CS454 Assessment

[designXDAC3]

Hi All,

I have downloaded Structural Bridge Design 2024 so I can analyse HB loading as I previously struggled to run the loading on the 2022 version. The new version is fine when using BD21, BD37 and BD86 to check 40T, 45HB and SV100 respectively, but when I switch to CS454 to run both 40T only and 45HB with checked, it seems to do the following:

1. 40T HA - it is applying footway loading only on the whole deck instead of model1 and model2 is applied outside the lanes.

2. 45HB with  HA model 1 - it only applies accidental wheel load, at time overlapping with HB vehicle.

3. 45HB with  HA model 2 - it applied HA in unspecified lanes (within pedestrian section).

Also the 40T and 45HB output come out as one 40 (normal), previously the two were split which is useful when designing a prestress beam so the class 1 and class 2 stresses are checked.

I would appreciate if you could assist and clarify if I am making mistake or the software has a glitch.

Regards

Ayub

[designXDAC3]

Grillage in Zip file

[dave_geeves]

Hi,

Thanks for raising this and for attaching your model.  I also couldn't make out the load patterns that were being created.  I believe this is being fixed and a patch released imminently (if not already).

Kind regards

Dave Geeves

[designXDAC3]

Thank you Dave for confirming the problem, I did download the hotfix provided, but I am not sure if it included fixing the problem raised. The accidental load seem to be all over overlapping HB load and also being the main 40T HA load in the optimised loading. 

[dave_geeves]

Hi,

There were a couple of small changes I needed to make to the data in your model to get the optimisation to work correctly.

The first seems to be a small glitch in the software such that if the footway is absent on one side of the roadway, the load optimisation seems to think there is no footway at all.  This not only prevents any footway loading being produced but it also prevents the correct selection of footway and accidental loading for individual influences.  To get over this I made the north footway just 1mm wide.

This then allowed me to adjust the settings for the Accidental load and pedestrian load in the load optimisation form.

The assessment standard suggests that only members supporting footways/verges and central reserves should be assessed for accidental loading.  So accidental loading need only be applied to influences of beams supporting the footway/verge.

For most of the influences that you have selected they are not supporting the footway so that accidental load should not be considered, and this is achieved by selection "None" for the accidental load and the member selected is a "Main member".  The last influence in your list could be said to support the footway so for this influence only I selected "Vehicle - non cantilevered member" and the member is supporting the footway only.

This then produces a load pattern as shown

There is no ALL model 1 loading as in both the single vehicle and convoy cases the two lanes would be most southward to get the most adverse effect effect with the remaining area at the north.  As the HB vehicle straddles these two lanes and leaves less than 2.5 m there will be no ALL model 1 loading.

I hope all this helps and if this has answered your question then please mark my reply as a solution so that others may benefit.

Thanks

Kind regards

Dave Geeves

[designXDAC3]

Hi Dave,

Thank you for the assistance, the reason I removed the verge at the top is because I was modelling half deck of dual carriageway and the top area represented a central reserve. There is a wide verge below, but it is protected by with a parapet and I was using selected the "none (effective barrier)" to prevent any AW on that verge. I realise that modelling half deck did not allow me to set same travel direction for the lanes, but I was happy to proceed so long the HA plus HB/SV and AIL were placed in the two lanes or made to straddle for optimisation. 

I resorted to set up load combinations manually (a bit tedius), I will do what you suggested and if I can complete the full process.

Many Thanks

Ayub