International Journal of Highway Engineering (한국도로학회논문집)

Korean Society of Road Engineers (한국도로학회)
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Degree of Restraint(DOR) of Longitudinal Steel at Continuously Reinforced Concrete Pavement(CRCP) Against Environmental Loadings

환경하중에 의한 연속철근콘크리트(CRCP) 종방향 철근의 구속정도

  • Nam, Jeong-Hee (Highway pavement research division, SOC research Institute, Korea Institute of Construction Technology) ;
  • Ahn, Sang Hyeok (Highway pavement research division, SOC research Institute, Korea Institute of Construction Technology)
  • 남정희 (한국건설기술연구원 SOC연구소 도로포장연구실) ;
  • 안상혁 (한국건설기술연구원 SOC연구소 도로포장연구실)
  • Received : 2014.11.13
  • Accepted : 2014.11.28
  • Published : 2014.12.18
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Abstract

PURPOSES : The purpose of this study is to evaluate the degree of restraint (DOR) of longitudinal steel at continuously reinforced concrete pavement (CRCP) against environmental loadings. METHODS : To measure the longitudinal steel strain, 3-electrical resistance and self-temperature compensation gauges were installed to CRCP test section (thickness = 250mm, steel ratio = 0.7%) and continuously measured 10 min. intervals during 259 days. In order to properly analyze the steel strains first, temperature compensation process has been conducted. Secondly, measured steel strains were divided into 12 phases with different events such as before paving, during concrete hardening, and after first cracking, etc. RESULTS : Thermal strain rate (TSR) concept is defined as the linear strain variations with temperature changes and restraints rate of longitudinal steel against environmental loadings (especially thermal loading) with different cases is defined as degree of restraint(DOR). New concept of DOR could be indirect indicator of crack width behaviors of CRCP. CONCLUSIONS : Before paving, DOR of longitudinal steel is almost same at the coefficient of thermal expansion of steel ($12.44m/m/^{\circ}C$) because of no restraint boundary condition. After concrete pouring, DOR is gradually changed into -1 due to concrete stiffness developing with hydration. After first cracking at crack induced area, values of DOR are around -3~-5. The negative DOR stands for the crack width behavior instead of steel strain behavior. During winter season, DOR reached to -5.77 as the highest, but spring this values gradually reduced as -1.7 as the lowest. Based on this observation, we can presume crack width decreased over time within the time frame of this study. This finding is not consistent with the current theory on crack width variations over time, so further study is necessary to identify the causes of crack width reducing. One of the reasons could be related to concrete stress re-distribution and stress relaxation.

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References

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