Features of 3D analysis and chasedown analysis

The following table compares the features of the three analysis types that can be used to generate sets of forces suitable for static design.

Note: In the table the term '3D Analysis' refers to any of 1st-order linear, 1st order non-linear, 2nd order linear, 2nd order non-linear analysis types.


Feature	3D Analysis	Grillage Chasedown	FE Chasedown
Examples / When useful?	Gravity and Lateral analysis (Notional/Wind/Seismic)	“Beam & Slab” buildings	Flat slab and “Beam & Slab” buildings
Special Features	Pattern loading Automatic EC2 sway sensitivity assessment and sway amplification Automatically centralised analysis wires (improved rigid offsets / rigid zones) Option to mesh slabs in the 3D analysis	Mimics traditional design approach (sub-frame analysis) Pattern loading	Mimics traditional design approach (isolated floor analysis) Slab Pattern loading
Benefits	Member Design considers sway and differential axial deformation effects. Caters for slabs that contribute to the lateral load resisting system	Member design based on traditional sub frame is considered simultaneously with that for 3D Analysis	Member design based on traditional sub frame is considered simultaneously with that for 3D Analysis Irregular slab panel design automatically catered for
Analysis Model	3D model of entire building: either meshed 2-way slabs, or, slab loads decomposed to beams	series of 3D sub models: all column and wall stacks immediately above and below the sub-model either meshed 2-way slabs, or, slab loads decomposed to beams	series of 3D sub models: all column and wall stacks immediately above and below the sub-model all 2-way slabs meshed
Analysis Method	Whole model in one pass	Each sub model sequentially from top to bottom – chasing member loads down	Each sub model sequentially from top to bottom – chasing member loads down
Analysis Type	First order First order - Kamp Second order - P-D	First order	First order
Supports	External supports as defined by the user	Ends of members above/below each sub model are automatically supported	Ends of members above/below each sub model are automatically supported
Loading	Gravity and Lateral Loads	Gravity Loads only	Gravity Loads only
Forces for design
RC Slab	Yes– All Combs	No forces	Yes – All Gravity loadcases
RC Beam	Yes– All Combs	Yes – All Gravity loadcases	Optional – All Gravity loadcases
RC Column	Yes– All Combs	Yes – All Gravity loadcases	Optional – All Gravity loadcases
RC Wall	Yes– All Combs	Yes – All Gravity loadcases	Optional – All Gravity loadcases
Steel/Composite Members	Yes – All Combs except patterns	Not required	Not required
Timber Members (via Tedds)	Yes	Yes	Yes
Foundation design	Yes – All Combs except patterns	Yes – All Gravity loadcases	Yes – All Gravity loadcases