Energy Absorption of Rubber-Rolled Pin
In the previous test, the load mitigation effect of rubber-rolled pin was examined within the elastic loading range. Next, the dropping height is increased from 10 cm to 150 cm and the elastic limit height was judged as the state of permanent strain remained obviously.
time (ms) time (ms)
(a) Type-А (b) Type-B
Figure 20 illustrates the strain (No. 7) – time relations by increasing the dropping height until the elastic limit state. It is found that the effect of mitigating the load at elastic limit level is similar to the previous elastic range, that is, the strain of 2500 г at H = 30 cm of type-A is reduced to 800 г (70% reduction) at H = 30 cm of type-B. It is also noticed that the elastic limit state of type-B (H = 150 cm) exhibits five times larger than the one of type-A (H = 30 cm). Therefore, the energy absorption of type-B has five times larger than the one of type-A, and therefore, type-B will be able to work under the elastic-plastic range of connecting plate for the considerable severe loading condition.
The following conclusions are drawn from this study.
3.1. Development of LFRR
(1) The maximum impact load of the LFRR in case of high kinetic energy is smaller than that of usual rubber, although its stiffness is large. Because, the LFRR can reduce the impact load by breaking the fiber in the rubber in case of high kinetic energy.
(2) The energy absorption ratio of LFRR is larger than the one of usual rubber. Therefore, the velocity after collision in case of LFRR becomes smaller than that of usual rubber, and such, the damage of bridge may be reduced for the earthquake shock.
(3) The LFRR is much better materials than usual rubber from the viewpoints of high absorbed energy and reducible effect of impact load at high input energy. Therefore, the LFRR is directly applied to the shock absorber of bridge restrainer system.
3.2. Development of Rubber-Rolled Pin
(1) The rubber-rolled pin exhibits obviously the mitigating effect of transmitting load to girders. This rate becomes smaller about 1/3-1/4 of the ordinary steel pin from the responding strains.
(2) The rubber-rolled pin has the transmitting and dispersing effects which would prevent the stress concentration of connecting plate in elastic and elastic-limit range.
(3) The energy absorption of rubber-rolled pin is about five times larger than the one of the ordinary steel pin. Thus, the rubber-rolled pin is advantageous as a bridge restrainer system for the severe loading condition.
Ishikawa, N., Sonoda, Y. and Hikosaka, H., 1997, Development of New Bridge Restrainer with Rubber-Rolled Pin for the Great Earthquake, Earthquake Resistant Engineering Structures, Computational Mechanics Publications, pp. 203-212.
Japan Road Association, 1996, Design Specification of Highway Bridge, Part V: Seismic Design [in Japanese].
Kawashima, K. and Unjoh, S., 1997, Impact of Hanshin/Awaji Earthquake on Seismic Design and Seismic Strengthening of Highway Bridge, Journal of Structural Mechanics and Earthquake Engineering, No. 556/I-38, pp. 1-30.
Nishimoto, Y., Kajita, Y., Ishikawa, N. and Nishikawa, S., 2000, An Experimental Study on Dynamic Properties of Laminated Fiber Reinforced Rubber as Shock Absorber of Bridge Restrainer System, Journal of Structural Engineering, Vol. 46A, pp. 1865-1874 [in Japanese].
Nishimoto, Y., Kajita, Y., Ishikawa, N. and Nishikawa, S., 2001, A Study on the Weight Dropping Impact Test and Prediction of the Impact Transmitted Load of Laminated Fiber Reinforced Rubber as a Shock Absorber for Bridge Restrainer System, Journal of Structural Engineering, Vol. 47A, pp. 1655-1664 [in Japanese].