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Self-centering concentrically-braced frame (SC-CBF) systems are being developed with the goal of providing adequate nonlinear drift capacity without significant damage or residual drift under the design basis earthquake. Analytical pushover and dynamic analyses were performed on several SC-CBF configurations to evaluate their response to earthquake loading. Each SC-CBF self-centered under earthquake loading. Some loss of post-tensioning occurred in one configuration. The dynamic response of the SC-CBF systems, however, was consistent with the intended behavior. A procedure is presented herein to calculate the design demands for the frame members. This design procedure is then validated with analytical results. Analysis results show that the design procedure accurately predicts the member force demands under earthquake loading.

Abstract:Structures designed in accordance with even the most modern buildings codes are expected to sustain damage during a severe earthquake; however; these structures are expected to protect the lives of the occupants. Damage to the structure can require expensive repairs; significant business downtime; and in some cases building demolition. If damage occurs to many structures within a city or region; the regional and national economy may be severely disrupted. To address these shortcomings with current seismic lateral force resisting systems and to work towards more resilient; sustainable cities; a new class of seismic lateral force resisting systems that sustains little or no damage under severe earthquakes has been developed. These new seismic lateral force resisting systems reduce or prevent structural damage to nonreplaceable structural elements by softening the structural response elastically through gap opening mechanisms. To dissipate seismic energy; friction elements or replaceable yielding energy dissipation elements are also included. Post-tensioning is often used as a part of these systems to return the structure to a plumb; upright position (self-center) after the earthquake has passed. This paper summarizes the state-of-the art for self-centering seismic lateral force resisting systems and outlines current research challenges for these systems. OPEN ACCESSBuildings 2014, 4 521

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In the current study, the performances of some decision tree (DT) techniques are evaluated for postearthquake soil liquefaction assessment. A database containing 620 records of seismic parameters and soil properties is used in this study. Three decision tree techniques are used here in two different ways, considering statistical and engineering points of view, to develop decision rules. The DT results are compared to the logistic regression (LR) model. The results of this study indicate that the DTs not only successfully predict liquefaction but they can also outperform the LR model. The best DT models are interpreted and evaluated based on an engineering point of view.

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