• Smart Structures and Systems
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• v.20 no.6
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• pp.739-757
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• 2017

The main goal of this study is to investigate the hysteretic behavior of polyurethane rubber springs in compression with and without precompression. The precompression is introduced to provide rigid force in the behavior, and thereby a precompressed rubber spring can be used for a restoring element. For the goal, this study prepares nine rubber springs for three suites which are all cylindrical in shape with a hole at the center. The rubber springs in each suite have different dimensions of diameter and length but have similar shape factors; thus, they are designed to have a similar compressive stiffness. Three rubber springs from the nine are tested with increasing compressive strain up to 30% strain to investigate the behavior of the rubber springs without precompression as well as the effect of the loading strain. The nine springs are compressed up to 30% strain with increasing precompressive strain from 0 to 20% at increments of 5%. The study analyzes the effective stiffness and damping ratio of the rubber springs with and without precompression, and the rigid force of the precompressed rubber springs is discussed. Finally, this study suggests a regression method to determine the minimum required precompression to eliminate residual strain after unloading.

• Computers and Concrete
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• v.20 no.3
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• pp.311-318
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• 2017

This paper investigates the utilization of waste tyre crumb rubber as the fine aggregate in precast concrete Paving block (PCPB). PCPB's are generally preferred for city roads, pedestrian crosswalk, parking lots and bus terminals. The main aim of this paper is to evaluate the mechanical properties of wet cast PCPB containing waste tyre crumb rubber. The mechanical properties were investigated using a density, compressive strength, split tensile strength and flexural strength tests at 7, 28 56 days according to the IS 15688:2006 and EN1338. The wet cast method was followed for producing PCPB samples. The fine aggregate (river sand) was replaced with waste tyre crumb in percentage of 5%, 10%, 15%, 20% and 25% by volume. All the test results were compared with the conventional PCPB (Without rubber). The test results indicate its feasibility for incorporating waste tyre crumb rubber in the production of PCPB by the wet cast method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.855-864
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• 2013

The dynamic characteristics of natural rubber bearings, which are used as isolator, are dependent on the main rubber's dynamic behaviors and nonlinear properties. Rubber materials tend to undergo an aging process under the influence of mechanical or environmental factors, so they inevitably end up facing damage. A main cause of aging like this is known to be oxidization, which occurs through the heat of reaction at high temperatures. Accordingly, in this study an accelerated thermal aging test was carried out in order to compare the characteristic values of the bearings before and after thermal aging occurs. As a result of this experiment, it was found that a thermal aging phenomenon could have some effects on shear stiffness, energy absorption, and equivalent damping coefficients of the bearings. Furthermore, a deterioration in the dynamic properties of the natural rubber bearings caused by the thermal aging was applied to an actual bridge and then the effects of such thermal aging on the seismic performance of the bridge were also compared and analyzed based on numerical analysis. As a result of this analysis, it was found that the changes in the basic properties of the natural rubber bearings caused by the thermal aging bring only a minor effect on the seismic performance of bridges.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.2A
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• pp.109-116
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• 2012

The dynamic properties of lead rubber bearings, which are used as isolator, are dependent on the main rubber's dynamic behaviors and nonlinear qualities. Rubber materials tend to undergo an aging process under the influence of mechanical or environmental factors, so they can end up inevitably facing damage. A main cause of such aging is known to be oxidization, which occurs through the heat of reaction at high temperatures. Accordingly, in this study an accelerated thermal aging test was carried out in order to compare the characteristic values of the bearings with each other before and after thermal aging occurs. As a result of this experiment, it was found that a thermal aging phenomenon could have an effect on shear stiffness, energy absorption, and equivalent damping coefficients. Furthermore, a decline in the dynamic properties of the lead rubber bearings by means of the thermal aging process was applied to an actual bridge and the effects of such thermal aging on the seismic performance of the bridge were also compared and analyzed based on numerical analysis. As a result of this analysis, it was found that the changes in the basic properties of the lead rubber bearings have a minor effect on the seismic performance of bridges.

