Development of novel high damping rubber damper for dynamic energy dissipation under direct axial cyclic load / Teh Tzyy Wooi

Teh , Tzyy Wooi (2024) Development of novel high damping rubber damper for dynamic energy dissipation under direct axial cyclic load / Teh Tzyy Wooi. PhD thesis, Universiti Malaya.

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Abstract

High Damping Rubber (HDR) has gained extensive utilization in structural bearings as seismic isolation devices. However, its application in dampers designed to effectively dissipate energy under direct axial loads, thereby mitigating structural responses induced by seismic excitations, remains unexplored. Presently, dampers that operate under direct axial conditions encompass cylinder-type viscous-fluid velocity-dependent devices and Viscoelastic (VE) dampers, commonly employed as isolators against seismic and wind-induced dynamics. Nevertheless, VE dampers exhibit reduced stiffness and energy dissipation capacity due to decreased storage and loss moduli triggered by cyclic loading temperatures. Conversely, viscous fluid dampers performance is significantly compromised upon liquid leakage, necessitating frequent maintenance and driving up overall life cycle costs. Integrating HDR dampers would overcome the limitations associated with existing dampers. Additionally, there is a pressing industry need for medium-sized dampers that provide improved durability and cost-effectiveness for small and medium-scale structures. This research aims to develop a novel damper utilizing Hyper Elastic Composite Material (HECM), an HDR material, and conduct experimental investigations to evaluate its damping ratio, compressibility, and elasticity behaviour under axial cyclic loads. The research project commences with a series of material tests on HECM employing the double shear method in EN 15129:2009 Clause 8.2.4.2.5 to identify the most suitable damping material for the damper under cyclic compression loading. The optimal HECM material is then employed to fabricate small scaled dampers with varying HECM thicknesses (6 mm, 8 mm, 10 mm) for examination under constant axial forces at different frequencies (0.01 Hz, 0.1 Hz, 0.25 Hz, 0.5 Hz). Results indicate the 10 mm-thick damper, with a damping ratio ranging from 10.05% to 13.7% across frequencies, demonstrating the remarkable potential of HECM for damper applications. Upon selecting the optimal damping material and thickness, a model response spectrum analysis (RSA) for building structures is conducted according to the National Annex (NA) to MS EN 1998-2017. This analysis predicts seismic base shear and displacement demand for full-scale damper testing parameters. Subsequently, full-scale dampers are developed using the three different HECM materials, which have achieved a damping ratio exceeding 10% using the shear method specified in EN 15129:2009 Clause 8.2.4.1.5. These dampers undergo damping tests and wind load tests in accordance with EN 15129 Clause 7.4.2.7 and Clause 7.4.2.8, respectively, incorporating parameters obtained from the model response spectrum analysis. Finite element models are then developed to simulate the hysteresis curves and damping properties of the HECM damper. After simulation, the HECM properties within the finite element model can be further developed and utilized for future damper designs to meet industry requirements. An empirical formula is derived to enable structural designers to estimate the mechanical properties of the tested damper. Based on the testing results, the developed damper achieves a damping ratio exceeding 10% and satisfies the requirements outlined in the response spectrum analysis for buildings. Consequently, the integration of HDR with HECM material, offering a novel damper solution, is expected to deliver compatible and competitive performance compared to viscoelastic and viscous-fluid dampers.

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