Comparative analysis and transformation relations between China and the US site classification systems in building seismic code provisions

In this study, based on 6 824 borehole profiles, we subdivide the site classes in GB 50011-2010 Code for Seismic Design of Buildings （Chinese code） into more homogeneous sub-classes by different values of the equivalent shear wave velocity （v_Se） and site overlaying layers （D）, and quantitatively analysis the effect of each parameters in the site classification schedule in the code. We build the relation between these sub-classes of the China code and classes of the US seismic design code National Earthquake Hazards Reduction Program Recommended Provisions for Seismic Regulations for New Buildings and Other Structures, carry out comparative analysis on two classification schedules, and build the probabilistic transformation relations for interconverting China site classes and the US site classes. The results show that: It is not appropriate to take the average shear wave velocity to a depth of 20 m （v_S20） as the proxy for v_Se in site classification of China code; for China site class Ⅱ and Ⅲ, different sub-classes have significantly different corresponding relations with the US site classes; the D effectively distinguishes the sites those velocity structures are similar at shallow layers while different at deeper layers; the main part of China site class Ⅱ and Ⅲ are both corresponding to the US site class D, the China site class Ⅱ leans to the US site class C, while the China site class Ⅲ leans to the US site class E; China site class Ⅳ is corresponding to the US site class E; most of the US site class C and D are both corresponding to China site class Ⅱ.It implies that the range of China site class Ⅱ is relatively vast.