IN SITU MONITORING AND ANALYSIS FOR STRESS-DEPENDENT STRAINS OF EARLY AGE CONCRETE STRUCTURES

Stress-dependent strains monitoring of early-age concrete structures by embedded vibrating wire sensors is investigated. A methodology to calculate stress-dependent strains form the very beginning of concrete placing is developed, which can be done directly by vibrating wire strain readings without the efforts to identify time dependent parameters such as expansion coefficients of early age concrete. Then a concrete V shaped strut of a long span bridge is instrumented and monitored continually for a period of 14 days by vibrating strain and temperature sensors. With the measured strain readings and temperature data, the process of stress-dependent strain calculation is validated and the strain evolution with concrete hardening is analyzed. The results show that the methodology is practicable in early age concrete structures and make stresses calculation more convenient and accurate. It can be used to indicate the strain developing mechanism and to identify the complicated relationships between hydration, deformation, and restraint of early age concrete.