我国隔震和消能减震结构的工程实践-土木工程毕业文献翻译.docx

西 南 交 通 大 学本科毕业设计外文文献翻译年 级: 2012级学 号: 姓 名: 专 业: 土木工程指导老师: 2016年 6月Engineering practice of seismic isolation and energy dissipation structures in ChinaThe concepts of seismic isolation and energy dissipation structures emerged in the early 1970s. In China, the first seismic isolation structure was finished in 1993, and the first energy dissipation structure was built at about the same time. Up to 2007, China had more than 600 seismic isolation and about 100 energy dissipation building structures. In 2008, the huge Wenchuan earthquake hit the southwest of China, which triggered a bloom of new seismic isolation and energy dissipation structures. This paper presents the development history and representative applications of seismic isolation and energy dissipation structures in China, reviews the state-of-the-practice of Chinese design, and discusses the challenges in the future applications. Major findings are as follows: Basic design procedures are becoming standardized after more than ten years of experiences, which mainly involve determination of design earthquake forces, selection of ground motions, modeling and time-history analyses, and performance criteria. Nonlinear time-history analyses using multiple ground motions are the characteristic of the design of seismic isolation and energy dissipation structures. Regulations, standardization and quality control of devices, balance between performance and cost, comparison with real responses, and regular inspection are identified as the issues that should be improved to further promote the application of seismic isolation and energy dissipation structures in China.seismic isolation structure, energy dissipation structure, development history, design practice1. IntroductionThe concept of modern seismic isolation emerged in the early 1970s in New Zealand, and the first seismic isolation building was also built in New Zealand in 1981. A few years later, Japan and the US had their own seismic isolation buildings in 1983 and 1984, respectively. Slightly later than these earthquake-prone countries, the application of the seismic isolation in China began, and the first building was finished in 1993. Up to 2007, the seismic isolation technology had been applied in over 20 countries. In terms of the application numbers, Japan, China, and the US are the leading countries in the world. Japan has more than 5000 seismic isolation buildings, and the number for the US is nearly 100. The highest seismic isolation buildings in Japan and the US have 50 stories and 29 stories, respectively. China has over 600 seismic isolation buildings, and the highest has 19 stories. In 1972, Kelly et al. proposed an idea to dissipate earthquake energy by installing some soft steel dampers as energy dissipation devices in the structure. This is deemed to be the origination of energy dissipation structures. In the beginning of 1980s, it was imported to China and the research on the new structure system started. Major efforts were made on the development of energy dissipation devices and the evaluation of energy dissipation structure performances in the beginning. Real applications started ten years later, i.e., in the early 1990s. Up to now, China has about 100 buildings using energy dissipation devices. In 2008, the huge Wenchuan earthquake hit the southwest of China, leading nearly 70000 deaths and 800 billion RMB economic losses. Great efforts from Chinese engineer society are made at evaluating the seismic capacity of existing structure systems and searching the alternative seismic technologies. A resonance workshop was held at China Academy of Engineering on June 28 to 29, 2008, and the application of seismic isolation and energy dissipation technologies was suggested as one of the solutions to improve the seismic performance of buildings. Applications of seismic isolation and energy dissipation technologies were significantly increased in Japan after the 1995 Kobe earthquake. Similarly, they were expected to be more wildly used in China in the following years due to the Wenchuan earthquake. This paper firstly presents the development history and some representative applications of seismic isolation and energy dissipation structures in China, then reviews the state-of-the-practice of Chinese design, and finally discusses the challenges of future application in China. 2. Development history and representative applications2.1. Seismic isolation structures Early in the 60s of last century, Chinese researchers studied seismic isolation buildings by using low-cost sliding systems, and several single-story and a four-story isolation buildings were constructed in 1980. In the late 1980s, Chinese started the research on the modern isolation technology, and a few research projects were carried out in the universities and research institutes. The real engineering applications started in 1993. The history of the engineering applications in China can be divided into the following four stages. From 1993 to 1994一A few pioneer seismic isolation buildings were constructed. Funded by the United Nations Industrial Development Organization (UNIDO), Zhou constructed an eight-story building in Shantou City of China by using the rubber bearings made in Malaysia. This is deemed to be the first seismic isolation building in China. Tang built another two buildings by using the lead rubber bearing made in China in 1993 and 1994, respectively. From 1995 to 1996一Based on the experience gained from the pioneer projects, the seismic isolation technology in China was greatly improved, and more applications were implemented in Guangdong, Yunnan, Sichuan and Shanxi provinces. Meanwhile, the potential market of rubber bearing was recognized by the Chinese rubber industry, which accelerated the research and manufacture of Chinese rubber bearing devices.From 1997 to 2000一Quite a few Chinese manufactures could produce