• Elastomers and Composites
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• v.47 no.2
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• pp.121-128
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• 2012

Waste EPDM(W-EPDM) collected from the automotive weather strip and the gasket of a laundry machine has not been effectively recycled. Using this W-EPDM powder and other ingredients, i.e., binder(polyolefin resin, polyolefin elastomer, etc.), filler and additives, various economic rubber composites were made by extrusion. In advance of main experiments, the effects of ultrasonic treatment of W-EPDM on the property of rubber composites, comparison in the property of the composites of W-EPDM with those of virgin and devulcanized EPDM, and waste tire rubber were investigated. Also, the properties of the rubber composites extruded with a 12-screw extruder were compared with those extruded with twin-screw extruder. Various W-EPDM composites for synthetic turf filler and car mat were extruded and injection molded, and 3 main properties of tensile strength, elongation and hardness were investigated to develop economical and proper recipes of the rubber composites.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.04a
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• pp.193-200
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• 2004

In this study, the impact load on bridge by vessel collision in consideration of fender system is evaluated by numerical method. The bow of object vessel(DWT5000) is standardized, and modeled by shell elements. The main body of objective vessel is modeled by beam elements that present mass distribution and stiffness of vessel. The buoyancy effect of vessel is considered as linear spring. The two types of fender systems, such as steel and rubber are analyzed in this study. In steel fender system, the steel plates that absorb collision energy by its collapse are modeled by shell element with stiffener. The steel is material modeled elastic-plastic material. In the rubber fender system, the rubber material is modeled hyper-elastic material and the main body of fender is modeled by solid elements. The global impact responses of vessel and fender system are evaluated by explicit dynamic scheme. The results show that the magnitude of vessel collision force are depended on the material behavior of fender system. Also the values of collision load are conservative compare to the those of design codes.

• Journal of KSNVE
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• v.9 no.1
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• pp.42-48
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• 1999

In this paper, a computer simulation method for dynamic analysis of the hydraulic engine mount system is proposed. The hydraulic engine mount system controls the damping characteristics using the viscosity of fluid flow The complex stiffness of the main rubber of the hydraulic engine mount system is computed by finite element analysis for the viscoelastic materials and hydro-static elements. A numerical analysis method is presented to solve nonlinear equations of the hydraulic engine mount system. which is composed of an engine mass, fluid in inertia track and a vertical inertia force of reciprocating mass in the engine. Also. dynamic properties of the hydraulic engine mount system are analyzed in the frequency domain. Effects of the hydraulic engine mount system running over the rough road are investigated using a vehicle dynamic model. These results are compared with those of the rubber mount system.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.429-436
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• 2005

In this study, we made two types of main control room floor systems (Type I, Type II) and several shaking table tests with and without isolation system were conducted to evaluate floor isolation effectiveness of LRB(Lead Rubber Bearing). Both type showed large difference according to input earthquake signals, but showed little difference according to floor type. It is required to make LRB of which design frequency is below 1Hz when applied to main control room of NPP, but considering much difficulties in making such LRB, it is recommended that consideration should be taken into account when applied to main control room of NPP.

• Korean Journal of Digital Imaging in Medicine
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• v.12 no.1
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• pp.15-18
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• 2010

Main component of radiography barrier aprons is lead. To manufacture a lead-free barrier sheath, barium sulfate and organic iodine-based chemicals should be mixed with rubber. Barrier capacity was tested in the medical field. To improve adaptation of rubber with the mixture, raw materials went through milling, agitation, and extruding processes. Three sheaths were manufactured with 30%, 80%, and 120% sulfate barium, respectively. This study found 10% lower barrier capacity of lead-free barrier than the traditional lead-containing rubber sheath. Problems, however, were confronted during the agitation and extruding processes. Mixing with rubber was a technically demanding job. Inconsistent depth, problems with thermal processing and dissipation were encountered as well.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.341-348
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• 2002

In these days, The base isolation system is often used to improve the seismic capacity of the structures instead of conventional techniques of strengthening the structural members. The purpose of this study is to evaluate dynamic property evaluation of control equipment using lead Lead Rubber Bearing. In this study, a base isolation test of seismic monitoring control cabinet with LRB(lead rubber bearing) was performed. The cabinet will be installed on access floor in MCR(main control room) of nuclear power plant. Details and dynamic characteristics of the access floor were considered in the construction of testing specimen. N-S component of El Centre earthquake was used as seismic input motion. Acceleration response spectrums in the top of cabinets showed that the first mode frequency of cabinet with LRB(lead rubber bearing) was shifted to 7.5 Hz in compared with 18Hz of cabinet without LRB and the maximum peak acceleration was reduced in a degree of22 percent from 2.35 g to 1.84 g