دانلود رایگان مقاله عایق الاستومری فیبر تقویت شده برای جداسازی لرزه ای پل

Abstract

Unbonded fiber reinforced elastomeric isolators (U-FREI) have been proposed as a viable alternative to traditional steel reinforced elastomeric isolators (SREI) for use in low-rise building base isolation systems. The viability of U-FREI for this particular application was confirmed through an extensive evaluation of their lateral response under the condition of no rotational deformations of the loading supports. In order to extend the use of U-FREI to bridge applications the consideration of rotational deformation in the analysis is necessary as it is an important component in bridge isolator design. Currently, no data exists in the literature for investigating the influence of rotational deformation on the lateral response of U-FREI, to the best of authors’ knowledge. Accordingly, an experimental and numerical study was completed on U-FREI to investigate their lateral behaviour under a range of vertical loads and rotational deformations in order to determine their suitability as a seismic isolator for bridges. The lateral stiffness and damping were computed experimentally for different levels of vertical pressure, angles of rotations and lateral deformations. Additionally, the resulting stress and strain state within the isolators under peak deformations was also evaluated numerically via 3D modelling and presented in this study.

7. Conclusions

This research paper investigates the effect of coupled verticalrotational deformation on the lateral response of unbonded Fiber-Reinforced Elastomeric Isolators (U-FREI). The investigation was carried out experimentally using a 3 DOF test apparatus and numerically using the commercially available finite element software MSC Marc [27]. The test apparatus employed for the experimental testing was designed to apply deformations in three different directions (i.e. vertical, rotational, and lateral) independently and/or in combination. Thus, it was able to conduct different loading conditions on the isolators expected during the lifetime of a bridge. The novelty of the experimental testing was based on the ability to include the effect of the rotational deformation, which is considered an important aspect in bridge bearings/isolators design, on the lateral response of the isolators. Additionally, threedimensional finite element modelling was performed on the isolators in order to evaluate the stresses and strains that develop under the peak applied load and deformations. The three isolators considered in this study had in-plane aspect ratios of 2.5, 2.5, and 4.5, but a constant shape factor of 6.0 was maintained. The main findings from the experimental study are: 1. A rotational deformation up to 0.03 rad had a negligible effect on the lateral response of all isolators in general, but was with the least significant for isolators with lower aspect ratios. 2. Increasing both the applied vertical load as well as the angle of rotation on the isolator caused a slight decrease in the lateral stiffness and small increase in the lateral damping. 3. The isolation periods of the considered isolators varied according to the values of the applied vertical loads and angle or rotation, with a maximum calculated value of approximately 2.90 s. Based on results from FEM the following main conclusions were drawn: 1. The hydrostatic rule can be used to define the distribution of pressures that are developed within the elastomeric isolators, not only vertical deformation, but also if under coupled vertical-lateral-rotational deformation. 2. Decreasing the aspect ratio of the isolator delay the occurrence of lift-off, this results in a lower rate of increase in the normal stresses and shear strains under rotational deformation. However, it also results in a larger rate of increase in stresses and strains developed within the isolator when subjected to lateral deformations.