Date of Publication
3-13-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Civil Engineering
Subject Categories
Civil Engineering | Engineering | Geotechnical Engineering
College
Gokongwei College of Engineering
Department/Unit
Civil Engineering
Thesis Advisor
Dr. Lessandro Estelito O. Garciano
Defense Panel Chair
Dr. Rodolfo P. Mendoza Jr.
Defense Panel Member
Dr. Andres Winston C. Oreta
Dr. Bernardo A. Lejano
Dr. Jonathan R. Dungca
Dr. Eric Augustus J. Tingtinga
Abstract/Summary
This research proposed the development of the low-cost fiber-reinforced elastomeric bearing (FREB) utilizing recycled butyl rubber (IIR) from used inner tubes. Firstly, the study examines the hardness and tensile strength of recycled butyl rubber through a hardness test and the uniaxial tensile test, respectively. The hardness test results are 52.5, 57.5, 50.5, 53.0, and 54 IRHD for specimens 1, 2, 3, 4, and 5 respectively. The tensile strength of the five samples is 8.5, 9.7, 9.6, 8.5, and 8.3 MPa respectively. The dumbbell specimen was analyzed using ANSYS commercial software to compare the experimental and numerical results. In this study, the Ogden 1st order model was suitable to utilize in the determination of the hyper-elastic material constants of recycled rubber. These material constants are applied in the modeling of the proposed low-cost FREB in FEA to define the hyper-elastic material. Secondly, the mechanical properties of FREB were evaluated through a compression test and a combined compression and shear test. After conducting the compression test, the observed maximum vertical load-carrying capacity was 1862 kN, and the compressive strength measured 23.85 MPa. Then, the evaluated compression modulus and vertical stiffness of the FREB were 31.81 kN/mm², and 16624.63 N/mm, respectively. The load-carrying capacity of the proposed FREB, 23.85 MPa is comparable with those of commercially available elastomeric bearings. These values indicate the material's significant strength and rigidity under vertical loading conditions, confirming its suitability for applications requiring high load-bearing capacity. After the compression test, the deformations observed in the materials are decoupling of the fiber and rubber and also fiber reinforcement failure. Through the horizontal test, the FREB displays quite stable hysteresis loops at each level of displacement amplitude. Using the force-displacement curve, the horizontal stiffness of the FREB was 0.636 kN/mm at a shear strain of 33% and 0.5013 kN/mm at a shear strain of 53%, respectively. Moreover, the shear modulus of the proposed FREB was 1.2 MPa at 33% shear strain and 0.95 MPa at 53% shear strain, respectively. The horizontal stiffness and shear modulus decreased while the displacement amplitudes increased. Subsequently, the calculated damping ratio was 14.8% and 16.9% at the 33% shear strain and 53% shear strain, respectively. The damping ratio increased from 14.8% to 16.9% due to the enlargement of the hysteresis loop area. The damping capacity of the bearing is inversely proportional to horizontal displacements. The mechanical properties of the proposed FREB are comparable with those of commercially available elastomeric bearings. In addition, the mechanical properties of the proposed elastomeric bearing were analyzed using FEM software. The validation of the mechanical properties of the low-cost fiber-reinforced elastomeric bearing was conducted between experimental results and numerical analysis. The comparison shows a good agreement between experiment and analysis. The structural performance of a two-story reinforced concrete school building, both with a fixed base and an isolated base featuring the proposed FREB was analyzed by nonlinear time history analysis using ETABS software. The proposed FREB base isolation system significantly develops the seismic resilience of the structure compared to a fixed-base system. By prolonging the time period and reducing the natural frequency, the isolated system reduces susceptibility to high-frequency ground motions, thereby minimizing acceleration forces and enhancing overall energy dissipation. The system effectively limits story drift in the upper levels, reduces lateral force transmission, and minimizes base shear, ensuring better protection for fundamental components of the structures. The isolated system absorbs and dissipates more input energy than the fixed-base system, highlighting its ability to mitigate seismic forces through controlled displacements and efficient damping mechanisms. This leads to reduced force transmission and lower accelerations throughout the structure, ultimately minimizing the risk of damage during seismic events. By contrast, the fixed system displays higher accelerations and prolonged oscillations, reflecting its limited capacity for energy dissipation and force reduction. Furthermore, the FREB isolators, developed from recycled butyl rubber, offer a low-cost and sustainable solution, making them particularly beneficial for improving seismic performance in developing regions. The findings demonstrate that this innovative isolation system provides a practical, cost-effective approach to reducing the seismic vulnerability of structures, ensuring enhanced safety and resilience in seismic prone areas of the developing country.
Abstract Format
html
Language
English
Format
Electronic
Keywords
Elastomers; Earthquake engineering
Recommended Citation
Thin, K. T. (2025). An experimental and numerical study of low-cost fiber reinforced elastomeric bearing (FREB) using recycled rubber for seismic base isolation application. Retrieved from https://animorepository.dlsu.edu.ph/etdd_civ/10
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Embargo Period
3-12-2026
