Q: How we can model a MIVAN system of walls in ETABS?
A: MIVAN system is in fact a kind of formwork for a rapid construction of multi-story building systems. In such a system beams are not used at all in most cases and all slabs are simple flat plates. Such a building system can be modelled in ETABS rather easily using wall and floor objects. However take a note that slab and walls both participate in bending when subjected to loads. Hence for a realistic modelling, floors and walls both should be modelled using shell type property. Floor as well as wall objects should be meshed adequately. But the problem with these models lies elsewhere. In such building systems almost always walls will be terminated on heavy beams and columns to create large uninterrupted areas for parking purpose in lower stories. In such models, adequate modelling of walls, transfer girders and supporting columns is a critical issue. In general such cases should be investigated adequately at a more fundamental level by checking stresses developing in walls. You may often require to model columns and transfer girders both using wall elements to achieve a proper connectivity with walls above. Such models will actually reveal the flow of loads when principal stresses are plotted in ETABS. In most such models staged analysis will also be needed. We have also noticed that sometimes in some deep girders which may have depth equal to the depth of story or even a higher depth arching action may be important which need be evaluated correctly to produce safe designs.