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A new replaceable hysteretic damper to better control seismic building damage, consisting of two or more adjacent steel vertical elements connected to each other with continuous mild/low strength steel shear links, is proposed and investigated in this paper. New Dampers, called Dissipative Columns (DC), continuously linked with X-shaped steel plates, provide additional stiffness and damping to a lateral system by using a basic and minimally invasive construction element: the column. Working in a way similar to coupled shear walls, the proposed element behavior is theoretically analyzed at linear and non-linear ranges. In fact, considering different restrained cases, a parametric analysis is developed in order both to evaluate the effect of the main geometrical and structural parameters and to provide the design capacity curves of this new damper. The DC can be considered a new damping device, easy to install in new as well as existing buildings in order to protect them from seismic damage. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

It has been a Canadian code requirement for 25 years to check whether concrete gravity-load columns can tolerate the building deformations due to the design earthquake; but the way this has typically been done using linear analysis significantly underestimates the seismic demands on gravity-load columns. Concern about the safety of gravity-load columns over the plastic hinge height of concrete shear walls, particularly elongated wall-like gravity-load columns, has resulted in new design requirements in Update No. 3 of Canadian Standard Association (CSA) A23.3-04 issued in August 2009. The current paper provides the background to these new requirements. If nonlinear analysis is not done, closely spaced seismic hoops shall be provided in all columns and walls that support gravity loads, and these members shall meet the same limit on maximum compression strain depth as concrete shear walls. The results of nonlinear analyses were used to validate this simple design rule, and to investigate factors that increase seismic demands on gravity-load columns such as diagonal cracking of concrete shear walls, localized damage of columns from cover spalling and bar buckling, and larger first storey heights. Nonlinear analysis has shown that 2.4 m (8 ft) long columns can lose over 50% of their axial load carrying capacity at an inelastic drift ratio of only 1%. Une exigence du code canadien depuis 25 ans est de vérifier si les colonnes de béton chargées par gravité peuvent résister aux déformations du bâtiment causées par un séisme type. Cette vérification était normalement réalisée par analyse linéaire et sous-estimait de manière significative les demandes sismiques sur les colonnes de béton chargées par gravité. Des préoccupations concernant la sécurité des colonnes de béton chargées par gravité quant à la hauteur des charnières plastiques des murs de contreventement en béton, plus particulièrement les colonnes de béton chargées par gravité allongées, similaires à un mur, ont engendré de nouvelles exigences de conception dans la mise à jour no 3 de la norme CSA A23.3-04 émise en août 2009. Le présent article traite de l'historique de ces nouvelles exigences. Si une analyse non linéaire n'est pas réalisée, des boucles sismiques peu espacées doivent être fournies dans toutes les colonnes et tous les murs qui supportent des charges par gravité, et ces membrures doivent rencontrer la même limite de profondeur de contrainte de compression maximale que les murs de contreventement en béton. Les résultats des analyses non linéaires ont été utilisés pour valider cette simple règle de conception et examiner les facteurs qui accroissent les demandes sismiques sur les colonnes de béton chargées par gravité, tels que la fissuration diagonale des murs de contreventement en béton, les dommages localisés sur les colonnes par l'effritement des surfaces et flambement des tiges, et des hauteurs plus élevées des premiers étages. Une analyse non linéaire a indiqué que des colonnes d'une longueur de 2,4 m (8 pi) peuvent perdre plus de 50 % de leur capacité portante axiale à un rapport de mouvement inélastique de seulement 1 %. [ABSTRACT FROM AUTHOR]

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Copyright of Technical Journal / Tehnički Glasnik is the property of Polytechnic of Varazdin and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)