桥梁隧道英汉文翻译.docx

1、桥梁隧道英汉文翻译LONG-TERM DETERIORATION OF HIGHDAMPING RUBBER BRIDGE BEARINGIn recent years, high damping rubber (HDR) bridge bearings have become widely used because of the excellent ability to provide high damping as well as flexibility. However, there are few systematic studies on the deterioration prob

2、lems of HDRs during their service life, and usually the long-term performance was not considered in the design stage. In this research, through accelerated thermal oxidation tests on HDR blocks, the property variations inside the HDR bridge bearing are examined. A deterioration prediction model is d

3、eveloped to estimate the property profiles. Then using a constitutive model and carrying out FEM analysis, the behavior of a HDR bridge bearing during its lifespan is clarified. A design procedure is proposed that takes the long-term performance in the site environment into consideration.Key Words:

4、high damping rubber bearing, thermal oxidation, deterioration, long-term performance1. INTRODUCTIONSince Hyogoken-Nanbu earthquake that occurred on January 17th, 1995, bridge bearings have been widely adopted in Japan as an effective means to weaken the severe damage of steel and concrete piers due

5、to an earthquake1), 2). Rubber is frequently applied in bridge bearings because of its special properties such as high elasticity and large elongation at failure. However, natural rubber cannot afford sufficient damping which is indispensable to a seismic isolation system. Usually rubber bearing is

6、used together with steel bars, lead plugs, or other types of damping devices. In order to add energy dissipation to the flexibility existing in laminated rubber bearings, in the early 1980s, the development in rubber technology led to new rubber compounds, which were termed high damping rubber (HDR)

7、. HDR material possesses both flexibility and high damping properties. The bridge bearings made of HDR can not only extend the natural period of the bridge, but also reduce the displacement response of structures3). Moreover, because of the inherent high damping characteristics of HDR, there is no n

8、eed of additional devices to achieve the required levels of protection from earthquakes for most applications, so that the seismic isolation system becomes more compact. In the manufacture process of HDR, natural rubber is vulcanized together with carbon black, plasticizer, oil and so on. Consequent

9、ly HDR possesses specific characteristics such as maximum strain-dependency of stress evolution, energy absorbing properties and hardening properties. Yuan et al.4) experimentally studied the dynamic behaviors of HDR bearing. Yoshida et al.5), 6) developed a mathematical model of HDR materials and p

10、roposed a three-dimensional finite element modeling methodology to simulate the behaviors of a HDR bearing numerically. Besides, a series of accelerated exposure tests were performed by Itoh et al.7),8) on various rubber materials including HDR to investigate the degradation effects of different env

11、ironmental factors. It was found that the thermal oxidation is the most predominant degradation factor affecting theHDR material. Since oxygen is able to permeate into the interior of a thick rubber, in this research the deterioration of HDR bridge bearings is assumed to be mainly caused by the ther

12、mal oxidation. For the purpose of clarifying the deterioration characteristics of bridge rubber bearings during their lifespan, some bearings practically in use were recalled and their mechanical properties were tested9)11). However, because of their scatter nature and the lack of data, the long-ter

13、m performance of HDR is not very clear. During the design process, usually the behaviors of deteriorated bridge rubber bearings during their lifespan are not considered.In the previous research, Itoh et al. 12), 13) studied the long-term performance of natural rubber (NR) bridge bearings. Through ac

14、celerated thermal oxidation tests carried out on NR blocks, the deterioration characteristics of both the outer and the interior regions were examined. Based on the test results, a prediction model was established to estimate the property profiles of the deteriorated NR bridge bearing. Then using th

15、e constitutive law proposed by Yoshida5), finite element model was built and the analysis was performed, which enabled the long-term performance of NR bridge bearing to be predicted. The relations among property variation, temperature, aging time and bearing size were also investigated.In this resea

16、rch, through the similar accelerated thermal oxidation tests on HDR blocks, the deterioration characteristics of HDR bridge bearings are studied, and their long-term mechanical performance is investigated by taking the site environment taken into consideration. The HDR specimens are provided by Toka

17、i Rubber Industries, Ltd. It is possible that when suffered by aging, the HDR from other companies may behave differently due to the difference of chemical compound. The deterioration characteristics of the HDR material with other compounding ingredients and additives will be discussed in the future

