Shape memory alloys in the form of bars are increasingly used to control structures under seismic loadings. This study investigates the hysteretic behavior and the ultimate energy dissipation capacity of large-diameter NiTi bars subjected to low- and high-cycle fatigue. Several specimens are subjected to quasi-static and to dynamic cyclic loading at different frequencies. The influence of the rate of loading on the shape of the hysteresis loops is analysed in terms of the amount of dissipated energy, equivalent viscous damping, variations of the loading/unloading stresses, and residual deformations. It is found that the log-log scale shows a linear relationship between the number of cycles to failure and the normalized amount of energy dissipated in one cycle, both for low- and for high-cycle fatigue. Based on the experimental results, a numerical model is proposed that consists of two springs with different restoring force characteristics (flag-shape and elastic-perfectly plastic) connected in series. The model can be used to characterize the hysteretic behavior of NiTi bars used as energy dissipation devices in advanced earthquake resistant structures. The model is validated with shake table tests conducted on a reinforced concrete structure equipped with 12.7 mm diameter NiTi bars as energy dissipation devices.
This paper investigates a new stainless-steel tube-in-tube damper (SS-TTD) designed for the passive control of structures subjected to seismic loadings. It consists of two tubes assembled in a telescopic configuration. A series of slits are cut on the walls of the exterior tube in order to create a series of strips with a large height-to-width ratio. The exterior tube is connected to the interior tube so that when the brace-type damper is subjected to forced axial displacements, the strips dissipate energy in the form of flexural plastic deformations. The performance of the SS-TTD is assessed experimentally through quasi-static and dynamic shaking table tests. Its ultimate energy dissipation capacity is quantitatively evaluated, and a procedure is proposed to predict the failure. The cumulative ductility of the SS-TTD is about 4-fold larger than that reported for other dampers based on slit-type plates in previous studies. Its ultimate energy dissipation capacity is 3- and 16-fold higher than that of slit-type plates made of mild steel and high-strength steel, respectively. Finally, two hysteretic models are investigated and compared to characterise the hysteretic behaviour of the SS-TTD under arbitrarily applied cyclic loads.
One of the gaps of knowledge for the application of the energy-based approach to conventional structures concerns the evaluation of the energy dissipation capacity of structural elements and systems. Addressing this issue calls for experimental data on structural members, structures or substructures subjected to realistic seismic loadings. The best source for such information is the dynamic shake table test. It can reproduce complex effects such as cumulative damage and rate-of-loading effects, that play an important role in the response of the structure. However this type of tests are very costly and time consuming. Therefore, it is necessary to complete the test information with numerical simulations. This paper provides information on the energy dissipation capacity of columns subjected to one and to two components of the seismic action. This information comes from shake table test conducted on RC waffle flat plate structures supported on isolated columns. The energy dissipated at the base of the columns until collapse is estimated applying different approaches.
La técnica de puzle es un método de aprendizaje cooperativo ampliamente implementado en ámbitos académicos que ha demostrado su eficacia en la adquisición de competencias fundamentales y transversales en la formación. La organización en grupos pequeños favorece la interacción entre alumnos y la división del trabajo en tareas separadas, fomentando la interdependencia positiva, característica fundamental en el aprendizaje cooperativo. Este trabajo presenta la aplicación de la técnica puzle a un bloque de la asignatura “Seminarios” del Máster en Ingeniería Sísmica de la Escuela Técnica Superior de Ingenieros Industriales de la Universidad Politécnica de Madrid. Tras su aplicación, se observa que el alumno adquiere de forma muy satisfactoria los contenidos de la materia, así como una mejora sustancial en la formación en competencias transversales y en el desarrollo de habilidades sociales. Los resultados positivos de esta experiencia ponen de manifiesto la necesidad de fomentar la implantación de metodologías docentes innovadoras en las enseñanzas técnicas universitarias.AbstractCooperative jigsaw method is widely spread in academic environments and it has demonstrated its efficiency on the acquisition of professional and transversal competences. The organization in small groups improves the interaction between students and the work partitioning in independent tasks, promoting the positive interdependence which is crucial for cooperative learning. The present study applies the jigsaw method to the “Seminars” course from MScs in Earthquake Engineering at Universidad Politécnica de Madrid. As a result of the application of this method, it is observed that the students learn the content of the subject, and improve substantially the transversal competences and social skills. This study supports the need of implementing innovative educational methods in the technical studies
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.