This paper presents the first phase of a comprehensive experimental study concerning the possible application of active control to structures under seismic excitations. In the laboratory, a single‐degree‐of‐freedom model structure was used which was controlled using prestressing tendons connected to a servohydraulic actuator. An optimal closed‐loop control scheme using a quadratic performance index was employed to reduce the response of structure under base motion generated by a large‐scale seismic simulator. The time delay between the observed motion and the implemented control forces, an important factor in control implementation, was integrated in the control algorithm. Using a carefully designed, fabricated, and calibrated experimental setup, the correlation between the analytical and experimental results was studied. Based on similitude relations, the experimental results obtained for the model structure were extrapolated to the full‐scale structures and are analyzed.

Experiments on Active Control of Seismic Structures

A research program is summarized in which collapse of a steel frame structure is predicted numerically and the accuracy of prediction is validated experimentally through earthquake simulator tests of two 1:8 scale models of a 4-story code-compliant prototype moment-resisting frame. We demonstrate that sidesway collapse can occur for realistic combinations of structural framing and earthquake ground motion; P-Δeffects and component deterioration dominate behavior of the frame near collapse; prediction of collapse is feasible using relatively simple analytical models provided that component deterioration is adequately represented in the analytical model; and response of the framing system near collapse is sensitive to the history that every important component of the frames experiences, implying that symmetric cyclic loading histories that are routinely used to test components provide insufficient information for modeling deterioration near collapse. © 2010 John Wiley & Sons, Ltd.

Prediction and validation of sidesway collapse of two scale models of a 4‐story steel moment frame

Shaking table test of a multi-story subway station under pulse-like ground motions

Recent studies have highlighted the beneficial role of foundation uplifting and the potential effectiveness of guiding the plastic hinge into the foundation soil by allowing full mobilization of bearing capacity during strong seismic shaking. With the inertia loading transmitted onto the superstructure being limited by the capacity of the foundation, this concept may provide an alternative method of in-ground seismic isolation: the so-called rocking isolation. Attempting to unravel the effectiveness of this alternative design method, this paper experimentally investigates the nonlinear response of a surface foundation on sand and its effect on the seismic performance of an idealized slender single-degree-of-freedom structure. Using a bridge pier as an illustrative prototype, three foundation design alternatives are considered, representing three levels of design conservatism. Their performance is investigated through static (monotonic and slow-cyclic pushover) loading, and reduced-scale shaking ta...

http://ssi.civil.ntua.gr/downloads/journals/2012-ASCE_Soil%20%20Foundation%20Structure%20Interaction%20with%20Mobilization%20Bearing%20Capacity%20Experimental%20Study%20on%20Sand.pdf

Soil-Foundation-Structure Interaction with Mobilization of Bearing Capacity: Experimental Study on Sand

SUMMARY
Pounding between adjacent bridge structures with insufficient separation distance has been identified as one of the primary causes of damage in many major earthquakes. It takes place because the closing relative movement is larger than the structural gap provided between the structures. This relative structural response is controlled not only by the dynamic properties of the participating structures but also by the characteristics of the ground excitations. The consequence of the spatial variation of ground motions has been studied by researchers; however, most of these studies were performed numerically. The objective of the present research is to experimentally evaluate the influence of spatial variation of ground motions on the pounding behaviour of three adjacent bridge segments. The investigation is performed using three shake tables. The input spatially varying ground excitations are simulated based on the New Zealand design spectra for soft soil, shallow soil and strong rock using an empirical coherency loss function. Results confirm that the spatially nonniform ground motions increase the relative displacement of adjacent bridge girders and pounding forces. Copyright © 2012 John Wiley & Sons, Ltd.

Experimental investigation of spatially varying effect of ground motions on bridge pounding

The feasibility and limitations of small-scale model studies in earthquake engineering and practice are summarized. Emphasis is placed on dynamic modeling theory; a study of the mechanical properties of model materials; the development of model construction techniques; and an evaluation of the accuracy of prototype response prediction through model case studies on components and simple structures. The basics of similitude theory and its application to the modeling of dynamically excited structures are reviewed and similitude laws for various types of models are developed. Materials for modeling of steel and reinforced concrete structures are examined with regard to cyclic load effects. Systematic material testing procedures are developed for the investigation of alternative model materials. Also, problems encountered in the construction of models are identified and recommendations are suggested to correct them. The research demonstrates that model analysis can be used in many cases to obtain quantitative information on the seismic behavior of complex structures which cannot be analyzed confidently by conventional techniques.

H Krawinkler

Papers

Theory and application of experimental model analysis in earthquake engineering