# Load Models Representative of Brazilian Actual Traffic in Girder-Type Short-Span Highway Bridges
## 9 Comparison between Target Values and the Effects Generated by Load Models  
In Figures 9-11 the target values are compared to the effects generated by load models 1 and 2; the NBR 7188 TB-450 model [23] is also used for comparisons, including its impact factor. Ratios between effects generated by each load model and the corresponding target values are shown in Table 8.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Bridge**} & \multirow{2}{*}{**Effect**} & \multicolumn{3}{c}{**Load Model**} & \multirow{2}{*}{**NBR 7188**} \\ \cline{3-3} \cline{5-5}  & & **1** & **2** & \\ \hline \multirow{2}{*}{S-10} & V & 0.88 & 0.87 & 0.70 \\  & M+ & 1.08 & 1.04 & 0.79 \\ \hline \multirow{2}{*}{S-20} & V & 0.96 & 0.95 & 0.83 \\  & M+ & 1.09 & 1.06 & 0.91 \\ \hline \multirow{2}{*}{S-30} & V & 0.94 & 0.93 & 0.87 \\  & M+ & 1.14 & 1.08 & 0.95 \\ \hline \multirow{2}{*}{S-40} & V & 0.97 & 0.95 & 0.93 \\  & M+ & 1.04 & 0.99 & 0.90 \\ \hline \multirow{2}{*}{C-10} & M+ & 1.10 & 1.06 & 0.80 \\  & V & 1.08 & 1.05 & 0.87 \\  & M\({}^{-}\) & 0.91 & 0.87 & 0.66 \\ \hline \multirow{2}{*}{C-20} & M+ & 1.04 & 1.00 & 0.87 \\  & V & 0.93 & 0.91 & 0.86 \\  & M\({}^{-}\) & 0.82 & 0.85 & 0.85 \\ \hline \multirow{2}{*}{C-30} & M+ & 1.09 & 1.04 & 0.93 \\  & V & 1.01 & 0.99 & 1.03 \\  & M\({}^{-}\) & 0.96 & 1.05 & 1.12 \\ \hline \multirow{2}{*}{C-40} & M+ & 1.01 & 0.97 & 0.89 \\  & V & 1.01 & 0.99 & 1.01 \\  & M\({}^{-}\) & 0.94 & 1.07 & 1.19 \\ \hline \multirow{2}{*}{F-2.5} & M\({}^{-}\) & 0.98 & 0.96 & 0.50 \\ \hline \multirow{2}{*}{F-5.0} & M\({}^{-}\) & 0.92 & 0.93 & 0.58 \\ \hline \multirow{2}{*}{F-7.5} & M\({}^{-}\) & 0.94 & 1.00 & 0.66 \\ \hline \multirow{2}{*}{F-10} & M\({}^{-}\) & 0.94 & 1.04 & 0.70 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Ratios between the effects generated by each load model and the corresponding target values.  
Figure 8: Plan view of the proposed load models: (**a**) load model 1; (**b**) load model 2. Units: m.  
Figure 11: Comparison between the effects generated by the load models and the target values. (**a**) Negative moments on continuous bridges. (**b**) Negative moments on cantilevers.  
Figure 10: Comparison between the effects generated by the load models and the target values. (**a**) Positive moments on simply supported bridges. (**b**) Positive moments on continuous bridges.  
Figure 9: Comparison between the effects generated by the load models and the target values. (**a**) Shear forces on simply supported bridges. (**b**) Shear forces on continuous bridges.  
Relative to the proposed load models 1 and 2, it can be seen that: (i) the negative moments were reasonably reproduced, except for the C-20 bridge; (ii) reasonable correlation was also achieved for the shear forces, except for the S-10 bridge; and (iii) the positive moments were the best represented effects by the new load models proposed.  
For the NBR 7188 load model, the results show that in most cases (20 among 24), the current Brazilian design code underestimates the effects of the actual traffic, especially for the negative moments in cantilevers and the shear forces in shorter bridges; the only exception is the negative moment in the continuous bridges C-30 and C-40. It finally confirms the conclusions noted earlier [30; 31], that the NBR 7188 standard does not properly represent the estimated extreme effects of the actual traffic and may need to be updated, as it appeared to be considerably against safety in some situations, whereas in others, it was considerably favorable to safety, which implies uneconomic design. The weighted error for the TB-450 model is 17.4%.