Seismic design of structures with advanced dissipation devices using energy-based methods

• Autores: Guillermo González Sanz
• Directores de la Tesis: Amadeo Benavent Climent (dir. tes.)
• Lectura: En la Universidad Politécnica de Madrid ( España ) en 2021
• Idioma: español
• Enlaces
  • Tesis en acceso abierto en: Archivo Digital UPM
• Resumen

  • This Thesis investigates the seismic design of frame structures equipped with advanced hysteretic dampers with recentering capability. The damper object of study is developed within a previous research project (Proyecto de Excelencia PE2012 TEP12 2429), led by Amadeo Benavent-Climent, and it consist on two components working in parallel: (i) a stainless-steel Tube-in-Tube Damper (TTD), and (ii) a Shape Memory Alloy (SMA) bar made of nickel-titanium (NiTi) alloy with superelastic properties. Each part of the advanced TTD-SMA damper is experimentally and numerically characterized separately. Static and dynamic tests have been performed to compare the behaviour of the damper under different strain rate conditions. The overall hysteretic behaviour under cyclic and seismic loadings is studied and the ultimate energy dissipation capacity until failure of each component is discussed. Refined numerical models are proposed to predict with accuracy the hysteretic behaviour and its failure. The sum of these two components turns into an advanced damper that combines high energy dissipation capacity of metal yielding with recentering properties of superelastic SMA. All this work is later used to the central part of the dissertation: seismic design of structures with advanced dissipation devices using energy-based methods. The energy-based design framework is presented and particularized to frame structures equipped with the advanced dampers studied. New equations are proposed to predict: (i) the elastic strain energy; (ii) the plastic strain energy at the instant of maximum deformations and at the end of the ground motion, and (iii) the maximum interstory drifts in each story. Afterwards, an extensive parametric study is carried out and the results are compared with the estimations obtained by the equations developed. A value for damage concentration index n=3 is proposed for this kind of structures. This new value used in conjunction with Akiyama’s damage distribution law and the optimum distribution adopted by JBC, provides a good estimation of the plastic strain energy distribution among stories. The control of residual deformations and the recentering capability is also studied since it is a key part of current seismic design. The parametric study is extended with the aim of obtaining the relation between normalized residual drift and the elastic to hysteretic energy ratio. As a result, two new equations are proposed to relate the normalized residual inter-story drifts with the quotient between the amount of energy stored in the form of elastic deformations and the amount of energy dissipated through plastic deformations in a single excursion up to the maximum displacement. This ratio should be greater than 1/3 to guarantee an appropriate recentering capacity of the whole frame with advanced TTD-SMA dampers. Finally, the experimental validation is carried out for the general case of a 3D reinforced concrete structure consisting of waffle-flat plates supported on isolated columns equipped with the studied advanced dampers. The specimen was subjected to bidirectional seismic loading in a shake table. The results of these tests were analysed in terms of: (i) response of the advanced dampers, (ii) balance of forces acting on the structure, (iii) total base shear force vs. displacement, (iv) response of columns, (v) energies, (vi) maximum displacements and residual displacements and (vii) ratios of cumulated plastic strain energy and maximum plastic deformation. From these tests, it is confirmed that the damage and the residual deformations on the main structure are drastically reduced, thanks to the use of advanced dampers with recentering capability.