Journal of South China University of Technology Natural Science Edition

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1 Journal of South China University of Technology Natural Science Edition Vol 45 No 8 August X * SF CF NCB FCR COD TU528 doi /j issn X * Foundation itemsupported by the National Natural Science Foundation of China ynding@ 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

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

/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

2 mm 7 85 g /cm 3 6 mm ~ 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 ~ 0 5 g /cm 3 5 ~ 10 mm Sika 7 2 SF22 SF kg /m 3 BCS kg /m kg /m kg /m 3 Table 1 Mix proportions of concrete BCS kg /m kg /m kg /m 3 - RC-65 /35-BN Ω m kg /m 3 BCS kg /m kg /m kg /m 3 BCS kg /m kg /m kg /m Table 2 2 Dosages of the conductive admixtures /kg m - 3 PC SF SF BCS BCS BCS BCS Fig 1 Conductive materials mm 100 mm 400 mm 1 d 28 d 100% 4 A /D B /C 4-5 FCR 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

3 Fig 2 δ ifxdx D BZi = 0 1 Measurement of FCR deflection and COD of bending beams 2 RILEM TC 162-TDF 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 SF SF BCS BCS BCS BCS 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% δ i D BZi δ i Fig Load-deflection curves of conductive concrete beams 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%

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 SF SF BCS BCS BCS BCS f eq 2 f eq 3 D f BZ2 D f BZ 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 SF SF BCS BCS BCS BCS Fig 4 Relationships between FCR and COD of conductive concrete with single-phase conductive material 5 22kg /m 3 SF22 1BCS % 20% 2BCS % 30% 0 88 ~ kg /m 3 SF44 1BCS % 5% kg /m 3 2BCS % - 15% SF22 SF44 r 2 4 -

5 Table 6 6 Fitted parameters of regression equation a b r 2 SF SF BCS BCS BCS BCS 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 Relationships between FCR and COD of concrete with b multi-phase conductive materials a

6 AZHARI F BANTHIA N Cement-based sensors with carbon fibers and carbon nanotubes for piezoresistive sensing J Cement & Concrete Composites RANADE R ZHANG J LYNCH J P et al Influence of micro-cracking on the composite resistivity of engineered cementitious composites J Cement & Concrete Research NGUYEN D L SONG J MANATHAMSOMBAT C et al Comparative electromechanical damage-sensing behaviors of six strain-hardening steel fiber-reinforced cementitious composites under direct tension J Composites Part B Engineering WEN S CHUNG D D L Self-sensing of flexural damage and strain in carbon fiber reinforced cement and effect of embedded steel reinforcing bars J Carbon WEN S CHUNG D D L Partial replacement of carbon fiber by carbon black in multifunctional cement-matrix composites J Carbon PENG Hai-longGAO Pei-weiWU Xiao-qiang et al Effect of graphite and carbon black on the mechanical and conductive properties of mortar with carbon fiber J Journal of Materials Science and Engineering J JIN Ting-yan TIAN Xiu-shu CUI Jian et al Mechanical and electrical properties of carbon fiber powder-steel slag cement based composites J Bulletin of the Chinese Ceramic Society DING Y N CHEN Z P ZHANG Y L et al Nano carbon black and carbon fiber as conductive materials for the diagnosing of the damage of concrete beam J Construction and Building Materials DING Yi-ning CHEN Long-feng Experimental studies of diphasic electric conduction concrete applying in the diagnosis of the damnification J Acta Materiae Compositae Sinica XIAO H G LI H OU J P Modeling of piezoresistivity of carbon black filled cement-based composites under multi-axial strain J Sensors & Actuators A Physical / XIAO H G LI H OU J P Self-monitoring properties of concrete columns with embedded cement-based strain sensors J Journal of Intelligent Material Systems & Structures PARRA-MONTESINOS G J REINHARDT H W NAA- MAN A E High performance fiber reinforced cement composites 6HPFRCC 6 M NetherlandsSpringer CCCW J FAN Xiao-ming DONG Xu SUN Ming-qing et al Electrical characteristic and piezoresistivity of carbon fiber graphite cement-based composites containing CCCW J Acta Materiae Compositae Sinica J J FAN Xiao-ming AO Fang SUN Ming-qing et al Piezoresistivity of carbon fiber graphite cement-based composites embedded in concrete column J Journal of Building Materials OU J P HAN B G Piezoresistive cement-based strain sensors and self-sensing concrete components J Journal of Intelligent Material Systems & Structures 2009 D YANG C Q WU Z S HUANG H Electrical properties of different types of carbon fiber reinforced plastics CFRPs and hybrid CFRPs J Carbon DING Y N Investigations into the relationship between deflection and crack mouth opening displacement of SFRC beam J Construction and Building Materials DING Y N ZHANG Y L THOMAS A The investigation J on strength and flexural toughness of fibre cocktail reinforced self-compacting high performance concrete J Construction and Building Materials RILEM TC 162-TDFTest and design methods for steel fibre reinforced concrete S

7 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 LiaoningChina 2 Radio Film and Television Design and Research InstituteBeijing China 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 SichuanChina 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

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