45 8 2017 8 Journal of South China University of Technology Natural Science Edition Vol 45 No 8 August 2017 1000-565X201708-0132-07 * 1 1 2 1 116024 2 100045 SF CF NCB FCR COD TU528 doi10 3969 /j issn 1000-565X 2017 08 019 2-3 - 1-17 1 4-5 8-9 1 5 8-12 7 13-14 6 2 5 8-9 9 18-19 - 1 2016-09-27 * 51578109 Foundation itemsupported by the National Natural Science Foundation of China51578109 1962- E-mailynding@ dlut edu cn
8 133 1 1 1 0 55 mm 7 85 g /cm 3 6 mm 1 3 10-5 ~ 7 10-5 Ω m P O 42 5R 12 ~ 15 μm 1 55 ~ 1 60 g /cm 3 0 ~ 5 mm 33 nm 0 75 Ω cm 2 51 0 3 ~ 0 5 g /cm 3 5 ~ 10 mm Sika 7 2 SF22 SF44 22 44 kg /m 3 BCS22-1 22 kg /m 3 1 1 4 36 kg /m 3 1 09 kg /m 3 Table 1 Mix proportions of concrete BCS22-2 22 kg /m 3 6 54 kg /m 3 0 5 390 155 848 822 272 5 7 63 1 kg /m 3 - RC-65 /35-BN 5 5 10-6 Ω m 65 1 64 kg /m 3 BCS44-1 44 kg /m 3 2 18 kg /m 3 0 55 kg /m 3 BCS44-2 44 kg /m 3 6 54 kg /m 3 0 55 kg /m 3 3 1 Table 2 2 Dosages of the conductive admixtures /kg m - 3 PC 0 00 0 00 0 SF22 0 00 0 00 22 SF44 0 00 0 00 44 BCS22-1 1 09 4 36 22 BCS22-2 1 64 6 54 22 BCS44-1 0 55 2 18 44 BCS44-2 0 55 6 54 44 1 Fig 1 Conductive materials 1 2 100 mm 100 mm 400 mm 1 d 28 d 100% 4 A /D B /C 4-5 FCR 3 300 mm 0 2 ± 0 02mm /min 3 5 mm LVDT IMC
134 45 2 2 Fig 2 δ ifxdx D BZi = 0 1 Measurement of FCR deflection and COD of bending beams 2 RILEM TC 162-TDF 2 1 3 28 d Table 3 3 Compressive and flexural strength of conductive concrete f cu / N mm - 2 F u / f u / N mm - 2 / kg m - 3 PC 35 6 13 23 4 0 0 00 SF22 36 2 14 97 4 5 22 00 SF44 37 8 19 46 5 8 44 00 BCS22-1 36 9 17 08 5 1 27 45 BCS22-2 37 4 18 22 5 5 30 18 BCS44-1 38 3 22 77 6 8 46 73 BCS44-2 35 9 26 29 7 9 51 09 3 PC SF22 BCS22-1 BCS22-2 f u 12 5% 27 5% 37 5% SF44 BCS44-1 BCS44-2 f u 45% 70% 97% 22 kg /m 3 SF22 BCS22-1 BCS22-2 f u 13% 22% 44 kg /m 3 SF44 BCS44-1 BCS44-2 f u 17% 36% 2 2 3 - δ i D BZi δ i Fig 3 3 - Load-deflection curves of conductive concrete beams 4 3 4 22 kg /m 3 SF22 1 BCS22-1 D f BZ2 D f BZ3 f eq 2 f eq 3 32% 20% 2BCS22-2 D f BZ2 f eq 2 D f BZ3 f eq 3 68% 40%
8 135 4 Table 4 20 Equivalent flexural strength and energy absorption of conductive concrete beams 20 D f BZ2 / mm f 1 eq 2 / D f BZ3 / f 1 eq 3 / / N mm - 2 mm N mm - 2 kg m - 3 PC 0 00 0 00 0 00 0 00 0 00 SF22 1 48 0 89 13 05 1 30 22 00 SF44 7 49 4 49 38 13 3 81 44 00 BCS22-1 1 96 1 18 17 21 1 72 27 45 BCS22-2 2 50 1 50 18 27 1 83 30 18 BCS44-1 9 02 5 41 51 55 5 16 46 73 BCS44-2 8 72 5 23 50 04 5 00 51 09 1f eq 2 f eq 3 D f BZ2 D f BZ3 2 3-4 5 - COD Y = a + bx 30% 44 kg /m 3 SF44 1BCS44-1 D f BZ2 f eq 2 D f BZ3 f eq 3 20% 35% 5% 2BCS44-2 D f BZ2 f eq 2 D f BZ3 f eq 3 17% 31% 15% SF22 SF44 F R i 5 2 a b X mm 6 Table 5 5 Residual load of conductive concrete beams F R 1 / F R 2 / F R 3 / F R 4 / / kg m - 3 SF22 5 21 5 29 4 13 3 55 22 00 SF44 16 47 12 73 10 10 8 61 44 00 BCS22-1 6 45 7 59 5 69 5 31 27 45 BCS22-2 7 97 7 59 5 31 4 93 30 18 BCS44-1 21 25 19 35 15 18 11 76 46 73 BCS44-2 19 03 18 13 17 00 14 28 51 09 Fig 4 Relationships between FCR and COD of conductive concrete with single-phase conductive material 5 22kg /m 3 SF22 1BCS22-1 39% 20% 2BCS22-2 6 41% 30% 0 88 ~ 0 98 44 kg /m 3 SF44 1BCS44-1 2 42% 5% 4 22 44 kg /m 3 2BCS44-2 48% - 15% SF22 SF44 r 2 4 -
