When carrying out an assessment using BD 86 the main problem is the large number of vehicle configurations that need to be analysed. An initial assessment is generally carried out to establish "reserve factors" for each of the five SV type loads for each design detail being considered. This is done for both normal and slow speeds, which affects the dynamic amplification factor applied and the unloaded length in front and behind the vehicle. The analysis should also be carried out for SV cases with and without associated lane loading and for both Ultimate and Serviceability limit state conditions. The associated load can be either standard HA loading or convoys of any of the Appendix D vehicles.

Once the reserve factors have been established, an assessment of a real STGO or SO vehicle can be carried out. If the assessment provides unsatisfactory results then further analysis can be carried out, limiting the range of movement of the vehicle and some associated loading. Another important consideration is the application of the Dynamic Amplification Factor which can be different values for each axle.

As can be seen a huge number of combinations need to be considered just for one detail and BD 86 seems to have been written with computer aided load optimisation in mind. SAM-LEAP5's load optimisation model is well suited to carrying out this form of assessment and the parameters for BD 86 can be seen in the screen shot of the data form below.

SAM-LEAP5 should provide the engineer with great benefits in being able to determine reserve factors for a number of design details in a very short time.