## 3 Database and Models
### Data Collection
**} & \multirow{2}{*}{**Specimen**} & \multirow{2}{*}{*** W/B**} & \multicolumn{6}{c}{**Steel Fiber**} & \multirow{2}{*}{***}{**PCS**} & \multirow{2}{*}{********\(\ast CS\)**} & \multirow{2}{*}{**Reference**} \\ \cline{3-3} \cline{5-10}  & & \multicolumn{1}{c}{**D/mm**} & & & & \multicolumn{1}{c}{**\(\ast\)**} & \multicolumn{1}{c}{**\(\ast\)**} & \multicolumn{1}{c}{**\(\ast\)**} & \multicolumn{1}{c}{**\(\ast\)**} & \multicolumn{1}{c}{**\(\ast\)**} & \multicolumn{1}{c}{**\(\ast\)**} \\ \hline
56 & Cube & 0.20 & 0.22 & 13.00 & 59.09 & 0.00 & 72.15 & 72.15 & [17] \\
57 & 70.7 mm \(\times\) & 0.20 & 0.22 & 13.00 & 59.09 & 1.00 & 72.15 & 125.10 & [17] \\
58 & 70.7 mm \(\times\) & 0.20 & 0.22 & 13.00 & 59.09 & 2.00 & 72.15 & 147.86 & [17] \\
59 & 70.7 mm & 0.20 & 0.22 & 13.00 & 59.09 & 3.00 & 72.15 & 160.17 & [17] \\ \hline
60 & & 0.25 & 0.24 & 13.00 & 54.17 & 0.00 & 108.04 & 108.04 & [18] \\
61 & Prism & 0.16 & 0.24 & 13.00 & 54.17 & 0.50 & 108.04 & 113.39 & [18] \\
62 & 40 mm \(\times\) 40 mm \(\times\) & 0.16 & 0.24 & 13.00 & 54.17 & 1.00 & 108.04 & 117.40 & [18] \\
63 & 160 mm & 0.16 & 0.24 & 13.00 & 54.17 & 1.50 & 108.04 & 135.66 & [18] \\
64 & & 0.16 & 0.24 & 13.00 & 54.17 & 2.00 & 108.04 & 167.67 & [18] \\ \hline
65 & Prism & 0.17 & 0.16 & 9.00 & 56.25 & 0.00 & 147.54 & 147.54 & [19] \\
66 & 40 mm \(\times\) 40 mm \(\times\) & 0.19 & 0.16 & 9.00 & 56.25 & 1.10 & 147.54 & 156.62 & [19] \\
67 & 160 mm & 0.19 & 0.16 & 9.00 & 56.25 & 2.10 & 147.54 & 194.07 & [19] \\  
\begin{table}
\begin{tabular}{l c c c c c c c c c} \hline \hline \multirow{2}{*}{**No. **} & \multirow{2}{*}{**Specimen Dimension**} & \multirow{2}{*}{*} **W/B** & \multicolumn{6}{c}{**Steel Fiber**} & \multirow{2}{*}{*} **PCS** & ************\% CS** & **Reference** \\ \cline{5-9}  & & \multicolumn{1}{c}{*} & \multicolumn{1}{c}{*} & \multicolumn{1}{c}{*} & \multicolumn{1}{c}{*} & \multicolumn{1}{c}{*} & \multicolumn{1}{c}{*} & \multicolumn{1}{c}{*} & \multicolumn{1}{c}{*} \\ \cline{5-9}  & & \multicolumn{1}{c}{*} & \multicolumn{1}{c}{*} & \multicolumn{1}{c}{*} & \multicolumn{1}{c}{*} & \multicolumn{1}{c}{*} & \multicolumn{1}{c}{*} & \multicolumn{1}{c}{*} & \multicolumn{1}{c}{*} \\ \hline
111 & & 0.16 & 0.22 & 13.50 & 61.36 & 0.00 & 125.80 & 125.80 & [25] \\
112 & & 0.16 & 0.22 & 13.5  
Therefore, a total of 166 compressive strength experimental data sets and 102 flexural strength experimental data sets were obtained to establish the training-testing database. Among the data, 80% (133 and 80) data sets were selected as training sets, and the remaining data sets (20% of the total data)  
\begin{table}
\begin{tabular}{l l l l l l l l l l} \hline \hline \multirow{2}{*}{**No. **} & \multirow{2}{*}{**Specimens**} & \multirow{2}{*}{**W/B**} & \multicolumn{4}{c}{**Steel Fiber**} & \multirow{2}{*}{**\({}^{\ast}\)**PFS**} & \multirow{2}{*}{**\({}^{\ast\ast}\)**FS**} & \multirow{2}{*}{**Reference**} \\ \cline{3-3} \cline{5-10}  & & & \multicolumn{1}{c}{**D/mm**  
were used for testing, respectively. The testing data were selected randomly to eliminate the effects of artificial selection on the results. In accordance with existing calculation models [31; 32; 33; 34; 35; 36; 37; 38], the water to binder ratio (\(W/B\)), the diameter (\(D\)), the length (\(L\)), the aspect ratio (\(AR\)), and the volume fraction (\(VF\)) of steel fibers, and the compressive strength (\(PCS\)) or the flexural strength (\(PFS\)) of UHPFRC without steel fibers were selected as the main input parameters, and the compressive strength (\(CS\)) or flexural strength (\(FS\)) of UHPFRC was used as the output variable. Table 3 shows the ranges of the input and the output variables in the compressive strength database and the flexural strength database in this study.