Carl Oberg's Communities Activities

Load Combinations Using Moving Loads

Carl Oberg — Fri, 15 Jan 2016 14:56:38 GMT

I have run into this problem several times now and have not found a good solution for it yet. I am modling a large structure in which I need to consider several loaded lanes of traffic traveling accross it. To generate the moving truck loads I am using STAAD's vehicle definition and load generation features. The structure I am analysing is approximately 96 feet long and i need to consider all possible load patterns for 4 lanes. From what I have found there is no way to include load generations within a load combination. To get around this I have taken load generated for each lane and put them into their own envelopes (i.e. all loads that get generated for the moving load in lane one get enveloped). In order to make the necessary AASHTO Load combinations I then have to export all results out of the prgram into Microsoft Excel where i can take the enveloped results and combine them with the results from any of the other static loads that have been applied. This is a very tedious and time consuming process in which there is great potential for human error. Is there any other way that these load generations can be combined with other load cases within the STAAD.pro program so that I do not have to export the data out and do it manually? Also, I am not able to use the STAAD.pro BEVA package for this as it is not approved for use by the DOT we are working for. Any input or suggestions on this would be much appreciated. Thanks.

Moving Load Generation - Vehicle Not Displaying

Carl Oberg — Thu, 03 Dec 2020 22:59:27 GMT

So I seem to be having an issue when using the moving load generator. I have defined a custom vehicle with axle loads and spacings. I then created the load generation case and then assigned the vehicle with the appropriate starting location and step increment. The issue I am having is that for some reason, the start location of the vehicle does not display on the screen when I select the moving load for some reason, so i cannot verity its starting at the location I want it to. In the past (prior to Connect) the vehicle and wheel locations would show up in red on the model and the reference wheel would be boxed. Is there a view setting or something else that I may have toggled off that would prevent me from seeing the vehicle start location? Thank you!

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Thu, 03 Dec 2020 23:00:26 GMT

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Fri, 27 Oct 2017 03:13:53 GMT

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STAAD.pro Global Statics Equilibrium Problem

Carl Oberg — Thu, 01 May 2014 17:28:01 GMT

Hello,

I am having some problems with a model I am trying to run for deflection purposes. The structure is a steel plate girder bridge with a composite concrete deck. I originally had the full structure modeled using beam elements for the girders and plate elements for the concrete deck. To make the connection between the girder and deck I used rigid master/slave body constraints. To verify the model was working properly I first ran it with only the 8" thick concrete deck weight applied. After the model was run I went to the post processing and looked at the statics equilibrium check and saw that the vertical load equilibrium was not being satisified for some reason and the sum of the reactions was about 15% less than the applied load. I went back and checked all my inputs and structure geometry to make sure there was not any error's or my part and from what I see everything looks ok.

In an effort to make trying to figure this issue out easier, I simplified the model to one girder with it's tributary deck width. Again, I ran the model with only the selfweight of the 8" concrete deck applied. As with the full model I got the same results where the sum of reactions was about 15% less than the total applied load. One thing I noticed with the model is that even though the applied selfweight load is in the -y direction, when the model is analyzed it results with a reaction force at one of the supports in the x-direction, which should not be the case. I have been through this model several times now and cannot figure out why this is happening. If anyone has had this problem before and know what may be causing, could you please let me know. I am attaching my simplified model in which am having the static equilibrium problem. Thanks.