Topic: Prestressing a Load application slab for testing


I am trying to model behavior of low rise wall specimens, and I am incorporating a clamping load using an external cable element to model the clamping that was required to attach the loading actuator to the specimen.

I have noticed, that when applying this prestressing load, the results after prestressing vary significantly dependent on how many steps over which I apply the load. Applied in one step, the cracking due to prestressing matched the observed behavior well, but if I apply the prestressing load over 100-200 steps, the prestressing load that results in cracking significantly increases.

Is there something in the external cable model that is step dependent as I am seeing? Nothing else is changed between the models, and I have confirmed that the same total cable load is achieved by the end of the model.


Re: Prestressing a Load application slab for testing

Of note, it does seem that there is some convergence to a solution when 100-200 steps are used. My concern is why the 1 step application of the prestressing force is causing cracking, when these smaller steps do not.

Re: Prestressing a Load application slab for testing

Dear rdevine,
1. we generally recommend to use 5-10 load steps even for loads not expected to get close to peak load, as local nonlinearities, both geometrical and material, can already be important.

2. Please always check the convergence errors - see Troubleshooting, 2.1.19 Problems reaching convergence and understanding ATENA convergence parameters and 2.4.2 I get the message "The execution is killed due to violation of stop iteration criteria", what does it mean?

3. If you seek comments/advice with respect to a particular model, please follow Troubleshooting, 2.1.1 to send us the model etc.