Static analysis cases computed by inTENS can linked to time varying loading profiles and batch processed to yield time stepping analyses. Each static case is continued from the previous step with the loading profile updated accordingly. Time stepping analysis can be controlled and processed within custom built wrappers.
Examples of where time stepping analysis has been used to simulate real life situations are illustrated below:
Time varying loading profiles for long duration high altitude balloons.
High altitude balloon long duration balloons will typically experience large variations in their internal pressure during the diurnal cycle. The balloon shell is typically formed from highly non linear visco-elastic materials, such as polyethylene, where strain response is a function of stress history. Long duration loading profiles incorporating many diurnal cycles can be created and applied to single gore models of balloons to assess strain long term response.
Failure propagation analysis
Time stepping analysis has been used to assess the ability of tension structures to withstand the failure of one or more elements. A file of allowable forces for each element can be created and a typical environmental load case applied (e.g. wind load case). The force in each element can be compared to its assigned allowable value and removed from the analysis as required. The sequence can then recommence from the previous state, model status updated accordingly, all controlled from within a custom wrapper. The structure will either stabilise of continue onto failure. Various sequences can be set up with difference initial ‘seed’ events to quickly test the robust nature of the structure.
Varying head hydrostatic loading
A custom geometric interrogation tool has been used to facilitate modelling of pond water loading on top of air inflated structures. Consider the case of a pond of water forming on the surface of an inflatable structure during a rainstorm of known intensity. At the end of the static analysis case the deflected geometry can be used to assess the revised characteristics of the pond, such as:
- Catchment area
- Lowest point
- Maximum contained volume
- Additional maximum volume of water added to pond in given time step (flow from catchment area and direct rain into the pond)
- Loaded area of FE model, for passing to static analysis case.
Updated loading information can be passed back to inTENS for a further static analysis case. The time stepping sequence continues until the structure fails, the pond stabilises of the pond dissipates.
Hydro flow assessment to size drainage requirements
The dynamic fluid flow capabilities of Tensys Hydro can be coupled with inTENS static solutions to assess changes in water surface flow over a membrane structure as the structure deflects.
The Hydro sequence is initially undertaken on an undeflected version of the inTENS model for a particular structure. Once the flow has reached saturation point a profile of vertical surface water loading is passed back to inTENS for static analysis. The deflected form is passed to Hydro for re assessment of surface flow characteristics. The loop can continue until either the structure fails or the flow stabilises.