal of the Structural Division, ASCE ST, Vol. 105, No. 9, (1979)
15. C. Miki, K. Homma T. Tominaga, “High strength and high performance steels and their use in bridge structures”, Journal of Constructional Steel Research, PP.3-20, (2002)
16. Reidar Bjorhovde, “Development and use of high performance Steel”, Journal of Constructional Steel Research, PP.393-400, (2004)
17. El-Tawil, S., Mikesell, T., and Kunnath, S.K., “Effect of local details and yield ration on behavior of FR steel connections.” Journal of Structural Engineering, ASCE, 126(1), 79-87, 2000.
18. ASTM, “Standard Practice for Strain-Controlled Fatigue Testing”, ASTM E606-04, (2004).
19. ASTM, “Standard Test Methods for Tension Testing of Metallic Materials”, ASTM E8/E 8M-08, (2008).
20. ASTM, “Manual On Low Cycle Fatigue Testing”, STP465, (1969).
21. European Convention for Constructional Steelwork (ECCS), “Seismic Design, Recommended testing procedure for assessing the behavior of structural steel elements under cyclic loads”, Technical Committee 1 - Structural Safety and Loadings, TWG1. 3 Rep. No. 45, (1986).
22. Applied Technology Council (ATC), “Guidelines for cyclic seismic testing of components of steel structures”, ATC-24, Redwood, Calif., (1992).