How to resolve CS 454 ALL 1 Moving Load Optimization issues in my model?

Hi,

I'm currently carrying out an assessment to ALL 1 as per CS454.

Currently I’m having a some issues as below:

CS454 table 5.9a specifies different notional lanes widths for single vehicle (3m lane width) and convoy of vehicles (2.5m width).

and in table 5.9c lane factors for each lane (1.0 for lane 1 and 2 and 0.5 for lane 3). The Lane factors are also interchangeable as per Table 5.9c.

Where the assessment live loading exceeds 7.5t Clause 5.16 also requires a udl of 5 kN/m3 to be applied over the remaining area of the carriageway.

For example I have a carriage of 9.144m, when considering the single vehicle loading 3 lanes of 3m should be specified with a remaining area of 0.144m and in the convoy vehicle loading 3 lanes of 2.5m with a remaining area of 1.644m. Now to be able to do this efficiently, the software needs to optimise the lanes/vehicles to get the most onerous loading for each element that is being checked. Currently in Lusas this is achieved by defining the kerbline rather than lanes and the software applies lanes/factors/vehicles as per code and in the most onerous locations for each of the elements. In Midas I believe this is achieved through the moving load optimisation, however I couldn’t get this to work.  The model you have sent me in your email also doesn’t have the moving load optimisation defined. Can you please send me a tutorial on how this can be defined/achieved and if lanes/factors/vehicles are optimised?

I have attached screenshots from relevant CS454 tables and clauses and have my model also attached.

Dear DK Lee,

Thanks, I look forward to receive your response. Please not this is quite urgent and the assessment is on hold due to this issue.

Regards,

In the mean time, I recommend that you should try it without using optimisation. You can manually define lanes and apply ALL Model 1, which is not so difficult.

Regards,
DK Lee
Technical Manager

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Dear DK Lee,

I have tried doing it manually however because the lane factors are interchangeable and remaining area could be in different locations, there will  be many scenarios that needs to be checked for each element. Few scenarios for longitudinal elements, few scenarios for transverse elements etc this is not efficient and waste of time. I can see moving load optimisation is defined but how does this work because right now its not working. Do you have a tutorial to show how this works? I can see there are tutorials on previous versions of MIDAS but nothing for version 2020 3.1. I am awaiting your response.

Regards,

- I have tried the moving load optimisation for ALL Model 1 single vehicle and convoy vehicles and found that UDL is applied in some cases but not in other cases. So, the developer is looking into it now. But, considering your urgent project, I recommend you use manual definition for your project.

Regards,
DK Lee
Technical Manager

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Dear DK Lee,

Thanks for your response.

Can you send a quick tutorial/screenshot to show how you have defined the moving load optimisation? I wasn't able to do this and when defined only got 1 lane, see screenshot attached to show how I am defining the moving load optimisation.

Please let me know what each of the inputs are and what I need to input to get 1 optimised lane of 9.144m divided into 3 lanes of 3m and a remainder area (I'm aware currently UDL is not applied in some cases but would like to test the vehicle load optimisation).

Regards,

Please find the attached sample model file and document. Thank you for your patience.

Regards,
DK Lee
Technical Manager

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Dear DK Lee,

Thanks for your response. Can you please double check the width lane and let me know why you have used 3.6? Shouldn't be this 3m?

Please see screenshot.

Kind Regards,

Also can you advise how I can see if the model has applied the udl or not as the moving load tracer only shows the vehicle load.

This has always been a question to me to be able to see what combination of load the software is applying. Is it possible to check how the loads (DL + SIDL + LL) is applied something similar to moving load tracer but for all loads?

Kind Regards,

3.  It is not possible to check how the load combination (DL + SIDL + LL) is applied. The applied loads can only be viewed by each load case as shown below.

Regards,
DK Lee
Technical Manager

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In the sample file, only one location of remaining area is considered for the purpose of showing above concept. For other possible location of remaining area, you should create more moving load cases.

Regards,
DK Lee
Technical Manager

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Dear DK Lee,

Thanks for your response and for providing the details of the workaround to the problem. Is the issue with remaining area going to get solved? Lusas algorithm is handling this with no issue.

Regards.

 

Technical Manager

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Thanks for your quick reply. I believe this is another solution to the problem and allows the assessor to be flexible with the remaining area to choose where it will be. However, I don't think this would be the best solution as it be more efficient if the software applied the UDL automatically by considering all cases and finding the optimum solution. I suggest this issue be resolved in future implementation.

Another issue I was having is combining ALL 1 with HB vehicles. In current version this is not achievable and only ALL2 can be combined with HB loading. CS454 Appendix C suggest HB can be combined with either ALL1 or ALL2 and for the assessment to be in accordance with the current standards ALL1 should be able to be combined with HB loading. Can you let me know if for the current version you have a workaround for this issue?

Regards,

Also can you let me know how the current workaround would work for when you have the remaining area in between lanes? Currently the workaround would only work if the remaining area is before lane 1 or after lane 3 but as the lanes are optimised how would I introduce a remaining area in between lane 1 and 2 and in between lane 2 and 3. Clause 5.11 of CS 454 states: The notional lanes for ALL model 1 shall be located to cause the most adverse loading effects on the member or element under consideration. Therefore these combinations will also need to be checked.

I look forward to your response.

Regards,

Dear DK Lee,

I have tried to implement your workaround to my model. However, I'm getting errors when using the moving load tracer and the model crashes. Please see screenshots attached and I have also attached the model.

Please let me know why this is happening.

Regards,

Technical Manager

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Dear DK Lee,

Thanks for your responses.

1- It would be great if you could implement combination of ALL Model 1 and HB in next releases as this is required to be checked under the new CS454.

2- I agree that the remaining area in between lanes may not be the most onerous case, so for now I can ignore this but it would be great if it is possible for software to do this and check for the different elements in future releases.

Regards,

It is fixed now. Here is the patch below.

https://drive.google.com/file/d/1I2DZ-80sdgp2WYBfaTjyb6zN0IUUyMdj/view?usp=sharing

Regards,
DK Lee
Technical Manager

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That's Great! Its now working for me as well.

Regards,