## 4 Analysis of Crack Width
### Estimation of Crack Widths  
The crack widths of the RC slab members were calculated using Equation (1) by considering the rebar stress of the tension reinforcement in the slab specimens. The cross-section dimensions of the slab were measured before the experiment and the as-built dimensions were used in calculations. Calculated crack widths in Tables 3 and 4 were generated using the measured load values obtained while the first measured crack widths were 0.3 mm and 0.5 mm, respectively. The ratios of calculated-to-measured crack width are presented in Tables 3 and 4, which demonstrates the difference in estimation. As given in Tables 3 and 4, the calculated-to-measured crack width ratio for specimens that are 300 mm thick (SA specimens) are mostly above 1, while this ratio drops below 1 for specimens that are 400 mm thick (SH-specimens). This ratio drops further below 1 for slabs that have a thickness of 500 mm (SK-specimens). All the slab specimens have the same top and bottom concrete cover. However, the rebar spacing is smaller for the 400 and 500 mm specimens (150 mm spacing; 6 in. spacing) than the 300 mm specimens (200 mm spacing; 8 in. spacing). With more bars provided for the 400 and 500 mm slab specimens, more cracks with smaller crack widths were observed compared to the 300 mm slab specimens. Measured values were larger for the 400 and 500 mm slab specimens than the calculated values. One possibility that there are discrepancies between crack width measurements and calculations in specimens with smaller bar spacings and larger thickness (SH and SK specimens) is that these specimens would have smaller crack widths than specimens with larger bar spacings and smaller thicknesses, and slight error may cause larger differences. One other note to make is that the measurements in this study were made only at the bottom side surface of the specimens for all specimens and no measurements on the bottom surface of the specimens due to the difficulties to be underneath the specimens, and the measurements at the bottom surface could have provided larger crack widths. The casting direction of the specimens did not have much effect on the occurrence of the design crack widths of 0.3 mm and 0.5 mm, as shown in Tables 3 and 4. Figure 5: Measured vs. calculated initial cracking load (unit: KN). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{ \begin{tabular}{c} **Specimen** \\ **Name** \\ \end{tabular}  } & \multirow{2}{*}{**Thickness**} & \multirow{2}{*}{**Rebar Stress**} & \begin{tabular}{c} **Bottom** \\ **Concrete** \\ **Cover** \\ \end{tabular}  & \begin{tabular}{c} **Rebar** \\ **Spacing** \\ **Factor** \\ \end{tabular}  & \begin{tabular}{c} **Neutral Axis** \\ **Width Using** \\ **Measured Load** \\ \end{tabular}  & \ \begin{tabular}{c} **Calculated-To-** \\ **Width Ratio** \\ \end{tabular}  \\ \cline{2-7}  & & \(H\) & \(f_{s}\) & \(d_{c}\) & \(s\) & k & \(w_{c}\) & \(w_{c}\)/\(w_{m}\) \\ \hline \multirow{2}{*}{
\begin{tabular}{c} **Unit:** \\ **A-H16 (PL)-1 \\ SA-H16 (PL)-1 \\ SA-H16 (OP)-1 \\ SA-H16 (PR)-1 \\ SA-H16 (PR)-2 \\ SA-H16 (PL)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (PL)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (PR)-2 \\ SA-H16 (OP)-2 \\ SA-H16 (Figure 6 shows the distribution of calculated-to-measured crack width ratios for the first major crack. There is more discrepancy between the measurements and calculations of crack width for specimens with increased thickness.