Reinforced concrete (RC) structural walls are used as seismic force-resisting systems in most modern high-rise buildings. It has been demonstrated that shear force amplification occurs in yielding RC walls during a strong earthquake due to higher vibration mode effects. Several numerical studies have been performed to predict the amplification factor. The complexity of seismic responses of RC walls in plastic hinge zones has led some to doubt predicted shear force amplification results when using nonlinear numerical analysis. The substructure hybrid test method provides the opportunity to experimentally evaluate the seismic response of an entire RC wall structure under actual earthquake forces. Hybrid tests were conducted on 8-story ductile regular RC walls using advanced controlling methods to investigate the phenomenon. The studied structure was divided into experimental and numerical subassemblies. The experimental test specimen corresponded to the first story of a model RC wall as a key region of interest, while the remaining wall was modeled numerically. A series of tests based on short-duration earthquake ground motions typical of eastern Canada seismic hazard regions resulted in higher than code-specified shear amplification factors. Considering the possibility of a large-magnitude, long-duration earthquake generated by the Cascadia Subduction Zone (CSZ) in western Canada, two numerical modeling methods were used for an inelastic time history analysis of a 10-story RC wall located in Vancouver subjected to ground motions selected from a subduction ground motion database based on the conditional spectrum (CS) method. It was found that a large-magnitude long-duration earthquake could cause several amplified shear cycles, raising concerns about the risk of brittle shear failure. Considering these results, a second hybrid test was performed using a newly build testing system and new test controls. Results of the tests confirm that multiple high shear demand, larger than code recommended values, occurred during the earthquake excitation.

During the process of movement, it has been observed that animals strive to achieve a state of resonance between the forces generated by contracting muscles and their inherent vibration frequencies. This frequency tuning mechanism enables the animal to minimize energy consumption [1]. In the context of leg and arm bones, when flexed by muscles, they function akin to pendulums, while tendons serve as nonlinear springs and shock absorbers. This study demonstrates the possibility of designing seismic metaisolators by tessellating unit cells with diverse architectures, resembling human bones and incorporating stretchable cables that imitate muscle tendons. Interestingly, these metaisolators invert their function: instead of aiming for resonance with earthquake frequencies, they leverage tendons to adjust the nonlinear stiffness of the system [1]-[3]. Moreover, the metaisolators can be constructed using environmentally sustainable components, eliminating the need for heavy industry. They can be partially or entirely created using commonplace 3D printers and materials that are biobased and/or recycled. The metallic components can be produced using standard lathe machines available from online suppliers of metal parts or generated through a desktop metal 3D printer.

References

[1] Fraternali, F., Singh, N., Amendola, A., Benzoni, G., Milton, G. W. 2021. A biomimetic sliding–stretching approach to seismic isolation. Nonlinear Dyn, 106(4), 3147-3159.

[2] Fraternali, F., Singh, N., Amendola, A., Benzoni, G., Milton, G. W. 2021. The 3D print job that keeps quake damage at bay. Nature, Research Highlight, 600(7887), 10.

[3] Fraternali, F., Singh, N., Amendola, A., Benzoni, G., & Milton, G. W. 2021. A scalable approach to the design of a 3d-printable sliding- stretching seismic isolator. Ingegneria Sismica – International Journal of Earthquake Engineering, 38(4).

This paper presents the analysis of RC frame subjected to progressive collapse within the framework of pseudo-dynamic testing. Since the WTC events, the latter topic is of growing importance in order to better understand the effect of damage propagation (local or global bearing loss).

On the one hand, due to their cost and complexity (size, instrumentation, dynamic loading application, etc.), experimental bearing loss tests on full-sized buildings are often limited in terms of storeys and reproducibility. On the other hand, numerical models accounting for geometrical and material non-linearity can be tricky to calibrate to closely match the real response of the considered structure.

Pseudo dynamic approach is appealing because it allows considering dynamic effects coming from inertial forces induced by the mobilized mass during the bearing loss. The pseudo-dynamic technics involves quasi-static tests which simplify the experimental setup and limit hydraulic power needed to impose the loading. One step further, sub-structuring permit to split the entire framed structure into an experimental part, which is in this case the critical structural element, and the rest of the structure is modeled through the finite element method. Experimental and numerical parts are coupled through the method proposed by [1].

In order to demonstrated the ability of the pseudo dynamic approach with sub-structuring to reproduce progressive collapse mechanism ([2]), a classical bearing loss scenario is considered. Full scale RC beams (4 and 6 meters long) are subjected to a central column removal. Pushover and pseudo dynamic tests are performed to compare the static and dynamic response. In this work, the leading idea is to benefit from the advantages of the pseudo dynamic technic combined with sub-structuring approach, to better characterize the whole structure repsonse accounting for dynamic effects.

[1] P. Pegon, A. V. Pinto.,Jr. Earth. Eng. Str. Dy., 2000.

[2] D. Bertrand, S. Grange, J-.B. Charrié., Jr. Build. Eng, 2022.

Passive energy dissipation systems, such as friction dampers (FDs), viscous dampers (VDs), and tuned-mass dampers (TMD) have been proposed to reduce the dynamic response of structures under seismic excitations. The efficacy of such devices towards the anti-earthquake design of structures seeks to minimize the extent of damage upon them, using absorbing a considerable amount of the seismic energy input due to their hysteretic behavior. In this field, a lot of researchers proposed friction dampers with huge dimensions and as well as expensive material [Pall et al. 1980; Grigorial et al 1993]. Mrad et al. [2021] in a comparison of 3 energy dissipation systems (TMD, VDs, and FDs) show that FDs can improve the performance of all structures under seismic action. Still, they are more suitable for low-rise buildings, as in high-rise buildings the number of them makes the total cost expensive. Titirla et al [2017] have proposed an innovative energy dissipation system, mentioning CAR1, which consists of very simple material and it is far from the heavy industry for this device to be able to be used in both developing and undeveloped countries. This device has a lot of advantages compared to other common friction dampers. Still, the main disadvantage is that to achieve high load capacity is necessary to have a big diameter of the devices or a big number of dampers which means that the total cost needs to increase [Titirla et al 2018]. This study aims to reply to the previously unanswered questions by i) finding an equilibrium between the cost and the advantages of this type of friction damper, by proposing and investigating various configurations, ii) examining the effectiveness of recycled metals and smart materials, as part of the main elements of the device, iii) investigating how structural systems respond to realistic dynamic or seismic loading.