Papers by Keyword: Dynamic Behaviour

Abstract: Ambient vibration instrumentation is a non-destructive in-situ testing method that can be used to assess the dynamic properties of a building. By analyzing the time histories of accelerations, velocities and displacements (both instantaneous maximum values, or averaged RMS values) and applying specific evaluation criteria, we can estimate the extent of any potential damage. In 2016 and 2021, the ISIM Timisoara building underwent in-situ testing through ambient vibration measurement, using different sensor placement schemes (horizontal, vertical with an external sensor, and sensor at the last level), to accurately characterize the complex structural system. Furthermore, an analysis of the interaction between the structure and the soil is also provided. The approach outlined in the article assists in evaluating the national-level vulnerability of the built environment.

Abstract: Previous studies have suggested that incorporating crumb rubber into concrete enhances impact resistance and energy absorption. However, these studies often overlook the associated reduction in compressive strength when crumb rubber replaces fine aggregates, leading to comparisons between concretes with different strengths. This study addresses this gap by investigating the dynamic behaviour of two geopolymer concrete mixes, G1-25R and G2-0R, both designed to achieve similar compressive strengths despite their differing compositions. Mix G1-25R includes 25% crumb rubber replacement of fine aggregates and a binder composed of 90% fly ash and 10% Ground Granulated Blast Furnace Slag (GGBFS), while Mix G2-0R has no crumb rubber and uses only fly ash as the binder. Dynamic performance was assessed using a drop tower setup across six testing configurations. Results indicate that both mixes exhibit comparable peak impact forces and energy absorption capacities, which is attributed primarily to their similar compressive strengths. Although G1-25R’s crumb rubber content enhances ductility in static compressive tests, this increased ductility does not significantly influence dynamic resistance when compared similar strength geopolymer concrete with no crumb rubber. These findings suggest that crumb rubber can be effectively recycled in geopolymer concrete, providing comparable impact resistance and energy absorption to traditional concrete.

Abstract: The results of experimental studies performed during the past decade at Saint-Petersburg State University in collaboration with the Mechanics and Materials Science Research Centre at Ningbo University (China) and Lobachevsky State University of Nizhny Novgorod (Russia) with the aim of investigating the basic regularities of the high rate straining of NiTi shape memory alloys are reviewed. The studies were concerned with the mechanical behaviour of these materials at high rate compression and tension, and the effect of high rate straining on the basic functional properties (shape memory effect and two-way shape memory). Special attention was given to the application of dynamic fracture theory to NiTi shock loading and to methods for obtaining experimental findings concerning the theoretical parameters involved in the criteria for determining the transition of these materials from an elastic to an inelastic state while high rate straining was applied. The effect of the quasi-equilibrium structure of NiTi on martensitic transformations and the role of this structure in the formation of more complicated effects than shape memory and superelasticity were studied. The results obtained are used to elaborate a method for the improvement of the functional properties of NiTi and a procedure for reversing two-way shape memory induction.

Abstract: the suspension system of an automobile helps to support the car body, engine and passengers, and at the same time absorbs shocks received from the ground while vehicle moves on rough roads. There are two types of suspension systems which are being used in the automobiles, namely, conventional suspension system and independent suspension system. in this paper it is aimed at studying the dynamic behaviour of the two types of suspension systems, using full car model.