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Fiber Bragg Grating Temperature Sensor System on a Twin-Deck Continuous Rigid Frame Bridge for Long Term Monitoring
Abstract:
In structural health monitoring, evaluation of bridge serviceability performance is based on vibration method. The vibration properties are influenced by temperature, humidity, wind and traffic load. Temperature differential in rigid frame bridge causes additional stress, which affects dynamic characteristics and induces concrete cracks. Thus analysis of temperature distribution is the basement of damage identification. Fiber Bragg grating (FBG) sensors are advanced materials for SHM. This paper introduces a temperature sensor monitoring system consisting of 52 temperature sensors on a twin-deck continuous rigid frame concrete bridge and analyzes temperature distribution on the twin decks of the bridge through August to December, 2006. Temperature at the same height sections differs little in the longitudinal direction along this bridge. The comparisons between maximum and minimum temperature each month reveal the asymmetry of transverse temperature distribution. The pavement has significant impact to the top slab temperature. In November the temperature declines sharply. The temperature on the external surface of top slab is lower than that of bottom for short box girders in winter because of shelters of flanges.
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Periodical:
Pages:
1611-1618
Citation:
Online since:
October 2010
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Сopyright:
© 2011 Trans Tech Publications Ltd. All Rights Reserved
Citation:
[39] 6 35.
[29] 7.
[33] 1.
[34] 7.
[33] 1 Minimum.
[28] 3.
[23] 5.
[22] 7.
[26] 2.
[25] 9.
[26] 2 Sept. Maximum.
[32] 9.
[28] 5.
[24] 2.
[27] 7.
[28] 5.
[27] 7 Minimum.
[22] 1.
[17] 9.
[18] 7.
[19] 7.
[20] 4.
[21] 7 Oct. Maximum.
[28] 8.
[24] 9.
[23] 2.
[25] 7.
[26] 7.
[25] 7 Minimum.
[16] 4 14.
[15] 3.
[17] 2.
[16] 7.
[17] 2 Nov. Maximum.
[20] 3.
[17] 9.
[11] 7.
[19] 6.
[20] 5.
[19] 6 Minimum.
[5] 7.
[2] 5.
[3] 7.
[6] 7.
[5] 7.
[6] 7 Dec. Maximum.
[6] 4.
[4] 1.
[4] 5.
[7] 5.
[7] 1.
[7] 5 Minimum.
3 -2. 6 -0. 8.
[1] 7 -0. 1.
[1] 7 At section I of upper-bridge, temperature at point d7 on external surface of middle of east top flange was 2. 3℃ to 4. 8℃ lower than at point d4 on the centerline on the external surface of the top slab, d11 in the middle of the east web 1. 2℃ to 7. 6℃ lower than d18 of the west. Temperature at point d13 on the internal surface of bottom slab was -2. 1℃ to 1. 4℃ different with d18 on the internal surface of west web, d15 on the external of bottom slab -2. 1℃ to 1. 4℃ different with that at internal surface point d13. As shown in table 3, for the cross section of upper bridge, transverse temperature in top slab and web was asymmetrical since the west is higher; internal surface of the west web and bottom slab was approximately the same, much higher than the middle of east web. Vertical temperature in the bottom slab differed little. Table. 4 Maximum and minimum temperature[℃] at section I of down-bridge every month Month temperature d4 d5 d8 d10 d11 d14 d15 d18 Aug. Maximum.
[39] 5.
[38] 8.
[37] 2.
[32] 1.
[31] 4.
[32] 8 34.
[31] 2 Minimum 28.
[27] 1.
[25] 6.
[24] 6.
[23] 9.
[25] 6 26.
[24] 6 Sept. Maximum 33 32 31.
[26] 8.
[25] 5.
[27] 4.
[28] 5.
[25] 8 Minimum.
[22] 5.
[22] 1.
[20] 7.
[20] 3 19.
[19] 9.