18、 study.2. ACCELERATED THERMAL OXIDATIONTESTSAmong different degradation factors such as oxidation, ultraviolet radiation, ozone, temperature, acid and humidity, it is found that thermal oxidation changes the HDR properties more greatly than other factors5), resulting in an increase of HDRs stiffness

19、 and a decreases of elongation at break as well as tensile strength. Besides, for thick rubbers, it is obvious that the surface is more easily affected by deterioration factors than the interior because of the diffusion-limited oxidation effect14), 15). In order to understand the variation of the ma

20、terial properties inside HDR bearings, accelerated tests were performed using rubber blocks focusing on the most significant degradation factor, thermal oxidation. The test method and results are described as follows.2.1 Accelerated thermal oxidation test methodFifteen HDR blocks were tested. The di

21、mension is 22015050mm (lengthwidththickness). The specimens were kept in a Thermal Aging Geer Oven. The acceleration test conditions are listed in Table 1. The temperatures were kept at three elevated temperatures, 60, 70, and 80 in the oven. For the test at each temperature, the experiment duration

22、 were set as 5 stages, with the maximum of 300 days. The similar tests have already been performed on NR10). When the aging test was finished, HDR blocks were sliced into pieces with a thickness of 2mm. From each slice, four specimens with No.3 dumbbell shape were cut out16), as shown in Fig.1. The

23、number of the specimens was 1,500 in total. Then through the tensile tests on these dumbbell specimens, the stress-strain curves were obtained, which represented the rubber properties at the corresponding position. In this research, strain energy was chosen for examination because it can exhibit the

24、 effect of thermal oxidation more remarkably than stresses at certain strains. In the following description, U100 stands for the strain energy corresponding to the strain of 100%, UB stands for the strain energy up to the break, and M100 stands for the stress corresponding to the strain of 100%. Sim

25、ilarly, U100 profile stands for the distribution of U100 inside HDR blocks, and property profile means the distribution of the mechanical properties such as stresses corresponding to certain strains, elongation at break (EB) and tensile strength (TS). As for the rubber breakage, EB is focused on. In

26、 addition, U0 and EB0 stand for U100 and EB in the initial state, respectively.2.2 Test results and examinationsThe profiles of U100/U0 and EB/EB0 at every test temperature are illustrated in Fig.2 and Fig.3, respectively. The horizontal axis shows the relative position with regard to the thickness

27、of HDR block. The values 0 and 1 on this axis correspond to the surface of the block. The vertical axis shows the normalized change of U100 with the original value regarded as 1.0 in Fig.2, and shows the normalized change of EB in Fig.3. In these figures, every point represents the mean value of fou

28、r specimens from the same slice. Because of the scatter nature of rubber materials, at any position four specimens are tested in order to improve the accuracy. Since the oxidized rubber inhibits the ingress of oxygen, and considering the shape of the rubber block, the four specimens are cut out in t

29、he area of at least 25mm, a half of the block thickness, away from the around surface. Thus these specimens only reflect the property variations in the thickness direction. The standard deviation of every four-specimen group is quite small and usually less than 5% of the mean value.From Fig.2 and Fi

30、g.3, it can be found that at the earliest stage of the test, the material properties at the outside surface change together with the interior regions. The property variation of the interior region soon reaches the equilibrium state and maintains stable. However, the properties near the surface keep

31、changing over the time, and change most greatly at the surface.From the surface to the interior, the properties vary less and less, until to a certain depth,which is called “critical depth”. The critical depth is about 11.5mm from the block surface at 60, 8.5mm at 70, and 6mm under 80. From the resu

32、lts of the same tests on NR blocks12), it is found that generally HDR and NR have a similar tendency of property variation. Both U100 and EB profiles display the features of a diffusion-limited oxidation. Initially the profiles are relatively homogeneous, but strong heterogeneity develops with aging

33、. The properties in the outer region change more than the interior and keep changing over the time. However, unlike the case of NR, the interior region of HDR block experiences a rapid increase and soon reaches the equilibrium state. In contrast, the interior region of NR block does not change at all. In addition, after the same aging time,