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[CIVIL NX] What does 'Notational Size of Member' in hydration heat analysis mean?


What does 'Notational Size of Member' in hydration heat analysis mean?



The h value is calculated for a cross-section, but since its effect on drying shrinkage cannot be neglected, it is common to apply 60% of the calculated value.

 When defining Creep / Shrinkage, the Notational Size of Member (h) refers to the geometric dimensions of the member and indicates how much the element is exposed to external conditions. For example, in the figure below, the open section (right) is more exposed to external conditions than the closed section (left), so it is expected to be more affected by drying shrinkage.

 The formula used to calculate the value of h is calculated for the cross-section only. As shown on the left side of the below figure, considering only the exposure to external conditions in the gray area and ignoring the yellow area. However, for massive concrete structures such as mat foundations or dams, which are the subjects of hydration heat analysis, the yellow area's influence on drying shrinkage is expected to be significant, as shown on the right side of the below figure.

 Therefore, the formulas specified in the design standards and program dialog box are suitable for use with members that can be geometrically modeled as line elements, such as bridges, so it is difficult to apply accurate values in hydration heat analysis.

 For example, in the following figure, if the light yellow part is referred to as the section, the value of h calculated by the formula is 4.8. However, since the influence of drying shrinkage on the light yellow part cannot be ignored, it is common to apply 60% of the calculated value, which is 2.88.

 The calculation method described above is not based on any reference from design cases or standards. There is no accurate standard for how much the h value should be reduced based on the shape of the model, so the appropriate value should be input according to the structural designer's judgment.

 In the hydration heat analysis of concrete structures, the notational size of member (h) is not a  variable that has a significant impact on the analysis results. Furthermore, there is no regulation in concrete design standards that explicitly requires considering drying shrinkage in hydration heat analysis. Therefore, as like the h value, the decision to consider drying shrinkage in hydration heat analysis is also up to the structural designer's judgment.

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