[19] 6.
[20] 5 Oct. Maximum.
[28] 4.
[27] 6.
[26] 6.
[23] 8.
[22] 9.
[25] 0.
[26] 1.
[23] 8 Minimum.
[16] 1.
[16] 4 16.
[14] 8.
[13] 5.
[15] 8 16.
[15] 1 Nov. Maximum.
[20] 1 20.
[19] 1.
[17] 0 16.
[18] 9 20.
[17] 1 Minimum.
[5] 6.
[5] 5.
[4] 5.
[4] 8.
[3] 5.
[5] 4.
[5] 9.
[5] 0 Dec. Maximum.
[6] 6.
[6] 5.
[5] 7.
[5] 0 4.
[6] 3.
[6] 6.
[5] 3 Minimum.
1 -1. 3 -0. 7 -2.
4 -0. 2 At section I of down-bridge (shown in table 4), temperature at point d4 on the external surface of top slab was -0. 3℃ to 5. 5 ℃ higher than at point d15 on the external of bottom slab, -0. 3℃ to 1℃ higher than at the middle point d5 of top slab. In the horizontal middle height of top slab, temperature at d5 on the centerline was 0. 4℃ to 1. 6℃ higher than at point d8 in middle of east flange. In the webs, temperature at point d10 on the internal surface of east web was -0. 5℃ to 1℃ different with that at d18 on the west, 0. 7℃ to 1. 3℃ higher than d11 in the middle of east. In the bottom slab, temperature at point d14 was -1. 2℃ to 0. 3℃ different with that at middle point d14, 0. 9℃ to 2. 9℃ higher than at d11. The table certifies that in the top slab, the external temperature was about 1℃ higher than the middle, and temperature on the centerline was about 1℃ higher than east flange; in the east web, temperature on the internal surface was about 1℃ higher than in the middle; The temperatures on the internal surface of east and west webs were similar. Temperature in the middle of east web was 2℃ higher than in the middle of bottom slab . As top slab was thinner than bottom slab, the vertical temperature difference of top slab was a little smaller than that of bottom. Table. 5 Maximum and minimum temperature[℃] at section II of upper-bridge for 5 months Month temperature d4 d7 d11 d15 d16 d17 Aug. Maximum.
[37] 5.
[43] 1.
[32] 3.
[34] 0.
[34] 2.
[31] 8 Minimum.
[25] 5.
[27] 4 23.
[24] 6.
[26] 7.
[24] 5 Sept. Maximum.
[30] 6.
[34] 1.
[25] 7.
[28] 2.
[28] 7.
[26] 6 Minimum 19.
[17] 4.
[18] 2.
[18] 5.
[22] 8.
[18] 6 Oct. Maximum.
[26] 1.
[28] 8 24.
[26] 4.
[26] 9.
[24] 4 Minimum.
[13] 6.
[12] 4.
[14] 7.
[15] 2.
[18] 3.
[14] 6 Nov. Maximum 18.
[19] 1.
[17] 9.
[20] 1.
[20] 7.
[18] 5 Minimum.
[2] 5 -2. 7.
[2] 9.
[4] 2.
[7] 9.
[4] 1 Dec. Maximum.
[3] 6.
[1] 4.
[4] 4.
[6] 3.
[8] 5.
[5] 3 Minimum -3 -10. 2 -2. 3 -1. 6.