qualified rubber bearing devices. In 1997, the corresponding technical specifications and product standards were established. Figure 1 presents the floor area of seismic isolation buildings up to 2000. A significant increase of applications in 1997 can be observed.Figure 1 Floor area of seismic isolated buildings (up to year 2000) From 2001 to present一A chapter about seismic isolation and energy dissipation structures was added to the Chinese Code for Seismic Design of Buildings issued in 2001,meaning that the seismic isolation structures were officially accepted. The number of seismic isolating buildings increased steadily during this period, and up to 2007, more than 600 isolation buildings had been constructed in more than 16 provinces, covering most seismic zones of China.A few representative projects are given in Figure 2. Figure 2(a) shows the first seismic isolation building mentioned above. Shantou City, where the building is located, was shaken in the 1994 Taiwan Strait earthquake with a magnitude of 7.3, and the building performed very well. People in the nearby conventional buildings felt very strong shaking, and some escaped from the windows, leading to 126 people injured, but those in the seismic isolation building were almost unaware of the earthquake. Figure 2(b) shows a high-rise seismic isolation building. This 19-story building was built in Shanxi province, China in 1999. It was the highest one for almost ten years until another high-rise building with 20 stories was constructed in Sichuan province of China after the Wenchuan earthquake. Figure 2(c) gives the picture of the new terminal of Kunming airport, which is the largest seismic isolation building in China .The seismic isolation layer consists of 535 lead rubber bearings and 1177 natural rubber bearings with a diameter of 1000 mm, and 54 viscous dampers. Figure 2(d) shows a seismic isolation building group in the subway hub area of Beijing. A very large platform (2-story RC frame) with a dimension of 1500 m x 2000 m was constructed, and 50 seismic isolation buildings (7-9 stories, RC frame) were built on the platform. The total floor area of these seismic isolation buildings is approximately 480000 m2, ranking the first in the world in terms of floor area. Figure 2(e) shows a seismic isolation building recently designed by the authors. It is the National Biohazard Safety Laboratory in Beijing. This building has extremely high demands in both safety and functionality, and thus seismic isolation becomes a good choice. The seismic performances including acceleration responses were carefully considered in the design. Figure 2(f) is the picture of the Shanghai F1 Circuit Press Center. The seismic isolating layer is set at the height of 31.6 m. This layer has three functions, i.e., to sustain gravity, to reduce the seismic forces, and to release thermal stress Figure 2 Representative applications of seismic isolation structures in China. (a) First building; (b)highest building; (c) largest building; (d)largest building group; (e) national biohazard safety laboratory; (f) Shanghai F1 circuit press center.2.2. Energy dissipation structures.The concept of energy dissipation structures was imported into China by Wang in the early 1980s, and since then Chinese researchers and engineers have done fundamental and innovative work on the energy dissipation devices and engineering applications. Specifically, at least the following four types of energy dissipation devices, i.e., metallic dampers, friction dampers, visco-elastic dampers, and viscous dampers, have been investigated. About the metallic dampers, Zhou conducted experimental studies of an energy dissipation brace composed of flexural steel members in 1980s. Since then, quite a few types of metallic dampers, including buckling restraint braces have been developed by Zhou et al. As for the friction damper, its study started from the late 1980s. Researchers, e.g., Zhou and Wu, improved the Pall friction dampers, Chen developed bolt-addressing friction dampers, and Qu et al. proposed a new friction mechanism, i.e., setting slots in RC/steel shear walls for energy dissipation. As for the visco-elastic dampers, Chen and Wu developed a design function for modeling the dampers, and Wu et al. conducted parametric studies on visco-elastic dampers. Research on viscous dampers started relatively late in China. Universities including Tsinghua University, Southeast University, Tongji University and Harbin Institute of Technology conducted preliminary researches on viscous dampers. Qian et al. conducted experimental studies on the seismic behaviors of viscous damping walls. With the progress of research, energy dissipation was gradually applied in engineering practice in China. Up to the present, about 100 energy dissipation structures have been constructed in China. Figure 3 gives a few representative energy dissipation structures in China. Figure 3(a) shows the first structure using Chinese self-developed buckling restraint braces (BRBs). The BRBs consist of steel core and external reinforced concrete restraint unit. The building was finished in2005, and totally 350 BRBs were installed. Figure 3(b) gives the picture of Bainian Fortune Plaza in Jiangsu province of China, which is 94.95 m high and is regarded as the highest Chinese building using viscous dampers. Originally, viscous damping walls were considered for this building; however, the conventional cylinder-type of viscous damper was finally applied due to the economical consideration. Figure 3(c) shows Shimao International Plaza, whose main and annex structures are connected by 40 dampers. The torsion effect of the annex structure and the wind vibration of the main structure are successfully controlled by the dampers. Figures 3(d) and (e) display the largest scale engineering applications of energy dissipation structures in retrofit and new projects, respectively. The