Tests to structural collapse of single degree of freedom frames subjected to earthquake excitations

This paper presents and analyzes experimental results of tests of 15 four-column frame specimens subjected to progressively increasing unidirectional ground shaking to collapse. The specimens were subdivided into groups of three different column slenderness ratios: 100, 150, and 200. Within each group, the column dimensions and supported mass varied. Ground motion of varying magnitudes was required to collapse the structure tested. The experimental setup is briefly described and results are presented. Test structure performance is compared with proposed limits for minimizing P-Δ effects in highway bridge piers. The stability factor is found to have a strong relation to the relative structural performance in this regard. Performance is also compared with capacity predicted by currently used strength and stability axial-moment interaction design equations by expressing these capacities in terms of acceleration and maximum base shear (as a fraction of the system's weight). The experimental results exceeded the maximum spectral accelerations calculated when considering second-order effects, but did not when considering only member strength. Finally, an example of how to use the experimental data for analytical model verification is presented, illustrating the shortcomings/inaccuracies of using a particular simplified model with constant structural damping.