Comparison of European and Japanese seismic design of steel building structures

This paper compares EuroCode 8 (EC8) and the Japanese seismic design code (BCJ) for steel moment frames and braced frames. Soil classification, magnitude and shape of unreduced elastic response spectra, distribution of seismic shear along the height, member ductility requirements, and behavior factor are compared. It was found that the two codes are relatively similar except for the seismic force stipulated for the serviceability limit state. EC8 gives an approximately 2.5 times larger force for this limit state. Behavior factors that allow for system ductility are significantly different between the two codes; for moment frames BCJ is more conservative by about 50%. Strength demanded by EC8 and BCJ is evaluated for steel moment frames and chevron braced frames. Although the behavior factor is less conservative in EC8, the net strength required by EC8 is significantly greater than the corresponding BCJ strength for steel moment frames, and it occurs because of the significantly larger design force stipulated for serviceability in EC8. With regard to braced frames, BCJ leads to larger lateral story strength except for chevron braced frames with slender braces.