Question
In heat of hydration analysis, an unreliable cracking index is calculated.
Answer
The cracking index is a value that is output at the nodes, so when modeling walls, the elements should be divided in the thickness direction.
Also, if not all elements share nodes, discontinuous results may be produced.
In midas Civil, it is not possible to consider reinforcing bars (rebars) in heat of hydration analysis. However, in midas FEA NX, it is possible to model rebar elements and consider them, and it also supports high-order solid elements.
If a Singular Error occurs during analysis, the most likely cause is that the thermal properties (specific heat, thermal conductivity) are not entered when defining the material. If thermal properties are not defined, a Singular Error will occur during analysis. The second major cause is that the convective boundary condition is not set. The surface of solid elements in contact with the atmosphere must all have convective boundary conditions defined. You should check to make sure that the convective boundary conditions for the elements activated in each construction stage are not missing.
There are cases where the crack index may be underestimated at the boundary between concrete and soil.
In this case, the boundary between the soil and concrete is influenced by the allowable tensile stress of the soil, resulting in distorted values. Here, the tensile strength of the soil is calculated using a formula used for concrete, making it an insignificant value. Additionally, the elastic modulus of the soil is smaller than that of concrete, resulting in a lower tensile strength. Consequently, the most disadvantageous cracking index is concentrated at the boundary between soil and concrete. To prevent such distortions in the results, it is appropriate to activate only the concrete part and exclude the part that contacts the soil to check the thermal cracking index.