Volume 2 • Issue 1 • 1000108 J Archit Eng Tech ISSN: 2168-9717 JAET, an open access journal Open Access Research Article Phocas and Sophocleous, J Archit Eng Tech 2013, 2:1 http://dx.doi.org/10.4172/2168-9717.1000108 Architectural Engineering Technology Keywords: Structural control; Cable braced frame; Hysteretic damper; Dual system Introduction he design of frame structures with additional control members for earthquake resistance refers primarily to the requirement for the primary systems to exhibit essentially a linear elastic behavior under seismic actions [1-3]. A reduction of the energy dissipation demand on primary structural systems was successfully aimed at by a number of researchers through integration of damping devices, such as passive metallic yielding-, friction-, viscoelastic- and viscous damping devices [4-7]. In principle the damping devices are added in moment resisting frames attached on steel bracings that may be of accountable self- weight and stifness [8-11]. he bracing components consist of steel members stressed in compression, tension and bending, and increase the overall stifness of the system [12,13]. In addition their seismic control resistance weakens by the fact that under cyclic loading in every half-loading cycle the compression diagonal buckles and it therefore cannot participate in the energy dissipation process. On the other side, a conventional bracing consisting only of cables is not suitable for earthquake resistant structures, due to the fact that the members become slack under their tension yielding and compression buckling. Driven by certain advantages in architectural, aesthetic, constructability and economic context, the implementation of tension- only bracings with damping devices in frame structures may be realized through the development of suitable bracing-damper conigurations, whereas all bracing members contribute during the entire load duration to the operation of the integrated damper. An optimization of the control system’s operation principles for earthquake structural resistance may thus be achieved. his concept was initially followed with the Pall- Marsh friction mechanism using slender cross braces [14]. In principle the rectangular damper deforms into a parallelogram, dissipating energy at the bolted joints through sliding friction. he kinematics of the system prevents the diagonals to buckle in compression; with the completion of a loading cycle, the hysteresis loops are identical for all bracing members. An alternative friction mechanism coniguration with cross braces has also been proposed in [15]. Recently proposed control systems that consist of hysteretic dampers and slender bracing members are based in their operation on relative *Corresponding author: Department of Architecture, Faculty of Engineering, University of Cyprus, 75 Kallipoleos St., P.O.Box 20537, 1678 Nicosia, Cyprus, Tel: +357-22892969; Fax: +357-22895056; E-mail: mcphocas@ucy.ac.cy Received January 16, 2013; Accepted June 24, 2013; Published June 26, 2013 Citation: Phocas MC, Sophocleous T (2013) Dual System Coniguration for Earthquake Safety. J Archit Eng Tech 2: 108. doi:10.4172/2168-9717.1000108 Copyright: © 2013 Phocas MC, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Dual System Configuration for Earthquake Safety Department of Architecture, Faculty of Engineering, University of Cyprus, 75 Kallipoleos Str., P.O.Box 20537, 1678 Nicosia, Cyprus Abstract Structural control through integration of passive damping devices within structures has proven to be a most promising strategy for earthquake safety. Within this research ield, the concept of adaptable dual control systems has been initially proposed for application in frame structures supplemented with a cross cable bracing with closed circuit and a hysteretic damper of steel plates. The control mechanism enables the elastic response of the primary structure through energy dissipation only effected by the damper that is activated by all bracing members. In extending the applicability range of the control concept in both, in engineering and broader architectural context, and further improving the controlled system’s performance, an alternative coniguration of the bracing-damper mechanism is investigated. Following the construction design of the control system members a numerical dynamic analysis of a SDOF system is performed for three representative international earthquake motions of differing frequency contents. The characteristic stiffness and yield force of the integrated damper are investigated in their optimum values for achieving high energy dissipation capacity of the system, while preventing possible increase of the maximum base shear and relative displacements. displacements between the tension members. Hysteresis is achieved through optimization of the integrated hysteretic dampers plates’ section. he cross braces with the articulated quadrilateral with steel dissipaters work only in tension, whereas energy dissipation develops through elasto-plastic lexure of the steel plates with varying depth [16]. A similar cross cable bracing coniguration with a central energy dissipater consisting of two steel plates that are interconnected through a rotational spring has been proposed [17]. Under seismic excitation four cables in tension rotate the steel plates in opposite directions. he remaining cables, which connect across the shortened diagonal, are stressed elastically in compression and do not become slack, when the loading direction changes, due to the permanent rotation of the steel plates. he research inquiry of utilizing the performance of mild steel in terms of strength, lexibility and minimal structural weight with the requirement for a smooth, non-coupled operation of the tension- only bracing-damper mechanism to the primary system under dynamic excitations initiated related studies [18] and has led to further development of possible conigurations for Adaptable Dual Control Structures, ADCS [19]. ADCS consist of a cable bracing with closed circuit and a hysteretic damper of steel plates. During strong ground motions relative displacements between the bracing and the frame member interconnected through the hysteretic damper yield to the damper’s own deformations and energy dissipation. ADCS is only responsible for the earthquake forces and enables in all cases the elastic response of the primary system. In principle, ADCS introduce a prototype connections design Marios C. Phocas* and Tonia Sophocleous Marios C. Phocas, Associate Professor, Interim Head,