[3] 3 -0. 9 As shown in table 5, at section II of upper-bridge, temperature at the external point d4 was -2. 7℃ to 3. 6℃ different with external of bottom slab. In the top slab, temperature at flange point d7 turn from 5. 6℃ higher than d4 in summer to 7. 2℃ lower in winter. In the west web, temperature at d16 was 2. 1℃ to 4. 2℃ higher than d17; temperature at middle point d17 of west web was about -0. 5℃ to 1. 5℃ different with d11 of east web. The table shows that in winter, temperature on the external surface of top slab was lower on the internal surface, because the height of section II is about 400cm, which is 200cm shorter than section I. The shorter box girder is sheltered by flanges, receiving less sunlight direct radiation. Also, the top slab is covered by a 17cm thick pavement consisted by 4cm modified asphalt concrete face layer, 5cm thick median grain concrete and 8cm thick waterproof concrete, which reduce thermal conduction in the top slab. Space between the twin bridge have the function of keeping thermal energy, so temperature redistribution happens in the box girder which causes lower temperature at point d7 than d4 except for low radiation of sunshine in winter. Temperatures on the internal surface of east and west webs are similar. Table. 6 Maximum and minimum temperature[℃] at section II of down-bridge for 5 months Month temperature d1 d11 d12 d15 d16 Aug. Maximum 38.
[38] 1 35.
[34] 5.
[34] 4 Minimum.
[25] 6.
[28] 9.
[27] 4.
[25] 4.
[27] 4 Sept. Maximum.
[30] 6.
[31] 1.
[29] 2.
[28] 8.
[28] 7 Minimum 18.
[22] 9.
[22] 3.
[18] 3.
[23] 6 Oct. Maximum.
[26] 5.
[28] 1.
[26] 7.
[26] 7.
[26] 7 Minimum.
[13] 9.
[15] 8.
[16] 9.
[15] 7.
[17] 7 Nov. Maximum.
[18] 5.
[19] 1 20.
[20] 6.
[19] 7 Minimum.
[2] 1 0.
[6] 3.
[4] 6.
[7] 8 Dec. Maximum.
[4] 4.
[6] 9.
[6] 7.
[8] 0 Minimum -3. 4 -9. 5.
7 -0. 8.
[2] 6 At section II of down-bridge, temperature at the flange point d1 of external surface of top slab was -2. 6℃ to 3. 5℃ different with point d15 of external surface of bottom slab. In winter temperature at d1 was lower than d15, which had the similar trend with section II of upper-bridge. In the east web, temperature at external point d12 is -3. 1℃ to 10. 2℃ higher than the middle point d11. Temperature at external point d16 of west web was -0. 6℃ to 1. 9℃ higher than at external point d12 of east web. Table 6 shows temperature in November descended the most than other months. In winter, temperature on external surface of bottom slab is higher than of top slab, and external surface of east web higher than its middle. The results certify the function of energy maintenance by space between two boxes. Conclusion This study is performed to investigate the temperature distribution of a twin-deck continuous rigid frame bridge. The results confirmed that the longitudinal temperature difference for bridge of south to north direction could be neglected, but temperature is various for different height of sections. In November the temperature declines rapidly. Temperature in the top slab is influenced significantly by the thickness of pavement. In summer under strong sunlight radiation, external surface of top slab has much higher temperature than the external of bottom slab; instead, in winter, webs of short box girders are sheltered by flanges, which caused lower temperature in top slab than in the bottom. As bottom slab is thicker than top, vertical temperature difference in bottom slab is a little bigger than the top, yet both of them are little for thin wall box girders. Transverse temperature distributions in twin bridges are not symmetrical. As space between the two box girders keeps energy, temperature is redistributed in sections, which cause temperatures on the top slab flange near the middle space higher than on the centerline of each box in summer and lower in winter. For short box girders such as 400cm height's, temperature on external surface of east web of down-bridge is higher than middle of the web in summer, but lower in winter, because of shelter of flanges. Yet for the same height box girder of upper-bridge, temperature on the external surface of west web is always higher than in the middle. Temperature on the internal surface of cross sections of box girders is approximately the same, and changes little in one day, so is the temperature on external surface of webs between twin boxes. Acknowledgement This work has been supported by the Key Projects in the National Science & Technology Pillar Program during the Eleventh Five-Year Plan Period, numbered 2006BAJ03B05, and named Health Monitoring and Diagnosis Technology of Major Buildings and Structures. References.