Development of a novel combined system of deformation amplification and added stiffness and damping: Analytical result and full scale pseudo-dynamic tests

Abstract

This research presents the theoretical and experimental development of a new system called: AmplifiedAdded Stiffness and Damping (AASD), which is a combination of an amplifying mechanism and a frictionalself-centering damper capable to support large deformations. The operation of the damper is basedon the well-known straps with friction principle. A first conceptual single acting device used for validatingthis principle and comparing the behavior of commercial straps (polyamide, aramid and carbon fiber)was built. Subsequently, two double acting prototypes with carbon fiber straps were built, since thismaterial showed the best performance. Both, the conceptual device and the two prototypes (named asI and II) have shown very stable constitutive relations. Because of its greater simplicity, the ‘‘prototypeII” represents a technically and economically attractive solution. Furthermore, due to its ability to accommodatelarge deformation in both directions, it is an ideal device to combine with amplifying mechanisms.A parametric numerical analysis performed on a single-story structure with AASD, showed awide range of parameters of AASD leading to reductions greater than 40% on displacement response. Afull-scale asymmetric one-story steel structure equipped with one AASD was built. The structure wassubjected to a variety of tests using a multi-axis pseudo-dynamic equipment recently installed in theLaboratory of Structural Engineering of the Pontificia Universidad Católica de Chile. So far, the authorsdidn’t find references of a full scale pseudo-dynamic test of this nature. The structure without AASD presenteda non-linear behavior mainly due to sliding of the bolted connections of the beams. Pseudodynamicseismic response tests were performed considering an artificial ground motion acting in onedirection. As expected, and due to the mass eccentricity (20% of its plan length), high concentration ofdeformations in the flexible edge of the structure without AASD was observed. Conversely, the structurewith AASD showed a great plan deformation uniformity (torsional balance), with reductions of nearly 40%in maximum edge deformation, which is consistent with the parametric analysis results. The eccentriclever arm used as amplifying mechanism, which have large amplifying ratio a = 11, worked in greataccordance with numerical simulations.