former one is the Ganghui Plaza in Shanghai, and it was retrofitted by using 88 dampers. The latter one is the Theme Exhibition Hall of 2010 EXPO, having 80000m2 floor area and using 44 dampers.Figure 3 Representative applications of energy dissipation structures in China. (a) First structure using Chinese self-developed BRBs; (b)highest structure using viscous dampers; (c)Shimao international plaza; (d)Ganghui plaza; (e) theme exhibition hall of 2010 EXPO.3. Seismic isolation and energy dissipation devices3.1. Seismic isolatorsThe most popular isolators in China are natural rubber bearings (NRBs) and lead rubber bearings (LRBs) with a circular cross-section. Quite a few Chinese companies are manufacturing seismic isolators at competitive prices. Chinese NRBs and LRBs consist of layers of natural rubber with thickness ranging from 2 to 15 mm, intercalated with stiff slender steel plates ranging from 2 to 5 mm in thickness. The thickness of the natural rubber layers and steel plates increases with the increase of diameters. For a circular isolator with diameter D and rubber layer with thickness tR, the shape factor is defined as Sl=D/4tR. The usual Sl values in China are in the range of 25 to 45. The control of Sl shape factor is to avoid buckling of the bearings in large lateral deformations and ensure large vertical stiffness to minimize the overturning effect. The vertical stiffness is between 1.0x106 and 8.0x106 kN/m, which increases with the increase of rubber bearings diameter. The second shape factor, S2, defined by the aspect ratio of the rubber included in the isolator S2=D/(ntR) (n=the number of rubber layers), is around 6. The manufacturers usually offer two types of bearings in terms of the rubbers shear modulus, i.e., 0.4 or 0.6 N/mm2. The allowable long-term compressive stress (due to gravity) ranges from 10 to 15 N/mm2. In Chinese design practice, the upper bound is used for ordinary building structures, whereas the lower bound is used for important buildings, whose failure would result in serious secondary disasters.The diameter of Chinese rubber bearing varies from 200 to 1200 mm with an interval of 50 mm (Figure 4(a).Rubber bearings with small diameters, e.g., 200 and 300 mm were popular in the past, but are not encouraged to use any more mainly due to their relatively small deformation capacity. The most commonly used in buildings are those with diameters between 500 to 800 mm. The design maximum deformation is set to about 250% to 300% in shear strain (commonly 450 to 550 mm for the 800 mm diameter).Figure 4 Seismic isolation and energy dissipation devices. (a)Rubber bearing; (b)pot type damper. LRBs are NRBs with a lead plug (usually 40 to 150 mm diameter) inserted in order to dissipate hysteretic energy. The yield force depends on the diameter of the lead plug and is around 100 kN for the 100 mm lead plug in diameter. LRBs have high initial stiffness (about 10 to 16 times the post-yield stiffness) for relatively low horizontal forces normally produced by wind.3.2. Energy dissipation devicesDifferent to seismic isolators, in which rubber bearings dominate, the energy dissipation devices (or simply called dampers) have much larger variety. The energy dissipation devices could be distributed in the structure or concentrated at the seismic isolation layer together with seismic isolators. The dampers mainly include the following five types: visco-elastic damper, viscous fluid damper, metal yielding damper, friction damper, and buckling restraint brace. Although it is classified as one of the metal yielding dampers in this paper, the buckling restraint brace is normally regard as an independent type in the engineer society. In the design practice, viscous dampers are most commonly used, followed by metal yield dampers and buckling restraint braces. The viscous fluid dampers provide a linearly or nonlinearly velocity proportional damping force. The force capacity of the viscous fluid dampers commonly adopted is in the range of 150 to 1500kN, the velocity proportional damping coefficients have values between 200 to 2000 kN s/m, and the common values of velocity proportional damping exponents are in the range of 0.2 to 1.0 with an interval of 0.05.The damping force is modeled to be linearly or nonlinearly velocity-proportional for analysis. Most dampers are effective for deformations only in one direction; hence, for the applications in seismic isolation buildings, at least four devices are needed per building to restrain the torsion effect. Recently a pot type damper shown in Figure 4(b) was used in the seismic isolation layer, which could provide damping forces in multiple directions.3.3. Authorization process of devicesFor practical applications, all devices must go through an authorization process before shipping to the construction sites. Commonly only delivery inspection is needed for a specific project. However, a type approval test should be conducted if the device is a new product, or the processing technique changes, or the manufacturer stop production for over a year. Both delivery inspection and type approval test should be conducted by the China Metrology Accreditation (CMA) organizations, and the qualified devices will obtain certifications. The number of devices to be tested is at least three for each type of devices and the qualification ratio should be 100%. Generally the tests have to present results of full-scale specimens; however, in some cases scaled specimen are used due to the limited loading capacity of the testing facilities. As examples, Figures 5(a) and (b) show the tests of rubber bearing and pot damper, respectively.Figure 5 Tests of seismic isolation and energy dissipation devices. (a)Rubber bearing; (b)pot damper.4. Design practice4.1. Design frameworkThree levels of earthquakes are considered in the Chinese building seismic design practice, i.e., 1) frequent earth-quakes-referring to the earth