# Influence of Girder Flaring on Load Effect in Girders of Composite Steel Bridges
## 6 Conclusions and Recommendations
### Conclusions About Flexural Effect  
* The tributary width concept that is often used in practice for regular bridges is reliable for determining the flexural dead load effect on the splayed interior and exterior girders. However, the AASHTO recommendation of equally sharing the superimposed dead load among the girders is not always very accurate, as this study showed that exterior girders receive higher loads from the parquet weight than interior girders.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Girder** & **Analytical** & **FE Exterior** & **FE First Interior** & **FE Intermediate** \\  & **Calculations** & **Girder (G1)** & **Girder (G2)** & **Girder (G3)** \\ \hline Stress (MPa) & 19.23 & 21.00 & 20.25 & 19.20 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Maximum tensile stress in unshored composite girders of reference bridge B1 at midspan due to future wearing surface and parquet weight.  
Figure 27: Dead load on a single composite girder of bridge B1 for the case of unshored construction.  
* Increasing the splayedness ratio leads to reductions in GDF for flexure in both interior and exterior girders. The relationship between the GDF and splayedness ratio is almost linear.
* The splayedness ratio and girder spacing ratio cannot be used as standalone indices in a splayed girder bridge without supporting them with the actual girder spacing. Therefore, to judge the magnitude of the flexural GDF of a splayed girder bridge, a splayedness parameter plus one girder spacing at a specific location within the bridge must be provided.
* The effect of the slab thickness on the flexural GDF for splayed girder bridges is moderate on the interior girders and negligible on the exterior girders. In addition, girder stiffness has little effect on the GDF for both interior and exterior girders. However, an increase in the number of girders beyond five can lead to some reduction in the GDF of the exterior girder, due to the possibility of rigid body rotation over the increased width of the bridge and large eccentric truck loading.
* There is a significant effect on the interior girders due to the addition of cross-bracing to splayed girder bridges, which is similar to the presence of the cross-bracing effect in regular bridges. Where the flexure GDF for interior girders dropped by more than 8% due to adding cross-bracings at 5 m spacing, it increased the exterior girder GDF by about 2%. The location of cross-bracing spacing in reference to the longitudinal truck axle positions is important, as axles directly above a cross-bracing are more equally distributed among the girders compared to axles located between cross-bracings.
* The AASHTO GDF for flexure yielded reasonable results compared to the FE models, where for the interior girders, the difference was between 2-13% on the conservative side. The high values of the flexure GDF compared with the finite element results, computed following the AASHTO specifications, were due to the presence of cross-bracing, the effect of which is not considered in the AASHTO formulas. The GDF results for exterior girders obtained using the AASHTO formulas were also very reliable, where the percentage difference was between \(-4\%\) and \(14\%\) when compared with the finite element analysis outcomes. The results representing slight conservatism were recorded in bridges with extreme parameter values that exceeded the AASHTO limits.