Problems and certainties in the experimental simulation of the seismic response of MDOF structures

A critical discussion of problems in the experimental simulation of seismic loads on civil structures is presented, primarily addressing issues concerning the choice of test method, (dynamic, static, or pseudodynamic), the selection of appropriate ground motions, and the method of controlling tests, (in force control, displacement control, or a combination of the two). Particular attention is given to the problem of the interaction between applied actions and observed response in structures with multiple degrees-of-freedom. Three examples of recent structural tests performed at the Universities in Pavia (Italy), California (San Diego), and Illinois (Urbana-Champaign) are cited to illustrate hybrid tests in which novel approaches have been used to maximize the utility of data from tests on multi-degree-of-freedom structures.