外文翻譯--利用傾角儀測量橋梁撓度（原文）

1、Using Inclinometers to Measure Bridge DeflectionXingmin Hou1; Xueshan Yang2; and Qiao Huang3Abstract: Deflection of a bridge span under designed loads is an important parameter for bridge safety evaluation. However, it i

2、s inconvenient to obtain the bridge deflections directly. For bridges over rivers, railways, or highways, a direct measurement method is impractical. A promising bridge deflection measurement method ?inclinometer method?

3、 is presented in this paper. It offers a simple, practical and inexpensive method of measuring static and dynamic deflections of bridge spans under loads, even for bridge spans that traverse great heights. Hundreds of ex

4、periments and practical tests on simple and continuous bridges, utilizing dynamic and static loads, under various vehicle speeds, show that the method has very high precision, which provides an authentic basis for new-bu

5、ilt bridge acceptance and old bridge safety evaluation. The method does not need fixed observation positions as other deflection measurement methods because the inclinometers are installed on the bridge directly, which i

6、ncreases measurement efficiency greatly. These features indicate that as a potential method of measuring bridge deflection, inclinometers have significant engineering application value and a promising future.DOI: 10.1061

7、/?ASCE?1084-0702?2005?10:5?564?CE Database subject headings: Measuring instruments; Deflection; Static tests; Dynamic tests; Bridges.IntroductionDeflection of a bridge span under designed loads is an important parameter

8、for bridge safety evaluation. Micrometers or displace- ment meters, which can obtain stable and reliable deflection re- sults, are widely employed in measuring bridge deflections di- rectly in older bridges’ maintenance,

9、 for bridge safety evaluation and for new-built bridge acceptance. Direct measurement, how- ever, requires steel wires connecting the bridge with the sensors that are supporting on the ground or a truss at some selected

10、measurement points. Such direct measurement is impractical for bridges over rivers, railways, highways, and sea and those bridges with very high clearances. Some noncontacting bridge deflection measurement methods have b

11、een invented to overcome the shortcomings of direct mea- surement method. Inertial deflection measurement method, which uses inertial vibration sensors, has high resolution and accuracy ?Xie et al. 1999?. As is well know

12、n, a deflection time history is a transient motion. Its frequency spectrum is broad, and mainfrequency components are low. Due to the limited low-frequency response ability of such an inertial seismic-transducer, the mea

13、- surement results need to be corrected. Further, this method cannot measure static deflection of a bridge span. Photoelectric bridge deflection measurement method is quasi-real time, high speed, and automatic. But the e

14、quipment is very expensive and the method easily affected by rain and fog. Moreover, the method is impractical for bridges that cannot find fixed observation areas within 500 m. A promising bridge deflection measurement

15、method, inclinom- eter method, is presented in this paper. Model QY inclinometer is an angle-measuring sensor, which is developed by the Measuring Instrument Division, Institute of Engineering Mechanics, China Earthquake

16、 Administration ?Harbin, China?. Fig. 1 shows the pic- ture of the QY inclinometer. The inclinometer consists of a ca- pacitance transducer and a passive servo system. It rotates as the bridge section rotates under loads

17、, and the inertial pendulum in the inclinometer inclines correspondingly. A capacitor can sense the pendulum inclination and generates a voltage output by an elaborately designed circuit, which is proportional to the cor

18、re- sponding angular change of the bridge section. From the voltage output, one can obtain the angular change of the bridge section. The sensitivity of the inclinometer is about 100 mV per minute of angle. The measuring

19、range of the inclinometers is 10 min of angle. The drift voltage value is within 0.2 angular second in half an hour. Thus, the angular changes at some selected positions on the bridge span can be measured, and from this,

20、 the deflection, angle, and curvature at any point on the bridge span can be calculated. In comparisons with conventional methods, the inclinometer method has the following features, which will be discussed more fully in

21、 subsequent sections: 1. No fixed observation positions are necessary near the bridge because the inclinometers are installed on the bridge directly ?Yang et al. 2002?. The method reduces the dependence on1PhD, Associate

22、 Professor, Institute of Engineering Mechanics ?IEM?, China Earthquake Administration ?CEA?, 29 Xuefu Rd., Harbin 150080, China; and Postdoctoral Researcher of Harbin Institute of Technology, 202 Haihe Road, Harbin 15009

23、0, China. 2Professor, Institute of Engineering Mechanics, China Earthquake Administration ?CEA?, 29 Xuefu Rd., Harbin 150080, China. 3Professor, Member of International Association for Bridge and Structural Engineering ?

