Assessment of a capacity spectrum seismic design approach against cyclic and seismic experiments on full-scale precast RC structures

Within the last decades, simplified methods alternative to dynamic nonlinear analysis have been developed to estimate the seismic performance of structures towards a performance-oriented design. Considering drift as the main parameter correlated with structural damage, its estimation is of main importance to assess the structural performance. While traditional force-based design deals with calibrated force reduction factors based on the expected structural ductility, other methods are based on the definition of a viscous damping factor defined as a function of the expected energy dissipated by the structure. An example is the Capacity Spectrum Method. This method can be applied even without any a-priori calibration or designer arbitrariness. This allows to consider several peculiarities of the seismic behavior of precast structures, which may be influenced by non-traditional hysteresis of connections and members, interaction with the cladding panels, P-δ effects, etc. The paper aims at verifying the soundness and accuracy of this method through the comparison of its predictions against the results of cyclic and pseudo-dynamic tests on precast structures, including single- and multi-story buildings either stiff or flexible, obtained on full-scale building prototypes tested within the framework of recent research projects (namely, “Precast Structures EC8”, “Safecast” and “Safecladding”). Two simple methodologies of determination of the equivalent viscous damping from a force-displacement cycle, based on the dissipated energy in relation to two different estimates of the elastic strain energy, are addressed and compared. Comments on the possible use of this procedure for the estimation of the seismic performance of precast structures are provided.