136 45 Table 6 6 Fitted parameters of regression equation a b r 2 SF22 5 88 2 04 0 87675 SF44 4 87 5 55 0 88241 BCS22-1 8 37 2 09 0 92510 BCS22-2 7 41 3 44 0 91982 BCS44-1 2 04 2 80 0 98372 BCS44-2 1 85 2 15 0 97193 5 - SF22 SF44 r 2 b b 2 04 ~ 5 55 a 1 85 ~ 8 37 a BCS22-1 BCS22-2 a a 3 5 Fig 5 1 2 3 - Relationships between FCR and COD of concrete with b multi-phase conductive materials a
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138 45 Self-Monitoring Performance of Cracking Development of Multiphase Conductive Concrete Subjected to Bending DING Yi-ning 1 HENG Zhen 1 HAN Zhi-bo 2 1 State Key Laboratory of Coastal and Offshore EngineeringDalian University of TechnologyDalian 116024LiaoningChina 2 Radio Film and Television Design and Research InstituteBeijing 100045China AbstractBy adding the macro steel fiber SF the carbon fiber CFand the nano-carbon black NCBinto the concrete as the multiphase conductive materials the influences of the SF the CF and the NCB on the mechanical properties and conductivity of the cracked concrete as well as on the self-monitoring performance of the crack development are investigated Thena relationship between the fractional change of the surface resistance FCR and the crack opening displacement CODof the conductive concrete beams is established The results show that 1the addition of the conductive materials can greatly enhance the flexural strength and toughness of the concrete 2the hybrid use of the NCB the CF and the SF shows a clear positive hybrid effect on the flexural behavior and the self-monitoring performance of the crack developmentand 3there is a linear relationship between the FCR and the COD Key wordsfibersnano-carbon blackconcrete crackingself-monitoringfractional change in resistancecrack opening displacement 125 Attack Angle Effects of Flutter Optimization of a Steel Truss Bridge and Corresponding Isolated Improvement CHEN Xing-yu WANG Bin LI Yong-le LIAO Hai-li CHEN Ke-yu Department of Bridge EngineeringSouthwest Jiaotong UniversityChengdu 610031SichuanChina AbstractSteel truss girders are a common structure type for long-span suspension bridges The flutter stability of this structure type is poor Thereforeaerodynamic optimization measures are usually adopted to increase the critical wind speed of the flutter In this investigationbased on a long-span steel truss girder bridge located at a mountain areathe wind tunnel tests of the section model were conducted to detect the critical wind speed of the flutterand the influences of the general aerodynamic measures including the central stabilizerthe horizontal stabilizer and the stabilizer under the top lateral bracing on the critical wind speed of the flutter were discussed It is found that the general aerodynamic measures have attack angle effects on the critical wind speed of the flutter Thereforeisolated aerodynamic measures are proposedwhich include the isolated horizontal stabilizerthe grating horizontal stabilizer and the isolated stabilizer under the top lateral bracing The results show that these isolated aerodynamic measures can improve the attack angle effects to a certain degreethus increasing the critical wind speed of the flutter Key wordssteel truss girderflutteroptimization measureattack angle effectisolated improvement