24、IABSE?, Harbin Institute of Technology, 202 Haihe Road, Harbin 150090, China. Note. Discussion open until February 1, 2006. Separate discussions must be submitted for individual papers. To extend the closing date by one

25、month, a written request must be filed with the ASCE Managing Editor. The manuscript for this paper was submitted for review and pos- sible publication on February 11, 2003; approved on October 20, 2004. This paper is pa

26、rt of the Journal of Bridge Engineering, Vol. 10, No. 5, September 1, 2005. ©ASCE, ISSN 1084-0702/2005/5-564–569/$25.00.564 / JOURNAL OF BRIDGE ENGINEERING © ASCE / SEPTEMBER/OCTOBER 2005J. Bridge Eng. 2005.10:

27、564-569.Downloaded from ascelibrary.org by Changsha University of Science and Technology on 05/30/13. Copyright ASCE. For personal use only; all rights reserved.Table 1 lists angular values of six inclinometers, calculat

28、ed deflections according to the six angular values at where 5 µm were installed, reads of the micrometers and relative errors for one of the experiments. A comparison between the inclinometer results ?calculation? a

29、nd the reads of micrometers ?direct mea- surements? is shown in Fig. 3. Fig. 4 was a static experiment for a two-span continuous beam. The steel beam was 6 m long also. An inclinometer was installed every 1 m. A micromet

30、er was installed between every two neighboring inclinometers. Table 2 lists the angular values, the calculated deflections, the reads of the micrometers, and rela- tive errors for one of the experiments. Comparative curv

31、es be- tween calculated and measured results are shown in Fig. 5. Doz- ens of static deflection experiments under different loads verified that using an inclinometer could obtain excellent deflection re- sults for both s

32、imple beams and continuous beams. Generally, the relative errors are within 5%. For large deflection areas, the rela- tive errors are within 2%.Dynamic Experimental VerificationFig. 6 shows a picture of the dynamic exper

33、iment for a simple beam. The steel beam was 6.045 m long and seven inclinometers were installed. Coordinates of the inclinometers were 0.270, 1.061, 1.873, 3.305, 4.098, 4.911, and 5.705 m, respectively. Three displaceme

34、nt meters were installed along the beam at 1.486, 2.082, and 4.512 m to record the time histories ?dynamic deflection? directly ?Fig. 7?. A working frequency band of the displacement meter was from 0 to 30 Hz, the sensit

35、ivity of the displacement meter was 0.2 mV/mm, the linearity was 2% and the resolution was 0.0025 mm. Loads of 9.0 and 14.5 kg were selected to simulate vehicles moving on the bridge. Fig. 8 shows the comparison between

36、records of three dis- placement meters and the calculated deflections at the same posi- tions based on QY inclinometers’ records. Two curves fit very well. The deflection curves of the whole beam at the 12th secondTable

37、1. Results of Simple Beam Static ExperimentsAngular value ?10?3 rad? Micrometer ?mm? Inclinometer ?mm? Relative error ?%?0.7068 0.449 0.429 ?4.390.6289 1.150 1.158 0.720.2518 1.420 1.445 1.73?0.2350 1.114 1.162 4.30?0.61

38、40 0.438 0.427 ?2.42?0.6890Table 2. Results of Continuous Beam Static ExperimentsAngular value ?10?3 rad? Inclinometer ?mm? Micrometer ?mm? Relative error ?%?2.0195 0.963 1.00 4.570.9125 1.945 1.917 ?1.441.2787 0.776 0.7

39、74 ?0.26?1.2110 ?0.471 ?0.468 0.64?0.2127 ?0.712 ?0.698 1.97?0.4167 ?0.322 ?0.302 6.21?0.6162Fig. 3. Comparison of inclinometer and micrometer results for a simple beam under static loadsFig. 4. Two-span continuous beam

40、experimentFig. 5. Comparison of inclinometer and micrometer results for a continuous beam under static loadsFig. 6. Dynamic deflection experiment for simple beamFig. 7. Illustration of dynamic deflection experiment for a

41、 simple beam566 / JOURNAL OF BRIDGE ENGINEERING © ASCE / SEPTEMBER/OCTOBER 2005J. Bridge Eng. 2005.10:564-569.Downloaded from ascelibrary.org by Changsha University of Science and Technology on 05/30/13. Copyright A