Innovative hybrid coupled wall systems to resist seismic action – HYCAD

Abstract

The EU-RFCS research project "HYCAD" [1] aims at contributing to the use of improved innovative hybrid coupled walls (HCW) for buildings in seismic areas, further developing the innovative HCWs proposed and analysed in the 2011-2013 RFCS research project Inno-Hyco [2]. The Inno-Hyco HCW system was made of a reinforced concrete (RC) wall coupled to two steel side columns via steel links, as shown in Fig. 1 (left). The RC wall carries almost all the horizontal shear force while the overturning moments are partially resisted by an axial tension-compression couple developed by the two steel columns rather than by the individual flexural action of the wall alone. The RC wall was designed to remain in the elastic field (or undergo limited damages only) while the steel links were designed as the only dissipative elements. The connections between the steel links (I-beams) and the steel side-columns were designed as a pinned connection which ensures the transmission of shear forces while the side-columns are subjected to compression/traction with reduced bending moments. The primary focus of this HCW solution was that, the structure could be repaired easily as the damages were consciously targeted in the steel links. Furthermore, the Inno-Hyco outcomes showed that the proposed HCW system can achieve controlled post-elastic ductile behaviour under medium-and high-intensity earthquakes, lateral stiffness, ability to avoid non-structural damage for the more frequent low-intensity earthquakes, seismic energy dissipation effectively concentrated in steel dissipa-tive components that can be easily replaced after seismic events, very limited damage in the RC wall etc. In addition , the proposed solutions were shown to be cost-effective with no particular problems in the construction process. Thus, the proposed HCW system was considered as an effective upgrade compared to the previous solutions with similar typologies [2]. However, more studies were deemed crucial in order to foster the application and diffusion of such an innovative structural system in the construction market. To that purpose, definite research advancements were proposed in the frame of the HYCAD EU-RFCS research project [1]-(1) Simpler yet accurate tools ORIGINAL ARTICLE Abstract This article summarizes the research carried out in the ongoing HYCAD project, which aims to improve the performances of a hybrid coupled wall (HCW) system for buildings in seismic areas, by further developing the HCW originally studied in the RFCS project INNO-HYCO. This HCW system consisted of a reinforced concrete (RC) wall coupled with two steel side-columns via steel coupling links. Encouraging outcomes were obtained such as: controlled post-elastic ductile behaviour under medium and high-intensity earthquakes, suitable lateral stiffness, seismic energy dis-sipation concentrating in the easily-replaceable steel links and very limited damage in the RC wall. However, advanced studies were required to bring this system into practice, addressing issues and develop advancements in the analysis, design, and detailing. This article summarizes the primary steps taken towards that purpose. Five new components were chosen in order to improve the performance of the HCW system: (1) Link-to-wall connections using post-tensioned tendons; (2) Composite walls with encased steel profiles instead of a conventional RC wall; (3) Rocking coupled wall system; (4) Dissipating devices as links and (5) Precast double slab wall systems. Combining these components, four new HCW systems were developed, pre-designed and analysed through numerical and experimental studies. Advanced yet simple techniques were proposed for the numerical analyses while test specimens are used to characterize local and global behaviour.