Voided slab rail loading vs relative displacement

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J Wolfe
Voided slab rail loading vs relative displacement

Hi Rick,
I'm working with a short span prestressed voided slab bridge (16 adjacent girders), and I have to distribute the barrier load 60% to the exterior girder and 40% to the first interior. However, the connectivity between girders is only enough to prevent relative vertical displacement. Is there any way to model this situation in PGSuper? Thank you so much, and Merry Christmas!

Rick Brice
Voided slab rail loading vs relative displacement

In PGSuper, relative displacement and load distribution are unrelated concepts. The Girder Connectivity setting is related to the live load distribution factors. There isn't a direct way to distribute the barrier loads 60%/40% - loads are equally distributed to a given number of girders.

There is a way to get the load distribution you want, it's just not direct.

Re-define your barriers in the Traffic Barriers library, so that its weight is 0.0 kip/ft/barrier. There will still be a railing system load and load response (moments, shears, etc) but they will be zero. The zero weight load will be distributed per the settings in the Project Criteria.

Create user defined loads of the intensity you want for your barrier loading and apply them to the exterior and first interior girder.

This will get the loading conditions you want.

J Wolfe
Voided slab rail loading vs relative displacement

Hi Rick,
Yes, sorry, I should have provided more information. I had removed the barrier load and added distributed user-defined loads to the two exterior girders 60/40 as you had mentioned already. I was wondering if there was a way to force equal relative displacements between the girders... which it doesn't sound like is possible at this time. It looks like I'd need to have 3 different girder designs (Ext, 1st Int, and the rest of the interior girders) to maintain similar displacements? The problem is that during erection, the rail won't be present on the girders, and so the deflections between girders need to be similar to pour the UHPC shear keys. Anyway, I appreciate the help, and will probably try to figure out a way to average the deflections. Unless you have other thoughts. Thanks so much!

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