Select Structural Subsystems
At the structural subsystem level, overall structural solutions are studied by the engineer and described in terms of supporting assemblies and materials. Alternative structural grids are first proposed by the engineer respecting the architectural constraints from the ASM. These grids determine primary layouts for structural assemblies and elements and permit the subsequent validation of subsystem proposals by the engineer with the help of the computer. Then, for each structural subsystem, supporting assemblies are proposed by the engineer (with assistance from the DKM on demand). Next, the computer generates and places assemblies within the layout of the structural grids (i. e. structural frames) and from architectural floor slabs (i. e. for floor assemblies). Depending on the flexibility of the building architecture, the engineer and/or the DKM can propose alternative load transfer solutions based on the following factors: overall building characteristics (e. g. building location, seismic zone, type of building, size, number of stories, and construction area), building geometry (e. g. overall building dimensions and aspect ratios, main functional and bay dimensions) and predominant (i. e. global) architectural layout/dimensional constraints (i. e. that apply to the building as a whole). For a given structural layout, an approximate number of structural assemblies are obtained by the computer so that all feasible structural solutions can be ranked and evaluated by the DKM based on building requirements and preference factors. At this level, the engineer seeks to unify (if possible) the structural grids for the entire building. For buildings with multiple structural zones, structural subsystem descriptions can be detailed further. For example, in a building consisting of an apartment zone over an office zone over a parking zone, all the zones share the same vertical subsystems but each zone may require its own horizontal load transfer solution. Ensuring compatibility between the different assemblies selected can be achieved by the DKM using meta-knowledge heuristics. For example, a concrete rigid frame is compatible with a waffle slab.