Restrained Shrinkage Model

I've been putting my efforts into developing my finite element model that simulates the behavior of the restrained shrinkage models constructed and tested by Radabaugh (Radabaugh, 2001). The specimens were 9' by 9' reinforced slabs constructed fully composite with W12x65 girders. Radabaugh construced two specimens whose only difference was in the type of formwork that was used in construction. The specimens were reinforced with #4 and # 5 bars spced at 12" in the longitudinal direction and at 8" in the transverse direction. The specimens are shown below.

I modeled the specimen using ANSYS. The concrete was modeled using SOLID65 nonlinear concrete elements, the reinforcement was modeled using LINK8 elements, and the girders were modeled using SHELL63 elements. Also, the specimens were constructed with diaphrams at the supports. These were modeled using BEAM4 elements. The model is shown in the figure below.

A quick note of interest concerning the use of shell elements for modeling girders. I initially used shell elements which did not have a DOF for in-plane membrane forces. When the analysis was run, the simulation did not behave correctly (i.e. girders appeared to "hinge" out of plane and did not exhibit propoer flexural behavior). Obviously, in-plane forces are how girders carry flexure. Thus, be sure to use shell elements that have membrane force capabilities when using shells to model girders.