DEVELOPMENT OF NEW BRIDGE RESTRAINER USING LAMINATED FIBER REINFORCED RUBBER

Nobutaka Ishikawa1, Yasushi Nishimoto1 and Toru Ukishima2

1 National Defense Academy, Yokosuka 238-0022, Japan
E-mail: cgishikawa@m4.dion. ne. jp
2Shibata Industrial Co. Ltd., Akashi 674-0082, Japan

Abstract

This paper presents an experimental approach for the development of new bridge restrainer system using laminated fiber reinforced rubber (LFRR). After Kobe earthquake on January 1995, the design concept for the bridge restrainer has been revised so that the bridge should install the shock absorber which may be prevented from falling down due to earthquake shock. However, the shock absorbing system for the bridge restrainer has been required to satisfy the two performance requirements of high energy absorption and reduction of impact load. To this end, the laminated fiber reinforced rubber was developed to apply to the new bridge restrainer system as a shock absorber. In this study, the three kinds of tests of static compression, rapid speed loading and weight dropping impact for the LFRR specimen were first performed in order to investigate the efficiency of LFRR as a shock absorber. Then, the rubber-rolled pin was also developed as a new bridge restrainer system from the viewpoints of impact load reduction and high energy absorption.

Keywords: bridge restrainer, laminated fiber reinforced rubber, impact test, shock absorber 1. Introduction

As one of many fallout accidents of bridge girders occurred by the Kobe earthquake on January 1995 in Japan (Kawashima et al., 1997), the bridge restrainer system was damaged by impulsive loading in many places. Thus, the new bridge restrainer system has become needed to develop the shock absorbing device in order to prevent it from the failure if the equivalent earthquake occurs (Japan Road Association, 1996). In case of severe earthquake, a shock absorber is required to reduce the impact load which acts on the falling down prevention devices and also to absorb the high kinetic energy of girders. However, it is difficult to satisfy these two performance requirements at the same time. Although the high stiffness of a material is required in order to absorb the kinetic energy, it can not reduce the impact load. Therefore, a new shock absorber using the laminated fiber reinforced rubber (LFRR) is developed as shown in Figure 1 (Nishimoto et al., 2000, 2001).

In this study, the efficiency of LFRR is first investigated by performing three kinds of tests (static compression, rapid speed loading and weight dropping impact tests) from the viewpoints of two performance requirements of impact load reduction and high energy absorption. Second, the rubber-rolled pin using LFRR is developed as a new bridge restrainer by carrying out the impact

Fig. 1. LFRR. 809

M. Pandey et al. (eds), Advances in Engineering Structures, Mechanics & Construction, 809-821. © 2006 Springer. Printed in the Netherlands.

Fiber

Rubber

High tension (HMF)

Middle tension (MMF)

Low tension (LMF)

Hardness degrees of 50 (R50)

Hardness degrees of 65 (R65)

Material

6-nylon

6,6-nylon

Vinylon

Natural rubber

Tensile strength

5292(N/3cm)

2646(N/3cm)

1764(N/3cm)

10.2(MPa)

20(MPa)

Elongation percentage at break

40(%)

25(%)

20(%)

600(%)

600(%)

Table 2. Test cases.

Specimen

Static compression test

Rapid speed Loading test

Weight

dropping

test

R50

о

о

о

R65

о

о

о

LMF1

о

LMF5

Q

О

О

LMF25

О

о

о

LMF50

Q

MM FI

О

MMF5

О

о

О

MMF25

О

MMF50

О

HMFl

О

HMF5

О

О

О

HMF25

О

test (Ishikawa et al., 1997). Finally, effects of LFRR and rubber-rolled pin are discussed from the viewpoints of mitigation of impact load and the energy absorption.