Contents lists available at ScienceDirect Soil Dynamics and Earthquake Engineering journal homepage: www.elsevier.com/locate/soildyn Seismic characteristics of X-cable braced frames bundled with a pre- compressed spring M.H. Mehrabi ⁎ , Zainah Ibrahim ⁎ , S.S. Ghodsi, Meldi Suhatril Department of Civil Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia ARTICLEINFO Keywords: Cable-braced Systems Seismic control Steel frames Nonlinear response ABSTRACT The performance of steel structures can be enhanced against lateral loads by various methods; of these, bracing systemsarethemostcommon.Paststudieshaveshownthattension-onlybracedframesprovidemorestructural stability,andhenceoferbetterresistancewhenthe frameissubjectedtolateralloads.Inacomparisonbetween a braced and bare frame, the additional efciency ofered by the bracing depends on the selection of bracing system.Thispaperproposesacablebracesystemwithapre-compressedspring(PCS)thatbundlesthewire-rope bracing members at the intersection point. Both experimental and analytical studies are conducted, and no loosening in the cable is observed, as the cables are held tension by the spring's force; thus the ability of the bracing system to cause impulses is eliminated. The fnal strength of the cables is reached at larger lateral displacement of the frame compared to ordinary cross cable bracing system. The equations involved in the proposed technique are discussed before being verifed using fnite element (FE) solutions based on ABAQUS analysis. It can be concluded that the ductility and strength of the tested specimens was signifcantly improved by means of the proposed technique. 1. Introduction Accordingtomodernseismiccodes,inelasticdeformationscanform indissipativezones.Thisraisesthepossiblerepaircostsofstructuresin areas of high seismicity, and thus increases the need for repairable and replaceable structural systems to maintain the benefts of high ductility while reducing repair costs. Conventional seismically resistant struc- tural systems, such as those designed to be moment resisting or with braced frames, can be assessed with respect to ductility and stifness, andfromthispointofview,theiradvantagesanddisadvantagescanbe evaluated. A required lateral stifness for moment-resisting steel frames (MRFs) located in regions with high seismic levels is provided to pre- vent storey drift amplifcation [1]. Nevertheless, unexpected large storey drifts may still occur as the result of extremely severe earth- quakes. Lateral stifness retroftting of MRFs has been underscored to some extent by former studies [2,3]. CBFs have been recognized as an efective method for providing lateral stifness and strength [4]. This type of seismic retroftting technique is generally utilised in steel structures that are located in regions with high seismic activity records within the past 30 years. However,thereareseverallessfavourablecharacteristicsofthistypeof retroftting, including low drift capacity and higher acceleration. Comparisons between MRFs and CBFs have shown that CBFs can substantially increase stifness to control storey drift. Shortly after the KobeearthquakethatdevastatedsouthernJapan,asurveyofdamageto 452 steel braced frames afected was conducted [5]. Based on this survey, only 6% had collapsed, while 31% had experienced severe damage and 63% had sustained moderate to minor damage. Such en- hancementsinseismicperformanceandreductionsinstoreydriftalong withoptimisedmaterialusagehasledtoseveralresearchersinthefeld focusing on the behaviour of steel wire ropes, connections, and sub- assemblies under seismic excitation [6,7]. Further studies in cases of eccentricallybracedframes [8,9],dissipativebracingsystems [10],and non-compression braces [11] have also been carried out to improve seismic resistance in the bracing members. The application of tension-only elements has been investigated in many studies [12–14].Inthecurrentstudytheterm"cable"isageneral term referring to a range of tension-only elements, including carbon fbre cables and wire ropes. Cables have negligible resistance to bending, and are thus defned as fexible tension members. Application ofcablesinbuildingshas,however,beenexaminedbysomeresearchers [15]. Several researchers have explored the contribution of cables combined with diferent types of dampers, including Phocas and Po- canschi, [16] who studied the performance of hysteretic damper de- vices together with a cross-bracing mechanism and a kinetic closed- circuitconfguration.Researchinvestigatingcombinedsystems,suchas https://doi.org/10.1016/j.soildyn.2018.10.014 Received 22 February 2018; Received in revised form 12 October 2018; Accepted 13 October 2018 ⁎ Corresponding authors. E-mail addresses: mehrabi_mh@yahoo.com (M.H. Mehrabi), zainah@um.edu.my (Z. Ibrahim). Soil Dynamics and Earthquake Engineering 116 (2019) 732–746 0267-7261/ © 2018 Elsevier Ltd. All rights reserved. T