Effects Of Composition Steel Bars On The Thermal Stress Field Of Early-Age Concrete Wall Of Open-Cut Metro Station Structures-Numerical Modeling Analysis

At the early age of the concrete, the thermal stress will cause the cracking damage on the concrete structure. During the process of design and construction, according with the experience, the arrangement principle of the composition steel bars is summed as "thinner,denser,outer ". To study the effects of the composition steel bars, the finite-element analysis software, ANSYS, is adopted to compute the temperature field and thermal stress field of the side wall of an open-cut metro station structure in Shenzhen at the early age of the concrete.Research focused on the effects of the composition steel bars on the temperature field and thermal stress field of the early-age concrete. By comparing the results of whether the influence of the composition steel bars on the temperature field and thermal stress field of the early-age concrete was considered or not, proved the composition steel bars could reduce the thermal stress of the early-age concrete, and avoid the cracking damage due to hydration in the concrete wall. A 3-D simulation model is employed, with the hydration heat being modeled via a function dependent on the temperature and extent of reaction, to make a numerical simulation to the early-age concrete. Firstly, during the thermal analysis, nodes of the steel bars and concrete will be coupled in the process of heat-transfer; then, during the structural analysis, the longitudinal springs, which were used to simulate the mechanical effect of the steel and the concrete, will be set to link the steel bars and concrete. The distribution of the temperature field and the thermal stress field proved that the composition steel bars could reduce the stress and protect the concrete from the cracking damage.By simulating the temperature and the thermal stress of the early-age concrete under four work situations with different diameter, spacing, location of the composition steel bars, the result indicated that under the same boundary condition, arranging the composition steel bars near the flank with smaller diameter and smaller spacing could effectively reduce the concrete thermal stress and prevent the concrete from cracking damage.